From: Florian Westphal Date: Tue, 29 Nov 2016 01:17:34 +0000 (+0100) Subject: netfilter: ipv6: nf_defrag: drop mangled skb on ream error X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=9b57da0630c9fd36ed7a20fc0f98dc82cc0777fa;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git netfilter: ipv6: nf_defrag: drop mangled skb on ream error Dmitry Vyukov reported GPF in network stack that Andrey traced down to negative nh offset in nf_ct_frag6_queue(). Problem is that all network headers before fragment header are pulled. Normal ipv6 reassembly will drop the skb when errors occur further down the line. netfilter doesn't do this, and instead passed the original fragment along. That was also fine back when netfilter ipv6 defrag worked with cloned fragments, as the original, pristine fragment was passed on. So we either have to undo the pull op, or discard such fragments. Since they're malformed after all (e.g. overlapping fragment) it seems preferrable to just drop them. Same for temporary errors -- it doesn't make sense to accept (and perhaps forward!) only some fragments of same datagram. Fixes: 029f7f3b8701cc7ac ("netfilter: ipv6: nf_defrag: avoid/free clone operations") Reported-by: Dmitry Vyukov Debugged-by: Andrey Konovalov Diagnosed-by: Eric Dumazet Signed-off-by: Florian Westphal Acked-by: Eric Dumazet Signed-off-by: Pablo Neira Ayuso --- diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c b/net/ipv6/netfilter/nf_conntrack_reasm.c index e4347aeb2e65..9948b5ce52da 100644 --- a/net/ipv6/netfilter/nf_conntrack_reasm.c +++ b/net/ipv6/netfilter/nf_conntrack_reasm.c @@ -576,11 +576,11 @@ int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user) /* Jumbo payload inhibits frag. header */ if (ipv6_hdr(skb)->payload_len == 0) { pr_debug("payload len = 0\n"); - return -EINVAL; + return 0; } if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0) - return -EINVAL; + return 0; if (!pskb_may_pull(skb, fhoff + sizeof(*fhdr))) return -ENOMEM; diff --git a/net/ipv6/netfilter/nf_defrag_ipv6_hooks.c b/net/ipv6/netfilter/nf_defrag_ipv6_hooks.c index f7aab5ab93a5..f06b0471f39f 100644 --- a/net/ipv6/netfilter/nf_defrag_ipv6_hooks.c +++ b/net/ipv6/netfilter/nf_defrag_ipv6_hooks.c @@ -69,7 +69,7 @@ static unsigned int ipv6_defrag(void *priv, if (err == -EINPROGRESS) return NF_STOLEN; - return NF_ACCEPT; + return err == 0 ? NF_ACCEPT : NF_DROP; } static struct nf_hook_ops ipv6_defrag_ops[] = {