The patch titled
Subject: mm/usercopy: use memory range to be accessed for wraparound check
has been added to the -mm tree. Its filename is
mm-usercopy-use-memory-range-to-be-accessed-for-wraparound-check.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-usercopy-use-memory-range-to-be-accessed-for-wraparound-check.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-usercopy-use-memory-range-to-be-accessed-for-wraparound-check.patch
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------------------------------------------------------
From: "Isaac J. Manjarres" <isaacm@xxxxxxxxxxxxxx>
Subject: mm/usercopy: use memory range to be accessed for wraparound check
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@xxxxxxxxxxxxxx
Fixes: f5509cc18daa ("mm: Hardened usercopy")
Signed-off-by: Prasad Sodagudi <psodagud@xxxxxxxxxxxxxx>
Signed-off-by: Isaac J. Manjarres <isaacm@xxxxxxxxxxxxxx>
Co-developed-by: Prasad Sodagudi <psodagud@xxxxxxxxxxxxxx>
Reviewed-by: William Kucharski <william.kucharski@xxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Trilok Soni <tsoni@xxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/usercopy.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/usercopy.c~mm-usercopy-use-memory-range-to-be-accessed-for-wraparound-check
+++ a/mm/usercopy.c
@@ -147,7 +147,7 @@ static inline void check_bogus_address(c
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. */
_
Patches currently in -mm which might be from isaacm@xxxxxxxxxxxxxx are
mm-usercopy-use-memory-range-to-be-accessed-for-wraparound-check.patch
