linux-kernel - [PATCH net] virtio-net: don't free skb immediately on kick failure

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Message-Id: <1395390601-13177-1-git-send-email-jasowang@redhat.com>
Date:	Fri, 21 Mar 2014 16:30:01 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	rusty@...tcorp.com.au, mst@...hat.com,
	virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	Jason Wang <jasowang@...hat.com>,
	Heinz Graalfs <graalfs@...ux.vnet.ibm.com>
Subject: [PATCH net] virtio-net: don't free skb immediately on kick failure

We free the skb immediately on kick failure during xmit without detaching it
from the virtqueue. This may lead double free for the skb during
free_unused_bufs(). This patch fixes this by not freeing it on kick failure and
let it to be freed through free_unused_bufs().

Fixes 67975901183799af8e93ec60e322f9e2a1940b9b
("virtio_net: verify if virtqueue_kick() succeeded").

Cc: Rusty Russell <rusty@...tcorp.com.au>
Cc: Michael S. Tsirkin <mst@...hat.com>
Cc: Heinz Graalfs <graalfs@...ux.vnet.ibm.com>
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
 drivers/net/virtio_net.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 5632a99..d833d38 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -882,8 +882,10 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
 		if (net_ratelimit())
 			dev_warn(&dev->dev,
 				 "Unexpected TXQ (%d) queue failure: %d\n", qnum, err);
-		dev->stats.tx_dropped++;
-		kfree_skb(skb);
+		if (err) {
+			dev->stats.tx_dropped++;
+			kfree_skb(skb);
+		}
 		return NETDEV_TX_OK;
 	}
 
-- 
1.8.3.2

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