From e97ac12859dbf4d3ee0eddb9798867541d1d1e1e Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Tue, 8 Dec 2015 23:35:19 +0100 Subject: [PATCH] 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: 029f7f3b8701cc7a ("netfilter: ipv6: nf_defrag: avoid/free clone operations") Reported-by: Valdis Kletnieks Tested-by: Valdis Kletnieks Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/ipv6/netfilter/nf_conntrack_reasm.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c b/net/ipv6/netfilter/nf_conntrack_reasm.c index 912bc3afc183..6e5f0e0d49e0 100644 --- a/net/ipv6/netfilter/nf_conntrack_reasm.c +++ b/net/ipv6/netfilter/nf_conntrack_reasm.c @@ -441,11 +441,14 @@ 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->next = fp; - break; + + iter = head; + while (iter) { + if (iter->next == prev) { + iter->next = fp; + break; + } + iter = iter->next; } skb_morph(prev, head); -- 2.20.1