Commit-ID: ce56a86e2ade45d052b3228cdfebe913a1ae7381
Gitweb: https://git.kernel.org/tip/ce56a86e2ade45d052b3228cdfebe913a1ae7381
Author: Craig Bergstrom <craigb@xxxxxxxxxx>
AuthorDate: Thu, 19 Oct 2017 13:28:56 -0600
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
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 <craigb@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Luis R. Rodriguez <mcgrof@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Toshi Kani <toshi.kani@xxxxxx>
Cc: dsafonov@xxxxxxxxxxxxx
Cc: kirill.shutemov@xxxxxxxxxxxxxxx
Cc: mhocko@xxxxxxxx
Cc: oleg@xxxxxxxxxx
Link: http://lkml.kernel.org/r/20171019192856.39672-1-craigb@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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);
+}
--
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