netdev - [PATCH 07/11] can: bcm: check for null sk before deferencing it via the call to sock

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Message-Id: <20171019111945.13580-8-mkl@pengutronix.de>
Date:   Thu, 19 Oct 2017 13:19:41 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, linux-can@...r.kernel.org,
        kernel@...gutronix.de, Colin Ian King <colin.king@...onical.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH 07/11] can: bcm: check for null sk before deferencing it via the call to sock_net

From: Colin Ian King <colin.king@...onical.com>

The assignment of net via call sock_net will dereference sk. This
is performed before a sanity null check on sk, so there could be
a potential null dereference on the sock_net call if sk is null.
Fix this by assigning net after the sk null check. Also replace
the sk == NULL with the more usual !sk idiom.

Detected by CoverityScan CID#1431862 ("Dereference before null check")

Fixes: 384317ef4187 ("can: network namespace support for CAN_BCM protocol")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
Acked-by: Oliver Hartkopp <socketcan@...tkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 net/can/bcm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/can/bcm.c b/net/can/bcm.c
index 47a8748d953a..13690334efa3 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -1493,13 +1493,14 @@ static int bcm_init(struct sock *sk)
 static int bcm_release(struct socket *sock)
 {
 	struct sock *sk = sock->sk;
-	struct net *net = sock_net(sk);
+	struct net *net;
 	struct bcm_sock *bo;
 	struct bcm_op *op, *next;
 
-	if (sk == NULL)
+	if (!sk)
 		return 0;
 
+	net = sock_net(sk);
 	bo = bcm_sk(sk);
 
 	/* remove bcm_ops, timer, rx_unregister(), etc. */
-- 
2.14.2