From 0110d6f22f392f976e84ab49da1b42f85b64a3c5 Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Tue, 13 Apr 2010 04:59:44 +0000 Subject: [PATCH] tun: orphan an skb on tx The following situation was observed in the field: tap1 sends packets, tap2 does not consume them, as a result tap1 can not be closed. This happens because tun/tap devices can hang on to skbs undefinitely. As noted by Herbert, possible solutions include a timeout followed by a copy/change of ownership of the skb, or always copying/changing ownership if we're going into a hostile device. This patch implements the second approach. Note: one issue still remaining is that since skbs keep reference to tun socket and tun socket has a reference to tun device, we won't flush backlog, instead simply waiting for all skbs to get transmitted. At least this is not user-triggerable, and this was not reported in practice, my assumption is other devices besides tap complete an skb within finite time after it has been queued. A possible solution for the second issue would not to have socket reference the device, instead, implement dev->destructor for tun, and wait for all skbs to complete there, but this needs some thought, probably too risky for 2.6.34. Signed-off-by: Michael S. Tsirkin Tested-by: Yan Vugenfirer Acked-by: Herbert Xu Signed-off-by: David S. Miller --- drivers/net/tun.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 96c39bddc78c..43265207d463 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -387,6 +387,10 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev) } } + /* Orphan the skb - required as we might hang on to it + * for indefinite time. */ + skb_orphan(skb); + /* Enqueue packet */ skb_queue_tail(&tun->socket.sk->sk_receive_queue, skb); dev->trans_start = jiffies; -- 2.20.1