scsi: core: Fix error handling of scsi_host_alloc()

After device is initialized via device_initialize(), or its name is set via
dev_set_name(), the device has to be freed via put_device().  Otherwise
device name will be leaked because it is allocated dynamically in
dev_set_name().

Fix the leak by replacing kfree() with put_device(). Since
scsi_host_dev_release() properly handles IDA and kthread removal, remove
special-casing these from the error handling as well.

Link: https://lore.kernel.org/r/20210602133029.2864069-2-ming.lei@redhat.com
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Hannes Reinecke <hare@suse.de>
Tested-by: John Garry <john.garry@huawei.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: John Garry <john.garry@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/hosts.c

@@ -388,8 +388,10 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 	mutex_init(&shost->scan_mutex);
 
 	index = ida_simple_get(&host_index_ida, 0, 0, GFP_KERNEL);
-	if (index < 0)
-		goto fail_kfree;
+	if (index < 0) {
+		kfree(shost);
+		return NULL;
+	}
 	shost->host_no = index;
 
 	shost->dma_channel = 0xff;
@@ -481,7 +483,7 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 		shost_printk(KERN_WARNING, shost,
 			"error handler thread failed to spawn, error = %ld\n",
 			PTR_ERR(shost->ehandler));
-		goto fail_index_remove;
+		goto fail;
 	}
 
 	shost->tmf_work_q = alloc_workqueue("scsi_tmf_%d",
@@ -490,17 +492,18 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 	if (!shost->tmf_work_q) {
 		shost_printk(KERN_WARNING, shost,
 			     "failed to create tmf workq\n");
-		goto fail_kthread;
+		goto fail;
 	}
 	scsi_proc_hostdir_add(shost->hostt);
 	return shost;
+ fail:
+	/*
+	 * Host state is still SHOST_CREATED and that is enough to release
+	 * ->shost_gendev. scsi_host_dev_release() will free
+	 * dev_name(&shost->shost_dev).
+	 */
+	put_device(&shost->shost_gendev);
 
- fail_kthread:
-	kthread_stop(shost->ehandler);
- fail_index_remove:
-	ida_simple_remove(&host_index_ida, shost->host_no);
- fail_kfree:
-	kfree(shost);
 	return NULL;
 }
 EXPORT_SYMBOL(scsi_host_alloc);