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References: <CAHmME9rtoPwxUSnktxzKso14iuVCWT7BE_-_8PAC=pGw1iJnQg@mail.gmail.com>
 <46ca5661-4bd1-6733-0140-d6e6dea1ab33@virtuozzo.com>
In-Reply-To: <46ca5661-4bd1-6733-0140-d6e6dea1ab33@virtuozzo.com>
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Tue, 19 Jun 2018 22:17:25 +0200
Message-ID: <CAHmME9qqsgz2faVP8FTbJvKTzX-5qQU1aHGbkzT6b05PZ4nkuw@mail.gmail.com>
Subject: Re: Possible regression in "slab, slub: skip unnecessary kasan_cache_shutdown()"
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To: aryabinin@virtuozzo.com
Cc: Alexander Potapenko <glider@google.com>, Dmitry Vyukov <dvyukov@google.com>, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, Andrew Morton <akpm@linux-foundation.org>, kasan-dev@googlegroups.com, Linux-MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>, Shakeel Butt <shakeelb@google.com>

Hi Andrey,

On Tue, Jun 19, 2018 at 7:33 PM Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:
> What's the status of CONFIG_SLUB_DEBUG in your config?
>
> AFAICS __kmem_cache_empty() is broken for CONFIG_SLUB_DEBUG=n. We use slabs_node() there
> which is always 0 for CONFIG_SLUB_DEBUG=n.
>
> The problem seems not limited to __kmem_cache_empty(), __kmem_cache_shutdown() and __kmem_cache_shrink()
> are also rely on correctness of the slabs_node(). Presumably this might cause some problems while
> destroying memcg kmem caches.

CONFIG_SLUB_DEBUG is not set in the crash I sent.

Enabling it "fixes" the problem! This either means that KASAN+SLUB
should enable SLUB_DEBUG, or the extra overhead from SLUB_DEBUG is
just making the bug more rare but not actually eliminating it.

Jason