From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pablo Neira Ayuso Subject: [PATCH 16/23] netfilter: ipv6: nf_defrag: fix NULL deref panic Date: Fri, 18 Dec 2015 21:26:42 +0100 Message-ID: <1450470409-31427-17-git-send-email-pablo@netfilter.org> References: <1450470409-31427-1-git-send-email-pablo@netfilter.org> Cc: davem@davemloft.net, netdev@vger.kernel.org To: netfilter-devel@vger.kernel.org Return-path: In-Reply-To: <1450470409-31427-1-git-send-email-pablo@netfilter.org> Sender: netdev-owner@vger.kernel.org List-Id: netfilter-devel.vger.kernel.org From: Florian Westphal 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 912bc3a..6e5f0e0d 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); -- 2.1.4