netfilter: ipv6: avoid nf_iterate recursion

The previous patch changed nf_ct_frag6_gather() to morph reassembled skb
with the previous one.

This means that the return value is always NULL or the skb argument.
So change it to an err value.

Instead of invoking NF_HOOK recursively with threshold to skip already-called hooks
we can now just return NF_ACCEPT to move on to the next hook except for
-EINPROGRESS (which means skb has been queued for reassembly), in which case we
return NF_STOLEN.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 5 insertions, 6 deletions

diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index cac2169..0c68c8e 100644
--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c
@@ -300,10 +300,10 @@ static int handle_fragments(struct net *net, struct sw_flow_key *key,
 			    u16 zone, struct sk_buff *skb)
 {
 	struct ovs_skb_cb ovs_cb = *OVS_CB(skb);
+	int err;
 
 	if (key->eth.type == htons(ETH_P_IP)) {
 		enum ip_defrag_users user = IP_DEFRAG_CONNTRACK_IN + zone;
-		int err;
 
 		memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
 		err = ip_defrag(net, skb, user);
@@ -314,14 +314,13 @@ static int handle_fragments(struct net *net, struct sw_flow_key *key,
 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
 	} else if (key->eth.type == htons(ETH_P_IPV6)) {
 		enum ip6_defrag_users user = IP6_DEFRAG_CONNTRACK_IN + zone;
-		struct sk_buff *reasm;
 
 		memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
-		reasm = nf_ct_frag6_gather(net, skb, user);
-		if (!reasm)
-			return -EINPROGRESS;
+		err = nf_ct_frag6_gather(net, skb, user);
+		if (err)
+			return err;
 
-		key->ip.proto = ipv6_hdr(reasm)->nexthdr;
+		key->ip.proto = ipv6_hdr(skb)->nexthdr;
 		ovs_cb.mru = IP6CB(skb)->frag_max_size;
 #endif
 	} else {