linux-kernel - [47/74] af_packet: Dont use skb after dev_queue

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Message-Id: <20100204171514.818399920@linux.site>
Date:	Thu, 04 Feb 2010 09:12:18 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Jarek Poplawski <jarkao2@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: [47/74] af_packet: Dont use skb after dev_queue_xmit()

2.6.32-stable review patch.  If anyone has any objections, please let us know.

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

From: Jarek Poplawski <jarkao2@...il.com>

[ Upstream commit eb70df13ee52dbc0f2c0ffd8ed34a8cd27440baf ]

tpacket_snd() can change and kfree an skb after dev_queue_xmit(),
which is illegal.

With debugging by: Stephen Hemminger <shemminger@...tta.com>

Reported-by: Michael Breuer <mbreuer@...jas.com>
With help from: David S. Miller <davem@...emloft.net>
Signed-off-by: Jarek Poplawski <jarkao2@...il.com>
Tested-by: Michael Breuer<mbreuer@...jas.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 net/packet/af_packet.c |   19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1028,8 +1028,20 @@ static int tpacket_snd(struct packet_soc
 
 		status = TP_STATUS_SEND_REQUEST;
 		err = dev_queue_xmit(skb);
-		if (unlikely(err > 0 && (err = net_xmit_errno(err)) != 0))
-			goto out_xmit;
+		if (unlikely(err > 0)) {
+			err = net_xmit_errno(err);
+			if (err && __packet_get_status(po, ph) ==
+				   TP_STATUS_AVAILABLE) {
+				/* skb was destructed already */
+				skb = NULL;
+				goto out_status;
+			}
+			/*
+			 * skb was dropped but not destructed yet;
+			 * let's treat it like congestion or err < 0
+			 */
+			err = 0;
+		}
 		packet_increment_head(&po->tx_ring);
 		len_sum += tp_len;
 	} while (likely((ph != NULL) || ((!(msg->msg_flags & MSG_DONTWAIT))
@@ -1039,9 +1051,6 @@ static int tpacket_snd(struct packet_soc
 	err = len_sum;
 	goto out_put;
 
-out_xmit:
-	skb->destructor = sock_wfree;
-	atomic_dec(&po->tx_ring.pending);
 out_status:
 	__packet_set_status(po, ph, status);
 	kfree_skb(skb);


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