linux-kernel - Re: [RFT PATCH 2/2] memory: fsl_ifc: fix leak of private memory on probe failure

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Date:   Thu, 27 May 2021 11:19:30 -0400
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Liu Shuo <b35362@...escale.com>,
        Prabhakar Kushwaha <prabhakar@...escale.com>,
        Li Yang <leoyang.li@....com>,
        Dipen Dudhat <Dipen.Dudhat@...escale.com>,
        linux-kernel@...r.kernel.org, Raghav Dogra <raghav.dogra@....com>
Subject: Re: [RFT PATCH 2/2] memory: fsl_ifc: fix leak of private memory on
 probe failure

On 27/05/2021 11:01, Dan Carpenter wrote:
> On Thu, May 27, 2021 at 10:42:40AM -0400, Krzysztof Kozlowski wrote:
>> On probe error the driver should free the memory allocated for private
>> structure.  Fix this by using resource-managed allocation.
>>
>> Fixes: a20cbdeffce2 ("powerpc/fsl: Add support for Integrated Flash Controller")
>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
>>
>> ---
>>
>> Only build tested.
>> ---
>>  drivers/memory/fsl_ifc.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/memory/fsl_ifc.c b/drivers/memory/fsl_ifc.c
>> index a6324044a085..3ee7183b20fb 100644
>> --- a/drivers/memory/fsl_ifc.c
>> +++ b/drivers/memory/fsl_ifc.c
>> @@ -209,7 +209,8 @@ static int fsl_ifc_ctrl_probe(struct platform_device *dev)
>>  
>>  	dev_info(&dev->dev, "Freescale Integrated Flash Controller\n");
>>  
>> -	fsl_ifc_ctrl_dev = kzalloc(sizeof(*fsl_ifc_ctrl_dev), GFP_KERNEL);
>> +	fsl_ifc_ctrl_dev = devm_kzalloc(&dev->dev, sizeof(*fsl_ifc_ctrl_dev),
>> +					GFP_KERNEL);
>>  	if (!fsl_ifc_ctrl_dev)
>>  		return -ENOMEM;
> 
> You'd need to remove the kfree(ctrl) in the remove function as well or
> it will lead to a double free.

Yeah, thanks, I spotted it now also looking for more leaks.
> 
> Unrelated to your patch but related to Smatch.  The Smatch check for
> resource leaks which I mentioned check_unwind.c doesn't look for
> kmalloc() leaks because those are quite complicated to deal with.
> kmalloc() allocations are so much more common and that if you have a 5%
> false positive rate, then it's just overwhelming.  There is a separate
> Smatch check for that but it's garbage and I need to re-write it.

Indeed I was thinking about this kmalloc. It should be the last one -
the IRQs seem to be handled.



Best regards,
Krzysztof