linux-kernel - Re: [PATCH] slab: store tagged freelist for off-slab slabmgmt

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Date:   Wed, 03 Apr 2019 09:07:50 -0400
From:   Qian Cai <cai@....pw>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] slab: store tagged freelist for off-slab slabmgmt

On Wed, 2019-04-03 at 13:23 +0200, Andrey Konovalov wrote:
> On Wed, Apr 3, 2019 at 4:29 AM Qian Cai <cai@....pw> wrote:
> > 
> > The commit 51dedad06b5f ("kasan, slab: make freelist stored without
> > tags") calls kasan_reset_tag() for off-slab slab management object
> > leading to freelist being stored non-tagged. However, cache_grow_begin()
> > -> alloc_slabmgmt() -> kmem_cache_alloc_node() which assigns a tag for
> > the address and stores in the shadow address. As the result, it causes
> > endless errors below during boot due to drain_freelist() ->
> > slab_destroy() -> kasan_slab_free() which compares already untagged
> > freelist against the stored tag in the shadow address. Since off-slab
> > slab management object freelist is such a special case, so just store it
> > tagged. Non-off-slab management object freelist is still stored untagged
> > which has not been assigned a tag and should not cause any other
> > troubles with this inconsistency.
> 
> Hi Qian,
> 
> Could you share the config (or other steps) you used to reproduce this?

https://git.sr.ht/~cai/linux-debug/blob/master/config

Additional command-line option to boot:

page_poison=on crashkernel=768M earlycon page_owner=on numa_balancing=enable
systemd.unified_cgroup_hierarchy=1 debug_guardpage_minorder=1