linux-kernel - Re: [PATCH 00/11] cross rename v3

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Date:	Tue, 14 Jan 2014 10:58:50 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:	"mszeredi@...e.cz" <mszeredi@...e.cz>, selinux@...ho.nsa.gov,
	linux-security-module@...r.kernel.org,
	Al Viro <viro@...iv.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	Zach Brown <zab@...hat.com>, Jan Kara <jack@...e.cz>,
	Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH 00/11] cross rename v3

On Mon, Jan 13, 2014 at 11:03 PM, Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
> Miklos Szeredi wrote:
>> Cross rename (A, B) is equivalent to plain rename(A, B) + plain rename
>> (B, A) done as a single atomic operation.  If security module allows
>> both then cross rename is allowed.  If at least one is denied then the
>> cross rename is denied.
>
> Yes, the functionality itself is fine. The problem is how LSM users check
> their permissions for the functionality.
>
>>
>> This is prepared for in "[PATCH 06/11] security: add flags to rename
>> hooks" and actually done in "[PATCH 07/11] vfs: add cross-rename".
>>
>> Security people are free to implement a explicit security check for
>> cross rename, but I don't think that is in the scope of this patchset.
>>
> I don't know how their permissions are checked, but I think that
> swapping /A/B and /C/D should check not only
>
>   Remove a name from directory A
>   Add a name to directory C
>
> but also
>
>   Add a name to directory A
>   Remove a name from directory C
>
> using their security labels.
>
> Without making changes to security/*/ directory, SELinux/SMACK/TOMOYO/AppArmor
> might fail to check the latter permissions.

Those permissions will be checked.   Please see security/security.c in
patch 07/11 of the series.

Of course, review is appreciated.

Thanks,
Miklos
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