Messages in this thread Patch in this message | | | Date | Mon, 10 May 2010 15:33:04 -0700 | From | Greg KH <> | Subject | [093/117] tun: orphan an skb on tx |
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2.6.33-stable review patch. If anyone has any objections, please let us know.
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From: Michael S. Tsirkin <mst@redhat.com>
[ Upstream commit 0110d6f22f392f976e84ab49da1b42f85b64a3c5 ]
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 <mst@redhat.com> Tested-by: Yan Vugenfirer <yvugenfi@redhat.com> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> --- drivers/net/tun.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -380,6 +380,10 @@ static netdev_tx_t tun_net_xmit(struct s } } + /* 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;
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