conntrack: fix {nf, ip}_ct_iterate_cleanup endless loops

[NETFILTER]: conntrack: fix {nf,ip}_ct_iterate_cleanup endless loops

Fix {nf,ip}_ct_iterate_cleanup unconfirmed list handling:

- unconfirmed entries can not be killed manually, they are removed on
  confirmation or final destruction of the conntrack entry, which means
  we might iterate forever without making forward progress.

  This can happen in combination with the conntrack event cache, which
  holds a reference to the conntrack entry, which is only released when
  the packet makes it all the way through the stack or a different
  packet is handled.

- taking references to an unconfirmed entry and using it outside the
  locked section doesn't work, the list entries are not refcounted and
  another CPU might already be waiting to destroy the entry

What the code really wants to do is make sure the references of the hash
table to the selected conntrack entries are released, so they will be
destroyed once all references from skbs and the event cache are dropped.

Since unconfirmed entries haven't even entered the hash yet, simply mark
them as dying and skip confirmation based on that.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

4 files changed, 4 insertions, 4 deletions

diff --git a/include/linux/netfilter_ipv4/ip_conntrack_core.h b/include/linux/netfilter_ipv4/ip_conntrack_core.h
index 907d4f5ca5dc..e3a6df07aa4b 100644
--- a/include/linux/netfilter_ipv4/ip_conntrack_core.h
+++ b/include/linux/netfilter_ipv4/ip_conntrack_core.h
@@ -45,7 +45,7 @@ static inline int ip_conntrack_confirm(struct sk_buff **pskb)
 	int ret = NF_ACCEPT;
 
 	if (ct) {
-		if (!is_confirmed(ct))
+		if (!is_confirmed(ct) && !is_dying(ct))
 			ret = __ip_conntrack_confirm(pskb);
 		ip_ct_deliver_cached_events(ct);
 	}
diff --git a/include/net/netfilter/nf_conntrack_core.h b/include/net/netfilter/nf_conntrack_core.h
index 7fdc72c01356..85634e1865c3 100644
--- a/include/net/netfilter/nf_conntrack_core.h
+++ b/include/net/netfilter/nf_conntrack_core.h
@@ -64,7 +64,7 @@ static inline int nf_conntrack_confirm(struct sk_buff **pskb)
 	int ret = NF_ACCEPT;
 
 	if (ct) {
-		if (!nf_ct_is_confirmed(ct))
+		if (!nf_ct_is_confirmed(ct) && !nf_ct_is_dying(ct))
 			ret = __nf_conntrack_confirm(pskb);
 		nf_ct_deliver_cached_events(ct);
 	}
diff --git a/net/ipv4/netfilter/ip_conntrack_core.c b/net/ipv4/netfilter/ip_conntrack_core.c
index 8556a4f4f60a..f8b3009ba66e 100644
--- a/net/ipv4/netfilter/ip_conntrack_core.c
+++ b/net/ipv4/netfilter/ip_conntrack_core.c
@@ -1242,7 +1242,7 @@ get_next_corpse(int (*iter)(struct ip_conntrack *i, void *data),
 	list_for_each_entry(h, &unconfirmed, list) {
 		ct = tuplehash_to_ctrack(h);
 		if (iter(ct, data))
-			goto found;
+			set_bit(IPS_DYING_BIT, &ct->status);
 	}
 	write_unlock_bh(&ip_conntrack_lock);
 	return NULL;
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 9b02ec4012fb..cb29ba7e206c 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1052,7 +1052,7 @@ get_next_corpse(int (*iter)(struct nf_conn *i, void *data),
 	list_for_each_entry(h, &unconfirmed, list) {
 		ct = nf_ct_tuplehash_to_ctrack(h);
 		if (iter(ct, data))
-			goto found;
+			set_bit(IPS_DYING_BIT, &ct->status);
 	}
 	write_unlock_bh(&nf_conntrack_lock);
 	return NULL;