linux-kernel - Re: [PATCH] vfs: fix IMA lockdep circular locking dependency

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Message-ID: <20120530205612.GY11775@ZenIV.linux.org.uk>
Date:	Wed, 30 May 2012 21:56:13 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Eric Paris <eparis@...isplace.org>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Mimi Zohar <zohar@...ibm.com>,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vfs: fix IMA lockdep circular locking dependency

On Wed, May 30, 2012 at 01:28:09PM -0700, Linus Torvalds wrote:
> On Wed, May 30, 2012 at 1:24 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> > On Wed, May 30, 2012 at 03:42:47PM -0400, Eric Paris wrote:
> >> security_file_mmap() would pretty much only be used in do_mmap_pgoff()
> >> (or validate_mmap_request)
> >
> > Callers, actually - the whole point is to lift it out of under ->mmap_sem.
> > The tricky part is reqprot vs. prot mess.
> 
> See how I solved reqprot vs prot in my suggested original patch. You
> have it somewhere in your inbox, I know, because you called me out on
> the fact that my original email forgot to attach it ;)
> 
> It actually cleaned things up, and made the calling conventions
> simpler. Just always pass in "reqprot", and have the security layer do
> the trivial "calculate final prot".

If only it would be trivial ;-/  Take a look at !MMU case (or at the
description in the posting upthread if you want to avoid seeing your
breakfast one more time - the code in validate_mmap_request() is
really ugly).
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