From: Paul Burton paul.burton@mips.com
commit 074a1e1167afd82c26f6d03a9a8b997d564bb241 upstream.
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 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/mips/mm/mmap.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/arch/mips/mm/mmap.c +++ b/arch/mips/mm/mmap.c @@ -203,6 +203,11 @@ unsigned long arch_randomize_brk(struct
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);