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ipv6: tcp: fix potential NULL deref in tcp_v6_send_reset() 

syzbot found a crash in tcp_v6_send_reset() caused by my latest
change.

Problem is that if an skb has been queued to socket prequeue,
skb_dst(skb)->dev can not anymore point to the device.

Fortunately in this case the socket pointer is not NULL.

A similar issue has been fixed in commit 0f85feae6b ("tcp: fix
more NULL deref after prequeue changes"), I should have known better.

Fixes: 323a53c412 ("ipv6: tcp: enable flowlabel reflection in some RST packets")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2019-06-07 12:23:48 -07:00 committed by David S. Miller
parent e8a492cd53
commit 392096736a
1 changed files with 1 additions and 1 deletions
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2
net/ipv6/tcp_ipv6.c
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@ -934,7 +934,7 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
if (!sk && !ipv6_unicast_destination(skb))
return;
net = dev_net(skb_dst(skb)->dev);
net = sk ? sock_net(sk) : dev_net(skb_dst(skb)->dev);
#ifdef CONFIG_TCP_MD5SIG
rcu_read_lock();
hash_location = tcp_parse_md5sig_option(th);