From: "Isaac J. Manjarres" <isa...@codeaurora.org> 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-isa...@codeaurora.org Fixes: f5509cc18daa ("mm: Hardened usercopy") Signed-off-by: Prasad Sodagudi <psoda...@codeaurora.org> Signed-off-by: Isaac J. Manjarres <isa...@codeaurora.org> Co-developed-by: Prasad Sodagudi <psoda...@codeaurora.org> Reviewed-by: William Kucharski <william.kuchar...@oracle.com> Acked-by: Kees Cook <keesc...@chromium.org> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org> Cc: Trilok Soni <ts...@codeaurora.org> Cc: <sta...@vger.kernel.org> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- mm/usercopy.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/usercopy.c b/mm/usercopy.c index 2a09796edef8d..98e924864554c 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -147,7 +147,7 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n, bool to_user) { /* Reject if object wraps past end of memory. */ - if (ptr + n < ptr) + if (ptr + (n - 1) < ptr) usercopy_abort("wrapped address", NULL, to_user, 0, ptr + n); /* Reject if NULL or ZERO-allocation. */ -- 2.20.1
