linux-kernel - Re: use after free in sysfs_find

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Message-ID: <CACVXFVN8EDMgHyshxX41er463rMsbUSrzs9pX17NdDg4PVHSvw@mail.gmail.com>
Date:	Wed, 20 Mar 2013 09:02:15 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Sasha Levin <levinsasha928@...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

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.

Thanks,
-- 
Ming Lei

Download attachment "sysfs-fix-readdir-v4.patch" of type "application/octet-stream" (2220 bytes)