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Date: Wed, 30 Sep 2020 14:50:59 +0200
From: Alexander Potapenko <glider@...gle.com>
To: Alexander Popov <alex.popov@...ux.com>
Cc: Kees Cook <keescook@...omium.org>, Jann Horn <jannh@...gle.com>,
Will Deacon <will@...nel.org>, Andrey Ryabinin <aryabinin@...tuozzo.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>,
Andrew Morton <akpm@...ux-foundation.org>, Masahiro Yamada <masahiroy@...nel.org>,
Masami Hiramatsu <mhiramat@...nel.org>, Steven Rostedt <rostedt@...dmis.org>,
Peter Zijlstra <peterz@...radead.org>, Krzysztof Kozlowski <krzk@...nel.org>,
Patrick Bellasi <patrick.bellasi@....com>, David Howells <dhowells@...hat.com>,
Eric Biederman <ebiederm@...ssion.com>, Johannes Weiner <hannes@...xchg.org>,
Laura Abbott <labbott@...hat.com>, Arnd Bergmann <arnd@...db.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Daniel Micay <danielmicay@...il.com>,
Andrey Konovalov <andreyknvl@...gle.com>, Matthew Wilcox <willy@...radead.org>,
Pavel Machek <pavel@...x.de>, Valentin Schneider <valentin.schneider@....com>,
kasan-dev <kasan-dev@...glegroups.com>,
Linux Memory Management List <linux-mm@...ck.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com>,
LKML <linux-kernel@...r.kernel.org>, notify@...nel.org
Subject: Re: [PATCH RFC v2 2/6] mm/slab: Perform init_on_free earlier
On Tue, Sep 29, 2020 at 8:35 PM Alexander Popov <alex.popov@...ux.com> wrote:
>
> Currently in CONFIG_SLAB init_on_free happens too late, and heap
> objects go to the heap quarantine being dirty. Lets move memory
> clearing before calling kasan_slab_free() to fix that.
>
> Signed-off-by: Alexander Popov <alex.popov@...ux.com>
Reviewed-by: Alexander Potapenko <glider@...gle.com>
> ---
> mm/slab.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/mm/slab.c b/mm/slab.c
> index 3160dff6fd76..5140203c5b76 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -3414,6 +3414,9 @@ static void cache_flusharray(struct kmem_cache *cachep, struct array_cache *ac)
> static __always_inline void __cache_free(struct kmem_cache *cachep, void *objp,
> unsigned long caller)
> {
> + if (unlikely(slab_want_init_on_free(cachep)))
> + memset(objp, 0, cachep->object_size);
> +
> /* Put the object into the quarantine, don't touch it for now. */
> if (kasan_slab_free(cachep, objp, _RET_IP_))
> return;
> @@ -3432,8 +3435,6 @@ void ___cache_free(struct kmem_cache *cachep, void *objp,
> struct array_cache *ac = cpu_cache_get(cachep);
>
> check_irq_off();
> - if (unlikely(slab_want_init_on_free(cachep)))
> - memset(objp, 0, cachep->object_size);
> kmemleak_free_recursive(objp, cachep->flags);
> objp = cache_free_debugcheck(cachep, objp, caller);
> memcg_slab_free_hook(cachep, virt_to_head_page(objp), objp);
> --
> 2.26.2
>
--
Alexander Potapenko
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
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