Commit-ID: ce56a86e2ade45d052b3228cdfebe913a1ae7381 Gitweb: https://git.kernel.org/tip/ce56a86e2ade45d052b3228cdfebe913a1ae7381 Author: Craig Bergstrom <cra...@google.com> AuthorDate: Thu, 19 Oct 2017 13:28:56 -0600 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Fri, 20 Oct 2017 09:48:00 +0200
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 <cra...@google.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Andy Lutomirski <l...@kernel.org> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Josh Poimboeuf <jpoim...@redhat.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Luis R. Rodriguez <mcg...@suse.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Toshi Kani <toshi.k...@hp.com> Cc: dsafo...@virtuozzo.com Cc: kirill.shute...@linux.intel.com Cc: mho...@suse.com Cc: o...@redhat.com Link: http://lkml.kernel.org/r/20171019192856.39672-1-cra...@google.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- 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 c40a95c..322d25a 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 a996798..320c623 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); +}
