linux-kernel - Re: Possible regression in "slab, slub: skip unnecessary kasan_cache

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Date:   Tue, 19 Jun 2018 15:16:58 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Shakeel Butt <shakeelb@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Possible regression in "slab, slub: skip unnecessary kasan_cache_shutdown()"

On Tue, Jun 19, 2018 at 3:04 PM, Jason A. Donenfeld <Jason@...c4.com> wrote:
> HI Dimitry,
>
> On Tue, Jun 19, 2018 at 6:55 AM Dmitry Vyukov <dvyukov@...gle.com> wrote:
>> Your code frees all entries before freeing the cache, right? If you
>> add total_entries check before freeing the cache, it does not fire,
>> right?
>
> Yes, certainly.
>
>> Are you using SLAB or SLUB? We stress kernel pretty heavily, but with
>> SLAB, and I suspect Shakeel may also be using SLAB. So if you are
>> using SLUB, there is significant chance that it's a bug in the SLUB
>> part of the change.
>
> Nice intuition; I am indeed using SLUB rather than SLAB...

Now the reasonable question is: does SLUB path of
f9e13c0a5a33d1eaec374d6d4dab53a4f72756a0 have a bug?
syzbot has stressed SLAB version to death, and any such issues would
pop up very loudly, but I am not sure what is the amount of testing
for SLUB.