linux-kernel - Re: [PATCH 4/4] mm/slub: free KFENCE objects in slab_free

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Message-ID: <CA+fCnZecUGRdqwfebu9C+hBN3_mW_VNhjm4FUXOo9Xak58NKdQ@mail.gmail.com>
Date: Thu, 21 Dec 2023 00:44:39 +0100
From: Andrey Konovalov <andreyknvl@...il.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Marco Elver <elver@...gle.com>, Chengming Zhou <chengming.zhou@...ux.dev>, 
	Christoph Lameter <cl@...ux.com>, Pekka Enberg <penberg@...nel.org>, David Rientjes <rientjes@...gle.com>, 
	Joonsoo Kim <iamjoonsoo.kim@....com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Hyeonggon Yoo <42.hyeyoo@...il.com>, 
	Alexander Potapenko <glider@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com
Subject: Re: [PATCH 4/4] mm/slub: free KFENCE objects in slab_free_hook()

On Tue, Dec 12, 2023 at 12:42 PM Vlastimil Babka <vbabka@...e.cz> wrote:
>
> On 12/11/23 23:11, Andrey Konovalov wrote:
> > On Wed, Dec 6, 2023 at 3:45 PM Marco Elver <elver@...gle.com> wrote:
> >>
> >> The is_kfence_address() implementation tolerates tagged addresses,
> >> i.e. if it receives a tagged non-kfence address, it will never return
> >> true.
>
> So just to be sure, it can't happen that a genuine kfence address would then
> become KASAN tagged and handed out, and thus when tested by
> is_kfence_address() it would be a false negative?

No, this should not happen. KFENCE objects never get tags assigned to them.