linux-kernel - Re: [PATCH -V6 00/26] New ACL format for better NFSv4 acl interoperability

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Date:	Mon, 12 Sep 2011 15:38:24 -0700
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	"J. Bruce Fields" <bfields@...ldses.org>
CC:	Valdis.Kletnieks@...edu,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	agruen@...nel.org, akpm@...ux-foundation.org, dhowells@...hat.com,
	linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	LSM <linux-security-module@...r.kernel.org>,
	Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH -V6 00/26] New ACL format for better NFSv4 acl interoperability

On 9/12/2011 3:20 PM, J. Bruce Fields wrote:
> On Mon, Sep 12, 2011 at 02:34:04PM -0700, Casey Schaufler wrote:
>> On 9/7/2011 5:46 PM, Valdis.Kletnieks@...edu wrote:
>>> On Mon, 05 Sep 2011 15:42:17 PDT, Casey Schaufler said:
>>>> On 9/5/2011 10:25 AM, Aneesh Kumar K.V wrote:
>>>>> The following set of patches implements VFS and ext4 changes needed to implement
>>>>> a new acl model for linux. Rich ACLs are an implementation of NFSv4 ACLs,
>>>>> extended by file( masks to fit into the standard POSIX file permission model.
>>>>> They are designed to work seamlessly locally as well as across the NFSv4 and
>>>>> CIFS/SMB2 network file system protocols.
>>>> POSIX ACLs predate the LSM and can't be done as an LSM due to
>>>> the interactions between mode bits and ACLs as defined by the
>>>> POSIX DRAFT specification.
> I don't know LSM so don't understand what you mean when you say that
> interactions between mode bits and ACLs would make an ACL model hard to
> implement as an LSM.

POSIX ACLs require that the file permission bits change when
the ACL changes. This interaction violates the strict "additional
restriction" model of the LSM.


> But in any case the rich acl/mode bit interactions are similar to the
> posix acl/mode bit interactions, so the same issue probably applies.

It would help if you knew for sure and could explain the interaction
in sufficient detail to justify the position.

>
> --b.
>

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