Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754210Ab0DULrf (ORCPT ); Wed, 21 Apr 2010 07:47:35 -0400 Received: from goliath.siemens.de ([192.35.17.28]:20884 "EHLO goliath.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753899Ab0DULra (ORCPT ); Wed, 21 Apr 2010 07:47:30 -0400 Message-ID: <4BCEE599.1020501@siemens.com> Date: Wed, 21 Apr 2010 13:46:33 +0200 From: Jan Kiszka User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 MIME-Version: 1.0 To: "Michael S. Tsirkin" CC: "stable@kernel.org" , "David S. Miller" , Herbert Xu , Paul Moore , David Woodhouse , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , qemu-devel Subject: Re: [PATCH] tun: orphan an skb on tx References: <20100413145944.GA7716@redhat.com> <20100421113557.GA31606@redhat.com> In-Reply-To: <20100421113557.GA31606@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2657 Lines: 78 Michael S. Tsirkin wrote: > On Tue, Apr 13, 2010 at 05:59:44PM +0300, Michael S. Tsirkin wrote: >> 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 >> >> --- >> >> 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; >> -- >> 1.7.0.2.280.gc6f05 > > This is commit 0110d6f22f392f976e84ab49da1b42f85b64a3c5 in net-2.6 > Please cherry-pick this fix in stable kernels (2.6.32 and 2.6.33). > > Thanks! > Before I forget again: Tested-by: Jan Kiszka (namely the field test of our customer) Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/