[PATCH v2] af-packet: fix oops when socket is not present

[Eric Leblond <eric@regit.org>]

Due to a NULL dereference, the following patch is causing oops
in normal trafic condition:

commit c0de08d04215031d68fa13af36f347a6cfa252ca
Author: Eric Leblond <eric@regit.org>
Date:   Thu Aug 16 22:02:58 2012 +0000

    af_packet: don't emit packet on orig fanout group

This buggy patch was a feature fix and has reached most stable
branches.

When skb->sk is NULL and when packet fanout is used, there is a
crash in match_fanout_group where skb->sk is accessed.
This patch fixes the issue by returning false as soon as the
socket is NULL: this correspond to the wanted behavior because
the kernel as to resend the skb to all the listening socket in
this case.

Signed-off-by: Eric Leblond <eric@regit.org>
---
 net/core/dev.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index b4978e2..83232a1 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1666,7 +1666,7 @@ static inline int deliver_skb(struct sk_buff *skb,
 
 static inline bool skb_loop_sk(struct packet_type *ptype, struct sk_buff *skb)
 {
-	if (ptype->af_packet_priv == NULL)
+	if (!ptype->af_packet_priv || !skb->sk)
 		return false;
 
 	if (ptype->id_match)
-- 
1.7.10.4