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author | Paul Burton <paul.burton@mips.com> | 2019-05-28 19:05:03 +0200 |
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committer | Paul Burton <paul.burton@mips.com> | 2019-05-29 21:04:18 +0200 |
commit | 074a1e1167afd82c26f6d03a9a8b997d564bb241 (patch) | |
tree | ff9ea1d7d4d7d0990c4587be41a7cf1df8b93963 /arch/mips | |
parent | MIPS: TXx9: Fix boot crash in free_initmem() (diff) | |
download | linux-074a1e1167afd82c26f6d03a9a8b997d564bb241.tar.xz linux-074a1e1167afd82c26f6d03a9a8b997d564bb241.zip |
MIPS: Bounds check virt_addr_valid
The virt_addr_valid() function is meant to return true iff
virt_to_page() will return a valid struct page reference. This is true
iff the address provided is found within the unmapped address range
between PAGE_OFFSET & MAP_BASE, but we don't currently check for that
condition. Instead we simply mask the address to obtain what will be a
physical address if the virtual address is indeed in the desired range,
shift it to form a PFN & then call pfn_valid(). This can incorrectly
return true if called with a virtual address which, after masking,
happens to form a physical address corresponding to a valid PFN.
For example we may vmalloc an address in the kernel mapped region
starting a MAP_BASE & obtain the virtual address:
addr = 0xc000000000002000
When masked by virt_to_phys(), which uses __pa() & in turn CPHYSADDR(),
we obtain the following (bogus) physical address:
addr = 0x2000
In a common system with PHYS_OFFSET=0 this will correspond to a valid
struct page which should really be accessed by virtual address
PAGE_OFFSET+0x2000, causing virt_addr_valid() to incorrectly return 1
indicating that the original address corresponds to a struct page.
This is equivalent to the ARM64 change made in commit ca219452c6b8
("arm64: Correctly bounds check virt_addr_valid").
This fixes fallout when hardened usercopy is enabled caused by the
related commit 517e1fbeb65f ("mm/usercopy: Drop extra
is_vmalloc_or_module() check") which removed a check for the vmalloc
range that was present from the introduction of the hardened usercopy
feature.
Signed-off-by: Paul Burton <paul.burton@mips.com>
References: ca219452c6b8 ("arm64: Correctly bounds check virt_addr_valid")
References: 517e1fbeb65f ("mm/usercopy: Drop extra is_vmalloc_or_module() check")
Reported-by: Julien Cristau <jcristau@debian.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: YunQiang Su <ysu@wavecomp.com>
URL: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=929366
Cc: stable@vger.kernel.org # v4.12+
Cc: linux-mips@vger.kernel.org
Cc: Yunqiang Su <ysu@wavecomp.com>
Diffstat (limited to 'arch/mips')
-rw-r--r-- | arch/mips/mm/mmap.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c index 2f616ebeb7e0..7755a1fad05a 100644 --- a/arch/mips/mm/mmap.c +++ b/arch/mips/mm/mmap.c @@ -203,6 +203,11 @@ unsigned long arch_randomize_brk(struct mm_struct *mm) int __virt_addr_valid(const volatile void *kaddr) { + unsigned long vaddr = (unsigned long)vaddr; + + if ((vaddr < PAGE_OFFSET) || (vaddr >= MAP_BASE)) + return 0; + return pfn_valid(PFN_DOWN(virt_to_phys(kaddr))); } EXPORT_SYMBOL_GPL(__virt_addr_valid); |