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

From: Alexander Popov <alex.popov@linux.com>
To: Alexander Potapenko <glider@google.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: Thu, 3 Dec 2020 22:50:27 +0300	[thread overview]
Message-ID: <1772bc7d-e87f-0f62-52a8-e9d9ac99f5e3@linux.com> (raw)
In-Reply-To: <CAG_fn=WY9OFKuy6utMHOgyr+1DYNsuzVruGCGHMDnEnaLY6s9g@mail.gmail.com>

On 30.09.2020 15:50, Alexander Potapenko wrote:
> 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>

Hello!

Can this particular patch be considered for the mainline kernel?

Note: I summarized the results of the experiment with the Linux kernel heap
quarantine in a short article, for future reference:
https://a13xp0p0v.github.io/2020/11/30/slab-quarantine.html

Best regards,
Alexander

>> ---
>>  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
>>
> 
> 