Re: use after free in sysfs_find_dirent

From: Ming Lei
Date: Tue Mar 19 2013 - 21:02:21 EST

Hi Sasha,

On Wed, Mar 20, 2013 at 12:28 AM, Sasha Levin <levinsasha928@xxxxxxxxx> 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.

Ming Lei

Attachment: sysfs-fix-readdir-v4.patch
Description: Binary data