| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.17 074/101] netfilter: ipv6: nf_defrag: drop skb dst before queueing | Date | Fri, 20 Jul 2018 14:14:20 +0200 |
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4.17-stable review patch. If anyone has any objections, please let me know.
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From: Florian Westphal <fw@strlen.de>
commit 84379c9afe011020e797e3f50a662b08a6355dcf upstream.
Eric Dumazet reports: Here is a reproducer of an annoying bug detected by syzkaller on our production kernel [..] ./b78305423 enable_conntrack Then : sleep 60 dmesg | tail -10 [ 171.599093] unregister_netdevice: waiting for lo to become free. Usage count = 2 [ 181.631024] unregister_netdevice: waiting for lo to become free. Usage count = 2 [ 191.687076] unregister_netdevice: waiting for lo to become free. Usage count = 2 [ 201.703037] unregister_netdevice: waiting for lo to become free. Usage count = 2 [ 211.711072] unregister_netdevice: waiting for lo to become free. Usage count = 2 [ 221.959070] unregister_netdevice: waiting for lo to become free. Usage count = 2
Reproducer sends ipv6 fragment that hits nfct defrag via LOCAL_OUT hook. skb gets queued until frag timer expiry -- 1 minute.
Normally nf_conntrack_reasm gets called during prerouting, so skb has no dst yet which might explain why this wasn't spotted earlier.
Reported-by: Eric Dumazet <eric.dumazet@gmail.com> Reported-by: John Sperbeck <jsperbeck@google.com> Signed-off-by: Florian Westphal <fw@strlen.de> Tested-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- net/ipv6/netfilter/nf_conntrack_reasm.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/net/ipv6/netfilter/nf_conntrack_reasm.c +++ b/net/ipv6/netfilter/nf_conntrack_reasm.c @@ -585,6 +585,8 @@ int nf_ct_frag6_gather(struct net *net, fq->q.meat == fq->q.len && nf_ct_frag6_reasm(fq, skb, dev)) ret = 0; + else + skb_dst_drop(skb); out_unlock: spin_unlock_bh(&fq->q.lock);
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