net/smc: fix TCP fallback socket release

clcsock can be released while kernel_accept() references it in TCP
listen worker. Also, clcsock needs to wake up before released if TCP
fallback is used and the clcsock is blocked by accept. Add a lock to
safely release clcsock and call kernel_sock_shutdown() to wake up
clcsock from accept in smc_release().

Reported-by: syzbot+0bf2e01269f1274b4b03@syzkaller.appspotmail.com
Reported-by: syzbot+e3132895630f957306bc@syzkaller.appspotmail.com
Signed-off-by: Myungho Jung <mhjungk@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/smc.h

@@ -219,6 +219,10 @@ struct smc_sock {				/* smc sock container */
 						 * started, waiting for unsent
 						 * data to be sent
 						 */
+	struct mutex            clcsock_release_lock;
+						/* protects clcsock of a listen
+						 * socket
+						 * */
 };
 
 static inline struct smc_sock *smc_sk(const struct sock *sk)