netfilter: nf_conntrack: fix racy timer handling with reliable events

Existing code assumes that del_timer returns true for alive conntrack entries. However, this is not true if reliable events are enabled. In that case, del_timer may return true for entries that were just inserted in the dying list. Note that packets / ctnetlink may hold references to conntrack entries that were just inserted to such list. This patch fixes the issue by adding an independent timer for event delivery. This increases the size of the ecache extension. Still we can revisit this later and use variable size extensions to allocate this area on demand. Tested-by: Oliver Smith <[email protected]> Signed-off-by: Pablo Neira Ayuso <[email protected]>
mna · Aug 31, 2012 · 5b423f6 · 5b423f6
1 parent 3f509c6
commit 5b423f6
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Showing 2 changed files with 12 additions and 5 deletions.
diff --git a/include/net/netfilter/nf_conntrack_ecache.h b/include/net/netfilter/nf_conntrack_ecache.h
@@ -18,6 +18,7 @@ struct nf_conntrack_ecache {
 	u16 ctmask;		/* bitmask of ct events to be delivered */
 	u16 expmask;		/* bitmask of expect events to be delivered */
 	u32 pid;		/* netlink pid of destroyer */
+	struct timer_list timeout;
 };
 
 static inline struct nf_conntrack_ecache *

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
@@ -249,12 +249,15 @@ static void death_by_event(unsigned long ul_conntrack)
 {
 	struct nf_conn *ct = (void *)ul_conntrack;
 	struct net *net = nf_ct_net(ct);
+	struct nf_conntrack_ecache *ecache = nf_ct_ecache_find(ct);
+
+	BUG_ON(ecache == NULL);
 
 	if (nf_conntrack_event(IPCT_DESTROY, ct) < 0) {
 		/* bad luck, let's retry again */
-		ct->timeout.expires = jiffies +
+		ecache->timeout.expires = jiffies +
 			(random32() % net->ct.sysctl_events_retry_timeout);
-		add_timer(&ct->timeout);
+		add_timer(&ecache->timeout);
 		return;
 	}
 	/* we've got the event delivered, now it's dying */
@@ -268,17 +271,20 @@ static void death_by_event(unsigned long ul_conntrack)
 void nf_ct_insert_dying_list(struct nf_conn *ct)
 {
 	struct net *net = nf_ct_net(ct);
+	struct nf_conntrack_ecache *ecache = nf_ct_ecache_find(ct);
+
+	BUG_ON(ecache == NULL);
 
 	/* add this conntrack to the dying list */
 	spin_lock_bh(&nf_conntrack_lock);
 	hlist_nulls_add_head(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode,
 			     &net->ct.dying);
 	spin_unlock_bh(&nf_conntrack_lock);
 	/* set a new timer to retry event delivery */
-	setup_timer(&ct->timeout, death_by_event, (unsigned long)ct);
-	ct->timeout.expires = jiffies +
+	setup_timer(&ecache->timeout, death_by_event, (unsigned long)ct);
+	ecache->timeout.expires = jiffies +
 		(random32() % net->ct.sysctl_events_retry_timeout);
-	add_timer(&ct->timeout);
+	add_timer(&ecache->timeout);
 }
 EXPORT_SYMBOL_GPL(nf_ct_insert_dying_list);