tcp: do not release socket ownership in tcp_close()
syzkaller was able to hit the WARN_ON(sock_owned_by_user(sk));
in tcp_close()
While a socket is being closed, it is very possible other
threads find it in rtnetlink dump.
tcp_get_info() will acquire the socket lock for a short amount
of time (slow = lock_sock_fast(sk)/unlock_sock_fast(sk, slow);),
enough to trigger the warning.
Fixes: 67db3e4bfbc9 ("tcp: no longer hold ehash lock while calling tcp_get_info()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 2827fa5..43ef83b 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2416,16 +2416,10 @@ void tcp_close(struct sock *sk, long timeout)
sock_hold(sk);
sock_orphan(sk);
- /* It is the last release_sock in its life. It will remove backlog. */
- release_sock(sk);
-
-
- /* Now socket is owned by kernel and we acquire BH lock
- * to finish close. No need to check for user refs.
- */
local_bh_disable();
bh_lock_sock(sk);
- WARN_ON(sock_owned_by_user(sk));
+ /* remove backlog if any, without releasing ownership. */
+ __release_sock(sk);
percpu_counter_inc(sk->sk_prot->orphan_count);
@@ -2494,6 +2488,7 @@ void tcp_close(struct sock *sk, long timeout)
out:
bh_unlock_sock(sk);
local_bh_enable();
+ release_sock(sk);
sock_put(sk);
}
EXPORT_SYMBOL(tcp_close);