Re: [PATCH RFC v2 2/6] mm/slab: Perform init_on_free earlier

From: Alexander Potapenko <glider@google.com>
To: Alexander Popov <alex.popov@linux.com>
Cc: Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>,
	 Will Deacon <will@kernel.org>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	 Dmitry Vyukov <dvyukov@google.com>,
	Christoph Lameter <cl@linux.com>,
	Pekka Enberg <penberg@kernel.org>,
	 David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	 Andrew Morton <akpm@linux-foundation.org>,
	Masahiro Yamada <masahiroy@kernel.org>,
	 Masami Hiramatsu <mhiramat@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	 Peter Zijlstra <peterz@infradead.org>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	 Patrick Bellasi <patrick.bellasi@arm.com>,
	David Howells <dhowells@redhat.com>,
	 Eric Biederman <ebiederm@xmission.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	 Laura Abbott <labbott@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
	 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Daniel Micay <danielmicay@gmail.com>,
	 Andrey Konovalov <andreyknvl@google.com>,
	Matthew Wilcox <willy@infradead.org>,
	 Pavel Machek <pavel@denx.de>,
	Valentin Schneider <valentin.schneider@arm.com>,
	 kasan-dev <kasan-dev@googlegroups.com>,
	 Linux Memory Management List <linux-mm@kvack.org>,
	Kernel Hardening <kernel-hardening@lists.openwall.com>,
	 LKML <linux-kernel@vger.kernel.org>,
	notify@kernel.org
Subject: Re: [PATCH RFC v2 2/6] mm/slab: Perform init_on_free earlier
Date: Wed, 30 Sep 2020 14:50:59 +0200	[thread overview]
Message-ID: <CAG_fn=WY9OFKuy6utMHOgyr+1DYNsuzVruGCGHMDnEnaLY6s9g@mail.gmail.com> (raw)
In-Reply-To: <20200929183513.380760-3-alex.popov@linux.com>

On Tue, Sep 29, 2020 at 8:35 PM Alexander Popov <alex.popov@linux.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@linux.com>
Reviewed-by: Alexander Potapenko <glider@google.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

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