Subject: [PATCH 4.4 18/29] slcan: Dont transmit uninitialized stack data in padding

From: Greg Kroah-Hartman <[email-masked]>
Date: Sat, 11 Apr 2020 14:08:48 +0200

From: Richard Palethorpe <[email-masked]>

[ Upstream commit b9258a2cece4ec1f020715fe3554bc2e360f6264 ]

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 <[email-masked]>
Fixes: a1044e36e457 ("can: add slcan driver for serial/USB-serial CAN adapters")
Reviewed-by: Kees Cook <[email-masked]>
Cc: [email-masked]
Cc: [email-masked]
Cc: [email-masked]
Cc: [email-masked]
Cc: [email-masked]
Cc: [email-masked]
Acked-by: Marc Kleine-Budde <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
Signed-off-by: Greg Kroah-Hartman <[email-masked]>
---
 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
@@ -147,7 +147,7 @@ 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':
@@ -186,8 +186,6 @@ 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++) {