linux-kernel - Re: [PATCH v4 54/57] x86/mm: convert arch_within_stack

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Message-ID: <CAGXu5j+EG2eyVQAp2Bk0JrV0B4QeLjRYnQj54QBTDh8CbCvyDg@mail.gmail.com>
Date:   Tue, 23 Aug 2016 21:37:01 -0400
From:   Kees Cook <keescook@...omium.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Nilay Vaish <nilayvaish@...il.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>,
        Byungchul Park <byungchul.park@....com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v4 54/57] x86/mm: convert arch_within_stack_frames() to
 use the new unwinder

On Tue, Aug 23, 2016 at 5:08 PM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> On Tue, Aug 23, 2016 at 01:31:20PM -0700, Andy Lutomirski wrote:
>> On Aug 23, 2016 12:11 AM, "Linus Torvalds"
>> So the fact that this seems to have any significant effect on
>> performance suggests to me that it's being run unnecessarily
>
> Yeah, I think check_object_size() is being run unnecessarily in a lot of
> cases.  Calling it only when size is non-const would probably speed
> things up a lot.

Yup, this is at the top of my list to fix. The non-const is only done
on a handful of architectures, and it needs to be done everywhere.

-Kees

-- 
Kees Cook
Nexus Security