linux-kernel - Re: [Patch 1/2] selinux: ajust rules for ATTR

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Date:	Tue, 18 Aug 2009 04:46:25 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Stephen Smalley <sds@...ho.nsa.gov>
Cc:	Amerigo Wang <amwang@...hat.com>, linux-kernel@...r.kernel.org,
	esandeen@...hat.com, eteo@...hat.com, eparis@...hat.com,
	linux-fsdevel@...r.kernel.org, akpm@...ux-foundation.org,
	viro@...iv.linux.org.uk
Subject: Re: [Patch 1/2] selinux: ajust rules for ATTR_FORCE

Stephen Smalley <sds@...ho.nsa.gov> writes:

>> [I'm still not sure what selinux want to do. normally inode_permission()
>> should check truncate() permission, and this FILE__SIZE checks something
>> again...? And we want to check FILE__WRITE for ATTR_[AMC]TIME?]
>
> Explicit setting of mode, owner, group, or timestamps is to be checked
> by the setattr permission, while implicit setting of timestamps or size
> is mediated by the write permission.

E.g. mode change has implicit ATTR_CTIME change. So it meant, we should
check the both of FILE__SETATTR and FILE__WRITE?

> ATTR_FORCE is supposed to suppress permission checking altogether, and
> shouldn't be mixed with multiple attribute changes if some should be
> subject to permission checks while others should not.

I disagree. In fact, ATTR_FORCE is just used for ATTR_KILL_S[UG]ID, and
notify_change() is disallowing the mixed ATTR_MODE and ATTR_KILL_*. I
think it should be enough.

If ATTR_FORCE is confusable, I think we can just add new ATTR_FORCE_MODE
or ATTR_FORCE_KILL, and replace with current ATTR_FORCE. I'm ok either
way.  But, with this change, ATTR_FORCE has no users.

Thanks.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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