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authorPaul Burton <paul.burton@mips.com>2019-05-28 20:05:03 +0300
committerPaul Burton <paul.burton@mips.com>2019-05-29 22:04:18 +0300
commit074a1e1167afd82c26f6d03a9a8b997d564bb241 (patch)
treeff9ea1d7d4d7d0990c4587be41a7cf1df8b93963 /arch/mips
parentc5eac1f5326b0b67e50ad5d560d7e68e6c95ef14 (diff)
downloadlinux-074a1e1167afd82c26f6d03a9a8b997d564bb241.tar.xz
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.c5
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);