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Date: Fri, 26 Oct 2007 21:33:37 +0100
From: Al Viro <viro@ftp.linux.org.uk>
To: John Johansen <jjohansen@suse.de>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
       linux-security-module@vger.kernel.org, Tony Jones <tonyj@suse.de>,
       Andreas Gruenbacher <agruen@suse.de>
Subject: Re: [AppArmor 19/45] Add struct vfsmount parameters to vfs_rename()
Message-ID: <20071026203337.GF8181@ftp.linux.org.uk>
References: <20071026064024.243943043@suse.de> <20071026064049.534093497@suse.de> <20071026073749.GE8181@ftp.linux.org.uk> <20071026182352.GA32415@suse.de>
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On Fri, Oct 26, 2007 at 11:23:53AM -0700, John Johansen wrote:

> In the current code, both vfsmounts are always identical, and so one of
> the two should go, agreed.
> 
> The thought behind passing both vfsmounts was that they could differ but
> point to the same super_block, in which case renames would still be
> possible at least from a filesystem point of view. The essential
> restriction here is that both files must be on the same device; the vfs
> restriction of not allowing cross-mount renames is arbitrary.

It's called "access control".  Pathname-based one, BTW.  And yes, it's
100% deliberate.

> Cross-mount renames are not allowed currently, and granted, they may not
> be very useful, either.

<raised brows>
Excuse me, but IIRC LSM was supposed to _add_ restrictions, not to remove
existing security checks.
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