Commit 39209673 authored Jun 07, 2019 by Eric Dumazet Committed by David S. Miller Jun 09, 2019

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 0f85feae ("tcp: fix
more NULL deref after prequeue changes"), I should have known better.

Fixes: 323a53c4 ("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>

parent e8a492cd

net/ipv6/tcp_ipv6.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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);

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