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Subject: Re: [PATCH] dmaengine: fsl-edma: use struct_size() in kzalloc()
To:     Angelo Dureghello <angelo@sysam.it>
Cc:     Dan Williams <dan.j.williams@intel.com>,
        Vinod Koul <vkoul@kernel.org>, dmaengine@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20190104212545.GA16927@embeddedor>
 <20190106194059.GA2120@jerusalem>
From:   "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Message-ID: <ea4226b9-2bdc-1125-29e0-ea9158898283@embeddedor.com>
Date:   Sun, 6 Jan 2019 14:33:57 -0600
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On 1/6/19 1:40 PM, Angelo Dureghello wrote:
> On Fri, Jan 04, 2019 at 03:25:45PM -0600, Gustavo A. R. Silva wrote:
>> One of the more common cases of allocation size calculations is finding the
>> size of a structure that has a zero-sized array at the end, along with memory
>> for some number of elements for that array. For example:
>>
>> struct foo {
>>      int stuff;
>>      void *entry[];
>> };
>>
>> instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);
>>
>> Instead of leaving these open-coded and prone to type mistakes, we can now
>> use the new struct_size() helper:
>>
>> instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);
>>
>> This code was detected with the help of Coccinelle.
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
>> ---
>>   drivers/dma/fsl-edma-common.c | 4 +---
>>   1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/drivers/dma/fsl-edma-common.c b/drivers/dma/fsl-edma-common.c
>> index 8876c4c1bb2c..fe529100674f 100644
>> --- a/drivers/dma/fsl-edma-common.c
>> +++ b/drivers/dma/fsl-edma-common.c
>> @@ -339,9 +339,7 @@ static struct fsl_edma_desc *fsl_edma_alloc_desc(struct fsl_edma_chan *fsl_chan,
>>   	struct fsl_edma_desc *fsl_desc;
>>   	int i;
>>   
>> -	fsl_desc = kzalloc(sizeof(*fsl_desc) +
>> -			   sizeof(struct fsl_edma_sw_tcd) *
>> -			   sg_len, GFP_NOWAIT);
>> +	fsl_desc = kzalloc(struct_size(fsl_desc, tcd, sg_len), GFP_NOWAIT);
>>   	if (!fsl_desc)
>>   		return NULL;
>>
> 
> Tested-by: Angelo Dureghello <angelo@sysam.it>
> 

Thanks, Angelo.

--
Gustavo