linux-kernel - Re: [PATCH 1/1] overlayfs: apply device cgroup and security permissions to overlay files

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Date:	Sun, 29 Apr 2012 17:03:04 +0200
From:	Sedat Dilek <sedat.dilek@...glemail.com>
To:	Andy Whitcroft <apw@...onical.com>
Cc:	Miklos Szeredi <miklos@...redi.hu>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] overlayfs: apply device cgroup and security
 permissions to overlay files

On Tue, Mar 6, 2012 at 5:12 PM, Andy Whitcroft <apw@...onical.com> wrote:
> On Mon, Mar 05, 2012 at 06:18:23PM +0100, Miklos Szeredi wrote:
>> Andy Whitcroft <apw@...onical.com> writes:
>>
>> > When checking permissions on an overlayfs inode we do not take into
>> > account either device cgroup restrictions nor security permissions.
>> > This allows a user to mount an overlayfs layer over a restricted device
>> > directory and by pass those permissions to open otherwise restricted
>> > files.
>> >
>> > Use devcgroup_inode_permission() and security_inode_permission() against
>> > the underlying inodes when calculating ovl_permission().
>>
>> Andy,
>>
>> Thanks for the patch.
>>
>> __devcgroup_inode_permission() and security_inode_permission() are not
>> exported to modules, so this will not work if overlayfs is a module.
>>
>> We could export those but I think a better solution is to split out the
>> part of inode_permission() that doesn't check for a read-only fs and
>> export that.
>
> Yeah that makes much more sense.  I got caught out by some exports
> required for aufs3 which was also applied in my test environment.
>
> How about the following pair of patches?
>
> -apw
> --

Hi,

what is the status of this patch?

Ubuntu has it included in precise kernel and it fixes a security issues as well.
[1] says:
CVE-2012-0055
BugLink: http://bugs.launchpad.net/bugs/915941
BugLink: http://bugs.launchpad.net/bugs/918212

What's up with the followup (splitted) patches which should replace
this single one?
My inbox says:
[PATCH 1/2] inode_only_permission: export inode level permissions checks
[PATCH 2/2] overlayfs: switch to use inode_only_permissions

As I build OverlayFS as module those two new patches would be much appreciated.
To quote Miklos:
"__devcgroup_inode_permission() and security_inode_permission() are not
exported to modules, so this will not work if overlayfs is a module."

Thanks for any clarification in advance.

- Sedat -

[1] http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-precise.git;a=commit;h=59aa87f808b13463bc717ad69362b5372f6c5574
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