From: Isaac J. Manjarres Date: Tue, 13 Aug 2019 22:37:37 +0000 (-0700) Subject: mm/usercopy: use memory range to be accessed for wraparound check X-Git-Tag: v4.9.190~61 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=faf6760c93af392f2ef115367d5711dab068f50f;p=platform%2Fkernel%2Flinux-amlogic.git mm/usercopy: use memory range to be accessed for wraparound check commit 951531691c4bcaa59f56a316e018bc2ff1ddf855 upstream. Currently, when checking to see if accessing n bytes starting at address "ptr" will cause a wraparound in the memory addresses, the check in check_bogus_address() adds an extra byte, which is incorrect, as the range of addresses that will be accessed is [ptr, ptr + (n - 1)]. This can lead to incorrectly detecting a wraparound in the memory address, when trying to read 4 KB from memory that is mapped to the the last possible page in the virtual address space, when in fact, accessing that range of memory would not cause a wraparound to occur. Use the memory range that will actually be accessed when considering if accessing a certain amount of bytes will cause the memory address to wrap around. Link: http://lkml.kernel.org/r/1564509253-23287-1-git-send-email-isaacm@codeaurora.org Fixes: f5509cc18daa ("mm: Hardened usercopy") Signed-off-by: Prasad Sodagudi Signed-off-by: Isaac J. Manjarres Co-developed-by: Prasad Sodagudi Reviewed-by: William Kucharski Acked-by: Kees Cook Cc: Greg Kroah-Hartman Cc: Trilok Soni Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [kees: backport to v4.9] Signed-off-by: Kees Cook Signed-off-by: Greg Kroah-Hartman --- diff --git a/mm/usercopy.c b/mm/usercopy.c index 3c8da0af9695..7683c22551ff 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -124,7 +124,7 @@ static inline const char *check_kernel_text_object(const void *ptr, static inline const char *check_bogus_address(const void *ptr, unsigned long n) { /* Reject if object wraps past end of memory. */ - if ((unsigned long)ptr + n < (unsigned long)ptr) + if ((unsigned long)ptr + (n - 1) < (unsigned long)ptr) return ""; /* Reject if NULL or ZERO-allocation. */