On Fri, Dec 17, 2021 at 07:37:43PM +0900, Tetsuo Handa wrote:
> I think we can apply this patch as-is...
Unfortunately I don't think so, don't we end up still with a race
in between the first part of device_add() and the kobject_add()
which adds the kobject to generic layer and in return enables the
disk_release() call for the disk? I count 5 error paths in between
including kobject_add() which can fail as well.
If correct then something like the following may be needed:
diff --git a/block/genhd.c b/block/genhd.c
index 3c139a1b6f04..08ab7ce63e57 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -539,9 +539,10 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
out_device_del:
device_del(ddev);
out_disk_release_events:
- disk_release_events(disk);
+ if (!kobject_alive(&ddev->kobj))
+ disk_release_events(disk);
out_free_ext_minor:
- if (disk->major == BLOCK_EXT_MAJOR)
+ if (!kobject_alive(&ddev->kobj) && disk->major == BLOCK_EXT_MAJOR)
blk_free_ext_minor(disk->first_minor);
return ret;
}
diff --git a/include/linux/kobject.h b/include/linux/kobject.h
index c740062b4b1a..4884aedbd4e0 100644
--- a/include/linux/kobject.h
+++ b/include/linux/kobject.h
@@ -117,6 +117,23 @@ extern void kobject_get_ownership(struct kobject *kobj,
kuid_t *uid, kgid_t *gid);
extern char *kobject_get_path(struct kobject *kobj, gfp_t flag);
+/**
+ * kobject_alive - Returns whether a kobject_add() has succeeded
+ * @kobj: the object to test
+ *
+ * This will return whether a kobject has been successfully added already with
+ * kobject_add(). It is useful for subsystems which have a kobj_type with its
+ * own kobj_type release() routine and want to verify that it will be called
+ * as otherwise if kobject_add() failed the subsystem is in charge of doing that
+ * cleanup.
+ */
+static inline bool kobject_alive(struct kobject *kobj)
+{
+ if (!kobj || kref_read(&kobj->kref) == 0)
+ return false;
+ return true;
+}
+
/**
* kobject_has_children - Returns whether a kobject has children.
* @kobj: the object to test
