linux-kernel - Re: Odd-sized kmem_cache_alloc and slub

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Date:   Mon, 17 Aug 2020 20:31:35 +0200
From:   Marco Elver <elver@...gle.com>
To:     Pekka Enberg <penberg@...il.com>
Cc:     Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Christoph Lameter <cl@...ux.com>,
        Kees Cook <keescook@...omium.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: Odd-sized kmem_cache_alloc and slub_debug=Z

On Fri, 7 Aug 2020 at 21:06, Pekka Enberg <penberg@...il.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@...omium.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