net: smc: fix spurious error message from __sock_release()

Commit 67f562e3 ("net/smc: transfer fasync_list in case of fallback")
leaves the socket's fasync list pointer within a container socket as well.
When the latter is destroyed, '__sock_release()' warns about its non-empty
fasync list, which is a dangling pointer to previously freed fasync list
of an underlying TCP socket. Fix this spurious warning by nullifying
fasync list of a container socket.

Fixes: 67f562e3 ("net/smc: transfer fasync_list in case of fallback")
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/af_smc.c

@@ -924,6 +924,7 @@ static int smc_switch_to_fallback(struct smc_sock *smc, int reason_code)
 		smc->clcsock->file->private_data = smc->clcsock;
 		smc->clcsock->wq.fasync_list =
 			smc->sk.sk_socket->wq.fasync_list;
+		smc->sk.sk_socket->wq.fasync_list = NULL;
 
 		/* There might be some wait entries remaining
 		 * in smc sk->sk_wq and they should be woken up