[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>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 10 deletions

diff --git a/net/ipv4/netfilter/ip_conntrack_netlink.c b/net/ipv4/netfilter/ip_conntrack_netlink.c
index 33891bb1fde4..0d4cc92391fa 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, struct netlink_callback *cb)
                         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;
 }