linux-kernel - Re: [RFC][PATCH] x86: Verify access

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Message-ID: <20170119202218.GB20931@redhat.com>
Date:   Thu, 19 Jan 2017 15:22:18 -0500
From:   "Frank Ch. Eigler" <fche@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     David Smith <dsmith@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH] x86: Verify access_ok() context

Hi, Thomas -

On Thu, Jan 19, 2017 at 07:12:48PM +0100, Thomas Gleixner wrote:
> [...]
> It does matter very much, because the fact that the warning triggers tells
> me that it's placed in code which is NOT executed in task context.
> [...]
> We are not papering over problems.

Understood.  We were interpreting the comments around access_ok to
mean that the underlying hazard condition was different (stricter)
than in_task().  If the warning could be made to match that hazard
condition more precisely, then safe but non-in_task() callers can use
access_ok() without the warning.

- FChE