netfilter: ipv6: nf_defrag: drop skb dst before queueing
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: NEric Dumazet <eric.dumazet@gmail.com> Reported-by: NJohn Sperbeck <jsperbeck@google.com> Signed-off-by: NFlorian Westphal <fw@strlen.de> Tested-by: NEric Dumazet <edumazet@google.com> Reported-by: Nsyzbot <syzkaller@googlegroups.com> Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>
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