net/smc: hold conns_lock before calling smc_lgr_register_conn()

After smc_lgr_create(), the newly created link group is added
to smc_lgr_list, thus is accessible from other context.
Although link group creation is serialized by
smc_create_lgr_pending, the new link group may still be accessed
concurrently. For example, if ib_device is no longer active,
smc_ib_port_event_work() will call smc_port_terminate(), which
in turn will call __smc_lgr_terminate() on every link group of
this device. So conns_lock is required here.
Signed-off-by: Huaping Zhou <zhp@smail.nju.edu.cn>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/smc_core.c

@@ -652,7 +652,10 @@ int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini)
 		rc = smc_lgr_create(smc, ini);
 		if (rc)
 			goto out;
+		lgr = conn->lgr;
+		write_lock_bh(&lgr->conns_lock);
 		smc_lgr_register_conn(conn); /* add smc conn to lgr */
+		write_unlock_bh(&lgr->conns_lock);
 	}
 	conn->local_tx_ctrl.common.type = SMC_CDC_MSG_TYPE;
 	conn->local_tx_ctrl.len = SMC_WR_TX_SIZE;