linux-kernel - Re: [PATCH v2] x86/fsgsbase/64: Fix the base write helper functions

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Message-ID: <20181101101517.GA108479@gmail.com>
Date:   Thu, 1 Nov 2018 11:15:17 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     "Chang S. Bae" <chang.seok.bae@...el.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ravi Shankar <ravi.v.shankar@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] x86/fsgsbase/64: Fix the base write helper functions


* Chang S. Bae <chang.seok.bae@...el.com> wrote:

> Factor out the code to change index from the relavant helpers. Now,
> the code is located in do_arch_prctl_64().

typo.

> 
> The helper functions that purport to write the base should just write it
> only. It shouldn't have magic optimizations to change the index.
> 
> putreg() in ptrace does not write the current task, but a stopped task.
> 
> v2: Fix further on the task write functions. Revert the changes on the
> task read helpers.
> 
> Suggested-by: Andy Lutomirski <luto@...nel.org>
> Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>

But most importantly, the changelog is confusing: please start the 
changelog with outlining the problem in an easy to digest fashion, 
starting with the highest level problem description and then successively 
iterating down towards the details.

The title says 'fix' so I suppose this fixes something, it doesn't just 
'factor out'?

Thanks,

	Ingo