net/smc: Ensure correct state of the socket in send path

When smc_sendmsg() is called before the SMC socket initialization has
completed, smc_tx_sendmsg() will access un-initialized fields of the
SMC socket which results in a null-pointer dereference.
Fix this by checking the socket state first in smc_tx_sendmsg().

Fixes: e0e4b8f ("net/smc: Add SMC statistics support")
Reported-by: syzbot+5dda108b672b54141857@syzkaller.appspotmail.com
Reviewed-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Guvenc Gulce <guvenc@linux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/smc_tx.c

@@ -154,6 +154,9 @@ int smc_tx_sendmsg(struct smc_sock *smc, struct msghdr *msg, size_t len)
 		goto out_err;
 	}
 
+	if (sk->sk_state == SMC_INIT)
+		return -ENOTCONN;
+
 	if (len > conn->sndbuf_desc->len)
 		SMC_STAT_RMB_TX_SIZE_SMALL(smc, !conn->lnk);
 
@@ -164,8 +167,6 @@ int smc_tx_sendmsg(struct smc_sock *smc, struct msghdr *msg, size_t len)
 		SMC_STAT_INC(smc, urg_data_cnt);
 
 	while (msg_data_left(msg)) {
-		if (sk->sk_state == SMC_INIT)
-			return -ENOTCONN;
 		if (smc->sk.sk_shutdown & SEND_SHUTDOWN ||
 		    (smc->sk.sk_err == ECONNABORTED) ||
 		    conn->killed)