From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: kernel panic in skb_copy_bits Date: Fri, 28 Jun 2013 02:37:42 -0700 Message-ID: <1372412262.3301.251.camel__47016.6563209661$1372412483$gmane$org@edumazet-glaptop> References: <51CBAA48.3080802@oracle.com> <1372311118.3301.214.camel@edumazet-glaptop> <51CD0E67.4000008@oracle.com> <1372402340.3301.229.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1372402340.3301.229.camel@edumazet-glaptop> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Joe Jin Cc: Frank Blaschka , "zheng.x.li@oracle.com" , Ian Campbell , Stefano Stabellini , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Xen Devel , Jan Beulich , "David S. Miller" List-Id: xen-devel@lists.xenproject.org OK please try the following patch [PATCH] neighbour: fix a race in neigh_destroy() There is a race in neighbour code, because neigh_destroy() uses skb_queue_purge(&neigh->arp_queue) without holding neighbour lock, while other parts of the code assume neighbour rwlock is what protects arp_queue Convert all skb_queue_purge() calls to the __skb_queue_purge() variant Use __skb_queue_head_init() instead of skb_queue_head_init() to make clear we do not use arp_queue.lock And hold neigh->lock in neigh_destroy() to close the race. Reported-by: Joe Jin Signed-off-by: Eric Dumazet --- net/core/neighbour.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/net/core/neighbour.c b/net/core/neighbour.c index 2569ab2..b7de821 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -231,7 +231,7 @@ static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev) we must kill timers etc. and move it to safe state. */ - skb_queue_purge(&n->arp_queue); + __skb_queue_purge(&n->arp_queue); n->arp_queue_len_bytes = 0; n->output = neigh_blackhole; if (n->nud_state & NUD_VALID) @@ -286,7 +286,7 @@ static struct neighbour *neigh_alloc(struct neigh_table *tbl, struct net_device if (!n) goto out_entries; - skb_queue_head_init(&n->arp_queue); + __skb_queue_head_init(&n->arp_queue); rwlock_init(&n->lock); seqlock_init(&n->ha_lock); n->updated = n->used = now; @@ -708,7 +708,9 @@ void neigh_destroy(struct neighbour *neigh) if (neigh_del_timer(neigh)) pr_warn("Impossible event\n"); - skb_queue_purge(&neigh->arp_queue); + write_lock_bh(&neigh->lock); + __skb_queue_purge(&neigh->arp_queue); + write_unlock_bh(&neigh->lock); neigh->arp_queue_len_bytes = 0; if (dev->netdev_ops->ndo_neigh_destroy) @@ -858,7 +860,7 @@ static void neigh_invalidate(struct neighbour *neigh) neigh->ops->error_report(neigh, skb); write_lock(&neigh->lock); } - skb_queue_purge(&neigh->arp_queue); + __skb_queue_purge(&neigh->arp_queue); neigh->arp_queue_len_bytes = 0; } @@ -1210,7 +1212,7 @@ int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new, write_lock_bh(&neigh->lock); } - skb_queue_purge(&neigh->arp_queue); + __skb_queue_purge(&neigh->arp_queue); neigh->arp_queue_len_bytes = 0; } out: