Re: [PATCH v2 6/9] kasan: improve slab object description

From	Andrey Konovalov <andreyknvl@google.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 6/9] kasan: improve slab object description
Date	2017-03-06 19:20 +0100
Message-ID	<ti5oK-3Ar-9@gated-at.bofh.it> (permalink)
References	(3 earlier) <tgYz0-3Rj-21@gated-at.bofh.it> <ti1bt-uP-45@gated-at.bofh.it> <ti1bs-uP-43@gated-at.bofh.it> <ti4iZ-2PO-11@gated-at.bofh.it> <ti4iZ-2PO-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Mon, Mar 6, 2017 at 6:05 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
> On Mon, Mar 6, 2017 at 5:12 PM, Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:
>> On 03/06/2017 04:45 PM, Andrey Konovalov wrote:
>>> On Fri, Mar 3, 2017 at 3:39 PM, Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:
>>>>
>>>>
>>>> On 03/03/2017 04:52 PM, Alexander Potapenko wrote:
>>>>> On Fri, Mar 3, 2017 at 2:31 PM, Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:
>>>>>> On 03/02/2017 04:48 PM, Andrey Konovalov wrote:
>>>>>>> Changes slab object description from:
>>>>>>>
>>>>>>> Object at ffff880068388540, in cache kmalloc-128 size: 128
>>>>>>>
>>>>>>> to:
>>>>>>>
>>>>>>> The buggy address belongs to the object at ffff880068388540
>>>>>>>  which belongs to the cache kmalloc-128 of size 128
>>>>>>> The buggy address is located 123 bytes inside of
>>>>>>>  128-byte region [ffff880068388540, ffff8800683885c0)
>>>>>>>
>>>>>>> Makes it more explanatory and adds information about relative offset
>>>>>>> of the accessed address to the start of the object.
>>>>>>>
>>>>>>
>>>>>> I don't think that this is an improvement. You replaced one simple line with a huge
>>>>>> and hard to parse text without giving any new/useful information.
>>>>>> Except maybe offset, it useful sometimes, so wouldn't mind adding it to description.
>>>>> Agreed.
>>>>> How about:
>>>>> ===========
>>>>> Access 123 bytes inside of 128-byte region [ffff880068388540, ffff8800683885c0)
>>>>> Object at ffff880068388540 belongs to the cache kmalloc-128
>>>>> ===========
>>>>> ?
>>>>>
>>>>
>>>> I would just add the offset in the end:
>>>>         Object at ffff880068388540, in cache kmalloc-128 size: 128 accessed at offset y
>>>
>>> Access can be inside or outside the object, so it's better to
>>> specifically say that.
>>>
>>
>> That what access offset and object's size tells us.
>>
>>
>>> I think we can do (basically what Alexander suggested):
>>>
>>> Object at ffff880068388540 belongs to the cache kmalloc-128 of size 128
>>> Access 123 bytes inside of 128-byte region [ffff880068388540, ffff8800683885c0)
>>
>> This is just wrong and therefore very confusing. The message says that we access 123 bytes,
>> while in fact we access x-bytes at offset 123. IOW 123 sounds like access size here not the offset.
>
> What about
>
> Object at ffff880068388540 belongs to cache kmalloc-128 of size 128
> Accessed address is 123 bytes inside of [ffff880068388540, ffff8800683885c0)
>
> ?

Another alternative:

Accessed address is 123 bytes inside of [ffff880068388540, ffff8800683885c0)
Object belongs to cache kmalloc-128 of size 128

>
>>
>>
>>> What do you think?
>>>
>>
>> Not better.

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[PATCH v2 6/9] kasan: improve slab object description Andrey Konovalov <andreyknvl@google.com> - 2017-03-02 14:50 +0100
  Re: [PATCH v2 6/9] kasan: improve slab object description Alexander Potapenko <glider@google.com> - 2017-03-03 17:50 +0100
    Re: [PATCH v2 6/9] kasan: improve slab object description Andrey Konovalov <andreyknvl@google.com> - 2017-03-06 14:50 +0100
      Re: [PATCH v2 6/9] kasan: improve slab object description Andrey Konovalov <andreyknvl@google.com> - 2017-03-06 18:10 +0100
        Re: [PATCH v2 6/9] kasan: improve slab object description Andrey Konovalov <andreyknvl@google.com> - 2017-03-06 19:20 +0100

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