Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751771Ab3FZUoI (ORCPT ); Wed, 26 Jun 2013 16:44:08 -0400 Received: from shards.monkeyblade.net ([149.20.54.216]:47224 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750843Ab3FZUoG (ORCPT ); Wed, 26 Jun 2013 16:44:06 -0400 Date: Wed, 26 Jun 2013 13:44:05 -0700 (PDT) Message-Id: <20130626.134405.464630881670006463.davem@davemloft.net> To: eric.dumazet@gmail.com Cc: nschichan@freebox.fr, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, edumazet@google.com, xiyou.wangcong@gmail.com Subject: Re: [PATCH v3.10-rc7] net: fix kernel deadlock with interface rename and netdev name retrieval. From: David Miller In-Reply-To: <1372264414.3301.198.camel@edumazet-glaptop> References: <1372260222-8597-1-git-send-email-nschichan@freebox.fr> <1372264414.3301.198.camel@edumazet-glaptop> X-Mailer: Mew version 6.5 on Emacs 24.1 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1772 Lines: 40 From: Eric Dumazet Date: Wed, 26 Jun 2013 09:33:34 -0700 > On Wed, 2013-06-26 at 17:23 +0200, Nicolas Schichan wrote: >> When the kernel (compiled with CONFIG_PREEMPT=n) is performing the >> rename of a network interface, it can end up waiting for a workqueue >> to complete. If userland is able to invoke a SIOCGIFNAME ioctl or a >> SO_BINDTODEVICE getsockopt in between, the kernel will deadlock due to >> the fact that read_secklock_begin() will spin forever waiting for the >> writer process (the one doing the interface rename) to update the >> devnet_rename_seq sequence. >> >> This patch fixes the problem by adding a helper (netdev_get_name()) >> and using it in the code handling the SIOCGIFNAME ioctl and >> SO_BINDTODEVICE setsockopt. >> >> The netdev_get_name() helper uses raw_seqcount_begin() to avoid >> spinning forever, waiting for devnet_rename_seq->sequence to become >> even. cond_resched() is used in the contended case, before retrying >> the access to give the writer process a chance to finish. >> >> The use of raw_seqcount_begin() will incur some unneeded work in the >> reader process in the contended case, but this is better than >> deadlocking the system. >> >> Signed-off-by: Nicolas Schichan >> --- > > This goes back to commit c91f6df2db49 > ("sockopt: Change getsockopt() of SO_BINDTODEVICE to return an interface > name") in linux-3.8 > > Acked-by: Eric Dumazet Applied and queued up for -stable, thanks everyone. -- 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/