Re: [RFC PATCH v2] iommu/amd: gray the 'irq_remap_table' object for kmemleak

Michael Wang
2015-11-25T15:15:06Z

On 11/25/2015 04:08 PM, Joerg Roedel wrote:
> On Fri, Nov 20, 2015 at 12:33:50PM +0100, Michael Wang wrote:
>> The kmemleak testing on 3.18.24 show:
>>
>> unreferenced object 0xffff880233ff9010 (size 16):
>> comm "swapper/0", pid 1, jiffies 4294937440 (age 2010.490s)
>> hex dump (first 16 bytes):
>> 0a 0a 00 00 20 00 00 00 00 44 fb 33 02 88 ff ff .... ....D.3....
>> backtrace:
>> [<ffffffff8118192d>] create_object+0x10d/0x2d0
>> [<ffffffff815c2d4b>] kmemleak_alloc+0x5b/0xc0
>> [<ffffffff8116dd19>] kmem_cache_alloc_trace+0xb9/0x160
>> [<ffffffff814ffe51>] get_irq_table+0x151/0x380
>>
>> This is caused by the 'irq_lookup_table' was allocated with
>> __get_free_pages() which won't create kmemleak object, thus it's
>> pointers won't be count as referencing 'irq_remap_table' in
>> kmemleak scan.
>
> Isn't it better to allocate the kmemleak object manually instead of
> ignoring all irq-table pointers? With this patch we might not notice any
> real leak of irq-tables.

We've considered that too, but found that the irq-tables is not
dynamically alloc/free, they won't be freed once initialized, so there
is no leaking for such object :-)

Regards,
Michael Wang

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> Joerg
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