In an effort to separate intentional arithmetic wrap-around from
unexpected wrap-around, we need to refactor places that depend on this
kind of math. One of the most common code patterns of this is:
VAR + value < VAR
Notably, this is considered "undefined behavior" for signed and pointer
types, which the kernel works around by using the -fno-strict-overflow
option in the build[1] (which used to just be -fwrapv). Regardless, we
want to get the kernel source to the position where we can meaningfully
instrument arithmetic wrap-around conditions and catch them when they
are unexpected, regardless of whether they are signed[2], unsigned[3],
or pointer[4] types.
Refactor open-coded wrap-around addition test to use add_would_overflow().
This paves the way to enabling the wrap-around sanitizers in the future.
Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
Link: https://github.com/KSPP/linux/issues/26 [2]
Link: https://github.com/KSPP/linux/issues/27 [3]
Link: https://github.com/KSPP/linux/issues/344 [4]
Cc: Sathya Prakash <sathya.prak...@broadcom.com>
Cc: Sreekanth Reddy <sreekanth.re...@broadcom.com>
Cc: Suganath Prabu Subramani <suganath-prabu.subram...@broadcom.com>
Cc: "James E.J. Bottomley" <j...@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.peter...@oracle.com>
Cc: mpt-fusionlinux....@broadcom.com
Cc: linux-s...@vger.kernel.org
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
drivers/scsi/mpt3sas/mpt3sas_ctl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/scsi/mpt3sas/mpt3sas_ctl.c
b/drivers/scsi/mpt3sas/mpt3sas_ctl.c
index 147cb7088d55..b36a9188720f 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_ctl.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_ctl.c
@@ -2382,7 +2382,7 @@ _ctl_diag_read_buffer(struct MPT3SAS_ADAPTER *ioc, void
__user *arg)
karg.bytes_to_read));
/* Truncate data on requests that are too large */
- if ((diag_data + karg.bytes_to_read < diag_data) ||
+ if ((add_would_overflow(diag_data, karg.bytes_to_read)) ||
(diag_data + karg.bytes_to_read > request_data + request_size))
copy_size = request_size - karg.starting_offset;
else
--
2.34.1
