From patchwork Tue Apr 13 14:59:44 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 50078 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [199.232.76.165]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 7E17DB7D0C for ; Wed, 14 Apr 2010 01:05:28 +1000 (EST) Received: from localhost ([127.0.0.1]:54194 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1O1hg5-0002WF-CB for incoming@patchwork.ozlabs.org; Tue, 13 Apr 2010 11:05:25 -0400 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1O1hfD-0002On-PC for qemu-devel@nongnu.org; Tue, 13 Apr 2010 11:04:31 -0400 Received: from [140.186.70.92] (port=58095 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1O1hf7-0002MD-FN for qemu-devel@nongnu.org; Tue, 13 Apr 2010 11:04:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1O1hf4-00049A-IO for qemu-devel@nongnu.org; Tue, 13 Apr 2010 11:04:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:28890) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1O1hf4-000490-9e for qemu-devel@nongnu.org; Tue, 13 Apr 2010 11:04:22 -0400 Received: from int-mx03.intmail.prod.int.phx2.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.16]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o3DF3UWr031012 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Tue, 13 Apr 2010 11:03:30 -0400 Received: from redhat.com (dhcp-0-94.tlv.redhat.com [10.35.0.94]) by int-mx03.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with SMTP id o3DF3Qmm012064; Tue, 13 Apr 2010 11:03:27 -0400 Date: Tue, 13 Apr 2010 17:59:44 +0300 From: "Michael S. Tsirkin" Message-ID: <20100413145944.GA7716@redhat.com> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.19 (2009-01-05) X-Scanned-By: MIMEDefang 2.67 on 10.5.11.16 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. Cc: Paul Moore , David Woodhouse , "Michael S. Tsirkin" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, qemu-devel , Herbert Xu , Jan Kiszka , "David S. Miller" Subject: [Qemu-devel] [PATCH] tun: orphan an skb on tx X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org 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 Tested-by: Jan Kiszka --- Please review the below, and consider for 2.6.34, and stable trees. drivers/net/tun.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 96c39bd..4326520 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;