[overlayfs] Fixes against ubuntu-quantal.git#master-next

Sedat Dilek sedat.dilek at googlemail.com
Mon Apr 30 13:54:12 UTC 2012

On Mon, Apr 30, 2012 at 2:28 PM, Andy Whitcroft <apw at canonical.com> wrote:
> On Sat, Apr 28, 2012 at 04:55:13PM +0200, Sedat Dilek wrote:
>> On Sat, Apr 28, 2012 at 2:49 PM, Sedat Dilek <sedat.dilek at googlemail.com> wrote:
>> > On Sat, Apr 28, 2012 at 1:59 PM, Sedat Dilek <sedat.dilek at googlemail.com> wrote:
>> >> Hi,
>> >>
>> >> I wanted to play with OverlayFS against Linux-3.4-rc4.
>> >>
>> >> As Ubuntu kernel-team has rebased it in ubuntu-quantal.git#master-next.
>> >> I made my life easy and took this repo as base for my fixes (or trying to fix).
> The version applied to Ubuntu Precise was a backported version of the
> upstream v12 branch.  So I suspect much of the issues are coming from
> that being a backported version.  For Ubuntu Quantal I have reverted
> what we had and pulled a clean v12 plus the security fix we had on top.
> I have then applied similar fixes to pull that forward to v3.4-rc4 and
> it seems to pass very light touch testing here:
>  http://git.kernel.org/?p=linux/kernel/git/apw/overlayfs.git;a=shortlog;h=refs/heads/overlayfs.v12apw1
> I am pushing it out for perusal as people are asking me about it.  This
> includes an updated permissions fix.
> -apw

[ CC Jordi Pojol ]

Hi Andy,

thanks for updating the OverlayFS-v12 patchset!

Looks like my d_make_root() fix was not complete :-(.
Reverting mine and using yours helped me to run OverlayFS ***w/o***
crashes or call-traces.

Patches applied on top of Linux v3.4-rc5:
1. 100-overlayfs_v12.patch (OpenWrt)
2. my include-fix (should be the same like the one from apw)
3. my touch_atime-fix (same as apw has)
4. d_make_root-fix from quantal (by apw)

I tested OverlayFS with a modified test06.sh script from Jordi Pojol
(testcase-script attached, see [2]).

You will need "[PATCH] fs: Increase limit filesystem stacking depth to
3" to run it successfully (patch attached).

Without it you will see in dmesg:
[  476.709418] overlayfs: maximum fs stacking depth exceeded

Depth "2" was defined in "fs: limit filesystem stacking depth" patch
from Miklos.
Not sure if I can loosen that a bit (security issue?).
Jordy told me in private conversation he has dropped that patch completely.

I will re-test with Andy's "overlayfs.v12apw1" GIT branch [3] (pulled
into Linux v3.4-rc5).

Hope this helps other users and developers.

- Sedat -

[1] https://dev.openwrt.org/browser/trunk/target/linux/generic/patches-3.3/100-overlayfs_v12.patch
[2] http://livenet.selfip.com/ftp/debian/overlayfs/test/test06.sh
[3] http://git.kernel.org/?p=linux/kernel/git/apw/overlayfs.git;a=shortlog;h=refs/heads/overlayfs.v12apw1
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