Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <678ac92ab790dba9198f9ca14f405651b97c8502.1688561016.git.andreyknvl@google.com>
 <CANpmjNO+spktteYZezk7PGLFOyoeuFyziKiU-1GXbpeyKLZLPg@mail.gmail.com>
In-Reply-To: <CANpmjNO+spktteYZezk7PGLFOyoeuFyziKiU-1GXbpeyKLZLPg@mail.gmail.com>
From:   Andrey Konovalov <andreyknvl@gmail.com>
Date:   Wed, 5 Jul 2023 15:19:06 +0200
Message-ID: <CA+fCnZenzRuxS4qjzFiYm05zNxHBSAkTUK7-1zixXXDUQb3g3w@mail.gmail.com>
Subject: Re: [PATCH] kasan, slub: fix HW_TAGS zeroing with slub_debug
To:     Marco Elver <elver@google.com>
Cc:     andrey.konovalov@linux.dev, Mark Rutland <mark.rutland@arm.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        kasan-dev@googlegroups.com,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        Catalin Marinas <catalin.marinas@arm.com>,
        Peter Collingbourne <pcc@google.com>,
        Feng Tang <feng.tang@intel.com>, stable@vger.kernel.org,
        Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        linux-kernel@vger.kernel.org,
        Andrey Konovalov <andreyknvl@google.com>,
        Will Deacon <will@kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Wed, Jul 5, 2023 at 2:51=E2=80=AFPM Marco Elver <elver@google.com> wrote=
:
>
> On Wed, 5 Jul 2023 at 14:44, <andrey.konovalov@linux.dev> wrote:
> >
> > From: Andrey Konovalov <andreyknvl@google.com>
> >
> > Commit 946fa0dbf2d8 ("mm/slub: extend redzone check to extra allocated
> > kmalloc space than requested") added precise kmalloc redzone poisoning
> > to the slub_debug functionality.
> >
> > However, this commit didn't account for HW_TAGS KASAN fully initializin=
g
> > the object via its built-in memory initialization feature. Even though
> > HW_TAGS KASAN memory initialization contains special memory initializat=
ion
> > handling for when slub_debug is enabled, it does not account for in-obj=
ect
> > slub_debug redzones. As a result, HW_TAGS KASAN can overwrite these
> > redzones and cause false-positive slub_debug reports.
> >
> > To fix the issue, avoid HW_TAGS KASAN memory initialization when slub_d=
ebug
> > is enabled altogether. Implement this by moving the __slub_debug_enable=
d
> > check to slab_post_alloc_hook. Common slab code seems like a more
> > appropriate place for a slub_debug check anyway.
> >
> > Fixes: 946fa0dbf2d8 ("mm/slub: extend redzone check to extra allocated =
kmalloc space than requested")
> > Cc: <stable@vger.kernel.org>
> > Reported-by: Mark Rutland <mark.rutland@arm.com>
>
> Is it fixing this issue:
>
>   https://lore.kernel.org/all/20230628154714.GB22090@willie-the-truck/

Yes, my bad, messed up the Reported-by tag. The correct one should be:

Reported-by: Will Deacon <will@kernel.org>

> Other than the question above, it looks sane:
>
> Acked-by: Marco Elver <elver@google.com>

Thank you, Marco!