linux-kernel - Re: [PATCH v2] sparc: kernel/sbus.c: fix memory leakage

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Message-ID: <50F7EED3.1050309@oldelvet.org.uk>
Date:	Thu, 17 Jan 2013 12:30:11 +0000
From:	Richard Mortimer <richm@...elvet.org.uk>
To:	Cong Ding <dinggnu@...il.com>
CC:	Sam Ravnborg <sam@...nborg.org>,
	"David S. Miller" <davem@...emloft.net>,
	sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sparc: kernel/sbus.c: fix memory leakage



On 17/01/2013 11:56, Cong Ding wrote:
> On Thu, Jan 17, 2013 at 10:41:59AM +0000, Richard Mortimer wrote:
>>
>>
>> On 16/01/2013 22:01, Cong Ding wrote:
>>> the variable iommu and strbuf are not freed if it goes to error.
>>>
>>> Signed-off-by: Cong Ding <dinggnu@...il.com>
>>> ---
>>>   arch/sparc/kernel/sbus.c |    2 ++
>>>   1 file changed, 2 insertions(+)
>>>
>>> diff --git a/arch/sparc/kernel/sbus.c b/arch/sparc/kernel/sbus.c
>>> index 1271b3a..78aa26b 100644
>>> --- a/arch/sparc/kernel/sbus.c
>>> +++ b/arch/sparc/kernel/sbus.c
>>> @@ -656,6 +656,8 @@ static void __init sbus_iommu_init(struct platform_device *op)
>>>   	return;
>>>
>>>   fatal_memory_error:
>>> +	kfree(strbuf);
>>
>> strbuf will be uninitialized if the iommu allocation fails. I don't
>> have a particular preference for how to fix this but tend to dislike
>> initial assignment with NULL because it hides other control flow
>> issues.
> Sorry I didn't notice strbuf will be uninitialized here. But if we don't
> initially assign a NULL value to strbuf, I cannot find a way to handle it
> besides the first version patch. Did you have any suggestions? For me, I like
> the first version.

Two thoughts...

1 - just use a goto target for the iommu allocation failure and make 
that skip the strbuf free call. The others use the existing 
fatal_memory_error label.

2 - Move the strbuf kzalloc up 2 lines so that it occurs before the test 
for iommu.

2b - In case (2) above the failure test could be changed to
if (!iommu || !strbuf)
to remove duplication of goto.

I'd probably go for 2/2b to address Sam's initial comment.

Regards

Richard


> - cong
>>
>> Regards
>>
>> Richard
>>
>>> +	kfree(iommu);
>>>   	prom_printf("sbus_iommu_init: Fatal memory allocation error.\n");
>>>   }
>>>
>>>
--
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