linux-kernel - Re: [PATCH] mm, kfence: support kmem_dump

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Message-ID: <d179e539-1da6-c489-b2b4-ad97367bd73a@suse.cz>
Date:   Thu, 7 Apr 2022 11:57:42 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Marco Elver <elver@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, kernel test robot <oliver.sang@...el.com>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>
Subject: Re: [PATCH] mm, kfence: support kmem_dump_obj() for KFENCE objects

On 4/7/22 11:48, Marco Elver wrote:
> On Thu, 7 Apr 2022 at 11:43, Vlastimil Babka <vbabka@...e.cz> wrote:
>>
>> On 4/6/22 15:15, Marco Elver wrote:
>> > Calling kmem_obj_info() via kmem_dump_obj() on KFENCE objects has been
>> > producing garbage data due to the object not actually being maintained
>> > by SLAB or SLUB.
>> >
>> > Fix this by implementing __kfence_obj_info() that copies relevant
>> > information to struct kmem_obj_info when the object was allocated by
>> > KFENCE; this is called by a common kmem_obj_info(), which also calls the
>> > slab/slub/slob specific variant now called __kmem_obj_info().
>> >
>> > For completeness, kmem_dump_obj() now displays if the object was
>> > allocated by KFENCE.
>> >
>> > Link: https://lore.kernel.org/all/20220323090520.GG16885@xsang-OptiPlex-9020/
>> > Fixes: b89fb5ef0ce6 ("mm, kfence: insert KFENCE hooks for SLUB")
>> > Fixes: d3fb45f370d9 ("mm, kfence: insert KFENCE hooks for SLAB")
>> > Reported-by: kernel test robot <oliver.sang@...el.com>
>> > Signed-off-by: Marco Elver <elver@...gle.com>
>> > Reviewed-by: Hyeonggon Yoo <42.hyeyoo@...il.com>
>>
>> Thanks.
>> Given the impact on slab, and my series exposing the bug, I will add this to
>> slab tree.
> 
> It's already in Andrew's tree:
> https://lore.kernel.org/all/20220406192351.2E115C385A5@smtp.kernel.org/T/#u

Ah, missed that.

> Does your series and this patch merge cleanly?

Yeah the dependency is not on the code level.

> If so, maybe leaving in
> -mm is fine. Of course I don't mind either way and it's up to you and
> Andrew.

Yeah should be fine as linux-next will be safe with both trees merged. Thanks.

> Thanks,
> -- Marco