netfilter: conntrack: re-fetch conntrack after insertion

commit 56b14ecec97f39118bf85c9ac2438c5a949509ed upstream. In case the conntrack is clashing, insertion can free skb->_nfct and set skb->_nfct to the already-confirmed entry. This wasn't found before because the conntrack entry and the extension space used to free'd after an rcu grace period, plus the race needs events enabled to trigger. Reported-by: <[email protected]> Fixes: 71d8c47 ("netfilter: conntrack: introduce clash resolution on insertion race") Fixes: 2ad9d7747c10 ("netfilter: conntrack: free extension area immediately") Signed-off-by: Florian Westphal <[email protected]> Signed-off-by: Pablo Neira Ayuso <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
javashin · Jun 6, 2022 · 92a999d · 92a999d
1 parent b50fb8d
commit 92a999d
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/include/net/netfilter/nf_conntrack_core.h b/include/net/netfilter/nf_conntrack_core.h
@@ -58,8 +58,13 @@ static inline int nf_conntrack_confirm(struct sk_buff *skb)
 	int ret = NF_ACCEPT;
 
 	if (ct) {
-		if (!nf_ct_is_confirmed(ct))
+		if (!nf_ct_is_confirmed(ct)) {
 			ret = __nf_conntrack_confirm(skb);
+
+			if (ret == NF_ACCEPT)
+				ct = (struct nf_conn *)skb_nfct(skb);
+		}
+
 		if (likely(ret == NF_ACCEPT))
 			nf_ct_deliver_cached_events(ct);
 	}