From mboxrd@z Thu Jan  1 00:00:00 1970
From: danborkmann@iogearbox.net
Subject: [PATCH] af_packet: tpacket_destruct_skb, deref skb after BUG_ON
 assertion
Date: Sun, 09 Oct 2011 17:19:19 +0200
Message-ID: <20111009171919.10922hrx8qjm2f7b@webmail.your-server.de>
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To: "David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org
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This tiny patch derefs the skb only after BUG_ON(skb==NULL) was evaluated
and not before. Patched against latest Linus tree.

Thanks,
Daniel

Signed-off-by: Daniel Borkmann <danborkmann@iogearbox.net>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index fabb4fa..d9d833b 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1167,11 +1167,12 @@ ring_is_full:

  static void tpacket_destruct_skb(struct sk_buff *skb)
  {
-	struct packet_sock *po = pkt_sk(skb->sk);
+	struct packet_sock *po;
  	void *ph;

  	BUG_ON(skb == NULL);

+	po = pkt_sk(skb->sk);
  	if (likely(po->tx_ring.pg_vec)) {
  		ph = skb_shinfo(skb)->destructor_arg;
  		BUG_ON(__packet_get_status(po, ph) != TP_STATUS_SENDING);