linux-kernel - Re: [PATCH v3 11/13] kmemleak: disable kasan instrumentation for kmemleak

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Date:	Mon, 29 Sep 2014 18:10:01 +0400
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc:	Andrey Ryabinin <a.ryabinin@...sung.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Konstantin Serebryany <kcc@...gle.com>,
	Dmitry Chernenkov <dmitryc@...gle.com>,
	Andrey Konovalov <adech.fo@...il.com>,
	Yuri Gribov <tetra2005@...il.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Christoph Lameter <cl@...ux.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Hansen <dave.hansen@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Vegard Nossum <vegard.nossum@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Dave Jones <davej@...hat.com>,
	x86@...nel.org, "linux-mm@...ck.org" <linux-mm@...ck.org>,
	Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH v3 11/13] kmemleak: disable kasan instrumentation for kmemleak

On Fri, Sep 26, 2014 at 9:36 PM, Andrey Ryabinin <ryabinin.a.a@...il.com> wrote:
> 2014-09-26 21:10 GMT+04:00 Dmitry Vyukov <dvyukov@...gle.com>:
>> Looks good to me.
>>
>> We can disable kasan instrumentation of this file as well.
>>
>
> Yes, but why? I don't think we need that.


Just gut feeling. Such tools usually don't play well together. For
example, due to asan quarantine lots of leaks will be missed (if we
pretend that tools work together, end users will use them together and
miss bugs). I won't be surprised if leak detector touches freed
objects under some circumstances as well.
We can do this if/when discover actual compatibility issues, of course.


>> On Wed, Sep 24, 2014 at 5:44 AM, Andrey Ryabinin <a.ryabinin@...sung.com> wrote:
>>> kmalloc internally round up allocation size, and kmemleak
>>> uses rounded up size as object's size. This makes kasan
>>> to complain while kmemleak scans memory or calculates of object's
>>> checksum. The simplest solution here is to disable kasan.
>>>
>>> Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
>>> ---
>>>  mm/kmemleak.c | 6 ++++++
>>>  1 file changed, 6 insertions(+)
>>>
>>> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
>>> index 3cda50c..9bda1b3 100644
>>> --- a/mm/kmemleak.c
>>> +++ b/mm/kmemleak.c
>>> @@ -98,6 +98,7 @@
>>>  #include <asm/processor.h>
>>>  #include <linux/atomic.h>
>>>
>>> +#include <linux/kasan.h>
>>>  #include <linux/kmemcheck.h>
>>>  #include <linux/kmemleak.h>
>>>  #include <linux/memory_hotplug.h>
>>> @@ -1113,7 +1114,10 @@ static bool update_checksum(struct kmemleak_object *object)
>>>         if (!kmemcheck_is_obj_initialized(object->pointer, object->size))
>>>                 return false;
>>>
>>> +       kasan_disable_local();
>>>         object->checksum = crc32(0, (void *)object->pointer, object->size);
>>> +       kasan_enable_local();
>>> +
>>>         return object->checksum != old_csum;
>>>  }
>>>
>>> @@ -1164,7 +1168,9 @@ static void scan_block(void *_start, void *_end,
>>>                                                   BYTES_PER_POINTER))
>>>                         continue;
>>>
>>> +               kasan_disable_local();
>>>                 pointer = *ptr;
>>> +               kasan_enable_local();
>>>
>>>                 object = find_and_get_object(pointer, 1);
>>>                 if (!object)
>>> --
>>> 2.1.1
>>>
>>
>
>
> --
> Best regards,
> Andrey Ryabinin
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