linux-kernel - Re: OOPS in configfs when doing d

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Message-ID: <4D6242AD.2090600@suse.cz>
Date:	Mon, 21 Feb 2011 11:47:09 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	jlbec@...lplan.org
CC:	npiggin@...nel.dk, Al Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jirislaby@...il.com>
Subject: Re: OOPS in configfs when doing d_delete

On 02/21/2011 11:44 AM, Joel Becker wrote:
> On Mon, Feb 21, 2011 at 11:20:18AM +0100, Jiri Slaby wrote:
>> when configfs_attach_group fails in configfs_register_subsystem:
>>         dentry = d_alloc(configfs_sb->s_root, &name);
>>         if (dentry) {
>>                 d_add(dentry, NULL);
>>
>>                 err = configfs_attach_group(sd->s_element, &group->cg_item,
>>                                             dentry);
>>                 if (err) {
>>                         d_delete(dentry);
>>                         dput(dentry);
>>
>>
>> d_delete kills the kernel. I don't know what the actual bug is here, but
>> d_delete looks broken anyway:
>>         spin_lock(&dentry->d_lock);
>>         inode = dentry->d_inode;
>>         isdir = S_ISDIR(inode->i_mode);  <======== dereference
>>         if (dentry->d_count == 1) {
>>                 if (inode && !spin_trylock(&inode->i_lock)) {
>>                     ^^^^^  <============= test
>>
>> It seems like a superfluous test, not a potential null dereference to
>> me, right?
> 
> 	I think you're right about the superfluous test, but I need more
> investigation to see what's going on.  Thanks for the report.
> 	What was causing attach_group() to fail?  Do you know?

Dunno, I just modprobe'd the configfs example from Doc dir
(configfs_example_macros).

regards,
-- 
js
suse labs
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