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tcp: fix a possible lockdep splat in tcp_done() 

syzbot found that if __inet_inherit_port() returns an error,
we call tcp_done() after inet_csk_prepare_forced_close(),
meaning the socket lock is no longer held.

We might fix this in a different way in net-next, but
for 5.4 it seems safer to relax the lockdep check.

Fixes: d983ea6f16 ("tcp: add rcu protection around tp->fastopen_rsk")
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 2019-10-14 06:47:57 -07:00 committed by David S. Miller
parent c9b96eb6da
commit cab209e571
1 changed files with 6 additions and 2 deletions
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8
net/ipv4/tcp.c
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@ -3842,8 +3842,12 @@ void tcp_done(struct sock *sk)
{
struct request_sock *req;
req = rcu_dereference_protected(tcp_sk(sk)->fastopen_rsk,
lockdep_sock_is_held(sk));
/* We might be called with a new socket, after
* inet_csk_prepare_forced_close() has been called
* so we can not use lockdep_sock_is_held(sk)
*/
req = rcu_dereference_protected(tcp_sk(sk)->fastopen_rsk, 1);
if (sk->sk_state == TCP_SYN_SENT || sk->sk_state == TCP_SYN_RECV)
TCP_INC_STATS(sock_net(sk), TCP_MIB_ATTEMPTFAILS);