From ce56a86e2ade45d052b3228cdfebe913a1ae7381 Mon Sep 17 00:00:00 2001 From: Craig Bergstrom Date: Thu, 19 Oct 2017 13:28:56 -0600 Subject: [PATCH] x86/mm: Limit mmap() of /dev/mem to valid physical addresses Currently, it is possible to mmap() any offset from /dev/mem. If a program mmaps() /dev/mem offsets outside of the addressable limits of a system, the page table can be corrupted by setting reserved bits. For example if you mmap() offset 0x0001000000000000 of /dev/mem on an x86_64 system with a 48-bit bus, the page fault handler will be called with error_code set to RSVD. The kernel then crashes with a page table corruption error. This change prevents this page table corruption on x86 by refusing to mmap offsets higher than the highest valid address in the system. Signed-off-by: Craig Bergstrom Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Toshi Kani Cc: dsafonov@virtuozzo.com Cc: kirill.shutemov@linux.intel.com Cc: mhocko@suse.com Cc: oleg@redhat.com Link: http://lkml.kernel.org/r/20171019192856.39672-1-craigb@google.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/io.h | 4 ++++ arch/x86/mm/mmap.c | 12 ++++++++++++ 2 files changed, 16 insertions(+) diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h index c40a95c33bb8..322d25ae23ab 100644 --- a/arch/x86/include/asm/io.h +++ b/arch/x86/include/asm/io.h @@ -110,6 +110,10 @@ build_mmio_write(__writeq, "q", unsigned long, "r", ) #endif +#define ARCH_HAS_VALID_PHYS_ADDR_RANGE +extern int valid_phys_addr_range(phys_addr_t addr, size_t size); +extern int valid_mmap_phys_addr_range(unsigned long pfn, size_t size); + /** * virt_to_phys - map virtual addresses to physical * @address: address to remap diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index a99679826846..320c6237e1d1 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -174,3 +174,15 @@ const char *arch_vma_name(struct vm_area_struct *vma) return "[mpx]"; return NULL; } + +int valid_phys_addr_range(phys_addr_t addr, size_t count) +{ + return addr + count <= __pa(high_memory); +} + +int valid_mmap_phys_addr_range(unsigned long pfn, size_t count) +{ + phys_addr_t addr = (phys_addr_t)pfn << PAGE_SHIFT; + + return valid_phys_addr_range(addr, count); +}