[NETFILTER]: ctnetlink: fix deadlock in table dumping

[NETFILTER]: ctnetlink: fix deadlock in table dumping

[Patrick McHardy]

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Fix a deadlock in ctnetlink (introduced early in 2.6.18-rc by myself).
Please apply to 2.6.18.


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[NETFILTER]: ctnetlink: fix deadlock in table dumping

ip_conntrack_put must not be called while holding ip_conntrack_lock
since destroy_conntrack takes it again.

Signed-off-by: Patrick McHardy <kaber@trash.net>

---
commit 8ebd6bb0f469f2759f39e73adee6916a3d975393
tree ebd73ee261508d483654416b03610910a2968e21
parent 338fe5c67e8fb799c9e3470331db6f3c60a31b1e
author Patrick McHardy <kaber@trash.net> Wed, 16 Aug 2006 13:32:27 +0200
committer Patrick McHardy <kaber@trash.net> Wed, 16 Aug 2006 13:32:27 +0200

 net/ipv4/netfilter/ip_conntrack_netlink.c |   17 +++++++----------
 net/netfilter/nf_conntrack_netlink.c      |   17 +++++++----------
 2 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/net/ipv4/netfilter/ip_conntrack_netlink.c b/net/ipv4/netfilter/ip_conntrack_netlink.c
index 33891bb..0d4cc92 100644
--- a/net/ipv4/netfilter/ip_conntrack_netlink.c
+++ b/net/ipv4/netfilter/ip_conntrack_netlink.c
@@ -415,21 +415,18 @@ ctnetlink_dump_table(struct sk_buff *skb
 			cb->args[0], *id);
 
 	read_lock_bh(&ip_conntrack_lock);
+	last = (struct ip_conntrack *)cb->args[1];
 	for (; cb->args[0] < ip_conntrack_htable_size; cb->args[0]++) {
 restart:
-		last = (struct ip_conntrack *)cb->args[1];
 		list_for_each_prev(i, &ip_conntrack_hash[cb->args[0]]) {
 			h = (struct ip_conntrack_tuple_hash *) i;
 			if (DIRECTION(h) != IP_CT_DIR_ORIGINAL)
 				continue;
 			ct = tuplehash_to_ctrack(h);
-			if (last != NULL) {
-				if (ct == last) {
-					ip_conntrack_put(last);
-					cb->args[1] = 0;
-					last = NULL;
-				} else
+			if (cb->args[1]) {
+				if (ct != last)
 					continue;
+				cb->args[1] = 0;
 			}
 			if (ctnetlink_fill_info(skb, NETLINK_CB(cb->skb).pid,
 		                        	cb->nlh->nlmsg_seq,
@@ -440,17 +437,17 @@ restart:
 				goto out;
 			}
 		}
-		if (last != NULL) {
-			ip_conntrack_put(last);
+		if (cb->args[1]) {
 			cb->args[1] = 0;
 			goto restart;
 		}
 	}
 out:
 	read_unlock_bh(&ip_conntrack_lock);
+	if (last)
+		ip_conntrack_put(last);
 
 	DEBUGP("leaving, last bucket=%lu id=%u\n", cb->args[0], *id);
-
 	return skb->len;
 }
 
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index af48459..6527d4e 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -429,9 +429,9 @@ ctnetlink_dump_table(struct sk_buff *skb
 			cb->args[0], *id);
 
 	read_lock_bh(&nf_conntrack_lock);
+	last = (struct nf_conn *)cb->args[1];
 	for (; cb->args[0] < nf_conntrack_htable_size; cb->args[0]++) {
 restart:
-		last = (struct nf_conn *)cb->args[1];
 		list_for_each_prev(i, &nf_conntrack_hash[cb->args[0]]) {
 			h = (struct nf_conntrack_tuple_hash *) i;
 			if (DIRECTION(h) != IP_CT_DIR_ORIGINAL)
@@ -442,13 +442,10 @@ restart:
 			 * then dump everything. */
 			if (l3proto && L3PROTO(ct) != l3proto)
 				continue;
-			if (last != NULL) {
-				if (ct == last) {
-					nf_ct_put(last);
-					cb->args[1] = 0;
-					last = NULL;
-				} else
+			if (cb->args[1]) {
+				if (ct != last)
 					continue;
+				cb->args[1] = 0;
 			}
 			if (ctnetlink_fill_info(skb, NETLINK_CB(cb->skb).pid,
 		                        	cb->nlh->nlmsg_seq,
@@ -459,17 +456,17 @@ restart:
 				goto out;
 			}
 		}
-		if (last != NULL) {
-			nf_ct_put(last);
+		if (cb->args[1]) {
 			cb->args[1] = 0;
 			goto restart;
 		}
 	}
 out:
 	read_unlock_bh(&nf_conntrack_lock);
+	if (last)
+		nf_ct_put(last);
 
 	DEBUGP("leaving, last bucket=%lu id=%u\n", cb->args[0], *id);
-
 	return skb->len;
 }
 

Re: [NETFILTER]: ctnetlink: fix deadlock in table dumping

[David Miller]

From: Patrick McHardy <kaber@trash.net>
Date: Thu, 17 Aug 2006 00:10:22 +0200

> Fix a deadlock in ctnetlink (introduced early in 2.6.18-rc by myself).
> Please apply to 2.6.18.

Applied, thanks Patrick.