linux-kernel - [PATCH] fs: sysfs: Fix reference leak in sysfs_break_active

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Message-ID: <8a4d3f0f-c5e3-4b70-a188-0ca433f9e6f9@rowland.harvard.edu>
Date: Wed, 13 Mar 2024 17:43:41 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: Tejun Heo <tj@...nel.org>
Cc: Bart Van Assche <bvanassche@....org>,
  Greg KH <gregkh@...uxfoundation.org>,
  Kernel development list <linux-kernel@...r.kernel.org>
Subject: [PATCH] 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 <stern@...land.harvard.edu>
Fixes: 2afc9166f79b ("scsi: sysfs: Introduce sysfs_{un,}break_active_protection()")
Cc: Bart Van Assche <bvanassche@....org>
Cc: <stable@...r.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);