fs: sysfs: Fix reference leak in sysfs_break_active_protection()

The sysfs_break_active_protection() routine has an obvious reference
leak in its error path.  If the call to kernfs_find_and_get() fails then
kn will be NULL, so the companion sysfs_unbreak_active_protection()
routine won't get called (and would only cause an access violation by
trying to dereference kn->parent if it was called).  As a result, the
reference to kobj acquired at the start of the function will never be
released.

Fix the leak by adding an explicit kobject_put() call when kn is NULL.

Signed-off-by: Alan Stern <[email protected]>
Fixes: 2afc916 ("scsi: sysfs: Introduce sysfs_{un,}break_active_protection()")
Cc: Bart Van Assche <[email protected]>
Cc: [email protected]
Reviewed-by: Bart Van Assche <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: AlanStern

fs/sysfs/file.c

@@ -463,6 +463,8 @@ struct kernfs_node *sysfs_break_active_protection(struct kobject *kobj,
 	kn = kernfs_find_and_get(kobj->sd, attr->name);
 	if (kn)
 		kernfs_break_active_protection(kn);
+	else
+		kobject_put(kobj);
 	return kn;
 }
 EXPORT_SYMBOL_GPL(sysfs_break_active_protection);