From 0b3e336601b82c6afa0e9cf21db9cb8793e25399 Mon Sep 17 00:00:00 2001 From: Laura Abbott Date: Fri, 20 Jul 2018 14:41:54 -0700 Subject: [PATCH] arm64: Add support for STACKLEAK gcc plugin This adds support for the STACKLEAK gcc plugin to arm64 by implementing stackleak_check_alloca(), based heavily on the x86 version, and adding the two helpers used by the stackleak common code: current_top_of_stack() and on_thread_stack(). The stack erasure calls are made at syscall returns. Additionally, this disables the plugin in hypervisor and EFI stub code, which are out of scope for the protection. Acked-by: Alexander Popov Reviewed-by: Mark Rutland Reviewed-by: Kees Cook Signed-off-by: Laura Abbott Signed-off-by: Will Deacon --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/processor.h | 15 +++++++++++++++ arch/arm64/kernel/entry.S | 3 +++ arch/arm64/kernel/process.c | 22 ++++++++++++++++++++++ arch/arm64/kvm/hyp/Makefile | 3 ++- drivers/firmware/efi/libstub/Makefile | 3 ++- 6 files changed, 45 insertions(+), 2 deletions(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 27fd50e86dfe..1494d5cfd681 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -108,6 +108,7 @@ config ARM64 select HAVE_ARCH_MMAP_RND_BITS select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT select HAVE_ARCH_SECCOMP_FILTER + select HAVE_ARCH_STACKLEAK select HAVE_ARCH_THREAD_STRUCT_WHITELIST select HAVE_ARCH_TRACEHOOK select HAVE_ARCH_TRANSPARENT_HUGEPAGE diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index e02612105d78..79657ad91397 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -266,5 +266,20 @@ extern void __init minsigstksz_setup(void); #define SVE_SET_VL(arg) sve_set_current_vl(arg) #define SVE_GET_VL() sve_get_current_vl() +/* + * For CONFIG_GCC_PLUGIN_STACKLEAK + * + * These need to be macros because otherwise we get stuck in a nightmare + * of header definitions for the use of task_stack_page. + */ + +#define current_top_of_stack() \ +({ \ + struct stack_info _info; \ + BUG_ON(!on_accessible_stack(current, current_stack_pointer, &_info)); \ + _info.high; \ +}) +#define on_thread_stack() (on_task_stack(current, current_stack_pointer, NULL)) + #endif /* __ASSEMBLY__ */ #endif /* __ASM_PROCESSOR_H */ diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index d1440f84668b..09dbea221a27 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -902,6 +902,9 @@ ret_to_user: cbnz x2, work_pending finish_ret_to_user: enable_step_tsk x1, x2 +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK + bl stackleak_erase +#endif kernel_exit 0 ENDPROC(ret_to_user) diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 740b31f77ade..7f1628effe6d 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -493,3 +493,25 @@ void arch_setup_new_exec(void) { current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0; } + +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK +void __used stackleak_check_alloca(unsigned long size) +{ + unsigned long stack_left; + unsigned long current_sp = current_stack_pointer; + struct stack_info info; + + BUG_ON(!on_accessible_stack(current, current_sp, &info)); + + stack_left = current_sp - info.low; + + /* + * There's a good chance we're almost out of stack space if this + * is true. Using panic() over BUG() is more likely to give + * reliable debugging output. + */ + if (size >= stack_left) + panic("alloca() over the kernel stack boundary\n"); +} +EXPORT_SYMBOL(stackleak_check_alloca); +#endif diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile index 4313f7475333..2fabc2dc1966 100644 --- a/arch/arm64/kvm/hyp/Makefile +++ b/arch/arm64/kvm/hyp/Makefile @@ -3,7 +3,8 @@ # Makefile for Kernel-based Virtual Machine module, HYP part # -ccflags-y += -fno-stack-protector -DDISABLE_BRANCH_PROFILING +ccflags-y += -fno-stack-protector -DDISABLE_BRANCH_PROFILING \ + $(DISABLE_STACKLEAK_PLUGIN) KVM=../../../../virt/kvm diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index a34e9290a699..25dd2a14560d 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -20,7 +20,8 @@ cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \ -D__NO_FORTIFY \ $(call cc-option,-ffreestanding) \ - $(call cc-option,-fno-stack-protector) + $(call cc-option,-fno-stack-protector) \ + $(DISABLE_STACKLEAK_PLUGIN) GCOV_PROFILE := n KASAN_SANITIZE := n