nvme-tcp: don't access released socket during error recovery

While the error recovery work is temporarily failing reconnect attempts,
running the 'nvme list' command causes a kernel NULL pointer dereference
by calling getsockname() with a released socket.

During error recovery work, the nvme tcp socket is released and a new one
created, so it is not safe to access the socket without proper check.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Fixes: 02c57a8 ("nvme-tcp: print actual source IP address through sysfs "address" attr")
Reviewed-by: Martin Belanger <martin.belanger@dell.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/tcp.c

@@ -2489,13 +2489,19 @@ static int nvme_tcp_get_address(struct nvme_ctrl *ctrl, char *buf, int size)
 
 	len = nvmf_get_address(ctrl, buf, size);
 
+	mutex_lock(&queue->queue_lock);
+
+	if (!test_bit(NVME_TCP_Q_LIVE, &queue->flags))
+		goto done;
 	ret = kernel_getsockname(queue->sock, (struct sockaddr *)&src_addr);
 	if (ret > 0) {
 		if (len > 0)
 			len--; /* strip trailing newline */
 		len += scnprintf(buf + len, size - len, "%ssrc_addr=%pISc\n",
 				(len) ? "," : "", &src_addr);
 	}
+done:
+	mutex_unlock(&queue->queue_lock);
 
 	return len;
 }