linux-kernel - Re: [PATCH mm v2 30/33] kasan: implement stack ring for tag-based modes

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Message-ID: <CA+fCnZcGM9_H4LJAKj0QSKQ3qX-vF=V_rL_C8xVmaTvW15c6iw@mail.gmail.com>
Date:   Mon, 5 Sep 2022 22:40:18 +0200
From:   Andrey Konovalov <andreyknvl@...il.com>
To:     Marco Elver <elver@...gle.com>
Cc:     andrey.konovalov@...ux.dev,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Peter Collingbourne <pcc@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Florian Mayer <fmayer@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH mm v2 30/33] kasan: implement stack ring for tag-based modes

On Wed, Aug 3, 2022 at 10:29 PM Marco Elver <elver@...gle.com> wrote:
>
> > Does your "The rest looks fine now" comment refer only to this patch
> > or to the whole series? If it's the former, could you PTAL at the
> > other patches?
>
> I just looked again. Apart from the comments I just sent, overall it
> looks fine (whole series).

Great, thanks! I'll put your Reviewed-by on all patches except the
ones I will change in v3.

> Does test_kasan exercise the ring wrapping around? One thing that
> might be worth doing is adding a multi-threaded stress test, where you
> have 2+ threads doing lots of allocations, frees, and generating
> reports.

There's probably not a lot of sense in adding this test: this part is
tested during kernel boot. Even with defconfig, the stack ring
overflows multiple times.

I will, however, add a test for a complicated use-after-free scenario
to make sure that KASAN points at the right kmalloc/kfree calls.
Before I get to implementing [1], the report contents will have to be
checked manually though.

Thanks!

[1] https://bugzilla.kernel.org/show_bug.cgi?id=212203