[PATCH 3.16 245/245] slcan: Don't transmit uninitialized stack data in padding

Ben Hutchings
2020-04-23T23:07:37Z

From: Richard Palethorpe <rpalethorpe@suse.com>

commit b9258a2cece4ec1f020715fe3554bc2e360f6264 upstream.

struct can_frame contains some padding which is not explicitly zeroed in
slc_bump. This uninitialized data will then be transmitted if the stack
initialization hardening feature is not enabled (CONFIG_INIT_STACK_ALL).

This commit just zeroes the whole struct including the padding.

Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
Fixes: a1044e36e457 ("can: add slcan driver for serial/USB-serial CAN adapters")
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: linux-can@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: security@kernel.org
Cc: wg@grandegger.com
Cc: mkl@pengutronix.de
Cc: davem@davemloft.net
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/net/can/slcan.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -150,7 +150,7 @@ static void slc_bump(struct slcan *sl)
u32 tmpid;
char *cmd = sl->rbuff;

- cf.can_id = 0;
+ memset(&cf, 0, sizeof(cf));

switch (*cmd) {
case 'r':
@@ -189,8 +189,6 @@ static void slc_bump(struct slcan *sl)
else
return;

- *(u64 *) (&cf.data) = 0; /* clear payload */
-
/* RTR frames may have a dlc > 0 but they never have any data bytes */
if (!(cf.can_id & CAN_RTR_FLAG)) {
for (i = 0; i < cf.can_dlc; i++) {