From de53c3786a3ce162a1c815d0c04c766c23ec9c0a Mon Sep 17 00:00:00 2001 From: Jiri Kosina Date: Fri, 5 Jan 2018 22:35:41 +0100 Subject: [PATCH 01/28] x86/pti: Unbreak EFI old_memmap EFI_OLD_MEMMAP's efi_call_phys_prolog() calls set_pgd() with swapper PGD that has PAGE_USER set, which makes PTI set NX on it, and therefore EFI can't execute it's code. Fix that by forcefully clearing _PAGE_NX from the PGD (this can't be done by the pgprot API). _PAGE_NX will be automatically reintroduced in efi_call_phys_epilog(), as _set_pgd() will again notice that this is _PAGE_USER, and set _PAGE_NX on it. Tested-by: Dimitri Sivanich Signed-off-by: Jiri Kosina Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner Acked-by: Dave Hansen Cc: Andrea Arcangeli Cc: Ard Biesheuvel Cc: Linus Torvalds Cc: Matt Fleming Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-efi@vger.kernel.org Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/nycvar.YFH.7.76.1801052215460.11852@cbobk.fhfr.pm --- arch/x86/platform/efi/efi_64.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c index 39c4b35ac7a4..61975b6bcb1a 100644 --- a/arch/x86/platform/efi/efi_64.c +++ b/arch/x86/platform/efi/efi_64.c @@ -134,7 +134,9 @@ pgd_t * __init efi_call_phys_prolog(void) pud[j] = *pud_offset(p4d_k, vaddr); } } + pgd_offset_k(pgd * PGDIR_SIZE)->pgd &= ~_PAGE_NX; } + out: __flush_tlb_all(); From 01c9b17bf673b05bb401b76ec763e9730ccf1376 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 5 Jan 2018 09:44:36 -0800 Subject: [PATCH 02/28] x86/Documentation: Add PTI description Add some details about how PTI works, what some of the downsides are, and how to debug it when things go wrong. Also document the kernel parameter: 'pti/nopti'. Signed-off-by: Dave Hansen Signed-off-by: Thomas Gleixner Reviewed-by: Randy Dunlap Reviewed-by: Kees Cook Cc: Moritz Lipp Cc: Daniel Gruss Cc: Michael Schwarz Cc: Richard Fellner Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Hugh Dickins Cc: Andi Lutomirsky Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180105174436.1BC6FA2B@viggo.jf.intel.com --- .../admin-guide/kernel-parameters.txt | 21 +- Documentation/x86/pti.txt | 186 ++++++++++++++++++ 2 files changed, 200 insertions(+), 7 deletions(-) create mode 100644 Documentation/x86/pti.txt diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 520fdec15bbb..905991745d26 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2685,8 +2685,6 @@ steal time is computed, but won't influence scheduler behaviour - nopti [X86-64] Disable kernel page table isolation - nolapic [X86-32,APIC] Do not enable or use the local APIC. nolapic_timer [X86-32,APIC] Do not use the local APIC timer. @@ -3255,11 +3253,20 @@ pt. [PARIDE] See Documentation/blockdev/paride.txt. - pti= [X86_64] - Control user/kernel address space isolation: - on - enable - off - disable - auto - default setting + pti= [X86_64] Control Page Table Isolation of user and + kernel address spaces. Disabling this feature + removes hardening, but improves performance of + system calls and interrupts. + + on - unconditionally enable + off - unconditionally disable + auto - kernel detects whether your CPU model is + vulnerable to issues that PTI mitigates + + Not specifying this option is equivalent to pti=auto. + + nopti [X86_64] + Equivalent to pti=off pty.legacy_count= [KNL] Number of legacy pty's. Overwrites compiled-in diff --git a/Documentation/x86/pti.txt b/Documentation/x86/pti.txt new file mode 100644 index 000000000000..d11eff61fc9a --- /dev/null +++ b/Documentation/x86/pti.txt @@ -0,0 +1,186 @@ +Overview +======== + +Page Table Isolation (pti, previously known as KAISER[1]) is a +countermeasure against attacks on the shared user/kernel address +space such as the "Meltdown" approach[2]. + +To mitigate this class of attacks, we create an independent set of +page tables for use only when running userspace applications. When +the kernel is entered via syscalls, interrupts or exceptions, the +page tables are switched to the full "kernel" copy. When the system +switches back to user mode, the user copy is used again. + +The userspace page tables contain only a minimal amount of kernel +data: only what is needed to enter/exit the kernel such as the +entry/exit functions themselves and the interrupt descriptor table +(IDT). There are a few strictly unnecessary things that get mapped +such as the first C function when entering an interrupt (see +comments in pti.c). + +This approach helps to ensure that side-channel attacks leveraging +the paging structures do not function when PTI is enabled. It can be +enabled by setting CONFIG_PAGE_TABLE_ISOLATION=y at compile time. +Once enabled at compile-time, it can be disabled at boot with the +'nopti' or 'pti=' kernel parameters (see kernel-parameters.txt). + +Page Table Management +===================== + +When PTI is enabled, the kernel manages two sets of page tables. +The first set is very similar to the single set which is present in +kernels without PTI. This includes a complete mapping of userspace +that the kernel can use for things like copy_to_user(). + +Although _complete_, the user portion of the kernel page tables is +crippled by setting the NX bit in the top level. This ensures +that any missed kernel->user CR3 switch will immediately crash +userspace upon executing its first instruction. + +The userspace page tables map only the kernel data needed to enter +and exit the kernel. This data is entirely contained in the 'struct +cpu_entry_area' structure which is placed in the fixmap which gives +each CPU's copy of the area a compile-time-fixed virtual address. + +For new userspace mappings, the kernel makes the entries in its +page tables like normal. The only difference is when the kernel +makes entries in the top (PGD) level. In addition to setting the +entry in the main kernel PGD, a copy of the entry is made in the +userspace page tables' PGD. + +This sharing at the PGD level also inherently shares all the lower +layers of the page tables. This leaves a single, shared set of +userspace page tables to manage. One PTE to lock, one set of +accessed bits, dirty bits, etc... + +Overhead +======== + +Protection against side-channel attacks is important. But, +this protection comes at a cost: + +1. Increased Memory Use + a. Each process now needs an order-1 PGD instead of order-0. + (Consumes an additional 4k per process). + b. The 'cpu_entry_area' structure must be 2MB in size and 2MB + aligned so that it can be mapped by setting a single PMD + entry. This consumes nearly 2MB of RAM once the kernel + is decompressed, but no space in the kernel image itself. + +2. Runtime Cost + a. CR3 manipulation to switch between the page table copies + must be done at interrupt, syscall, and exception entry + and exit (it can be skipped when the kernel is interrupted, + though.) Moves to CR3 are on the order of a hundred + cycles, and are required at every entry and exit. + b. A "trampoline" must be used for SYSCALL entry. This + trampoline depends on a smaller set of resources than the + non-PTI SYSCALL entry code, so requires mapping fewer + things into the userspace page tables. The downside is + that stacks must be switched at entry time. + d. Global pages are disabled for all kernel structures not + mapped into both kernel and userspace page tables. This + feature of the MMU allows different processes to share TLB + entries mapping the kernel. Losing the feature means more + TLB misses after a context switch. The actual loss of + performance is very small, however, never exceeding 1%. + d. Process Context IDentifiers (PCID) is a CPU feature that + allows us to skip flushing the entire TLB when switching page + tables by setting a special bit in CR3 when the page tables + are changed. This makes switching the page tables (at context + switch, or kernel entry/exit) cheaper. But, on systems with + PCID support, the context switch code must flush both the user + and kernel entries out of the TLB. The user PCID TLB flush is + deferred until the exit to userspace, minimizing the cost. + See intel.com/sdm for the gory PCID/INVPCID details. + e. The userspace page tables must be populated for each new + process. Even without PTI, the shared kernel mappings + are created by copying top-level (PGD) entries into each + new process. But, with PTI, there are now *two* kernel + mappings: one in the kernel page tables that maps everything + and one for the entry/exit structures. At fork(), we need to + copy both. + f. In addition to the fork()-time copying, there must also + be an update to the userspace PGD any time a set_pgd() is done + on a PGD used to map userspace. This ensures that the kernel + and userspace copies always map the same userspace + memory. + g. On systems without PCID support, each CR3 write flushes + the entire TLB. That means that each syscall, interrupt + or exception flushes the TLB. + h. INVPCID is a TLB-flushing instruction which allows flushing + of TLB entries for non-current PCIDs. Some systems support + PCIDs, but do not support INVPCID. On these systems, addresses + can only be flushed from the TLB for the current PCID. When + flushing a kernel address, we need to flush all PCIDs, so a + single kernel address flush will require a TLB-flushing CR3 + write upon the next use of every PCID. + +Possible Future Work +==================== +1. We can be more careful about not actually writing to CR3 + unless its value is actually changed. +2. Allow PTI to be enabled/disabled at runtime in addition to the + boot-time switching. + +Testing +======== + +To test stability of PTI, the following test procedure is recommended, +ideally doing all of these in parallel: + +1. Set CONFIG_DEBUG_ENTRY=y +2. Run several copies of all of the tools/testing/selftests/x86/ tests + (excluding MPX and protection_keys) in a loop on multiple CPUs for + several minutes. These tests frequently uncover corner cases in the + kernel entry code. In general, old kernels might cause these tests + themselves to crash, but they should never crash the kernel. +3. Run the 'perf' tool in a mode (top or record) that generates many + frequent performance monitoring non-maskable interrupts (see "NMI" + in /proc/interrupts). This exercises the NMI entry/exit code which + is known to trigger bugs in code paths that did not expect to be + interrupted, including nested NMIs. Using "-c" boosts the rate of + NMIs, and using two -c with separate counters encourages nested NMIs + and less deterministic behavior. + + while true; do perf record -c 10000 -e instructions,cycles -a sleep 10; done + +4. Launch a KVM virtual machine. +5. Run 32-bit binaries on systems supporting the SYSCALL instruction. + This has been a lightly-tested code path and needs extra scrutiny. + +Debugging +========= + +Bugs in PTI cause a few different signatures of crashes +that are worth noting here. + + * Failures of the selftests/x86 code. Usually a bug in one of the + more obscure corners of entry_64.S + * Crashes in early boot, especially around CPU bringup. Bugs + in the trampoline code or mappings cause these. + * Crashes at the first interrupt. Caused by bugs in entry_64.S, + like screwing up a page table switch. Also caused by + incorrectly mapping the IRQ handler entry code. + * Crashes at the first NMI. The NMI code is separate from main + interrupt handlers and can have bugs that do not affect + normal interrupts. Also caused by incorrectly mapping NMI + code. NMIs that interrupt the entry code must be very + careful and can be the cause of crashes that show up when + running perf. + * Kernel crashes at the first exit to userspace. entry_64.S + bugs, or failing to map some of the exit code. + * Crashes at first interrupt that interrupts userspace. The paths + in entry_64.S that return to userspace are sometimes separate + from the ones that return to the kernel. + * Double faults: overflowing the kernel stack because of page + faults upon page faults. Caused by touching non-pti-mapped + data in the entry code, or forgetting to switch to kernel + CR3 before calling into C functions which are not pti-mapped. + * Userspace segfaults early in boot, sometimes manifesting + as mount(8) failing to mount the rootfs. These have + tended to be TLB invalidation issues. Usually invalidating + the wrong PCID, or otherwise missing an invalidation. + +1. https://gruss.cc/files/kaiser.pdf +2. https://meltdownattack.com/meltdown.pdf From 99c6fa2511d8a683e61468be91b83f85452115fa Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Sat, 6 Jan 2018 11:49:23 +0000 Subject: [PATCH 03/28] x86/cpufeatures: Add X86_BUG_SPECTRE_V[12] Add the bug bits for spectre v1/2 and force them unconditionally for all cpus. Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner Cc: gnomes@lxorguk.ukuu.org.uk Cc: Rik van Riel Cc: Andi Kleen Cc: Peter Zijlstra Cc: Linus Torvalds Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Dave Hansen Cc: Kees Cook Cc: Tim Chen Cc: Greg Kroah-Hartman Cc: Paul Turner Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/1515239374-23361-2-git-send-email-dwmw@amazon.co.uk --- arch/x86/include/asm/cpufeatures.h | 2 ++ arch/x86/kernel/cpu/common.c | 3 +++ 2 files changed, 5 insertions(+) diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 21ac898df2d8..1641c2f96363 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -342,5 +342,7 @@ #define X86_BUG_MONITOR X86_BUG(12) /* IPI required to wake up remote CPU */ #define X86_BUG_AMD_E400 X86_BUG(13) /* CPU is among the affected by Erratum 400 */ #define X86_BUG_CPU_MELTDOWN X86_BUG(14) /* CPU is affected by meltdown attack and needs kernel page table isolation */ +#define X86_BUG_SPECTRE_V1 X86_BUG(15) /* CPU is affected by Spectre variant 1 attack with conditional branches */ +#define X86_BUG_SPECTRE_V2 X86_BUG(16) /* CPU is affected by Spectre variant 2 attack with indirect branches */ #endif /* _ASM_X86_CPUFEATURES_H */ diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 2d3bd2215e5b..372ba3fb400f 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -902,6 +902,9 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) if (c->x86_vendor != X86_VENDOR_AMD) setup_force_cpu_bug(X86_BUG_CPU_MELTDOWN); + setup_force_cpu_bug(X86_BUG_SPECTRE_V1); + setup_force_cpu_bug(X86_BUG_SPECTRE_V2); + fpu__init_system(c); #ifdef CONFIG_X86_32 From 87590ce6e373d1a5401f6539f0c59ef92dd924a9 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 7 Jan 2018 22:48:00 +0100 Subject: [PATCH 04/28] sysfs/cpu: Add vulnerability folder As the meltdown/spectre problem affects several CPU architectures, it makes sense to have common way to express whether a system is affected by a particular vulnerability or not. If affected the way to express the mitigation should be common as well. Create /sys/devices/system/cpu/vulnerabilities folder and files for meltdown, spectre_v1 and spectre_v2. Allow architectures to override the show function. Signed-off-by: Thomas Gleixner Reviewed-by: Greg Kroah-Hartman Reviewed-by: Konrad Rzeszutek Wilk Cc: Peter Zijlstra Cc: Will Deacon Cc: Dave Hansen Cc: Linus Torvalds Cc: Borislav Petkov Cc: David Woodhouse Link: https://lkml.kernel.org/r/20180107214913.096657732@linutronix.de --- .../ABI/testing/sysfs-devices-system-cpu | 16 +++++++ drivers/base/Kconfig | 3 ++ drivers/base/cpu.c | 48 +++++++++++++++++++ include/linux/cpu.h | 7 +++ 4 files changed, 74 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu index f3d5817c4ef0..bd3a88e16d8b 100644 --- a/Documentation/ABI/testing/sysfs-devices-system-cpu +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu @@ -373,3 +373,19 @@ Contact: Linux kernel mailing list Description: information about CPUs heterogeneity. cpu_capacity: capacity of cpu#. + +What: /sys/devices/system/cpu/vulnerabilities + /sys/devices/system/cpu/vulnerabilities/meltdown + /sys/devices/system/cpu/vulnerabilities/spectre_v1 + /sys/devices/system/cpu/vulnerabilities/spectre_v2 +Date: Januar 2018 +Contact: Linux kernel mailing list +Description: Information about CPU vulnerabilities + + The files are named after the code names of CPU + vulnerabilities. The output of those files reflects the + state of the CPUs in the system. Possible output values: + + "Not affected" CPU is not affected by the vulnerability + "Vulnerable" CPU is affected and no mitigation in effect + "Mitigation: $M" CPU is affetcted and mitigation $M is in effect diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig index 2f6614c9a229..37a71fd9043f 100644 --- a/drivers/base/Kconfig +++ b/drivers/base/Kconfig @@ -235,6 +235,9 @@ config GENERIC_CPU_DEVICES config GENERIC_CPU_AUTOPROBE bool +config GENERIC_CPU_VULNERABILITIES + bool + config SOC_BUS bool select GLOB diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index 321cd7b4d817..825964efda1d 100644 --- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -501,10 +501,58 @@ static void __init cpu_dev_register_generic(void) #endif } +#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES + +ssize_t __weak cpu_show_meltdown(struct device *dev, + struct device_attribute *attr, char *buf) +{ + return sprintf(buf, "Not affected\n"); +} + +ssize_t __weak cpu_show_spectre_v1(struct device *dev, + struct device_attribute *attr, char *buf) +{ + return sprintf(buf, "Not affected\n"); +} + +ssize_t __weak cpu_show_spectre_v2(struct device *dev, + struct device_attribute *attr, char *buf) +{ + return sprintf(buf, "Not affected\n"); +} + +static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL); +static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL); +static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL); + +static struct attribute *cpu_root_vulnerabilities_attrs[] = { + &dev_attr_meltdown.attr, + &dev_attr_spectre_v1.attr, + &dev_attr_spectre_v2.attr, + NULL +}; + +static const struct attribute_group cpu_root_vulnerabilities_group = { + .name = "vulnerabilities", + .attrs = cpu_root_vulnerabilities_attrs, +}; + +static void __init cpu_register_vulnerabilities(void) +{ + if (sysfs_create_group(&cpu_subsys.dev_root->kobj, + &cpu_root_vulnerabilities_group)) + pr_err("Unable to register CPU vulnerabilities\n"); +} + +#else +static inline void cpu_register_vulnerabilities(void) { } +#endif + void __init cpu_dev_init(void) { if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups)) panic("Failed to register CPU subsystem"); cpu_dev_register_generic(); + cpu_register_vulnerabilities(); } diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 938ea8ae0ba4..c816e6f2730c 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -47,6 +47,13 @@ extern void cpu_remove_dev_attr(struct device_attribute *attr); extern int cpu_add_dev_attr_group(struct attribute_group *attrs); extern void cpu_remove_dev_attr_group(struct attribute_group *attrs); +extern ssize_t cpu_show_meltdown(struct device *dev, + struct device_attribute *attr, char *buf); +extern ssize_t cpu_show_spectre_v1(struct device *dev, + struct device_attribute *attr, char *buf); +extern ssize_t cpu_show_spectre_v2(struct device *dev, + struct device_attribute *attr, char *buf); + extern __printf(4, 5) struct device *cpu_device_create(struct device *parent, void *drvdata, const struct attribute_group **groups, From 61dc0f555b5c761cdafb0ba5bd41ecf22d68a4c4 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 7 Jan 2018 22:48:01 +0100 Subject: [PATCH 05/28] x86/cpu: Implement CPU vulnerabilites sysfs functions Implement the CPU vulnerabilty show functions for meltdown, spectre_v1 and spectre_v2. Signed-off-by: Thomas Gleixner Reviewed-by: Greg Kroah-Hartman Reviewed-by: Konrad Rzeszutek Wilk Cc: Peter Zijlstra Cc: Will Deacon Cc: Dave Hansen Cc: Linus Torvalds Cc: Borislav Petkov Cc: David Woodhouse Link: https://lkml.kernel.org/r/20180107214913.177414879@linutronix.de --- arch/x86/Kconfig | 1 + arch/x86/kernel/cpu/bugs.c | 29 +++++++++++++++++++++++++++++ 2 files changed, 30 insertions(+) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index cd5199de231e..e23d21ac745a 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -89,6 +89,7 @@ config X86 select GENERIC_CLOCKEVENTS_MIN_ADJUST select GENERIC_CMOS_UPDATE select GENERIC_CPU_AUTOPROBE + select GENERIC_CPU_VULNERABILITIES select GENERIC_EARLY_IOREMAP select GENERIC_FIND_FIRST_BIT select GENERIC_IOMAP diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index ba0b2424c9b0..76ad6cb44b40 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -10,6 +10,7 @@ */ #include #include +#include #include #include #include @@ -60,3 +61,31 @@ void __init check_bugs(void) set_memory_4k((unsigned long)__va(0), 1); #endif } + +#ifdef CONFIG_SYSFS +ssize_t cpu_show_meltdown(struct device *dev, + struct device_attribute *attr, char *buf) +{ + if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN)) + return sprintf(buf, "Not affected\n"); + if (boot_cpu_has(X86_FEATURE_PTI)) + return sprintf(buf, "Mitigation: PTI\n"); + return sprintf(buf, "Vulnerable\n"); +} + +ssize_t cpu_show_spectre_v1(struct device *dev, + struct device_attribute *attr, char *buf) +{ + if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1)) + return sprintf(buf, "Not affected\n"); + return sprintf(buf, "Vulnerable\n"); +} + +ssize_t cpu_show_spectre_v2(struct device *dev, + struct device_attribute *attr, char *buf) +{ + if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) + return sprintf(buf, "Not affected\n"); + return sprintf(buf, "Vulnerable\n"); +} +#endif From 262b6b30087246abf09d6275eb0c0dc421bcbe38 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Sat, 6 Jan 2018 18:41:14 +0100 Subject: [PATCH 06/28] x86/tboot: Unbreak tboot with PTI enabled This is another case similar to what EFI does: create a new set of page tables, map some code at a low address, and jump to it. PTI mistakes this low address for userspace and mistakenly marks it non-executable in an effort to make it unusable for userspace. Undo the poison to allow execution. Fixes: 385ce0ea4c07 ("x86/mm/pti: Add Kconfig") Signed-off-by: Dave Hansen Signed-off-by: Andrea Arcangeli Signed-off-by: Thomas Gleixner Cc: Alan Cox Cc: Tim Chen Cc: Jon Masters Cc: Dave Hansen Cc: Andi Kleen Cc: Jeff Law Cc: Paolo Bonzini Cc: Linus Torvalds Cc: Greg Kroah-Hartman Cc: David" Cc: Nick Clifton Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180108102805.GK25546@redhat.com --- arch/x86/kernel/tboot.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c index a4eb27918ceb..75869a4b6c41 100644 --- a/arch/x86/kernel/tboot.c +++ b/arch/x86/kernel/tboot.c @@ -127,6 +127,7 @@ static int map_tboot_page(unsigned long vaddr, unsigned long pfn, p4d = p4d_alloc(&tboot_mm, pgd, vaddr); if (!p4d) return -1; + pgd->pgd &= ~_PAGE_NX; pud = pud_alloc(&tboot_mm, p4d, vaddr); if (!pud) return -1; From 8d56eff266f3e41a6c39926269c4c3f58f881a8e Mon Sep 17 00:00:00 2001 From: Jike Song Date: Tue, 9 Jan 2018 00:03:41 +0800 Subject: [PATCH 07/28] x86/mm/pti: Remove dead logic in pti_user_pagetable_walk*() The following code contains dead logic: 162 if (pgd_none(*pgd)) { 163 unsigned long new_p4d_page = __get_free_page(gfp); 164 if (!new_p4d_page) 165 return NULL; 166 167 if (pgd_none(*pgd)) { 168 set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page))); 169 new_p4d_page = 0; 170 } 171 if (new_p4d_page) 172 free_page(new_p4d_page); 173 } There can't be any difference between two pgd_none(*pgd) at L162 and L167, so it's always false at L171. Dave Hansen explained: Yes, the double-test was part of an optimization where we attempted to avoid using a global spinlock in the fork() path. We would check for unallocated mid-level page tables without the lock. The lock was only taken when we needed to *make* an entry to avoid collisions. Now that it is all single-threaded, there is no chance of a collision, no need for a lock, and no need for the re-check. As all these functions are only called during init, mark them __init as well. Fixes: 03f4424f348e ("x86/mm/pti: Add functions to clone kernel PMDs") Signed-off-by: Jike Song Signed-off-by: Thomas Gleixner Cc: Alan Cox Cc: Andi Kleen Cc: Tom Lendacky Cc: Peter Zijlstra Cc: Tim Chen Cc: Jiri Koshina Cc: Dave Hansen Cc: Borislav Petkov Cc: Kees Cook Cc: Andi Lutomirski Cc: Linus Torvalds Cc: Greg KH Cc: David Woodhouse Cc: Paul Turner Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180108160341.3461-1-albcamus@gmail.com --- arch/x86/mm/pti.c | 32 ++++++-------------------------- 1 file changed, 6 insertions(+), 26 deletions(-) diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index 43d4a4a29037..ce38f165489b 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -149,7 +149,7 @@ pgd_t __pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd) * * Returns a pointer to a P4D on success, or NULL on failure. */ -static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address) +static __init p4d_t *pti_user_pagetable_walk_p4d(unsigned long address) { pgd_t *pgd = kernel_to_user_pgdp(pgd_offset_k(address)); gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO); @@ -164,12 +164,7 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address) if (!new_p4d_page) return NULL; - if (pgd_none(*pgd)) { - set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page))); - new_p4d_page = 0; - } - if (new_p4d_page) - free_page(new_p4d_page); + set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page))); } BUILD_BUG_ON(pgd_large(*pgd) != 0); @@ -182,7 +177,7 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address) * * Returns a pointer to a PMD on success, or NULL on failure. */ -static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address) +static __init pmd_t *pti_user_pagetable_walk_pmd(unsigned long address) { gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO); p4d_t *p4d = pti_user_pagetable_walk_p4d(address); @@ -194,12 +189,7 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address) if (!new_pud_page) return NULL; - if (p4d_none(*p4d)) { - set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page))); - new_pud_page = 0; - } - if (new_pud_page) - free_page(new_pud_page); + set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page))); } pud = pud_offset(p4d, address); @@ -213,12 +203,7 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address) if (!new_pmd_page) return NULL; - if (pud_none(*pud)) { - set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page))); - new_pmd_page = 0; - } - if (new_pmd_page) - free_page(new_pmd_page); + set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page))); } return pmd_offset(pud, address); @@ -251,12 +236,7 @@ static __init pte_t *pti_user_pagetable_walk_pte(unsigned long address) if (!new_pte_page) return NULL; - if (pmd_none(*pmd)) { - set_pmd(pmd, __pmd(_KERNPG_TABLE | __pa(new_pte_page))); - new_pte_page = 0; - } - if (new_pte_page) - free_page(new_pte_page); + set_pmd(pmd, __pmd(_KERNPG_TABLE | __pa(new_pte_page))); } pte = pte_offset_kernel(pmd, address); From e4d0e84e490790798691aaa0f2e598637f1867ec Mon Sep 17 00:00:00 2001 From: Tom Lendacky Date: Mon, 8 Jan 2018 16:09:21 -0600 Subject: [PATCH 08/28] x86/cpu/AMD: Make LFENCE a serializing instruction To aid in speculation control, make LFENCE a serializing instruction since it has less overhead than MFENCE. This is done by setting bit 1 of MSR 0xc0011029 (DE_CFG). Some families that support LFENCE do not have this MSR. For these families, the LFENCE instruction is already serializing. Signed-off-by: Tom Lendacky Signed-off-by: Thomas Gleixner Reviewed-by: Reviewed-by: Borislav Petkov Cc: Peter Zijlstra Cc: Tim Chen Cc: Dave Hansen Cc: Borislav Petkov Cc: Dan Williams Cc: Linus Torvalds Cc: Greg Kroah-Hartman Cc: David Woodhouse Cc: Paul Turner Link: https://lkml.kernel.org/r/20180108220921.12580.71694.stgit@tlendack-t1.amdoffice.net --- arch/x86/include/asm/msr-index.h | 2 ++ arch/x86/kernel/cpu/amd.c | 10 ++++++++++ 2 files changed, 12 insertions(+) diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h index ab022618a50a..1e7d710fef43 100644 --- a/arch/x86/include/asm/msr-index.h +++ b/arch/x86/include/asm/msr-index.h @@ -352,6 +352,8 @@ #define FAM10H_MMIO_CONF_BASE_MASK 0xfffffffULL #define FAM10H_MMIO_CONF_BASE_SHIFT 20 #define MSR_FAM10H_NODE_ID 0xc001100c +#define MSR_F10H_DECFG 0xc0011029 +#define MSR_F10H_DECFG_LFENCE_SERIALIZE_BIT 1 /* K8 MSRs */ #define MSR_K8_TOP_MEM1 0xc001001a diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index bcb75dc97d44..5b438d81beb2 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -829,6 +829,16 @@ static void init_amd(struct cpuinfo_x86 *c) set_cpu_cap(c, X86_FEATURE_K8); if (cpu_has(c, X86_FEATURE_XMM2)) { + /* + * A serializing LFENCE has less overhead than MFENCE, so + * use it for execution serialization. On families which + * don't have that MSR, LFENCE is already serializing. + * msr_set_bit() uses the safe accessors, too, even if the MSR + * is not present. + */ + msr_set_bit(MSR_F10H_DECFG, + MSR_F10H_DECFG_LFENCE_SERIALIZE_BIT); + /* MFENCE stops RDTSC speculation */ set_cpu_cap(c, X86_FEATURE_MFENCE_RDTSC); } From 9c6a73c75864ad9fa49e5fa6513e4c4071c0e29f Mon Sep 17 00:00:00 2001 From: Tom Lendacky Date: Mon, 8 Jan 2018 16:09:32 -0600 Subject: [PATCH 09/28] x86/cpu/AMD: Use LFENCE_RDTSC in preference to MFENCE_RDTSC With LFENCE now a serializing instruction, use LFENCE_RDTSC in preference to MFENCE_RDTSC. However, since the kernel could be running under a hypervisor that does not support writing that MSR, read the MSR back and verify that the bit has been set successfully. If the MSR can be read and the bit is set, then set the LFENCE_RDTSC feature, otherwise set the MFENCE_RDTSC feature. Signed-off-by: Tom Lendacky Signed-off-by: Thomas Gleixner Reviewed-by: Reviewed-by: Borislav Petkov Cc: Peter Zijlstra Cc: Tim Chen Cc: Dave Hansen Cc: Borislav Petkov Cc: Dan Williams Cc: Linus Torvalds Cc: Greg Kroah-Hartman Cc: David Woodhouse Cc: Paul Turner Link: https://lkml.kernel.org/r/20180108220932.12580.52458.stgit@tlendack-t1.amdoffice.net --- arch/x86/include/asm/msr-index.h | 1 + arch/x86/kernel/cpu/amd.c | 18 ++++++++++++++++-- 2 files changed, 17 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h index 1e7d710fef43..fa11fb1fa570 100644 --- a/arch/x86/include/asm/msr-index.h +++ b/arch/x86/include/asm/msr-index.h @@ -354,6 +354,7 @@ #define MSR_FAM10H_NODE_ID 0xc001100c #define MSR_F10H_DECFG 0xc0011029 #define MSR_F10H_DECFG_LFENCE_SERIALIZE_BIT 1 +#define MSR_F10H_DECFG_LFENCE_SERIALIZE BIT_ULL(MSR_F10H_DECFG_LFENCE_SERIALIZE_BIT) /* K8 MSRs */ #define MSR_K8_TOP_MEM1 0xc001001a diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index 5b438d81beb2..ea831c858195 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -829,6 +829,9 @@ static void init_amd(struct cpuinfo_x86 *c) set_cpu_cap(c, X86_FEATURE_K8); if (cpu_has(c, X86_FEATURE_XMM2)) { + unsigned long long val; + int ret; + /* * A serializing LFENCE has less overhead than MFENCE, so * use it for execution serialization. On families which @@ -839,8 +842,19 @@ static void init_amd(struct cpuinfo_x86 *c) msr_set_bit(MSR_F10H_DECFG, MSR_F10H_DECFG_LFENCE_SERIALIZE_BIT); - /* MFENCE stops RDTSC speculation */ - set_cpu_cap(c, X86_FEATURE_MFENCE_RDTSC); + /* + * Verify that the MSR write was successful (could be running + * under a hypervisor) and only then assume that LFENCE is + * serializing. + */ + ret = rdmsrl_safe(MSR_F10H_DECFG, &val); + if (!ret && (val & MSR_F10H_DECFG_LFENCE_SERIALIZE)) { + /* A serializing LFENCE stops RDTSC speculation */ + set_cpu_cap(c, X86_FEATURE_LFENCE_RDTSC); + } else { + /* MFENCE stops RDTSC speculation */ + set_cpu_cap(c, X86_FEATURE_MFENCE_RDTSC); + } } /* From 9ecccfaa7cb5249bd31bdceb93fcf5bedb8a24d8 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Tue, 9 Jan 2018 15:02:51 +0000 Subject: [PATCH 10/28] sysfs/cpu: Fix typos in vulnerability documentation Fixes: 87590ce6e ("sysfs/cpu: Add vulnerability folder") Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner --- Documentation/ABI/testing/sysfs-devices-system-cpu | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu index bd3a88e16d8b..258902db14bf 100644 --- a/Documentation/ABI/testing/sysfs-devices-system-cpu +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu @@ -378,7 +378,7 @@ What: /sys/devices/system/cpu/vulnerabilities /sys/devices/system/cpu/vulnerabilities/meltdown /sys/devices/system/cpu/vulnerabilities/spectre_v1 /sys/devices/system/cpu/vulnerabilities/spectre_v2 -Date: Januar 2018 +Date: January 2018 Contact: Linux kernel mailing list Description: Information about CPU vulnerabilities @@ -388,4 +388,4 @@ Description: Information about CPU vulnerabilities "Not affected" CPU is not affected by the vulnerability "Vulnerable" CPU is affected and no mitigation in effect - "Mitigation: $M" CPU is affetcted and mitigation $M is in effect + "Mitigation: $M" CPU is affected and mitigation $M is in effect From 612e8e9350fd19cae6900cf36ea0c6892d1a0dca Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Wed, 10 Jan 2018 12:28:16 +0100 Subject: [PATCH 11/28] x86/alternatives: Fix optimize_nops() checking The alternatives code checks only the first byte whether it is a NOP, but with NOPs in front of the payload and having actual instructions after it breaks the "optimized' test. Make sure to scan all bytes before deciding to optimize the NOPs in there. Reported-by: David Woodhouse Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Cc: Tom Lendacky Cc: Andi Kleen Cc: Tim Chen Cc: Peter Zijlstra Cc: Jiri Kosina Cc: Dave Hansen Cc: Andi Kleen Cc: Andrew Lutomirski Cc: Linus Torvalds Cc: Greg Kroah-Hartman Cc: Paul Turner Link: https://lkml.kernel.org/r/20180110112815.mgciyf5acwacphkq@pd.tnic --- arch/x86/kernel/alternative.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 3344d3382e91..e0b97e4d1db5 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -344,9 +344,12 @@ recompute_jump(struct alt_instr *a, u8 *orig_insn, u8 *repl_insn, u8 *insnbuf) static void __init_or_module noinline optimize_nops(struct alt_instr *a, u8 *instr) { unsigned long flags; + int i; - if (instr[0] != 0x90) - return; + for (i = 0; i < a->padlen; i++) { + if (instr[i] != 0x90) + return; + } local_irq_save(flags); add_nops(instr + (a->instrlen - a->padlen), a->padlen); From 445b69e3b75e42362a5bdc13c8b8f61599e2228a Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Wed, 10 Jan 2018 14:49:39 -0800 Subject: [PATCH 12/28] x86/pti: Make unpoison of pgd for trusted boot work for real The inital fix for trusted boot and PTI potentially misses the pgd clearing if pud_alloc() sets a PGD. It probably works in *practice* because for two adjacent calls to map_tboot_page() that share a PGD entry, the first will clear NX, *then* allocate and set the PGD (without NX clear). The second call will *not* allocate but will clear the NX bit. Defer the NX clearing to a point after it is known that all top-level allocations have occurred. Add a comment to clarify why. [ tglx: Massaged changelog ] Fixes: 262b6b30087 ("x86/tboot: Unbreak tboot with PTI enabled") Signed-off-by: Dave Hansen Signed-off-by: Thomas Gleixner Reviewed-by: Andrea Arcangeli Cc: Jon Masters Cc: "Tim Chen" Cc: gnomes@lxorguk.ukuu.org.uk Cc: peterz@infradead.org Cc: ning.sun@intel.com Cc: tboot-devel@lists.sourceforge.net Cc: andi@firstfloor.org Cc: luto@kernel.org Cc: law@redhat.com Cc: pbonzini@redhat.com Cc: torvalds@linux-foundation.org Cc: gregkh@linux-foundation.org Cc: dwmw@amazon.co.uk Cc: nickc@redhat.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180110224939.2695CD47@viggo.jf.intel.com --- arch/x86/kernel/tboot.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c index 75869a4b6c41..a2486f444073 100644 --- a/arch/x86/kernel/tboot.c +++ b/arch/x86/kernel/tboot.c @@ -127,7 +127,6 @@ static int map_tboot_page(unsigned long vaddr, unsigned long pfn, p4d = p4d_alloc(&tboot_mm, pgd, vaddr); if (!p4d) return -1; - pgd->pgd &= ~_PAGE_NX; pud = pud_alloc(&tboot_mm, p4d, vaddr); if (!pud) return -1; @@ -139,6 +138,17 @@ static int map_tboot_page(unsigned long vaddr, unsigned long pfn, return -1; set_pte_at(&tboot_mm, vaddr, pte, pfn_pte(pfn, prot)); pte_unmap(pte); + + /* + * PTI poisons low addresses in the kernel page tables in the + * name of making them unusable for userspace. To execute + * code at such a low address, the poison must be cleared. + * + * Note: 'pgd' actually gets set in p4d_alloc() _or_ + * pud_alloc() depending on 4/5-level paging. + */ + pgd->pgd &= ~_PAGE_NX; + return 0; } From 39b735332cb8b33a27c28592d969e4016c86c3ea Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Thu, 11 Jan 2018 21:46:23 +0000 Subject: [PATCH 13/28] objtool: Detect jumps to retpoline thunks A direct jump to a retpoline thunk is really an indirect jump in disguise. Change the objtool instruction type accordingly. Objtool needs to know where indirect branches are so it can detect switch statement jump tables. This fixes a bunch of warnings with CONFIG_RETPOLINE like: arch/x86/events/intel/uncore_nhmex.o: warning: objtool: nhmex_rbox_msr_enable_event()+0x44: sibling call from callable instruction with modified stack frame kernel/signal.o: warning: objtool: copy_siginfo_to_user()+0x91: sibling call from callable instruction with modified stack frame ... Signed-off-by: Josh Poimboeuf Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner Cc: gnomes@lxorguk.ukuu.org.uk Cc: Rik van Riel Cc: Andi Kleen Cc: thomas.lendacky@amd.com Cc: Peter Zijlstra Cc: Linus Torvalds Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Dave Hansen Cc: Kees Cook Cc: Tim Chen Cc: Greg Kroah-Hartman Cc: Paul Turner Link: https://lkml.kernel.org/r/1515707194-20531-2-git-send-email-dwmw@amazon.co.uk --- tools/objtool/check.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 9b341584eb1b..de053fb7049b 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -456,6 +456,13 @@ static int add_jump_destinations(struct objtool_file *file) } else if (rela->sym->sec->idx) { dest_sec = rela->sym->sec; dest_off = rela->sym->sym.st_value + rela->addend + 4; + } else if (strstr(rela->sym->name, "_indirect_thunk_")) { + /* + * Retpoline jumps are really dynamic jumps in + * disguise, so convert them accordingly. + */ + insn->type = INSN_JUMP_DYNAMIC; + continue; } else { /* sibling call */ insn->jump_dest = 0; From 258c76059cece01bebae098e81bacb1af2edad17 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Thu, 11 Jan 2018 21:46:24 +0000 Subject: [PATCH 14/28] objtool: Allow alternatives to be ignored Getting objtool to understand retpolines is going to be a bit of a challenge. For now, take advantage of the fact that retpolines are patched in with alternatives. Just read the original (sane) non-alternative instruction, and ignore the patched-in retpoline. This allows objtool to understand the control flow *around* the retpoline, even if it can't yet follow what's inside. This means the ORC unwinder will fail to unwind from inside a retpoline, but will work fine otherwise. Signed-off-by: Josh Poimboeuf Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner Cc: gnomes@lxorguk.ukuu.org.uk Cc: Rik van Riel Cc: Andi Kleen Cc: thomas.lendacky@amd.com Cc: Peter Zijlstra Cc: Linus Torvalds Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Dave Hansen Cc: Kees Cook Cc: Tim Chen Cc: Greg Kroah-Hartman Cc: Paul Turner Link: https://lkml.kernel.org/r/1515707194-20531-3-git-send-email-dwmw@amazon.co.uk --- tools/objtool/check.c | 62 ++++++++++++++++++++++++++++++++++++++----- tools/objtool/check.h | 2 +- 2 files changed, 57 insertions(+), 7 deletions(-) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index de053fb7049b..f40d46e24bcc 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -427,6 +427,40 @@ static void add_ignores(struct objtool_file *file) } } +/* + * FIXME: For now, just ignore any alternatives which add retpolines. This is + * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline. + * But it at least allows objtool to understand the control flow *around* the + * retpoline. + */ +static int add_nospec_ignores(struct objtool_file *file) +{ + struct section *sec; + struct rela *rela; + struct instruction *insn; + + sec = find_section_by_name(file->elf, ".rela.discard.nospec"); + if (!sec) + return 0; + + list_for_each_entry(rela, &sec->rela_list, list) { + if (rela->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", sec->name); + return -1; + } + + insn = find_insn(file, rela->sym->sec, rela->addend); + if (!insn) { + WARN("bad .discard.nospec entry"); + return -1; + } + + insn->ignore_alts = true; + } + + return 0; +} + /* * Find the destination instructions for all jumps. */ @@ -509,11 +543,18 @@ static int add_call_destinations(struct objtool_file *file) dest_off = insn->offset + insn->len + insn->immediate; insn->call_dest = find_symbol_by_offset(insn->sec, dest_off); + /* + * FIXME: Thanks to retpolines, it's now considered + * normal for a function to call within itself. So + * disable this warning for now. + */ +#if 0 if (!insn->call_dest) { WARN_FUNC("can't find call dest symbol at offset 0x%lx", insn->sec, insn->offset, dest_off); return -1; } +#endif } else if (rela->sym->type == STT_SECTION) { insn->call_dest = find_symbol_by_offset(rela->sym->sec, rela->addend+4); @@ -678,12 +719,6 @@ static int add_special_section_alts(struct objtool_file *file) return ret; list_for_each_entry_safe(special_alt, tmp, &special_alts, list) { - alt = malloc(sizeof(*alt)); - if (!alt) { - WARN("malloc failed"); - ret = -1; - goto out; - } orig_insn = find_insn(file, special_alt->orig_sec, special_alt->orig_off); @@ -694,6 +729,10 @@ static int add_special_section_alts(struct objtool_file *file) goto out; } + /* Ignore retpoline alternatives. */ + if (orig_insn->ignore_alts) + continue; + new_insn = NULL; if (!special_alt->group || special_alt->new_len) { new_insn = find_insn(file, special_alt->new_sec, @@ -719,6 +758,13 @@ static int add_special_section_alts(struct objtool_file *file) goto out; } + alt = malloc(sizeof(*alt)); + if (!alt) { + WARN("malloc failed"); + ret = -1; + goto out; + } + alt->insn = new_insn; list_add_tail(&alt->list, &orig_insn->alts); @@ -1035,6 +1081,10 @@ static int decode_sections(struct objtool_file *file) add_ignores(file); + ret = add_nospec_ignores(file); + if (ret) + return ret; + ret = add_jump_destinations(file); if (ret) return ret; diff --git a/tools/objtool/check.h b/tools/objtool/check.h index 47d9ea70a83d..dbadb304a410 100644 --- a/tools/objtool/check.h +++ b/tools/objtool/check.h @@ -44,7 +44,7 @@ struct instruction { unsigned int len; unsigned char type; unsigned long immediate; - bool alt_group, visited, dead_end, ignore, hint, save, restore; + bool alt_group, visited, dead_end, ignore, hint, save, restore, ignore_alts; struct symbol *call_dest; struct instruction *jump_dest; struct list_head alts; From 76b043848fd22dbf7f8bf3a1452f8c70d557b860 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Thu, 11 Jan 2018 21:46:25 +0000 Subject: [PATCH 15/28] x86/retpoline: Add initial retpoline support Enable the use of -mindirect-branch=thunk-extern in newer GCC, and provide the corresponding thunks. Provide assembler macros for invoking the thunks in the same way that GCC does, from native and inline assembler. This adds X86_FEATURE_RETPOLINE and sets it by default on all CPUs. In some circumstances, IBRS microcode features may be used instead, and the retpoline can be disabled. On AMD CPUs if lfence is serialising, the retpoline can be dramatically simplified to a simple "lfence; jmp *\reg". A future patch, after it has been verified that lfence really is serialising in all circumstances, can enable this by setting the X86_FEATURE_RETPOLINE_AMD feature bit in addition to X86_FEATURE_RETPOLINE. Do not align the retpoline in the altinstr section, because there is no guarantee that it stays aligned when it's copied over the oldinstr during alternative patching. [ Andi Kleen: Rename the macros, add CONFIG_RETPOLINE option, export thunks] [ tglx: Put actual function CALL/JMP in front of the macros, convert to symbolic labels ] [ dwmw2: Convert back to numeric labels, merge objtool fixes ] Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner Acked-by: Arjan van de Ven Acked-by: Ingo Molnar Cc: gnomes@lxorguk.ukuu.org.uk Cc: Rik van Riel Cc: Andi Kleen Cc: Josh Poimboeuf Cc: thomas.lendacky@amd.com Cc: Peter Zijlstra Cc: Linus Torvalds Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Dave Hansen Cc: Kees Cook Cc: Tim Chen Cc: Greg Kroah-Hartman Cc: Paul Turner Link: https://lkml.kernel.org/r/1515707194-20531-4-git-send-email-dwmw@amazon.co.uk --- arch/x86/Kconfig | 13 +++ arch/x86/Makefile | 10 ++ arch/x86/include/asm/asm-prototypes.h | 25 +++++ arch/x86/include/asm/cpufeatures.h | 2 + arch/x86/include/asm/nospec-branch.h | 128 ++++++++++++++++++++++++++ arch/x86/kernel/cpu/common.c | 4 + arch/x86/lib/Makefile | 1 + arch/x86/lib/retpoline.S | 48 ++++++++++ 8 files changed, 231 insertions(+) create mode 100644 arch/x86/include/asm/nospec-branch.h create mode 100644 arch/x86/lib/retpoline.S diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index e23d21ac745a..d1819161cc6c 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -429,6 +429,19 @@ config GOLDFISH def_bool y depends on X86_GOLDFISH +config RETPOLINE + bool "Avoid speculative indirect branches in kernel" + default y + help + Compile kernel with the retpoline compiler options to guard against + kernel-to-user data leaks by avoiding speculative indirect + branches. Requires a compiler with -mindirect-branch=thunk-extern + support for full protection. The kernel may run slower. + + Without compiler support, at least indirect branches in assembler + code are eliminated. Since this includes the syscall entry path, + it is not entirely pointless. + config INTEL_RDT bool "Intel Resource Director Technology support" default n diff --git a/arch/x86/Makefile b/arch/x86/Makefile index a20eacd9c7e9..974c61864978 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -235,6 +235,16 @@ KBUILD_CFLAGS += -Wno-sign-compare # KBUILD_CFLAGS += -fno-asynchronous-unwind-tables +# Avoid indirect branches in kernel to deal with Spectre +ifdef CONFIG_RETPOLINE + RETPOLINE_CFLAGS += $(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register) + ifneq ($(RETPOLINE_CFLAGS),) + KBUILD_CFLAGS += $(RETPOLINE_CFLAGS) -DRETPOLINE + else + $(warning CONFIG_RETPOLINE=y, but not supported by the compiler. Toolchain update recommended.) + endif +endif + archscripts: scripts_basic $(Q)$(MAKE) $(build)=arch/x86/tools relocs diff --git a/arch/x86/include/asm/asm-prototypes.h b/arch/x86/include/asm/asm-prototypes.h index ff700d81e91e..0927cdc4f946 100644 --- a/arch/x86/include/asm/asm-prototypes.h +++ b/arch/x86/include/asm/asm-prototypes.h @@ -11,7 +11,32 @@ #include #include #include +#include #ifndef CONFIG_X86_CMPXCHG64 extern void cmpxchg8b_emu(void); #endif + +#ifdef CONFIG_RETPOLINE +#ifdef CONFIG_X86_32 +#define INDIRECT_THUNK(reg) extern asmlinkage void __x86_indirect_thunk_e ## reg(void); +#else +#define INDIRECT_THUNK(reg) extern asmlinkage void __x86_indirect_thunk_r ## reg(void); +INDIRECT_THUNK(8) +INDIRECT_THUNK(9) +INDIRECT_THUNK(10) +INDIRECT_THUNK(11) +INDIRECT_THUNK(12) +INDIRECT_THUNK(13) +INDIRECT_THUNK(14) +INDIRECT_THUNK(15) +#endif +INDIRECT_THUNK(ax) +INDIRECT_THUNK(bx) +INDIRECT_THUNK(cx) +INDIRECT_THUNK(dx) +INDIRECT_THUNK(si) +INDIRECT_THUNK(di) +INDIRECT_THUNK(bp) +INDIRECT_THUNK(sp) +#endif /* CONFIG_RETPOLINE */ diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 1641c2f96363..f275447862f4 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -203,6 +203,8 @@ #define X86_FEATURE_PROC_FEEDBACK ( 7*32+ 9) /* AMD ProcFeedbackInterface */ #define X86_FEATURE_SME ( 7*32+10) /* AMD Secure Memory Encryption */ #define X86_FEATURE_PTI ( 7*32+11) /* Kernel Page Table Isolation enabled */ +#define X86_FEATURE_RETPOLINE ( 7*32+12) /* Generic Retpoline mitigation for Spectre variant 2 */ +#define X86_FEATURE_RETPOLINE_AMD ( 7*32+13) /* AMD Retpoline mitigation for Spectre variant 2 */ #define X86_FEATURE_INTEL_PPIN ( 7*32+14) /* Intel Processor Inventory Number */ #define X86_FEATURE_INTEL_PT ( 7*32+15) /* Intel Processor Trace */ #define X86_FEATURE_AVX512_4VNNIW ( 7*32+16) /* AVX-512 Neural Network Instructions */ diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h new file mode 100644 index 000000000000..e20e92ef2ca8 --- /dev/null +++ b/arch/x86/include/asm/nospec-branch.h @@ -0,0 +1,128 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef __NOSPEC_BRANCH_H__ +#define __NOSPEC_BRANCH_H__ + +#include +#include +#include + +#ifdef __ASSEMBLY__ + +/* + * This should be used immediately before a retpoline alternative. It tells + * objtool where the retpolines are so that it can make sense of the control + * flow by just reading the original instruction(s) and ignoring the + * alternatives. + */ +.macro ANNOTATE_NOSPEC_ALTERNATIVE + .Lannotate_\@: + .pushsection .discard.nospec + .long .Lannotate_\@ - . + .popsection +.endm + +/* + * These are the bare retpoline primitives for indirect jmp and call. + * Do not use these directly; they only exist to make the ALTERNATIVE + * invocation below less ugly. + */ +.macro RETPOLINE_JMP reg:req + call .Ldo_rop_\@ +.Lspec_trap_\@: + pause + jmp .Lspec_trap_\@ +.Ldo_rop_\@: + mov \reg, (%_ASM_SP) + ret +.endm + +/* + * This is a wrapper around RETPOLINE_JMP so the called function in reg + * returns to the instruction after the macro. + */ +.macro RETPOLINE_CALL reg:req + jmp .Ldo_call_\@ +.Ldo_retpoline_jmp_\@: + RETPOLINE_JMP \reg +.Ldo_call_\@: + call .Ldo_retpoline_jmp_\@ +.endm + +/* + * JMP_NOSPEC and CALL_NOSPEC macros can be used instead of a simple + * indirect jmp/call which may be susceptible to the Spectre variant 2 + * attack. + */ +.macro JMP_NOSPEC reg:req +#ifdef CONFIG_RETPOLINE + ANNOTATE_NOSPEC_ALTERNATIVE + ALTERNATIVE_2 __stringify(jmp *\reg), \ + __stringify(RETPOLINE_JMP \reg), X86_FEATURE_RETPOLINE, \ + __stringify(lfence; jmp *\reg), X86_FEATURE_RETPOLINE_AMD +#else + jmp *\reg +#endif +.endm + +.macro CALL_NOSPEC reg:req +#ifdef CONFIG_RETPOLINE + ANNOTATE_NOSPEC_ALTERNATIVE + ALTERNATIVE_2 __stringify(call *\reg), \ + __stringify(RETPOLINE_CALL \reg), X86_FEATURE_RETPOLINE,\ + __stringify(lfence; call *\reg), X86_FEATURE_RETPOLINE_AMD +#else + call *\reg +#endif +.endm + +#else /* __ASSEMBLY__ */ + +#define ANNOTATE_NOSPEC_ALTERNATIVE \ + "999:\n\t" \ + ".pushsection .discard.nospec\n\t" \ + ".long 999b - .\n\t" \ + ".popsection\n\t" + +#if defined(CONFIG_X86_64) && defined(RETPOLINE) + +/* + * Since the inline asm uses the %V modifier which is only in newer GCC, + * the 64-bit one is dependent on RETPOLINE not CONFIG_RETPOLINE. + */ +# define CALL_NOSPEC \ + ANNOTATE_NOSPEC_ALTERNATIVE \ + ALTERNATIVE( \ + "call *%[thunk_target]\n", \ + "call __x86_indirect_thunk_%V[thunk_target]\n", \ + X86_FEATURE_RETPOLINE) +# define THUNK_TARGET(addr) [thunk_target] "r" (addr) + +#elif defined(CONFIG_X86_32) && defined(CONFIG_RETPOLINE) +/* + * For i386 we use the original ret-equivalent retpoline, because + * otherwise we'll run out of registers. We don't care about CET + * here, anyway. + */ +# define CALL_NOSPEC ALTERNATIVE("call *%[thunk_target]\n", \ + " jmp 904f;\n" \ + " .align 16\n" \ + "901: call 903f;\n" \ + "902: pause;\n" \ + " jmp 902b;\n" \ + " .align 16\n" \ + "903: addl $4, %%esp;\n" \ + " pushl %[thunk_target];\n" \ + " ret;\n" \ + " .align 16\n" \ + "904: call 901b;\n", \ + X86_FEATURE_RETPOLINE) + +# define THUNK_TARGET(addr) [thunk_target] "rm" (addr) +#else /* No retpoline */ +# define CALL_NOSPEC "call *%[thunk_target]\n" +# define THUNK_TARGET(addr) [thunk_target] "rm" (addr) +#endif + +#endif /* __ASSEMBLY__ */ +#endif /* __NOSPEC_BRANCH_H__ */ diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 372ba3fb400f..7a671d1ae3cb 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -905,6 +905,10 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) setup_force_cpu_bug(X86_BUG_SPECTRE_V1); setup_force_cpu_bug(X86_BUG_SPECTRE_V2); +#ifdef CONFIG_RETPOLINE + setup_force_cpu_cap(X86_FEATURE_RETPOLINE); +#endif + fpu__init_system(c); #ifdef CONFIG_X86_32 diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile index 457f681ef379..d435c89875c1 100644 --- a/arch/x86/lib/Makefile +++ b/arch/x86/lib/Makefile @@ -26,6 +26,7 @@ lib-y += memcpy_$(BITS).o lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o lib-$(CONFIG_INSTRUCTION_DECODER) += insn.o inat.o lib-$(CONFIG_RANDOMIZE_BASE) += kaslr.o +lib-$(CONFIG_RETPOLINE) += retpoline.o obj-y += msr.o msr-reg.o msr-reg-export.o hweight.o diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S new file mode 100644 index 000000000000..cb45c6cb465f --- /dev/null +++ b/arch/x86/lib/retpoline.S @@ -0,0 +1,48 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#include +#include +#include +#include +#include +#include +#include + +.macro THUNK reg + .section .text.__x86.indirect_thunk.\reg + +ENTRY(__x86_indirect_thunk_\reg) + CFI_STARTPROC + JMP_NOSPEC %\reg + CFI_ENDPROC +ENDPROC(__x86_indirect_thunk_\reg) +.endm + +/* + * Despite being an assembler file we can't just use .irp here + * because __KSYM_DEPS__ only uses the C preprocessor and would + * only see one instance of "__x86_indirect_thunk_\reg" rather + * than one per register with the correct names. So we do it + * the simple and nasty way... + */ +#define EXPORT_THUNK(reg) EXPORT_SYMBOL(__x86_indirect_thunk_ ## reg) +#define GENERATE_THUNK(reg) THUNK reg ; EXPORT_THUNK(reg) + +GENERATE_THUNK(_ASM_AX) +GENERATE_THUNK(_ASM_BX) +GENERATE_THUNK(_ASM_CX) +GENERATE_THUNK(_ASM_DX) +GENERATE_THUNK(_ASM_SI) +GENERATE_THUNK(_ASM_DI) +GENERATE_THUNK(_ASM_BP) +GENERATE_THUNK(_ASM_SP) +#ifdef CONFIG_64BIT +GENERATE_THUNK(r8) +GENERATE_THUNK(r9) +GENERATE_THUNK(r10) +GENERATE_THUNK(r11) +GENERATE_THUNK(r12) +GENERATE_THUNK(r13) +GENERATE_THUNK(r14) +GENERATE_THUNK(r15) +#endif From da285121560e769cc31797bba6422eea71d473e0 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Thu, 11 Jan 2018 21:46:26 +0000 Subject: [PATCH 16/28] x86/spectre: Add boot time option to select Spectre v2 mitigation Add a spectre_v2= option to select the mitigation used for the indirect branch speculation vulnerability. Currently, the only option available is retpoline, in its various forms. This will be expanded to cover the new IBRS/IBPB microcode features. The RETPOLINE_AMD feature relies on a serializing LFENCE for speculation control. For AMD hardware, only set RETPOLINE_AMD if LFENCE is a serializing instruction, which is indicated by the LFENCE_RDTSC feature. [ tglx: Folded back the LFENCE/AMD fixes and reworked it so IBRS integration becomes simple ] Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner Cc: gnomes@lxorguk.ukuu.org.uk Cc: Rik van Riel Cc: Andi Kleen Cc: Josh Poimboeuf Cc: thomas.lendacky@amd.com Cc: Peter Zijlstra Cc: Linus Torvalds Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Dave Hansen Cc: Kees Cook Cc: Tim Chen Cc: Greg Kroah-Hartman Cc: Paul Turner Link: https://lkml.kernel.org/r/1515707194-20531-5-git-send-email-dwmw@amazon.co.uk --- .../admin-guide/kernel-parameters.txt | 28 ++++ arch/x86/include/asm/nospec-branch.h | 10 ++ arch/x86/kernel/cpu/bugs.c | 158 +++++++++++++++++- arch/x86/kernel/cpu/common.c | 4 - 4 files changed, 195 insertions(+), 5 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 905991745d26..8122b5f98ea1 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2599,6 +2599,11 @@ nosmt [KNL,S390] Disable symmetric multithreading (SMT). Equivalent to smt=1. + nospectre_v2 [X86] Disable all mitigations for the Spectre variant 2 + (indirect branch prediction) vulnerability. System may + allow data leaks with this option, which is equivalent + to spectre_v2=off. + noxsave [BUGS=X86] Disables x86 extended register state save and restore using xsave. The kernel will fallback to enabling legacy floating-point and sse state. @@ -3908,6 +3913,29 @@ sonypi.*= [HW] Sony Programmable I/O Control Device driver See Documentation/laptops/sonypi.txt + spectre_v2= [X86] Control mitigation of Spectre variant 2 + (indirect branch speculation) vulnerability. + + on - unconditionally enable + off - unconditionally disable + auto - kernel detects whether your CPU model is + vulnerable + + Selecting 'on' will, and 'auto' may, choose a + mitigation method at run time according to the + CPU, the available microcode, the setting of the + CONFIG_RETPOLINE configuration option, and the + compiler with which the kernel was built. + + Specific mitigations can also be selected manually: + + retpoline - replace indirect branches + retpoline,generic - google's original retpoline + retpoline,amd - AMD-specific minimal thunk + + Not specifying this option is equivalent to + spectre_v2=auto. + spia_io_base= [HW,MTD] spia_fio_base= spia_pedr= diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index e20e92ef2ca8..ea034fa6e261 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -124,5 +124,15 @@ # define THUNK_TARGET(addr) [thunk_target] "rm" (addr) #endif +/* The Spectre V2 mitigation variants */ +enum spectre_v2_mitigation { + SPECTRE_V2_NONE, + SPECTRE_V2_RETPOLINE_MINIMAL, + SPECTRE_V2_RETPOLINE_MINIMAL_AMD, + SPECTRE_V2_RETPOLINE_GENERIC, + SPECTRE_V2_RETPOLINE_AMD, + SPECTRE_V2_IBRS, +}; + #endif /* __ASSEMBLY__ */ #endif /* __NOSPEC_BRANCH_H__ */ diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 76ad6cb44b40..e4dc26185aa7 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -11,6 +11,9 @@ #include #include #include + +#include +#include #include #include #include @@ -21,6 +24,8 @@ #include #include +static void __init spectre_v2_select_mitigation(void); + void __init check_bugs(void) { identify_boot_cpu(); @@ -30,6 +35,9 @@ void __init check_bugs(void) print_cpu_info(&boot_cpu_data); } + /* Select the proper spectre mitigation before patching alternatives */ + spectre_v2_select_mitigation(); + #ifdef CONFIG_X86_32 /* * Check whether we are able to run this kernel safely on SMP. @@ -62,6 +70,153 @@ void __init check_bugs(void) #endif } +/* The kernel command line selection */ +enum spectre_v2_mitigation_cmd { + SPECTRE_V2_CMD_NONE, + SPECTRE_V2_CMD_AUTO, + SPECTRE_V2_CMD_FORCE, + SPECTRE_V2_CMD_RETPOLINE, + SPECTRE_V2_CMD_RETPOLINE_GENERIC, + SPECTRE_V2_CMD_RETPOLINE_AMD, +}; + +static const char *spectre_v2_strings[] = { + [SPECTRE_V2_NONE] = "Vulnerable", + [SPECTRE_V2_RETPOLINE_MINIMAL] = "Vulnerable: Minimal generic ASM retpoline", + [SPECTRE_V2_RETPOLINE_MINIMAL_AMD] = "Vulnerable: Minimal AMD ASM retpoline", + [SPECTRE_V2_RETPOLINE_GENERIC] = "Mitigation: Full generic retpoline", + [SPECTRE_V2_RETPOLINE_AMD] = "Mitigation: Full AMD retpoline", +}; + +#undef pr_fmt +#define pr_fmt(fmt) "Spectre V2 mitigation: " fmt + +static enum spectre_v2_mitigation spectre_v2_enabled = SPECTRE_V2_NONE; + +static void __init spec2_print_if_insecure(const char *reason) +{ + if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) + pr_info("%s\n", reason); +} + +static void __init spec2_print_if_secure(const char *reason) +{ + if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) + pr_info("%s\n", reason); +} + +static inline bool retp_compiler(void) +{ + return __is_defined(RETPOLINE); +} + +static inline bool match_option(const char *arg, int arglen, const char *opt) +{ + int len = strlen(opt); + + return len == arglen && !strncmp(arg, opt, len); +} + +static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void) +{ + char arg[20]; + int ret; + + ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, + sizeof(arg)); + if (ret > 0) { + if (match_option(arg, ret, "off")) { + goto disable; + } else if (match_option(arg, ret, "on")) { + spec2_print_if_secure("force enabled on command line."); + return SPECTRE_V2_CMD_FORCE; + } else if (match_option(arg, ret, "retpoline")) { + spec2_print_if_insecure("retpoline selected on command line."); + return SPECTRE_V2_CMD_RETPOLINE; + } else if (match_option(arg, ret, "retpoline,amd")) { + if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD) { + pr_err("retpoline,amd selected but CPU is not AMD. Switching to AUTO select\n"); + return SPECTRE_V2_CMD_AUTO; + } + spec2_print_if_insecure("AMD retpoline selected on command line."); + return SPECTRE_V2_CMD_RETPOLINE_AMD; + } else if (match_option(arg, ret, "retpoline,generic")) { + spec2_print_if_insecure("generic retpoline selected on command line."); + return SPECTRE_V2_CMD_RETPOLINE_GENERIC; + } else if (match_option(arg, ret, "auto")) { + return SPECTRE_V2_CMD_AUTO; + } + } + + if (!cmdline_find_option_bool(boot_command_line, "nospectre_v2")) + return SPECTRE_V2_CMD_AUTO; +disable: + spec2_print_if_insecure("disabled on command line."); + return SPECTRE_V2_CMD_NONE; +} + +static void __init spectre_v2_select_mitigation(void) +{ + enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline(); + enum spectre_v2_mitigation mode = SPECTRE_V2_NONE; + + /* + * If the CPU is not affected and the command line mode is NONE or AUTO + * then nothing to do. + */ + if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) && + (cmd == SPECTRE_V2_CMD_NONE || cmd == SPECTRE_V2_CMD_AUTO)) + return; + + switch (cmd) { + case SPECTRE_V2_CMD_NONE: + return; + + case SPECTRE_V2_CMD_FORCE: + /* FALLTRHU */ + case SPECTRE_V2_CMD_AUTO: + goto retpoline_auto; + + case SPECTRE_V2_CMD_RETPOLINE_AMD: + if (IS_ENABLED(CONFIG_RETPOLINE)) + goto retpoline_amd; + break; + case SPECTRE_V2_CMD_RETPOLINE_GENERIC: + if (IS_ENABLED(CONFIG_RETPOLINE)) + goto retpoline_generic; + break; + case SPECTRE_V2_CMD_RETPOLINE: + if (IS_ENABLED(CONFIG_RETPOLINE)) + goto retpoline_auto; + break; + } + pr_err("kernel not compiled with retpoline; no mitigation available!"); + return; + +retpoline_auto: + if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) { + retpoline_amd: + if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) { + pr_err("LFENCE not serializing. Switching to generic retpoline\n"); + goto retpoline_generic; + } + mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_AMD : + SPECTRE_V2_RETPOLINE_MINIMAL_AMD; + setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD); + setup_force_cpu_cap(X86_FEATURE_RETPOLINE); + } else { + retpoline_generic: + mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_GENERIC : + SPECTRE_V2_RETPOLINE_MINIMAL; + setup_force_cpu_cap(X86_FEATURE_RETPOLINE); + } + + spectre_v2_enabled = mode; + pr_info("%s\n", spectre_v2_strings[mode]); +} + +#undef pr_fmt + #ifdef CONFIG_SYSFS ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf) @@ -86,6 +241,7 @@ ssize_t cpu_show_spectre_v2(struct device *dev, { if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) return sprintf(buf, "Not affected\n"); - return sprintf(buf, "Vulnerable\n"); + + return sprintf(buf, "%s\n", spectre_v2_strings[spectre_v2_enabled]); } #endif diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 7a671d1ae3cb..372ba3fb400f 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -905,10 +905,6 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) setup_force_cpu_bug(X86_BUG_SPECTRE_V1); setup_force_cpu_bug(X86_BUG_SPECTRE_V2); -#ifdef CONFIG_RETPOLINE - setup_force_cpu_cap(X86_FEATURE_RETPOLINE); -#endif - fpu__init_system(c); #ifdef CONFIG_X86_32 From 9697fa39efd3fc3692f2949d4045f393ec58450b Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Thu, 11 Jan 2018 21:46:27 +0000 Subject: [PATCH 17/28] x86/retpoline/crypto: Convert crypto assembler indirect jumps Convert all indirect jumps in crypto assembler code to use non-speculative sequences when CONFIG_RETPOLINE is enabled. Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner Acked-by: Arjan van de Ven Acked-by: Ingo Molnar Cc: gnomes@lxorguk.ukuu.org.uk Cc: Rik van Riel Cc: Andi Kleen Cc: Josh Poimboeuf Cc: thomas.lendacky@amd.com Cc: Peter Zijlstra Cc: Linus Torvalds Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Dave Hansen Cc: Kees Cook Cc: Tim Chen Cc: Greg Kroah-Hartman Cc: Paul Turner Link: https://lkml.kernel.org/r/1515707194-20531-6-git-send-email-dwmw@amazon.co.uk --- arch/x86/crypto/aesni-intel_asm.S | 5 +++-- arch/x86/crypto/camellia-aesni-avx-asm_64.S | 3 ++- arch/x86/crypto/camellia-aesni-avx2-asm_64.S | 3 ++- arch/x86/crypto/crc32c-pcl-intel-asm_64.S | 3 ++- 4 files changed, 9 insertions(+), 5 deletions(-) diff --git a/arch/x86/crypto/aesni-intel_asm.S b/arch/x86/crypto/aesni-intel_asm.S index 16627fec80b2..3d09e3aca18d 100644 --- a/arch/x86/crypto/aesni-intel_asm.S +++ b/arch/x86/crypto/aesni-intel_asm.S @@ -32,6 +32,7 @@ #include #include #include +#include /* * The following macros are used to move an (un)aligned 16 byte value to/from @@ -2884,7 +2885,7 @@ ENTRY(aesni_xts_crypt8) pxor INC, STATE4 movdqu IV, 0x30(OUTP) - call *%r11 + CALL_NOSPEC %r11 movdqu 0x00(OUTP), INC pxor INC, STATE1 @@ -2929,7 +2930,7 @@ ENTRY(aesni_xts_crypt8) _aesni_gf128mul_x_ble() movups IV, (IVP) - call *%r11 + CALL_NOSPEC %r11 movdqu 0x40(OUTP), INC pxor INC, STATE1 diff --git a/arch/x86/crypto/camellia-aesni-avx-asm_64.S b/arch/x86/crypto/camellia-aesni-avx-asm_64.S index f7c495e2863c..a14af6eb09cb 100644 --- a/arch/x86/crypto/camellia-aesni-avx-asm_64.S +++ b/arch/x86/crypto/camellia-aesni-avx-asm_64.S @@ -17,6 +17,7 @@ #include #include +#include #define CAMELLIA_TABLE_BYTE_LEN 272 @@ -1227,7 +1228,7 @@ camellia_xts_crypt_16way: vpxor 14 * 16(%rax), %xmm15, %xmm14; vpxor 15 * 16(%rax), %xmm15, %xmm15; - call *%r9; + CALL_NOSPEC %r9; addq $(16 * 16), %rsp; diff --git a/arch/x86/crypto/camellia-aesni-avx2-asm_64.S b/arch/x86/crypto/camellia-aesni-avx2-asm_64.S index eee5b3982cfd..b66bbfa62f50 100644 --- a/arch/x86/crypto/camellia-aesni-avx2-asm_64.S +++ b/arch/x86/crypto/camellia-aesni-avx2-asm_64.S @@ -12,6 +12,7 @@ #include #include +#include #define CAMELLIA_TABLE_BYTE_LEN 272 @@ -1343,7 +1344,7 @@ camellia_xts_crypt_32way: vpxor 14 * 32(%rax), %ymm15, %ymm14; vpxor 15 * 32(%rax), %ymm15, %ymm15; - call *%r9; + CALL_NOSPEC %r9; addq $(16 * 32), %rsp; diff --git a/arch/x86/crypto/crc32c-pcl-intel-asm_64.S b/arch/x86/crypto/crc32c-pcl-intel-asm_64.S index 7a7de27c6f41..d9b734d0c8cc 100644 --- a/arch/x86/crypto/crc32c-pcl-intel-asm_64.S +++ b/arch/x86/crypto/crc32c-pcl-intel-asm_64.S @@ -45,6 +45,7 @@ #include #include +#include ## ISCSI CRC 32 Implementation with crc32 and pclmulqdq Instruction @@ -172,7 +173,7 @@ continue_block: movzxw (bufp, %rax, 2), len lea crc_array(%rip), bufp lea (bufp, len, 1), bufp - jmp *bufp + JMP_NOSPEC bufp ################################################################ ## 2a) PROCESS FULL BLOCKS: From 2641f08bb7fc63a636a2b18173221d7040a3512e Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Thu, 11 Jan 2018 21:46:28 +0000 Subject: [PATCH 18/28] x86/retpoline/entry: Convert entry assembler indirect jumps Convert indirect jumps in core 32/64bit entry assembler code to use non-speculative sequences when CONFIG_RETPOLINE is enabled. Don't use CALL_NOSPEC in entry_SYSCALL_64_fastpath because the return address after the 'call' instruction must be *precisely* at the .Lentry_SYSCALL_64_after_fastpath label for stub_ptregs_64 to work, and the use of alternatives will mess that up unless we play horrid games to prepend with NOPs and make the variants the same length. It's not worth it; in the case where we ALTERNATIVE out the retpoline, the first instruction at __x86.indirect_thunk.rax is going to be a bare jmp *%rax anyway. Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner Acked-by: Ingo Molnar Acked-by: Arjan van de Ven Cc: gnomes@lxorguk.ukuu.org.uk Cc: Rik van Riel Cc: Andi Kleen Cc: Josh Poimboeuf Cc: thomas.lendacky@amd.com Cc: Peter Zijlstra Cc: Linus Torvalds Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Dave Hansen Cc: Kees Cook Cc: Tim Chen Cc: Greg Kroah-Hartman Cc: Paul Turner Link: https://lkml.kernel.org/r/1515707194-20531-7-git-send-email-dwmw@amazon.co.uk --- arch/x86/entry/entry_32.S | 5 +++-- arch/x86/entry/entry_64.S | 12 +++++++++--- 2 files changed, 12 insertions(+), 5 deletions(-) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index ace8f321a5a1..a1f28a54f23a 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -44,6 +44,7 @@ #include #include #include +#include .section .entry.text, "ax" @@ -290,7 +291,7 @@ ENTRY(ret_from_fork) /* kernel thread */ 1: movl %edi, %eax - call *%ebx + CALL_NOSPEC %ebx /* * A kernel thread is allowed to return here after successfully * calling do_execve(). Exit to userspace to complete the execve() @@ -919,7 +920,7 @@ common_exception: movl %ecx, %es TRACE_IRQS_OFF movl %esp, %eax # pt_regs pointer - call *%edi + CALL_NOSPEC %edi jmp ret_from_exception END(common_exception) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index ed31d00dc5ee..59874bc1aed2 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -37,6 +37,7 @@ #include #include #include +#include #include #include "calling.h" @@ -187,7 +188,7 @@ ENTRY(entry_SYSCALL_64_trampoline) */ pushq %rdi movq $entry_SYSCALL_64_stage2, %rdi - jmp *%rdi + JMP_NOSPEC %rdi END(entry_SYSCALL_64_trampoline) .popsection @@ -266,7 +267,12 @@ entry_SYSCALL_64_fastpath: * It might end up jumping to the slow path. If it jumps, RAX * and all argument registers are clobbered. */ +#ifdef CONFIG_RETPOLINE + movq sys_call_table(, %rax, 8), %rax + call __x86_indirect_thunk_rax +#else call *sys_call_table(, %rax, 8) +#endif .Lentry_SYSCALL_64_after_fastpath_call: movq %rax, RAX(%rsp) @@ -438,7 +444,7 @@ ENTRY(stub_ptregs_64) jmp entry_SYSCALL64_slow_path 1: - jmp *%rax /* Called from C */ + JMP_NOSPEC %rax /* Called from C */ END(stub_ptregs_64) .macro ptregs_stub func @@ -517,7 +523,7 @@ ENTRY(ret_from_fork) 1: /* kernel thread */ movq %r12, %rdi - call *%rbx + CALL_NOSPEC %rbx /* * A kernel thread is allowed to return here after successfully * calling do_execve(). Exit to userspace to complete the execve() From 9351803bd803cdbeb9b5a7850b7b6f464806e3db Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Thu, 11 Jan 2018 21:46:29 +0000 Subject: [PATCH 19/28] x86/retpoline/ftrace: Convert ftrace assembler indirect jumps Convert all indirect jumps in ftrace assembler code to use non-speculative sequences when CONFIG_RETPOLINE is enabled. Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner Acked-by: Arjan van de Ven Acked-by: Ingo Molnar Cc: gnomes@lxorguk.ukuu.org.uk Cc: Rik van Riel Cc: Andi Kleen Cc: Josh Poimboeuf Cc: thomas.lendacky@amd.com Cc: Peter Zijlstra Cc: Linus Torvalds Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Dave Hansen Cc: Kees Cook Cc: Tim Chen Cc: Greg Kroah-Hartman Cc: Paul Turner Link: https://lkml.kernel.org/r/1515707194-20531-8-git-send-email-dwmw@amazon.co.uk --- arch/x86/kernel/ftrace_32.S | 6 ++++-- arch/x86/kernel/ftrace_64.S | 8 ++++---- 2 files changed, 8 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S index b6c6468e10bc..4c8440de3355 100644 --- a/arch/x86/kernel/ftrace_32.S +++ b/arch/x86/kernel/ftrace_32.S @@ -8,6 +8,7 @@ #include #include #include +#include #ifdef CC_USING_FENTRY # define function_hook __fentry__ @@ -197,7 +198,8 @@ ftrace_stub: movl 0x4(%ebp), %edx subl $MCOUNT_INSN_SIZE, %eax - call *ftrace_trace_function + movl ftrace_trace_function, %ecx + CALL_NOSPEC %ecx popl %edx popl %ecx @@ -241,5 +243,5 @@ return_to_handler: movl %eax, %ecx popl %edx popl %eax - jmp *%ecx + JMP_NOSPEC %ecx #endif diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S index c832291d948a..7cb8ba08beb9 100644 --- a/arch/x86/kernel/ftrace_64.S +++ b/arch/x86/kernel/ftrace_64.S @@ -7,7 +7,7 @@ #include #include #include - +#include .code64 .section .entry.text, "ax" @@ -286,8 +286,8 @@ trace: * ip and parent ip are used and the list function is called when * function tracing is enabled. */ - call *ftrace_trace_function - + movq ftrace_trace_function, %r8 + CALL_NOSPEC %r8 restore_mcount_regs jmp fgraph_trace @@ -329,5 +329,5 @@ GLOBAL(return_to_handler) movq 8(%rsp), %rdx movq (%rsp), %rax addq $24, %rsp - jmp *%rdi + JMP_NOSPEC %rdi #endif From e70e5892b28c18f517f29ab6e83bd57705104b31 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Thu, 11 Jan 2018 21:46:30 +0000 Subject: [PATCH 20/28] x86/retpoline/hyperv: Convert assembler indirect jumps Convert all indirect jumps in hyperv inline asm code to use non-speculative sequences when CONFIG_RETPOLINE is enabled. Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner Acked-by: Arjan van de Ven Acked-by: Ingo Molnar Cc: gnomes@lxorguk.ukuu.org.uk Cc: Rik van Riel Cc: Andi Kleen Cc: Josh Poimboeuf Cc: thomas.lendacky@amd.com Cc: Peter Zijlstra Cc: Linus Torvalds Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Dave Hansen Cc: Kees Cook Cc: Tim Chen Cc: Greg Kroah-Hartman Cc: Paul Turner Link: https://lkml.kernel.org/r/1515707194-20531-9-git-send-email-dwmw@amazon.co.uk --- arch/x86/include/asm/mshyperv.h | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h index 581bb54dd464..5119e4b555cc 100644 --- a/arch/x86/include/asm/mshyperv.h +++ b/arch/x86/include/asm/mshyperv.h @@ -7,6 +7,7 @@ #include #include #include +#include /* * The below CPUID leaves are present if VersionAndFeatures.HypervisorPresent @@ -186,10 +187,11 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void *output) return U64_MAX; __asm__ __volatile__("mov %4, %%r8\n" - "call *%5" + CALL_NOSPEC : "=a" (hv_status), ASM_CALL_CONSTRAINT, "+c" (control), "+d" (input_address) - : "r" (output_address), "m" (hv_hypercall_pg) + : "r" (output_address), + THUNK_TARGET(hv_hypercall_pg) : "cc", "memory", "r8", "r9", "r10", "r11"); #else u32 input_address_hi = upper_32_bits(input_address); @@ -200,13 +202,13 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void *output) if (!hv_hypercall_pg) return U64_MAX; - __asm__ __volatile__("call *%7" + __asm__ __volatile__(CALL_NOSPEC : "=A" (hv_status), "+c" (input_address_lo), ASM_CALL_CONSTRAINT : "A" (control), "b" (input_address_hi), "D"(output_address_hi), "S"(output_address_lo), - "m" (hv_hypercall_pg) + THUNK_TARGET(hv_hypercall_pg) : "cc", "memory"); #endif /* !x86_64 */ return hv_status; @@ -227,10 +229,10 @@ static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1) #ifdef CONFIG_X86_64 { - __asm__ __volatile__("call *%4" + __asm__ __volatile__(CALL_NOSPEC : "=a" (hv_status), ASM_CALL_CONSTRAINT, "+c" (control), "+d" (input1) - : "m" (hv_hypercall_pg) + : THUNK_TARGET(hv_hypercall_pg) : "cc", "r8", "r9", "r10", "r11"); } #else @@ -238,13 +240,13 @@ static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1) u32 input1_hi = upper_32_bits(input1); u32 input1_lo = lower_32_bits(input1); - __asm__ __volatile__ ("call *%5" + __asm__ __volatile__ (CALL_NOSPEC : "=A"(hv_status), "+c"(input1_lo), ASM_CALL_CONSTRAINT : "A" (control), "b" (input1_hi), - "m" (hv_hypercall_pg) + THUNK_TARGET(hv_hypercall_pg) : "cc", "edi", "esi"); } #endif From ea08816d5b185ab3d09e95e393f265af54560350 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Thu, 11 Jan 2018 21:46:31 +0000 Subject: [PATCH 21/28] x86/retpoline/xen: Convert Xen hypercall indirect jumps Convert indirect call in Xen hypercall to use non-speculative sequence, when CONFIG_RETPOLINE is enabled. Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner Acked-by: Arjan van de Ven Acked-by: Ingo Molnar Reviewed-by: Juergen Gross Cc: gnomes@lxorguk.ukuu.org.uk Cc: Rik van Riel Cc: Andi Kleen Cc: Josh Poimboeuf Cc: thomas.lendacky@amd.com Cc: Peter Zijlstra Cc: Linus Torvalds Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Dave Hansen Cc: Kees Cook Cc: Tim Chen Cc: Greg Kroah-Hartman Cc: Paul Turner Link: https://lkml.kernel.org/r/1515707194-20531-10-git-send-email-dwmw@amazon.co.uk --- arch/x86/include/asm/xen/hypercall.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h index 7cb282e9e587..bfd882617613 100644 --- a/arch/x86/include/asm/xen/hypercall.h +++ b/arch/x86/include/asm/xen/hypercall.h @@ -44,6 +44,7 @@ #include #include #include +#include #include #include @@ -217,9 +218,9 @@ privcmd_call(unsigned call, __HYPERCALL_5ARG(a1, a2, a3, a4, a5); stac(); - asm volatile("call *%[call]" + asm volatile(CALL_NOSPEC : __HYPERCALL_5PARAM - : [call] "a" (&hypercall_page[call]) + : [thunk_target] "a" (&hypercall_page[call]) : __HYPERCALL_CLOBBER5); clac(); From 5096732f6f695001fa2d6f1335a2680b37912c69 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Thu, 11 Jan 2018 21:46:32 +0000 Subject: [PATCH 22/28] x86/retpoline/checksum32: Convert assembler indirect jumps Convert all indirect jumps in 32bit checksum assembler code to use non-speculative sequences when CONFIG_RETPOLINE is enabled. Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner Acked-by: Arjan van de Ven Acked-by: Ingo Molnar Cc: gnomes@lxorguk.ukuu.org.uk Cc: Rik van Riel Cc: Andi Kleen Cc: Josh Poimboeuf Cc: thomas.lendacky@amd.com Cc: Peter Zijlstra Cc: Linus Torvalds Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Dave Hansen Cc: Kees Cook Cc: Tim Chen Cc: Greg Kroah-Hartman Cc: Paul Turner Link: https://lkml.kernel.org/r/1515707194-20531-11-git-send-email-dwmw@amazon.co.uk --- arch/x86/lib/checksum_32.S | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/x86/lib/checksum_32.S b/arch/x86/lib/checksum_32.S index 4d34bb548b41..46e71a74e612 100644 --- a/arch/x86/lib/checksum_32.S +++ b/arch/x86/lib/checksum_32.S @@ -29,7 +29,8 @@ #include #include #include - +#include + /* * computes a partial checksum, e.g. for TCP/UDP fragments */ @@ -156,7 +157,7 @@ ENTRY(csum_partial) negl %ebx lea 45f(%ebx,%ebx,2), %ebx testl %esi, %esi - jmp *%ebx + JMP_NOSPEC %ebx # Handle 2-byte-aligned regions 20: addw (%esi), %ax @@ -439,7 +440,7 @@ ENTRY(csum_partial_copy_generic) andl $-32,%edx lea 3f(%ebx,%ebx), %ebx testl %esi, %esi - jmp *%ebx + JMP_NOSPEC %ebx 1: addl $64,%esi addl $64,%edi SRC(movb -32(%edx),%bl) ; SRC(movb (%edx),%bl) From 7614e913db1f40fff819b36216484dc3808995d4 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Thu, 11 Jan 2018 21:46:33 +0000 Subject: [PATCH 23/28] x86/retpoline/irq32: Convert assembler indirect jumps Convert all indirect jumps in 32bit irq inline asm code to use non speculative sequences. Signed-off-by: Andi Kleen Signed-off-by: Thomas Gleixner Acked-by: Arjan van de Ven Acked-by: Ingo Molnar Cc: gnomes@lxorguk.ukuu.org.uk Cc: Rik van Riel Cc: Josh Poimboeuf Cc: thomas.lendacky@amd.com Cc: Peter Zijlstra Cc: Linus Torvalds Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Dave Hansen Cc: Kees Cook Cc: Tim Chen Cc: Greg Kroah-Hartman Cc: Paul Turner Link: https://lkml.kernel.org/r/1515707194-20531-12-git-send-email-dwmw@amazon.co.uk --- arch/x86/kernel/irq_32.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c index a83b3346a0e1..c1bdbd3d3232 100644 --- a/arch/x86/kernel/irq_32.c +++ b/arch/x86/kernel/irq_32.c @@ -20,6 +20,7 @@ #include #include +#include #ifdef CONFIG_DEBUG_STACKOVERFLOW @@ -55,11 +56,11 @@ DEFINE_PER_CPU(struct irq_stack *, softirq_stack); static void call_on_stack(void *func, void *stack) { asm volatile("xchgl %%ebx,%%esp \n" - "call *%%edi \n" + CALL_NOSPEC "movl %%ebx,%%esp \n" : "=b" (stack) : "0" (stack), - "D"(func) + [thunk_target] "D"(func) : "memory", "cc", "edx", "ecx", "eax"); } @@ -95,11 +96,11 @@ static inline int execute_on_irq_stack(int overflow, struct irq_desc *desc) call_on_stack(print_stack_overflow, isp); asm volatile("xchgl %%ebx,%%esp \n" - "call *%%edi \n" + CALL_NOSPEC "movl %%ebx,%%esp \n" : "=a" (arg1), "=b" (isp) : "0" (desc), "1" (isp), - "D" (desc->handle_irq) + [thunk_target] "D" (desc->handle_irq) : "memory", "cc", "ecx"); return 1; } From 117cc7a908c83697b0b737d15ae1eb5943afe35b Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Fri, 12 Jan 2018 11:11:27 +0000 Subject: [PATCH 24/28] x86/retpoline: Fill return stack buffer on vmexit In accordance with the Intel and AMD documentation, we need to overwrite all entries in the RSB on exiting a guest, to prevent malicious branch target predictions from affecting the host kernel. This is needed both for retpoline and for IBRS. [ak: numbers again for the RSB stuffing labels] Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner Tested-by: Peter Zijlstra (Intel) Cc: gnomes@lxorguk.ukuu.org.uk Cc: Rik van Riel Cc: Andi Kleen Cc: Josh Poimboeuf Cc: thomas.lendacky@amd.com Cc: Linus Torvalds Cc: Jiri Kosina Cc: Andy Lutomirski Cc: Dave Hansen Cc: Kees Cook Cc: Tim Chen Cc: Greg Kroah-Hartman Cc: Paul Turner Link: https://lkml.kernel.org/r/1515755487-8524-1-git-send-email-dwmw@amazon.co.uk --- arch/x86/include/asm/nospec-branch.h | 78 +++++++++++++++++++++++++++- arch/x86/kvm/svm.c | 4 ++ arch/x86/kvm/vmx.c | 4 ++ 3 files changed, 85 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index ea034fa6e261..402a11c803c3 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -7,6 +7,48 @@ #include #include +/* + * Fill the CPU return stack buffer. + * + * Each entry in the RSB, if used for a speculative 'ret', contains an + * infinite 'pause; jmp' loop to capture speculative execution. + * + * This is required in various cases for retpoline and IBRS-based + * mitigations for the Spectre variant 2 vulnerability. Sometimes to + * eliminate potentially bogus entries from the RSB, and sometimes + * purely to ensure that it doesn't get empty, which on some CPUs would + * allow predictions from other (unwanted!) sources to be used. + * + * We define a CPP macro such that it can be used from both .S files and + * inline assembly. It's possible to do a .macro and then include that + * from C via asm(".include ") but let's not go there. + */ + +#define RSB_CLEAR_LOOPS 32 /* To forcibly overwrite all entries */ +#define RSB_FILL_LOOPS 16 /* To avoid underflow */ + +/* + * Google experimented with loop-unrolling and this turned out to be + * the optimal version — two calls, each with their own speculation + * trap should their return address end up getting used, in a loop. + */ +#define __FILL_RETURN_BUFFER(reg, nr, sp) \ + mov $(nr/2), reg; \ +771: \ + call 772f; \ +773: /* speculation trap */ \ + pause; \ + jmp 773b; \ +772: \ + call 774f; \ +775: /* speculation trap */ \ + pause; \ + jmp 775b; \ +774: \ + dec reg; \ + jnz 771b; \ + add $(BITS_PER_LONG/8) * nr, sp; + #ifdef __ASSEMBLY__ /* @@ -74,6 +116,20 @@ #else call *\reg #endif +.endm + + /* + * A simpler FILL_RETURN_BUFFER macro. Don't make people use the CPP + * monstrosity above, manually. + */ +.macro FILL_RETURN_BUFFER reg:req nr:req ftr:req +#ifdef CONFIG_RETPOLINE + ANNOTATE_NOSPEC_ALTERNATIVE + ALTERNATIVE "jmp .Lskip_rsb_\@", \ + __stringify(__FILL_RETURN_BUFFER(\reg,\nr,%_ASM_SP)) \ + \ftr +.Lskip_rsb_\@: +#endif .endm #else /* __ASSEMBLY__ */ @@ -119,7 +175,7 @@ X86_FEATURE_RETPOLINE) # define THUNK_TARGET(addr) [thunk_target] "rm" (addr) -#else /* No retpoline */ +#else /* No retpoline for C / inline asm */ # define CALL_NOSPEC "call *%[thunk_target]\n" # define THUNK_TARGET(addr) [thunk_target] "rm" (addr) #endif @@ -134,5 +190,25 @@ enum spectre_v2_mitigation { SPECTRE_V2_IBRS, }; +/* + * On VMEXIT we must ensure that no RSB predictions learned in the guest + * can be followed in the host, by overwriting the RSB completely. Both + * retpoline and IBRS mitigations for Spectre v2 need this; only on future + * CPUs with IBRS_ATT *might* it be avoided. + */ +static inline void vmexit_fill_RSB(void) +{ +#ifdef CONFIG_RETPOLINE + unsigned long loops = RSB_CLEAR_LOOPS / 2; + + asm volatile (ANNOTATE_NOSPEC_ALTERNATIVE + ALTERNATIVE("jmp 910f", + __stringify(__FILL_RETURN_BUFFER(%0, RSB_CLEAR_LOOPS, %1)), + X86_FEATURE_RETPOLINE) + "910:" + : "=&r" (loops), ASM_CALL_CONSTRAINT + : "r" (loops) : "memory" ); +#endif +} #endif /* __ASSEMBLY__ */ #endif /* __NOSPEC_BRANCH_H__ */ diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 0e68f0b3cbf7..2744b97345b8 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -45,6 +45,7 @@ #include #include #include +#include #include #include "trace.h" @@ -4985,6 +4986,9 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu) #endif ); + /* Eliminate branch target predictions from guest mode */ + vmexit_fill_RSB(); + #ifdef CONFIG_X86_64 wrmsrl(MSR_GS_BASE, svm->host.gs_base); #else diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 62ee4362e1c1..d1e25dba3112 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -50,6 +50,7 @@ #include #include #include +#include #include "trace.h" #include "pmu.h" @@ -9403,6 +9404,9 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) #endif ); + /* Eliminate branch target predictions from guest mode */ + vmexit_fill_RSB(); + /* MSR_IA32_DEBUGCTLMSR is zeroed on vmexit. Restore it if needed */ if (debugctlmsr) update_debugctlmsr(debugctlmsr); From 352909b49ba0d74929b96af6dfbefc854ab6ebb5 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Thu, 11 Jan 2018 17:16:51 -0800 Subject: [PATCH 25/28] selftests/x86: Add test_vsyscall This tests that the vsyscall entries do what they're expected to do. It also confirms that attempts to read the vsyscall page behave as expected. If changes are made to the vsyscall code or its memory map handling, running this test in all three of vsyscall=none, vsyscall=emulate, and vsyscall=native are helpful. (Because it's easy, this also compares the vsyscall results to their vDSO equivalents.) Note to KAISER backporters: please test this under all three vsyscall modes. Also, in the emulate and native modes, make sure that test_vsyscall_64 agrees with the command line or config option as to which mode you're in. It's quite easy to mess up the kernel such that native mode accidentally emulates or vice versa. Greg, etc: please backport this to all your Meltdown-patched kernels. It'll help make sure the patches didn't regress vsyscalls. CSigned-off-by: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: Greg Kroah-Hartman Cc: H. Peter Anvin Cc: Hugh Dickins Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Kees Cook Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/2b9c5a174c1d60fd7774461d518aa75598b1d8fd.1515719552.git.luto@kernel.org Signed-off-by: Ingo Molnar --- tools/testing/selftests/x86/Makefile | 2 +- tools/testing/selftests/x86/test_vsyscall.c | 500 ++++++++++++++++++++ 2 files changed, 501 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/x86/test_vsyscall.c diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile index 7b1adeee4b0f..91fbfa8fdc15 100644 --- a/tools/testing/selftests/x86/Makefile +++ b/tools/testing/selftests/x86/Makefile @@ -7,7 +7,7 @@ include ../lib.mk TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall test_mremap_vdso \ check_initial_reg_state sigreturn ldt_gdt iopl mpx-mini-test ioperm \ - protection_keys test_vdso + protection_keys test_vdso test_vsyscall TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \ test_FCMOV test_FCOMI test_FISTTP \ vdso_restorer diff --git a/tools/testing/selftests/x86/test_vsyscall.c b/tools/testing/selftests/x86/test_vsyscall.c new file mode 100644 index 000000000000..7a744fa7b786 --- /dev/null +++ b/tools/testing/selftests/x86/test_vsyscall.c @@ -0,0 +1,500 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#define _GNU_SOURCE + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#ifdef __x86_64__ +# define VSYS(x) (x) +#else +# define VSYS(x) 0 +#endif + +#ifndef SYS_getcpu +# ifdef __x86_64__ +# define SYS_getcpu 309 +# else +# define SYS_getcpu 318 +# endif +#endif + +static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), + int flags) +{ + struct sigaction sa; + memset(&sa, 0, sizeof(sa)); + sa.sa_sigaction = handler; + sa.sa_flags = SA_SIGINFO | flags; + sigemptyset(&sa.sa_mask); + if (sigaction(sig, &sa, 0)) + err(1, "sigaction"); +} + +/* vsyscalls and vDSO */ +bool should_read_vsyscall = false; + +typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz); +gtod_t vgtod = (gtod_t)VSYS(0xffffffffff600000); +gtod_t vdso_gtod; + +typedef int (*vgettime_t)(clockid_t, struct timespec *); +vgettime_t vdso_gettime; + +typedef long (*time_func_t)(time_t *t); +time_func_t vtime = (time_func_t)VSYS(0xffffffffff600400); +time_func_t vdso_time; + +typedef long (*getcpu_t)(unsigned *, unsigned *, void *); +getcpu_t vgetcpu = (getcpu_t)VSYS(0xffffffffff600800); +getcpu_t vdso_getcpu; + +static void init_vdso(void) +{ + void *vdso = dlopen("linux-vdso.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD); + if (!vdso) + vdso = dlopen("linux-gate.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD); + if (!vdso) { + printf("[WARN]\tfailed to find vDSO\n"); + return; + } + + vdso_gtod = (gtod_t)dlsym(vdso, "__vdso_gettimeofday"); + if (!vdso_gtod) + printf("[WARN]\tfailed to find gettimeofday in vDSO\n"); + + vdso_gettime = (vgettime_t)dlsym(vdso, "__vdso_clock_gettime"); + if (!vdso_gettime) + printf("[WARN]\tfailed to find clock_gettime in vDSO\n"); + + vdso_time = (time_func_t)dlsym(vdso, "__vdso_time"); + if (!vdso_time) + printf("[WARN]\tfailed to find time in vDSO\n"); + + vdso_getcpu = (getcpu_t)dlsym(vdso, "__vdso_getcpu"); + if (!vdso_getcpu) { + /* getcpu() was never wired up in the 32-bit vDSO. */ + printf("[%s]\tfailed to find getcpu in vDSO\n", + sizeof(long) == 8 ? "WARN" : "NOTE"); + } +} + +static int init_vsys(void) +{ +#ifdef __x86_64__ + int nerrs = 0; + FILE *maps; + char line[128]; + bool found = false; + + maps = fopen("/proc/self/maps", "r"); + if (!maps) { + printf("[WARN]\tCould not open /proc/self/maps -- assuming vsyscall is r-x\n"); + should_read_vsyscall = true; + return 0; + } + + while (fgets(line, sizeof(line), maps)) { + char r, x; + void *start, *end; + char name[128]; + if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s", + &start, &end, &r, &x, name) != 5) + continue; + + if (strcmp(name, "[vsyscall]")) + continue; + + printf("\tvsyscall map: %s", line); + + if (start != (void *)0xffffffffff600000 || + end != (void *)0xffffffffff601000) { + printf("[FAIL]\taddress range is nonsense\n"); + nerrs++; + } + + printf("\tvsyscall permissions are %c-%c\n", r, x); + should_read_vsyscall = (r == 'r'); + if (x != 'x') { + vgtod = NULL; + vtime = NULL; + vgetcpu = NULL; + } + + found = true; + break; + } + + fclose(maps); + + if (!found) { + printf("\tno vsyscall map in /proc/self/maps\n"); + should_read_vsyscall = false; + vgtod = NULL; + vtime = NULL; + vgetcpu = NULL; + } + + return nerrs; +#else + return 0; +#endif +} + +/* syscalls */ +static inline long sys_gtod(struct timeval *tv, struct timezone *tz) +{ + return syscall(SYS_gettimeofday, tv, tz); +} + +static inline int sys_clock_gettime(clockid_t id, struct timespec *ts) +{ + return syscall(SYS_clock_gettime, id, ts); +} + +static inline long sys_time(time_t *t) +{ + return syscall(SYS_time, t); +} + +static inline long sys_getcpu(unsigned * cpu, unsigned * node, + void* cache) +{ + return syscall(SYS_getcpu, cpu, node, cache); +} + +static jmp_buf jmpbuf; + +static void sigsegv(int sig, siginfo_t *info, void *ctx_void) +{ + siglongjmp(jmpbuf, 1); +} + +static double tv_diff(const struct timeval *a, const struct timeval *b) +{ + return (double)(a->tv_sec - b->tv_sec) + + (double)((int)a->tv_usec - (int)b->tv_usec) * 1e-6; +} + +static int check_gtod(const struct timeval *tv_sys1, + const struct timeval *tv_sys2, + const struct timezone *tz_sys, + const char *which, + const struct timeval *tv_other, + const struct timezone *tz_other) +{ + int nerrs = 0; + double d1, d2; + + if (tz_other && (tz_sys->tz_minuteswest != tz_other->tz_minuteswest || tz_sys->tz_dsttime != tz_other->tz_dsttime)) { + printf("[FAIL] %s tz mismatch\n", which); + nerrs++; + } + + d1 = tv_diff(tv_other, tv_sys1); + d2 = tv_diff(tv_sys2, tv_other); + printf("\t%s time offsets: %lf %lf\n", which, d1, d2); + + if (d1 < 0 || d2 < 0) { + printf("[FAIL]\t%s time was inconsistent with the syscall\n", which); + nerrs++; + } else { + printf("[OK]\t%s gettimeofday()'s timeval was okay\n", which); + } + + return nerrs; +} + +static int test_gtod(void) +{ + struct timeval tv_sys1, tv_sys2, tv_vdso, tv_vsys; + struct timezone tz_sys, tz_vdso, tz_vsys; + long ret_vdso = -1; + long ret_vsys = -1; + int nerrs = 0; + + printf("[RUN]\ttest gettimeofday()\n"); + + if (sys_gtod(&tv_sys1, &tz_sys) != 0) + err(1, "syscall gettimeofday"); + if (vdso_gtod) + ret_vdso = vdso_gtod(&tv_vdso, &tz_vdso); + if (vgtod) + ret_vsys = vgtod(&tv_vsys, &tz_vsys); + if (sys_gtod(&tv_sys2, &tz_sys) != 0) + err(1, "syscall gettimeofday"); + + if (vdso_gtod) { + if (ret_vdso == 0) { + nerrs += check_gtod(&tv_sys1, &tv_sys2, &tz_sys, "vDSO", &tv_vdso, &tz_vdso); + } else { + printf("[FAIL]\tvDSO gettimeofday() failed: %ld\n", ret_vdso); + nerrs++; + } + } + + if (vgtod) { + if (ret_vsys == 0) { + nerrs += check_gtod(&tv_sys1, &tv_sys2, &tz_sys, "vsyscall", &tv_vsys, &tz_vsys); + } else { + printf("[FAIL]\tvsys gettimeofday() failed: %ld\n", ret_vsys); + nerrs++; + } + } + + return nerrs; +} + +static int test_time(void) { + int nerrs = 0; + + printf("[RUN]\ttest time()\n"); + long t_sys1, t_sys2, t_vdso = 0, t_vsys = 0; + long t2_sys1 = -1, t2_sys2 = -1, t2_vdso = -1, t2_vsys = -1; + t_sys1 = sys_time(&t2_sys1); + if (vdso_time) + t_vdso = vdso_time(&t2_vdso); + if (vtime) + t_vsys = vtime(&t2_vsys); + t_sys2 = sys_time(&t2_sys2); + if (t_sys1 < 0 || t_sys1 != t2_sys1 || t_sys2 < 0 || t_sys2 != t2_sys2) { + printf("[FAIL]\tsyscall failed (ret1:%ld output1:%ld ret2:%ld output2:%ld)\n", t_sys1, t2_sys1, t_sys2, t2_sys2); + nerrs++; + return nerrs; + } + + if (vdso_time) { + if (t_vdso < 0 || t_vdso != t2_vdso) { + printf("[FAIL]\tvDSO failed (ret:%ld output:%ld)\n", t_vdso, t2_vdso); + nerrs++; + } else if (t_vdso < t_sys1 || t_vdso > t_sys2) { + printf("[FAIL]\tvDSO returned the wrong time (%ld %ld %ld)\n", t_sys1, t_vdso, t_sys2); + nerrs++; + } else { + printf("[OK]\tvDSO time() is okay\n"); + } + } + + if (vtime) { + if (t_vsys < 0 || t_vsys != t2_vsys) { + printf("[FAIL]\tvsyscall failed (ret:%ld output:%ld)\n", t_vsys, t2_vsys); + nerrs++; + } else if (t_vsys < t_sys1 || t_vsys > t_sys2) { + printf("[FAIL]\tvsyscall returned the wrong time (%ld %ld %ld)\n", t_sys1, t_vsys, t_sys2); + nerrs++; + } else { + printf("[OK]\tvsyscall time() is okay\n"); + } + } + + return nerrs; +} + +static int test_getcpu(int cpu) +{ + int nerrs = 0; + long ret_sys, ret_vdso = -1, ret_vsys = -1; + + printf("[RUN]\tgetcpu() on CPU %d\n", cpu); + + cpu_set_t cpuset; + CPU_ZERO(&cpuset); + CPU_SET(cpu, &cpuset); + if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0) { + printf("[SKIP]\tfailed to force CPU %d\n", cpu); + return nerrs; + } + + unsigned cpu_sys, cpu_vdso, cpu_vsys, node_sys, node_vdso, node_vsys; + unsigned node = 0; + bool have_node = false; + ret_sys = sys_getcpu(&cpu_sys, &node_sys, 0); + if (vdso_getcpu) + ret_vdso = vdso_getcpu(&cpu_vdso, &node_vdso, 0); + if (vgetcpu) + ret_vsys = vgetcpu(&cpu_vsys, &node_vsys, 0); + + if (ret_sys == 0) { + if (cpu_sys != cpu) { + printf("[FAIL]\tsyscall reported CPU %hu but should be %d\n", cpu_sys, cpu); + nerrs++; + } + + have_node = true; + node = node_sys; + } + + if (vdso_getcpu) { + if (ret_vdso) { + printf("[FAIL]\tvDSO getcpu() failed\n"); + nerrs++; + } else { + if (!have_node) { + have_node = true; + node = node_vdso; + } + + if (cpu_vdso != cpu) { + printf("[FAIL]\tvDSO reported CPU %hu but should be %d\n", cpu_vdso, cpu); + nerrs++; + } else { + printf("[OK]\tvDSO reported correct CPU\n"); + } + + if (node_vdso != node) { + printf("[FAIL]\tvDSO reported node %hu but should be %hu\n", node_vdso, node); + nerrs++; + } else { + printf("[OK]\tvDSO reported correct node\n"); + } + } + } + + if (vgetcpu) { + if (ret_vsys) { + printf("[FAIL]\tvsyscall getcpu() failed\n"); + nerrs++; + } else { + if (!have_node) { + have_node = true; + node = node_vsys; + } + + if (cpu_vsys != cpu) { + printf("[FAIL]\tvsyscall reported CPU %hu but should be %d\n", cpu_vsys, cpu); + nerrs++; + } else { + printf("[OK]\tvsyscall reported correct CPU\n"); + } + + if (node_vsys != node) { + printf("[FAIL]\tvsyscall reported node %hu but should be %hu\n", node_vsys, node); + nerrs++; + } else { + printf("[OK]\tvsyscall reported correct node\n"); + } + } + } + + return nerrs; +} + +static int test_vsys_r(void) +{ +#ifdef __x86_64__ + printf("[RUN]\tChecking read access to the vsyscall page\n"); + bool can_read; + if (sigsetjmp(jmpbuf, 1) == 0) { + *(volatile int *)0xffffffffff600000; + can_read = true; + } else { + can_read = false; + } + + if (can_read && !should_read_vsyscall) { + printf("[FAIL]\tWe have read access, but we shouldn't\n"); + return 1; + } else if (!can_read && should_read_vsyscall) { + printf("[FAIL]\tWe don't have read access, but we should\n"); + return 1; + } else { + printf("[OK]\tgot expected result\n"); + } +#endif + + return 0; +} + + +#ifdef __x86_64__ +#define X86_EFLAGS_TF (1UL << 8) +static volatile sig_atomic_t num_vsyscall_traps; + +static unsigned long get_eflags(void) +{ + unsigned long eflags; + asm volatile ("pushfq\n\tpopq %0" : "=rm" (eflags)); + return eflags; +} + +static void set_eflags(unsigned long eflags) +{ + asm volatile ("pushq %0\n\tpopfq" : : "rm" (eflags) : "flags"); +} + +static void sigtrap(int sig, siginfo_t *info, void *ctx_void) +{ + ucontext_t *ctx = (ucontext_t *)ctx_void; + unsigned long ip = ctx->uc_mcontext.gregs[REG_RIP]; + + if (((ip ^ 0xffffffffff600000UL) & ~0xfffUL) == 0) + num_vsyscall_traps++; +} + +static int test_native_vsyscall(void) +{ + time_t tmp; + bool is_native; + + if (!vtime) + return 0; + + printf("[RUN]\tchecking for native vsyscall\n"); + sethandler(SIGTRAP, sigtrap, 0); + set_eflags(get_eflags() | X86_EFLAGS_TF); + vtime(&tmp); + set_eflags(get_eflags() & ~X86_EFLAGS_TF); + + /* + * If vsyscalls are emulated, we expect a single trap in the + * vsyscall page -- the call instruction will trap with RIP + * pointing to the entry point before emulation takes over. + * In native mode, we expect two traps, since whatever code + * the vsyscall page contains will be more than just a ret + * instruction. + */ + is_native = (num_vsyscall_traps > 1); + + printf("\tvsyscalls are %s (%d instructions in vsyscall page)\n", + (is_native ? "native" : "emulated"), + (int)num_vsyscall_traps); + + return 0; +} +#endif + +int main(int argc, char **argv) +{ + int nerrs = 0; + + init_vdso(); + nerrs += init_vsys(); + + nerrs += test_gtod(); + nerrs += test_time(); + nerrs += test_getcpu(0); + nerrs += test_getcpu(1); + + sethandler(SIGSEGV, sigsegv, 0); + nerrs += test_vsys_r(); + +#ifdef __x86_64__ + nerrs += test_native_vsyscall(); +#endif + + return nerrs ? 1 : 0; +} From f10ee3dcc9f0aba92a5c4c064628be5200765dc2 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 14 Jan 2018 00:23:57 +0100 Subject: [PATCH 26/28] x86/pti: Fix !PCID and sanitize defines The switch to the user space page tables in the low level ASM code sets unconditionally bit 12 and bit 11 of CR3. Bit 12 is switching the base address of the page directory to the user part, bit 11 is switching the PCID to the PCID associated with the user page tables. This fails on a machine which lacks PCID support because bit 11 is set in CR3. Bit 11 is reserved when PCID is inactive. While the Intel SDM claims that the reserved bits are ignored when PCID is disabled, the AMD APM states that they should be cleared. This went unnoticed as the AMD APM was not checked when the code was developed and reviewed and test systems with Intel CPUs never failed to boot. The report is against a Centos 6 host where the guest fails to boot, so it's not yet clear whether this is a virt issue or can happen on real hardware too, but thats irrelevant as the AMD APM clearly ask for clearing the reserved bits. Make sure that on non PCID machines bit 11 is not set by the page table switching code. Andy suggested to rename the related bits and masks so they are clearly describing what they should be used for, which is done as well for clarity. That split could have been done with alternatives but the macro hell is horrible and ugly. This can be done on top if someone cares to remove the extra orq. For now it's a straight forward fix. Fixes: 6fd166aae78c ("x86/mm: Use/Fix PCID to optimize user/kernel switches") Reported-by: Laura Abbott Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: stable Cc: Borislav Petkov Cc: Andy Lutomirski Cc: Willy Tarreau Cc: David Woodhouse Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1801140009150.2371@nanos --- arch/x86/entry/calling.h | 36 ++++++++++++++------------ arch/x86/include/asm/processor-flags.h | 2 +- arch/x86/include/asm/tlbflush.h | 6 ++--- 3 files changed, 23 insertions(+), 21 deletions(-) diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index 45a63e00a6af..3f48f695d5e6 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -198,8 +198,11 @@ For 32-bit we have the following conventions - kernel is built with * PAGE_TABLE_ISOLATION PGDs are 8k. Flip bit 12 to switch between the two * halves: */ -#define PTI_SWITCH_PGTABLES_MASK (1<= (1 << X86_CR3_PTI_SWITCH_BIT)); + BUILD_BUG_ON(TLB_NR_DYN_ASIDS >= (1 << X86_CR3_PTI_PCID_USER_BIT)); /* * The ASID being passed in here should have respected the * MAX_ASID_AVAILABLE and thus never have the switch bit set. */ - VM_WARN_ON_ONCE(asid & (1 << X86_CR3_PTI_SWITCH_BIT)); + VM_WARN_ON_ONCE(asid & (1 << X86_CR3_PTI_PCID_USER_BIT)); #endif /* * The dynamically-assigned ASIDs that get passed in are small @@ -112,7 +112,7 @@ static inline u16 user_pcid(u16 asid) { u16 ret = kern_pcid(asid); #ifdef CONFIG_PAGE_TABLE_ISOLATION - ret |= 1 << X86_CR3_PTI_SWITCH_BIT; + ret |= 1 << X86_CR3_PTI_PCID_USER_BIT; #endif return ret; } From a237f762681e2a394ca67f21df2feb2b76a3609b Mon Sep 17 00:00:00 2001 From: "W. Trevor King" Date: Fri, 12 Jan 2018 15:24:59 -0800 Subject: [PATCH 27/28] security/Kconfig: Correct the Documentation reference for PTI When the config option for PTI was added a reference to documentation was added as well. But the documentation did not exist at that point. The final documentation has a different file name. Fix it up to point to the proper file. Fixes: 385ce0ea ("x86/mm/pti: Add Kconfig") Signed-off-by: W. Trevor King Signed-off-by: Thomas Gleixner Cc: Dave Hansen Cc: linux-mm@kvack.org Cc: linux-security-module@vger.kernel.org Cc: James Morris Cc: "Serge E. Hallyn" Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/3009cc8ccbddcd897ec1e0cb6dda524929de0d14.1515799398.git.wking@tremily.us --- security/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/security/Kconfig b/security/Kconfig index 3d4debd0257e..b0cb9a5f9448 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -63,7 +63,7 @@ config PAGE_TABLE_ISOLATION ensuring that the majority of kernel addresses are not mapped into userspace. - See Documentation/x86/pagetable-isolation.txt for more details. + See Documentation/x86/pti.txt for more details. config SECURITY_INFINIBAND bool "Infiniband Security Hooks" From 99a9dc98ba52267ce5e062b52de88ea1f1b2a7d8 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Sun, 14 Jan 2018 11:27:13 +0100 Subject: [PATCH 28/28] x86,perf: Disable intel_bts when PTI MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The intel_bts driver does not use the 'normal' BTS buffer which is exposed through the cpu_entry_area but instead uses the memory allocated for the perf AUX buffer. This obviously comes apart when using PTI because then the kernel mapping; which includes that AUX buffer memory; disappears. Fixing this requires to expose a mapping which is visible in all context and that's not trivial. As a quick fix disable this driver when PTI is enabled to prevent malfunction. Fixes: 385ce0ea4c07 ("x86/mm/pti: Add Kconfig") Reported-by: Vince Weaver Reported-by: Robert Święcki Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Cc: Alexander Shishkin Cc: greg@kroah.com Cc: hughd@google.com Cc: luto@amacapital.net Cc: Vince Weaver Cc: torvalds@linux-foundation.org Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180114102713.GB6166@worktop.programming.kicks-ass.net --- arch/x86/events/intel/bts.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c index 141e07b06216..24ffa1e88cf9 100644 --- a/arch/x86/events/intel/bts.c +++ b/arch/x86/events/intel/bts.c @@ -582,6 +582,24 @@ static __init int bts_init(void) if (!boot_cpu_has(X86_FEATURE_DTES64) || !x86_pmu.bts) return -ENODEV; + if (boot_cpu_has(X86_FEATURE_PTI)) { + /* + * BTS hardware writes through a virtual memory map we must + * either use the kernel physical map, or the user mapping of + * the AUX buffer. + * + * However, since this driver supports per-CPU and per-task inherit + * we cannot use the user mapping since it will not be availble + * if we're not running the owning process. + * + * With PTI we can't use the kernal map either, because its not + * there when we run userspace. + * + * For now, disable this driver when using PTI. + */ + return -ENODEV; + } + bts_pmu.capabilities = PERF_PMU_CAP_AUX_NO_SG | PERF_PMU_CAP_ITRACE | PERF_PMU_CAP_EXCLUSIVE; bts_pmu.task_ctx_nr = perf_sw_context;