Commit 056368fc authored by Isaac J. Manjarres's avatar Isaac J. Manjarres Committed by Greg Kroah-Hartman

mm/usercopy: use memory range to be accessed for wraparound check

commit 95153169 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: f5509cc1 ("mm: Hardened usercopy")
Signed-off-by: default avatarPrasad Sodagudi <psodagud@codeaurora.org>
Signed-off-by: default avatarIsaac J. Manjarres <isaacm@codeaurora.org>
Co-developed-by: default avatarPrasad Sodagudi <psodagud@codeaurora.org>
Reviewed-by: default avatarWilliam Kucharski <william.kucharski@oracle.com>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Trilok Soni <tsoni@codeaurora.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent c8282f1b
......@@ -151,7 +151,7 @@ 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. */
......
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