[PATCH v2 15/16] scsi: utilize new cdev_device_add helper function

Logan Gunthorpe
2017-02-26T06:38:16Z

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-OTvnGxWRz7hWk0Htik3J/w@public.gmane.org>
---
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 243eab3..66b8805 100644
--- a/drivers/scsi/osd/osd_uld.c
+++ b/drivers/scsi/osd/osd_uld.c
@@ -399,9 +399,6 @@ 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);

@@ -410,7 +407,6 @@ static void __remove(struct device *dev)

if (oud->disk)
put_disk(oud->disk);
- ida_remove(&osd_minor_ida, oud->minor);

kfree(oud);
}
@@ -445,8 +441,20 @@ 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 */
@@ -460,59 +468,34 @@ 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;
@@ -529,9 +512,10 @@ 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