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tcp, ulp: remove socket lock assertion on ULP cleanup 

Eric reported that syzkaller triggered a splat in tcp_cleanup_ulp()
where assertion sock_owned_by_me() failed. This happened through
inet_csk_prepare_forced_close() first releasing the socket lock,
then calling into tcp_done(newsk) which is called after the
inet_csk_prepare_forced_close() and therefore without the socket
lock held. The sock_owned_by_me() assertion can generally be
removed as the only place where tcp_cleanup_ulp() is called from
now is out of inet_csk_destroy_sock() -> sk->sk_prot->destroy()
where socket is in dead state and unreachable. Therefore, add a
comment why the check is not needed instead.

Fixes: 8b9088f806 ("tcp, ulp: enforce sock_owned_by_me upon ulp init and cleanup")
Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann 2018-10-16 21:31:35 +02:00 committed by David S. Miller
parent 29ce85f349
commit aadd435591
1 changed files with 4 additions and 2 deletions
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6
net/ipv4/tcp_ulp.c
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@ -99,8 +99,10 @@ void tcp_cleanup_ulp(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
sock_owned_by_me(sk);
/* No sock_owned_by_me() check here as at the time the
* stack calls this function, the socket is dead and
* about to be destroyed.
*/
if (!icsk->icsk_ulp_ops)
return;