From fc350777c705a39a312728ac5e8a6f164a828f5d Mon Sep 17 00:00:00 2001 From: Joerg Marx Date: Thu, 20 May 2010 15:55:30 +0200 Subject: [PATCH] netfilter: nf_conntrack: fix a race in __nf_conntrack_confirm against nf_ct_get_next_corpse() This race was triggered by a 'conntrack -F' command running in parallel to the insertion of a hash for a new connection. Losing this race led to a dead conntrack entry effectively blocking traffic for a particular connection until timeout or flushing the conntrack hashes again. Now the check for an already dying connection is done inside the lock. Signed-off-by: Joerg Marx Signed-off-by: Patrick McHardy --- include/net/netfilter/nf_conntrack_core.h | 2 +- net/netfilter/nf_conntrack_core.c | 10 ++++++++++ 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/include/net/netfilter/nf_conntrack_core.h b/include/net/netfilter/nf_conntrack_core.h index dffde8e..3d7524f 100644 --- a/include/net/netfilter/nf_conntrack_core.h +++ b/include/net/netfilter/nf_conntrack_core.h @@ -61,7 +61,7 @@ static inline int nf_conntrack_confirm(struct sk_buff *skb) int ret = NF_ACCEPT; if (ct && ct != &nf_conntrack_untracked) { - if (!nf_ct_is_confirmed(ct) && !nf_ct_is_dying(ct)) + if (!nf_ct_is_confirmed(ct)) ret = __nf_conntrack_confirm(skb); if (likely(ret == NF_ACCEPT)) nf_ct_deliver_cached_events(ct); diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index b83c530..eeeb8bc 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -424,6 +424,16 @@ __nf_conntrack_confirm(struct sk_buff *skb) spin_lock_bh(&nf_conntrack_lock); + /* We have to check the DYING flag inside the lock to prevent + a race against nf_ct_get_next_corpse() possibly called from + user context, else we insert an already 'dead' hash, blocking + further use of that particular connection -JM */ + + if (unlikely(nf_ct_is_dying(ct))) { + spin_unlock_bh(&nf_conntrack_lock); + return NF_ACCEPT; + } + /* See if there's one in the list already, including reverse: NAT could have grabbed it without realizing, since we're not in the hash. If there is, we lost race. */ -- 1.8.2.3