linux-kernel - [PATCH AUTOSEL 5.5 057/106] slcan: Don't transmit uninitialized stack data in padding

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Date:   Wed, 15 Apr 2020 07:41:37 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Richard Palethorpe <rpalethorpe@...e.com>,
        Kees Cook <keescook@...omium.org>, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, security@...nel.org, wg@...ndegger.com,
        mkl@...gutronix.de, davem@...emloft.net,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 5.5 057/106] slcan: Don't transmit uninitialized stack data in padding

From: Richard Palethorpe <rpalethorpe@...e.com>

[ 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 <rpalethorpe@...e.com>
Fixes: a1044e36e457 ("can: add slcan driver for serial/USB-serial CAN adapters")
Reviewed-by: Kees Cook <keescook@...omium.org>
Cc: linux-can@...r.kernel.org
Cc: netdev@...r.kernel.org
Cc: security@...nel.org
Cc: wg@...ndegger.com
Cc: mkl@...gutronix.de
Cc: davem@...emloft.net
Acked-by: Marc Kleine-Budde <mkl@...gutronix.de>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/can/slcan.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan.c
index a3664281a33fc..4dfa459ef5c73 100644
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -148,7 +148,7 @@ 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':
@@ -187,8 +187,6 @@ 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++) {
-- 
2.20.1