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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: 029f7f3b87 ("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>
This commit is contained in:
Florian Westphal 2015-12-08 23:35:19 +01:00 committed by Pablo Neira Ayuso
parent e639f7ab07
commit e97ac12859
1 changed files with 8 additions and 5 deletions
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9
net/ipv6/netfilter/nf_conntrack_reasm.c
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@ -441,12 +441,15 @@ nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *prev, struct net_devic
return false; return false;
fp->next = prev->next; fp->next = prev->next;
skb_queue_walk(head, iter) {
if (iter->next != prev) iter = head;
continue; while (iter) {
if (iter->next == prev) {
iter->next = fp; iter->next = fp;
break; break;
} }
iter = iter->next;
}
skb_morph(prev, head); skb_morph(prev, head);
prev->next = head->next; prev->next = head->next;