From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: [net-next PATCH 1/3] net: fix race bug in fragmentation create code Date: Fri, 19 Apr 2013 03:00:06 +0200 Message-ID: <20130419010006.GE27889@order.stressinduktion.org> References: <20130418213637.14296.43143.stgit@dragon> <20130418213715.14296.43912.stgit@dragon> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: Eric Dumazet , "David S. Miller" , netdev@vger.kernel.org To: Jesper Dangaard Brouer Return-path: Received: from order.stressinduktion.org ([87.106.68.36]:51443 "EHLO order.stressinduktion.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967716Ab3DSBAH (ORCPT ); Thu, 18 Apr 2013 21:00:07 -0400 Content-Disposition: inline In-Reply-To: <20130418213715.14296.43912.stgit@dragon> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, Apr 18, 2013 at 11:37:27PM +0200, Jesper Dangaard Brouer wrote: > During creation of a new inet_frag_queue, the lru_list pointer is > updated after releasing the hash bucket lock, which can lead to a > race condition (and panic), if the inet_frag_queue is deleted > (very quickly) before the lru_list is valid. > > This race condition is should not be able to occur with current > LRU based evictor. For the planned direct hash based > evictor/clean strategy, this race condition is more likely to > occur. > > Signed-off-by: Jesper Dangaard Brouer > --- > > net/ipv4/inet_fragment.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c > index e97d66a..beec05b 100644 > --- a/net/ipv4/inet_fragment.c > +++ b/net/ipv4/inet_fragment.c > @@ -283,9 +283,9 @@ static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf, > > atomic_inc(&qp->refcnt); > hlist_add_head(&qp->list, &hb->chain); > + inet_frag_lru_add(nf, qp); > spin_unlock(&hb->chain_lock); > read_unlock(&f->lock); > - inet_frag_lru_add(nf, qp); > return qp; > } If I checked correctly, the current code does not have the race condition? I think this change is ok but maybe we can defer it until the direct hash cleanup patches land? Thanks, Hannes