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From:   Marco Elver <elver@google.com>
Date:   Mon, 17 Aug 2020 20:31:35 +0200
Message-ID: <CANpmjNNhG4VuGq2_kocsTD3CnCv-Y4Kvnz7_VuvZ9Eug+-T=Eg@mail.gmail.com>
Subject: Re: Odd-sized kmem_cache_alloc and slub_debug=Z
To:     Pekka Enberg <penberg@gmail.com>
Cc:     Alexander Potapenko <glider@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Christoph Lameter <cl@linux.com>,
        Kees Cook <keescook@chromium.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>
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On Fri, 7 Aug 2020 at 21:06, Pekka Enberg <penberg@gmail.com> wrote:
...
> Yeah, it reproduces with defconfig too, as long as you remember to
> pass "slub_debug=Z"... :-/
>
> The following seems to be the culprit:
>
> commit 3202fa62fb43087387c65bfa9c100feffac74aa6
> Author: Kees Cook <keescook@chromium.org>
> Date:   Wed Apr 1 21:04:27 2020 -0700
>
>     slub: relocate freelist pointer to middle of object
>
> Reverting this commit and one of it's follow up fixes from Kees from
> v5.8 makes the issue go away for me. Btw, please note that caches with
> size 24 and larger do not trigger this bug, so the issue is that with
> small enough object size, we're stomping on allocator metadata (I
> assume part of the freelist).

Was there a patch to fix this? Checking, just in case I missed it.

Thanks,
-- Marco