From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steffen Klassert Subject: Re: Fw:[Bug 70471] xfrm policy node will double unlink. Date: Tue, 18 Feb 2014 09:37:38 +0100 Message-ID: <20140218083737.GB32371@secunet.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: netdev , alan To: Xianpeng Zhao <673321875@qq.com> Return-path: Received: from a.mx.secunet.com ([195.81.216.161]:47917 "EHLO a.mx.secunet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754212AbaBRIhl (ORCPT ); Tue, 18 Feb 2014 03:37:41 -0500 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Feb 18, 2014 at 10:55:57AM +0800, Xianpeng Zhao wrote: > Hi Group, > I found a problem about xfrm policy. > > In corner case, xfrm policy node will be double unlinked from the list. > > The scenario like this: > In thread context, After removed the node from list, before remove the xfrm policy expire timer. At this point, a timer interrupt come, and call the run_timer_softirq to execute the xfrm_policy_timer to remove the expired policy node; because this policy node had already removed from list. this remove will cause the node double unlinked. Good catch! I wonder why I've never seen this. Do you have a reproducer for this bug? Looks like it is sufficient to reinitialize the bydst hlist in __xfrm_policy_unlink(). Then hlist_unhashed() will notice that this policy is not linked. Does the patch below help? diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index 121399d..225f439 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -1156,7 +1156,7 @@ static struct xfrm_policy *__xfrm_policy_unlink(struct xfrm_policy *pol, if (hlist_unhashed(&pol->bydst)) return NULL; - hlist_del(&pol->bydst); + hlist_del_init(&pol->bydst); hlist_del(&pol->byidx); list_del(&pol->walk.all); net->xfrm.policy_count[dir]--;