linux-kernel - Re: [PATCH 13/14] x86/unwind/orc: Add more unwinder warnings

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAG48ez2L5eBfU57_bFnSPSN7DUrocJB56wBLR6cE0e_5DdkURg@mail.gmail.com>
Date:   Thu, 12 Mar 2020 20:12:16 +0100
From:   Jann Horn <jannh@...gle.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     "the arch/x86 maintainers" <x86@...nel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Vince Weaver <vincent.weaver@...ne.edu>,
        Dave Jones <dsj@...com>, Miroslav Benes <mbenes@...e.cz>,
        Andy Lutomirski <luto@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 13/14] x86/unwind/orc: Add more unwinder warnings

On Thu, Mar 12, 2020 at 6:31 PM Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> Make sure warnings are displayed for all error scenarios (except when
> encountering an empty unwind hint).
[...]
>         /* End-of-stack check for kernel threads: */
>         if (orc->sp_reg == ORC_REG_UNDEFINED) {
> -               if (!orc->end)
> +               if (!orc->end) {
> +                       /*
> +                        * This is reported as an error for the caller, but
> +                        * otherwise it isn't worth warning about.  In theory
> +                        * it can only happen when hitting UNWIND_HINT_EMPTY in
> +                        * entry code, close to a kernel exit point.
> +                        */
>                         goto err;

But UNWIND_HINT_EMPTY sets end=1, right? And this is the branch for
end==0. What am I missing?