[PATCH v5 15/16] scsi: utilize new cdev_device_add helper function

[Logan Gunthorpe]

This driver did not set kobj.parent so it likely suffered from
a potential use after free race if the user unregistered the
device while it was in use.

This was not so straightforward a conversion but I think this patch
cleans up its probe's error path significantly.

This patch adds device_initialize, which is required for
cdev_device_add. Then it switches to put_device instead of kfree as
recommended by device_initialize's documentation. This removes a lot
from the error path which was already in __remove.
A couple things needed to be re-ordered to be entirely correct, though.
ida_remove is also moved out of __remove and into unregister to
simplify things and follow the pattern other devices are using.

This also drop an extra unnecessary get_device/put_device in the code.

Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
---
 drivers/scsi/osd/osd_uld.c | 56 +++++++++++++++++-----------------------------
 1 file changed, 20 insertions(+), 36 deletions(-)

diff --git a/drivers/scsi/osd/osd_uld.c b/drivers/scsi/osd/osd_uld.c
index e0ce5d2..4101c31 100644
--- a/drivers/scsi/osd/osd_uld.c
+++ b/drivers/scsi/osd/osd_uld.c
@@ -400,9 +400,6 @@ static void __remove(struct device *dev)
 
 	kfree(oud->odi.osdname);
 
-	if (oud->cdev.owner)
-		cdev_del(&oud->cdev);
-
 	osd_dev_fini(&oud->od);
 	scsi_device_put(scsi_device);
 
@@ -411,7 +408,6 @@ static void __remove(struct device *dev)
 
 	if (oud->disk)
 		put_disk(oud->disk);
-	ida_remove(&osd_minor_ida, oud->minor);
 
 	kfree(oud);
 }
@@ -446,8 +442,20 @@ static int osd_probe(struct device *dev)
 	if (NULL == oud)
 		goto err_retract_minor;
 
+	/* class device member */
+	device_initialize(&oud->class_dev);
 	dev_set_drvdata(dev, oud);
 	oud->minor = minor;
+	oud->class_dev.devt = MKDEV(SCSI_OSD_MAJOR, oud->minor);
+	oud->class_dev.class = &osd_uld_class;
+	oud->class_dev.parent = dev;
+	oud->class_dev.release = __remove;
+
+	/* hold one more reference to the scsi_device that will get released
+	 * in __release, in case a logout is happening while fs is mounted
+	 */
+	scsi_device_get(scsi_device);
+	osd_dev_init(&oud->od, scsi_device);
 
 	/* allocate a disk and set it up */
 	/* FIXME: do we need this since sg has already done that */
@@ -461,59 +469,34 @@ static int osd_probe(struct device *dev)
 	sprintf(disk->disk_name, "osd%d", oud->minor);
 	oud->disk = disk;
 
-	/* hold one more reference to the scsi_device that will get released
-	 * in __release, in case a logout is happening while fs is mounted
-	 */
-	scsi_device_get(scsi_device);
-	osd_dev_init(&oud->od, scsi_device);
-
 	/* Detect the OSD Version */
 	error = __detect_osd(oud);
 	if (error) {
 		OSD_ERR("osd detection failed, non-compatible OSD device\n");
-		goto err_put_disk;
+		goto err_free_osd;
 	}
 
 	/* init the char-device for communication with user-mode */
 	cdev_init(&oud->cdev, &osd_fops);
 	oud->cdev.owner = THIS_MODULE;
-	error = cdev_add(&oud->cdev,
-			 MKDEV(SCSI_OSD_MAJOR, oud->minor), 1);
-	if (error) {
-		OSD_ERR("cdev_add failed\n");
-		goto err_put_disk;
-	}
 
-	/* class device member */
-	oud->class_dev.devt = oud->cdev.dev;
-	oud->class_dev.class = &osd_uld_class;
-	oud->class_dev.parent = dev;
-	oud->class_dev.release = __remove;
 	error = dev_set_name(&oud->class_dev, "%s", disk->disk_name);
 	if (error) {
 		OSD_ERR("dev_set_name failed => %d\n", error);
-		goto err_put_cdev;
+		goto err_free_osd;
 	}
 
-	error = device_register(&oud->class_dev);
+	error = cdev_device_add(&oud->cdev, &oud->class_dev);
 	if (error) {
 		OSD_ERR("device_register failed => %d\n", error);
-		goto err_put_cdev;
+		goto err_free_osd;
 	}
 
-	get_device(&oud->class_dev);
-
 	OSD_INFO("osd_probe %s\n", disk->disk_name);
 	return 0;
 
-err_put_cdev:
-	cdev_del(&oud->cdev);
-err_put_disk:
-	scsi_device_put(scsi_device);
-	put_disk(disk);
 err_free_osd:
-	dev_set_drvdata(dev, NULL);
-	kfree(oud);
+	put_device(&oud->class_dev);
 err_retract_minor:
 	ida_remove(&osd_minor_ida, minor);
 	return error;
@@ -530,9 +513,10 @@ static int osd_remove(struct device *dev)
 			scsi_device);
 	}
 
-	device_unregister(&oud->class_dev);
-
+	cdev_device_del(&oud->cdev, &oud->class_dev);
+	ida_remove(&osd_minor_ida, oud->minor);
 	put_device(&oud->class_dev);
+
 	return 0;
 }
 
-- 
2.1.4