linux-kernel - [ 75/82] af-packet: fix oops when socket is not present

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Message-Id: <20121114053944.174312334@decadent.org.uk>
Date:	Wed, 14 Nov 2012 05:40:48 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Eric Leblond <eric@...it.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 75/82] af-packet: fix oops when socket is not present

3.2-stable review patch.  If anyone has any objections, please let me know.

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

From: Eric Leblond <eric@...it.org>

[ Upstream commit a3d744e995d2b936c500585ae39d99ee251c89b4 ]

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

commit c0de08d04215031d68fa13af36f347a6cfa252ca
Author: Eric Leblond <eric@...it.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@...it.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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 f500a69..480be72 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1633,7 +1633,7 @@ 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)


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