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

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Message-ID: <4b592848-ef06-ea8a-180a-3efc22b1bb0e@suse.cz>
Date:   Thu, 7 Apr 2022 11:43:31 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Marco Elver <elver@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     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 4/6/22 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.

Vlastimil