linux-kernel - Re: [PATCH 1/1] Kobject: bail early if no new_parent in kobject

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Message-ID: <20091005183753.4d77afcb@gondolin>
Date:	Mon, 5 Oct 2009 18:37:53 +0200
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Phil Carmody <ext-phil.2.carmody@...ia.com>
Cc:	gregkh@...e.de, linux-kernel@...r.kernel.org,
	Phil Carmody <ext-phil.2.carmody@...ia.com>
Subject: Re: [PATCH 1/1] Kobject: bail early if no new_parent in
 kobject_move()

On Thu,  1 Oct 2009 17:50:48 +0300,
Phil Carmody <ext-phil.2.carmody@...ia.com> wrote:

> From: Phil Carmody <ext-phil.2.carmody@...ia.com>
> 
> In the absense of kobj->kset, new_parent would remain NULL.
> NULL-dereference shenanighans then ensues in the subsequent
> sysfs_move_dir(..., new_parent) call. Bail early instead.

But sysfs_move_dir(..., NULL) should work and fall back to the sysfs
root...

<looks at code>

It seems that has been broken for some time. Should probably be
something like this instead (uncompiled); I can send it with proper
description and s-o-b once I gave it a test.

---
 fs/sysfs/dir.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- linux-2.6.orig/fs/sysfs/dir.c
+++ linux-2.6/fs/sysfs/dir.c
@@ -894,7 +894,8 @@ int sysfs_move_dir(struct kobject *kobj,
 
 	mutex_lock(&sysfs_rename_mutex);
 	BUG_ON(!sd->s_parent);
-	new_parent_sd = new_parent_kobj->sd ? new_parent_kobj->sd : &sysfs_root;
+	new_parent_sd = (new_parent_kobj && new_parent_kobj->sd) ?
+		new_parent_kobj->sd : &sysfs_root;
 
 	error = 0;
 	if (sd->s_parent == new_parent_sd)
--
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