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

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Message-ID: <CAHk-=wji2fMDpSwvR4U8FkKBx8=eZtg3CmWtH7hACzeHbBei8A@mail.gmail.com>
Date:   Wed, 18 Sep 2019 10:53:54 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Larry Finger <Larry.Finger@...inger.net>
Cc:     Christoph Hellwig <hch@....de>,
        Linux List Kernel Mailing <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 Wed, Sep 18, 2019 at 10:50 AM Larry Finger <Larry.Finger@...inger.net> wrote:
>
> Is there approved way for pages to be set to be executable by an external module
> that would not be a security issue?

Point to what external module and why.

Honestly, the likely answer is simply "no". Why would an external
module ever need to make something executable that isn't read-only
code? That's pretty fundamental. Marking data executable is fairly
questionable these days.

Instead, what might work is to have some higher-level concept that we
actually trust, and that isn't about making data executable, but about
doing something reasonable.

See the difference? Making things executable is not ok, but perhaps a
"alternative runtime code sequence" is ok.

                Linus