linux-kernel - Re: use after free in sysfs_find

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Message-ID: <20130320171756.GA28605@kroah.com>
Date:	Wed, 20 Mar 2013 10:17:56 -0700
From:	Greg Kroah-Hartman <greg@...ah.com>
To:	Sasha Levin <levinsasha928@...il.com>
Cc:	Ming Lei <tom.leiming@...il.com>, Hillf Danton <dhillf@...il.com>,
	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: use after free in sysfs_find_dirent

On Wed, Mar 20, 2013 at 10:34:40AM -0400, Sasha Levin wrote:
> 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 for testing, and thanks Ming, for finding and fixing this.

greg k-h
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