linux-kernel - Re: [kernel-hardening] [PATCH v2 1/7] bug: Clarify help text for BUG_ON_DATA

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Message-ID: <CAGXu5j+ZQbfc8AMmkuNJxyMtQX5oJYN6Cs52_8vvGLJQqSpkkA@mail.gmail.com>
Date:   Wed, 5 Apr 2017 12:32:26 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Ian Campbell <ijc@...lion.org.uk>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...hat.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Olof Johansson <olof@...om.net>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        George Spelvin <linux@...encehorizons.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        David Windsor <dwindsor@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>
Subject: Re: [kernel-hardening] [PATCH v2 1/7] bug: Clarify help text for BUG_ON_DATA_CORRUPTION

On Tue, Apr 4, 2017 at 10:47 PM, Ian Campbell <ijc@...lion.org.uk> wrote:
>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>> index 77fadface4f9..5ac4d1148385 100644
>> --- a/lib/Kconfig.debug
>> +++ b/lib/Kconfig.debug
>> @@ -1998,9 +1998,12 @@ config BUG_ON_DATA_CORRUPTION
>> >     bool "Trigger a BUG when data corruption is detected"
>> >     select DEBUG_LIST
>> >     help
>> > -     Select this option if the kernel should BUG when it encounters
>> > -     data corruption in kernel memory structures when they get checked
>> > -     for validity.
>> > +     This option enables several inexpensive data corruption checks.
>> > +     Most of these checks normally just WARN and try to further avoid
>> +       the corruption. Selecting this option upgrades these to BUGs so
>
> First it says it enables some checks, but here it says it upgrades them
> to BUGs which seems inconsistent.

Right, it does both. It uses Kconfig "select" to enable checks, and
raises checks from WARN to BUG.

>
>> +       that the offending process is killed. Additionally, the system
>> +       owner can furhter configure the system for immediate reboots
>
>                    "further"

Ah, thanks!

>
>> +       (via panic_on_oops sysctl) or crash dumps.
>>
>> >       If unsure, say N.
>>

-Kees

-- 
Kees Cook
Pixel Security