linux-kernel - Re: [RFC PATCH v2] iommu/amd: gray the 'irq_remap

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Message-ID: <5655D072.1000901@profitbricks.com>
Date:	Wed, 25 Nov 2015 16:14:58 +0100
From:	Michael Wang <yun.wang@...fitbricks.com>
To:	Joerg Roedel <joro@...tes.org>
Cc:	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2] iommu/amd: gray the 'irq_remap_table' object for
 kmemleak

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

> 
> 
> 
> 	Joerg
> 
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