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authorPatrick McHardy <kaber@trash.net>2009-06-22 14:14:16 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2009-07-30 14:40:21 -0700
commitd583e5291f0e456a872ec058bf36223dcad01e0a (patch)
treee7d1e4e1d116cb1ec991745278293f208849216f
parent3aa08795cb77ac09f25b61a48f1637b3dabe09c9 (diff)
downloadlinux-linaro-stable-d583e5291f0e456a872ec058bf36223dcad01e0a.tar.gz
netfilter: nf_conntrack: fix confirmation race condition
commit 5c8ec910e789a92229978d8fd1fce7b62e8ac711 upstream. New connection tracking entries are inserted into the hash before they are fully set up, namely the CONFIRMED bit is not set and the timer not started yet. This can theoretically lead to a race with timer, which would set the timeout value to a relative value, most likely already in the past. Perform hash insertion as the final step to fix this. Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--net/netfilter/nf_conntrack_core.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 8020db6274b8..c8bd559bbf8b 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -385,7 +385,6 @@ __nf_conntrack_confirm(struct sk_buff *skb)
/* Remove from unconfirmed list */
hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);
- __nf_conntrack_hash_insert(ct, hash, repl_hash);
/* Timer relative to confirmation time, not original
setting time, otherwise we'd get timer wrap in
weird delay cases. */
@@ -393,8 +392,16 @@ __nf_conntrack_confirm(struct sk_buff *skb)
add_timer(&ct->timeout);
atomic_inc(&ct->ct_general.use);
set_bit(IPS_CONFIRMED_BIT, &ct->status);
+
+ /* Since the lookup is lockless, hash insertion must be done after
+ * starting the timer and setting the CONFIRMED bit. The RCU barriers
+ * guarantee that no other CPU can find the conntrack before the above
+ * stores are visible.
+ */
+ __nf_conntrack_hash_insert(ct, hash, repl_hash);
NF_CT_STAT_INC(net, insert);
spin_unlock_bh(&nf_conntrack_lock);
+
help = nfct_help(ct);
if (help && help->helper)
nf_conntrack_event_cache(IPCT_HELPER, ct);