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

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Message-ID: <CA+55aFwXfD6vCj8sHuB33ctB-D8cfJN45h+iURXA6mR=S0mgwA@mail.gmail.com>
Date:	Wed, 30 May 2012 14:04:23 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
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 1:56 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>>
>> 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).

Don't bother with validate_mmap_request() for nommu. It's ugly, but it
does the same thing, and if it does something else, it's buggy anyway.

Generating 'prot' from 'reqprot' really *should* be as simple as what
I did in my patch. The fact that some places f*ck it up is their
problem - see for example mprotect (I think) that didn't take
MNT_NOEXEC into account.

Don't try to emulate those broken semantics. Just fix them.

                Linus
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