linux-kernel - Re: [PATCH] x86/mm: Remove set_pages_x() and set_pages

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Message-ID: <b4fa6ab6-ab30-fc05-0f9f-93c41e7e8c79@lwfinger.net>
Date:   Wed, 18 Sep 2019 12:49:56 -0500
From:   Larry Finger <Larry.Finger@...inger.net>
To:     Christoph Hellwig <hch@....de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] x86/mm: Remove set_pages_x() and set_pages_nx()

On 9/18/19 11:45 AM, Christoph Hellwig wrote:
> On Wed, Sep 18, 2019 at 11:41:21AM -0500, Larry Finger wrote:
>> In commit 185be15143aa ("x86/mm: Remove set_pages_x() and set_pages_nx()"),
>> the wrappers were removed as they did not provide a real benefit over
>> set_memory_x() and set_memory_nx(). This change causes a problem because
>> the wrappers were exported, but the underlying routines were not. As a
>> result, external modules that used the wrappers would need to recreate
>> a significant part of memory management.
> 
> And external modules do not matter for mainline decisions.  In fact
> ensuring random modules can't mess with the NX state was one of the
> reasons for this patch, as that is a security issue waiting to happen.
> 

Christoph,

Is there approved way for pages to be set to be executable by an external module 
that would not be a security issue?

Larry