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 <stern@rowland.harvard.edu>
Fixes: 2afc9166f79b ("scsi: sysfs: Introduce sysfs_{un,}break_active_protection()")
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: <stable@vger.kernel.org>

---

 fs/sysfs/file.c |    2 ++
 1 file changed, 2 insertions(+)

Index: usb-devel/fs/sysfs/file.c
===================================================================
--- usb-devel.orig/fs/sysfs/file.c
+++ usb-devel/fs/sysfs/file.c
@@ -463,6 +463,8 @@ struct kernfs_node *sysfs_break_active_p
 	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);

On 3/13/24 14:43, Alan Stern wrote:
> 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.

Reviewed-by: Bart Van Assche <bvanassche@acm.org>

On Wed, Mar 13, 2024 at 05:43:41PM -0400, Alan Stern wrote:
> 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 <stern@rowland.harvard.edu>
> Fixes: 2afc9166f79b ("scsi: sysfs: Introduce sysfs_{un,}break_active_protection()")
> Cc: Bart Van Assche <bvanassche@acm.org>
> Cc: <stable@vger.kernel.org>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun