[lucid/fsl-imx51, maverick, maverick/ti-omap4, natty/ti-omap4 CVE 1/1] can: Add missing socket check in can/bcm release.

[Andy Whitcroft]

From: Dave Jones <davej at redhat.com>

We can get here with a NULL socket argument passed from userspace,
so we need to handle it accordingly.

Signed-off-by: Dave Jones <davej at redhat.com>
Signed-off-by: David S. Miller <davem at davemloft.net>

(cherry picked from commit c6914a6f261aca0c9f715f883a353ae7ff51fe83)
CVE-2011-1598
BugLink: http://bugs.launchpad.net/bugs/796502
Signed-off-by: Andy Whitcroft <apw at canonical.com>
---
 net/can/bcm.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/net/can/bcm.c b/net/can/bcm.c
index 9d5e8ac..56d20a2 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -1424,9 +1424,14 @@ static int bcm_init(struct sock *sk)
 static int bcm_release(struct socket *sock)
 {
 	struct sock *sk = sock->sk;
-	struct bcm_sock *bo = bcm_sk(sk);
+	struct bcm_sock *bo;
 	struct bcm_op *op, *next;
 
+	if (sk == NULL)
+		return 0;
+
+	bo = bcm_sk(sk);
+
 	/* remove bcm_ops, timer, rx_unregister(), etc. */
 
 	unregister_netdevice_notifier(&bo->notifier);
-- 
1.7.4.1