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

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Message-ID: <lsq.1587683028.722482633@decadent.org.uk>
Date:   Fri, 24 Apr 2020 00:07:52 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        linux-can@...r.kernel.org, security@...nel.org,
        "Kees Cook" <keescook@...omium.org>, davem@...emloft.net,
        netdev@...r.kernel.org, wg@...ndegger.com,
        "Richard Palethorpe" <rpalethorpe@...e.com>, mkl@...gutronix.de
Subject: [PATCH 3.16 245/245] slcan: Don't transmit uninitialized stack
 data in padding

3.16.83-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Richard Palethorpe <rpalethorpe@...e.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@...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: Ben Hutchings <ben@...adent.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++) {