From ce56a86e2ade45d052b3228cdfebe913a1ae7381 Mon Sep 17 00:00:00 2001
From: Craig Bergstrom <craigb@google.com>
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 <craigb@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
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 <mingo@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 c40a95c33bb843..322d25ae23ab04 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 a9967982684649..320c6237e1d1d4 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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