linux-kernel - [PATCH v2] Fix "notes" kobject leak

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Date:	Tue, 23 Sep 2008 23:51:11 +0400
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Greg KH <gregkh@...e.de>
Cc:	linux-kernel@...r.kernel.org, akpm@...l.org
Subject: [PATCH v2] Fix "notes" kobject leak

> > > > --- a/kernel/module.c
> > > > +++ b/kernel/module.c
> > > > @@ -1174,6 +1174,7 @@ static void free_notes_attrs(struct module_notes_attrs *notes_attrs,
> > > >  			sysfs_remove_bin_file(notes_attrs->dir,
> > > >  					      &notes_attrs->attrs[i]);
> > > >  		kobject_del(notes_attrs->dir);
> > > > +		kobject_put(notes_attrs->dir);
> > > 
> > > Hm, no, that should just be a call to kobject_put() instead of
> > > kobject_del(), can you try that instead and see if that solves the issue
> > > (am at a conference and can't test that at the moment, sorry.)
> > 
> > Why?! kobject_del() puts parent kobject.
> 
> And that's about it (well, it also tears down the sysfs stuff.)
> 
> If you call kobject_put() instead, and it's the last put, it will also
> call kobject_del() and do everything else that it needs to do.
> 
> Try it and let me know if I'm right or not :)

OK, this works too.


[PATCH v2] Fix "notes" kobject leak

It happens every rmmod if KALLSYMS=y and SYSFS=y.

	# modprobe foo

kobject: 'foo' (ffffffffa00743d0): kobject_add_internal: parent: 'module', set: 'module'
kobject: 'holders' (ffff88017e7c5770): kobject_add_internal: parent: 'foo', set: '<NULL>'
kobject: 'foo' (ffffffffa00743d0): kobject_uevent_env
kobject: 'foo' (ffffffffa00743d0): fill_kobj_path: path = '/module/foo'
kobject: 'notes' (ffff88017fa9b668): kobject_add_internal: parent: 'foo', set: '<NULL>'
	  ^^^^^

	# rmmod foo

kobject: 'holders' (ffff88017e7c5770): kobject_cleanup
kobject: 'holders' (ffff88017e7c5770): auto cleanup kobject_del
kobject: 'holders' (ffff88017e7c5770): calling ktype release
kobject: (ffff88017e7c5770): dynamic_kobj_release
kobject: 'holders': free name
kobject: 'foo' (ffffffffa00743d0): kobject_cleanup
kobject: 'foo' (ffffffffa00743d0): does not have a release() function, it is broken and must be fixed.
kobject: 'foo' (ffffffffa00743d0): auto cleanup 'remove' event
kobject: 'foo' (ffffffffa00743d0): kobject_uevent_env
kobject: 'foo' (ffffffffa00743d0): fill_kobj_path: path = '/module/foo'
kobject: 'foo' (ffffffffa00743d0): auto cleanup kobject_del
kobject: 'foo': free name

	[whooops]

Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---

 kernel/module.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1173,7 +1173,7 @@ static void free_notes_attrs(struct module_notes_attrs *notes_attrs,
 		while (i-- > 0)
 			sysfs_remove_bin_file(notes_attrs->dir,
 					      &notes_attrs->attrs[i]);
-		kobject_del(notes_attrs->dir);
+		kobject_put(notes_attrs->dir);
 	}
 	kfree(notes_attrs);
 }
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