Commit e97ac128 authored Dec 08, 2015 by Florian Westphal Committed by Pablo Neira Ayuso Dec 09, 2015

netfilter: ipv6: nf_defrag: fix NULL deref panic



Valdis reports NULL deref in nf_ct_frag6_gather.
Problem is bogus use of skb_queue_walk() -- we miss first skb in the list
since we start with head->next instead of head.

In case the element we're looking for was head->next we won't find
a result and then trip over NULL iter.

(defrag uses plain NULL-terminated list rather than one terminated by
 head-of-list-pointer, which is what skb_queue_walk expects).

Fixes: 029f7f3b ("netfilter: ipv6: nf_defrag: avoid/free clone operations")
Reported-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Tested-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

parent e639f7ab

net/ipv6/netfilter/nf_conntrack_reasm.c

+8 −5

Original line number	Diff line number	Diff line
		@@ -441,12 +441,15 @@ nf_ct_frag6_reasm(struct frag_queue fq, struct sk_buff prev, struct net_devic
		return false;

		fp->next = prev->next;
		skb_queue_walk(head, iter) {
		if (iter->next != prev)
		continue;

		iter = head;
		while (iter) {
		if (iter->next == prev) {
		iter->next = fp;
		break;
		}
		iter = iter->next;
		}

		skb_morph(prev, head);
		prev->next = head->next;