linux-kernel - Re: [PATCH v2 11/20] kasan: add and integrate kasan boot parameters

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Message-ID: <20201112125453.GM29613@gaia>
Date:   Thu, 12 Nov 2020 12:54:54 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Marco Elver <elver@...gle.com>
Cc:     Andrey Konovalov <andreyknvl@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Will Deacon <will.deacon@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 11/20] kasan: add and integrate kasan boot parameters

On Thu, Nov 12, 2020 at 12:53:58PM +0100, Marco Elver wrote:
> On Thu, 12 Nov 2020 at 12:35, Catalin Marinas <catalin.marinas@....com> wrote:
> >
> > On Tue, Nov 10, 2020 at 11:20:15PM +0100, Andrey Konovalov wrote:
> > > Hardware tag-based KASAN mode is intended to eventually be used in
> > > production as a security mitigation. Therefore there's a need for finer
> > > control over KASAN features and for an existence of a kill switch.
> > >
> > > This change adds a few boot parameters for hardware tag-based KASAN that
> > > allow to disable or otherwise control particular KASAN features.
> > >
> > > The features that can be controlled are:
> > >
> > > 1. Whether KASAN is enabled at all.
> > > 2. Whether KASAN collects and saves alloc/free stacks.
> > > 3. Whether KASAN panics on a detected bug or not.
> > >
> > > With this change a new boot parameter kasan.mode allows to choose one of
> > > three main modes:
> > >
> > > - kasan.mode=off - KASAN is disabled, no tag checks are performed
> > > - kasan.mode=prod - only essential production features are enabled
> > > - kasan.mode=full - all KASAN features are enabled
> >
> > Alternative naming if we want to avoid "production" (in case someone
> > considers MTE to be expensive in a production system):
> >
> > - kasan.mode=off
> > - kasan.mode=on
> > - kasan.mode=debug
> 
> I believe this was what it was in RFC, and we had a long discussion on
> what might be the most intuitive options. Since KASAN is still a
> debugging tool for the most part, an "on" mode might imply we get all
> the debugging facilities of regular KASAN. However, this is not the
> case and misleading. Hence, we decided to be more explicit and avoid
> "on".

Even better, kasan.mode=fast ;).

-- 
Catalin