Re: [PATCH v1 1/8] kasan: Change the behavior of kmalloc_large_oob_right test

[Alexander Potapenko]

Turns out I've actually overintellectualized this test.
I've reworked this patch so that kmalloc_pagealloc_oob_right()
allocates a big chunk of memory from the page allocator (and therefore
is enabled only under CONFIG_SLUB).
kmalloc_large_oob_right() now allocates KMALLOC_MAX_CACHE_SIZE - 256
in both SLAB and SLUB modes.

I'll send the updated patch set later today.

On Tue, Feb 2, 2016 at 5:25 PM, Alexander Potapenko <glider@xxxxxxxxxx> wrote:
> The intention was to detect the situation in which a new allocator
> appears for which we don't know how it behaves if we allocate more
> than KMALLOC_MAX_CACHE_SIZE.
> I agree this makes little sense and we can just stick to
> CONFIG_SLAB/CONFIG_SLUB cases.
>
> However I think it's better to keep 'size = KMALLOC_MAX_CACHE_SIZE +
> something' to keep this code working in the case the value of
> KMALLOC_MAX_CACHE_SIZE changes.
>
> On Tue, Feb 2, 2016 at 4:29 PM, Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx> wrote:
>>
>>
>> On 02/02/2016 08:34 AM, Andrew Morton wrote:
>>> On Wed, 27 Jan 2016 19:25:06 +0100 Alexander Potapenko <glider@xxxxxxxxxx> wrote:
>>>
>>>> depending on which allocator (SLAB or SLUB) is being used
>>>>
>>>> ...
>>>>
>>>> --- a/lib/test_kasan.c
>>>> +++ b/lib/test_kasan.c
>>>> @@ -68,7 +68,22 @@ static noinline void __init kmalloc_node_oob_right(void)
>>>>  static noinline void __init kmalloc_large_oob_right(void)
>>>>  {
>>>>      char *ptr;
>>>> -    size_t size = KMALLOC_MAX_CACHE_SIZE + 10;
>>>> +    size_t size;
>>>> +
>>>> +    if (KMALLOC_MAX_CACHE_SIZE == KMALLOC_MAX_SIZE) {
>>>> +            /*
>>>> +             * We're using the SLAB allocator. Allocate a chunk that fits
>>>> +             * into a slab.
>>>> +             */
>>>> +            size = KMALLOC_MAX_CACHE_SIZE - 256;
>>>> +    } else {
>>>> +            /*
>>>> +             * KMALLOC_MAX_SIZE > KMALLOC_MAX_CACHE_SIZE.
>>>> +             * We're using the SLUB allocator. Allocate a chunk that does
>>>> +             * not fit into a slab to trigger the page allocator.
>>>> +             */
>>>> +            size = KMALLOC_MAX_CACHE_SIZE + 10;
>>>> +    }
>>>
>>> This seems a weird way of working out whether we're using SLAB or SLUB.
>>>
>>> Can't we use, umm, #ifdef CONFIG_SLAB?  If not that then let's cook up
>>> something standardized rather than a weird just-happens-to-work like
>>> this.
>>>
>>
>> Actually it would be simpler to not use KMALLOC_MAX_CACHE_SIZE at all.
>> Simply replace it with 2 or 3 PAGE_SIZEs.
>
>
>
> --
> Alexander Potapenko
> Software Engineer
>
> Google Germany GmbH
> Erika-Mann-StraÃe, 33
> 80636 MÃnchen
>
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-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-StraÃe, 33
80636 MÃnchen

GeschÃftsfÃhrer: Matthew Scott Sucherman, Paul Terence Manicle
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
Diese E-Mail ist vertraulich. Wenn Sie nicht der richtige Adressat sind,
leiten Sie diese bitte nicht weiter, informieren Sie den
Absender und lÃschen Sie die E-Mail und alle AnhÃnge. Vielen Dank.
This e-mail is confidential. If you are not the right addressee please
do not forward it, please inform the sender, and please erase this
e-mail including any attachments. Thanks.