linux-kernel - Re: use after free in sysfs_find

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Message-ID: <5149C900.6020709@gmail.com>
Date:	Wed, 20 Mar 2013 10:34:40 -0400
From:	Sasha Levin <levinsasha928@...il.com>
To:	Ming Lei <tom.leiming@...il.com>
CC:	Hillf Danton <dhillf@...il.com>, Dave Jones <davej@...hat.com>,
	Greg Kroah-Hartman <greg@...ah.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: use after free in sysfs_find_dirent

On 03/19/2013 09:02 PM, Ming Lei wrote:
> Hi Sasha,
> 
> On Wed, Mar 20, 2013 at 12:28 AM, Sasha Levin <levinsasha928@...il.com> wrote:
>> On 03/19/2013 07:54 AM, Ming Lei wrote:
>>
>> With v3 of the patch:
>>
>> [ 1275.665758] sysfs_dir_pos-973 sysfs_dirent use after free: tun(tun)-uevent, 2-1472641949
> 
> Thanks again for your test.
> 
> Looks it is caused by another bug in sysfs_readdir:  if filldir() returns
> failure(such as small buffer length passed from userspace, very probably
> for trinity) in case of 'if (filp->f_pos ==  0 or 1)',
> filp->private_data still will
> point to one refcount-balanced sysfs_dirent object.
> 
> V4 adds fix for this situation, please test attachment v4 patch.

With this one it didn't happen at all during overnight tests so looks like it did
the job.

Thanks!

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