linux-kernel - Re: [PATCH] mmc: cqhci: Fix a tiny potential memory leak on error condition

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Date:   Thu, 31 Jan 2019 12:12:17 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Alamy Liu <alamy.liu@...il.com>,
        Venkat Gopalakrishnan <venkatg@...eaurora.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        "open list:MULTIMEDIA CARD (MMC), SECURE DIGITAL (SD) AND..." 
        <linux-mmc@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: cqhci: Fix a tiny potential memory leak on error
 condition

On 31/01/19 12:10 PM, Adrian Hunter wrote:
> On 16/01/19 2:24 AM, Alamy Liu wrote:
>> In the error case:
>>    either cq_host->desc_base
>>        or cq_host->trans_desc_base
>> might have been granted memory successfully.
>>
>> The value of mmc_host->cqe_enabled stays 'false'.
>> Thus, cqhci_disable (mmc_cqe_ops->cqe_disable) won't be called to
>> free the memory.
>> Also, cqhci_disable() is designed to disable and free all resources,
>> not suitable to handle this corner case.
>>
>> Signed-off-by: Alamy Liu <alamy.liu@...il.com>
>> ---
>>  drivers/mmc/host/cqhci.c | 20 +++++++++++++++++++-
>>  1 file changed, 19 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/host/cqhci.c b/drivers/mmc/host/cqhci.c
>> index 974997b6cb..58ad8cd613 100644
>> --- a/drivers/mmc/host/cqhci.c
>> +++ b/drivers/mmc/host/cqhci.c
>> @@ -223,7 +223,7 @@ static int cqhci_host_alloc_tdl(struct cqhci_host *cq_host)
>>  					      &cq_host->trans_desc_dma_base,
>>  					      GFP_KERNEL);
>>  	if (!cq_host->desc_base || !cq_host->trans_desc_base)
>> -		return -ENOMEM;
>> +		goto err_free_dma;
>>  
>>  	pr_debug("%s: cqhci: desc-base: 0x%p trans-base: 0x%p\n desc_dma 0x%llx trans_dma: 0x%llx\n",
>>  		 mmc_hostname(cq_host->mmc), cq_host->desc_base, cq_host->trans_desc_base,
>> @@ -234,6 +234,24 @@ static int cqhci_host_alloc_tdl(struct cqhci_host *cq_host)
>>  		setup_trans_desc(cq_host, i);
>>  
>>  	return 0;
>> +
>> +err_free_dma:
>> +	if (cq_host->desc_base) {
>> +		dmam_free_coherent(mmc_dev(cq_host->mmc), cq_host->desc_size,
>> +				   cq_host->desc_base,
>> +				   cq_host->desc_dma_base);
>> +		cq_host->desc_base = NULL;
>> +		cq_host->desc_dma_base = 0;
>> +	}
>> +	if (cq_host->trans_desc_base) {
>> +		dmam_free_coherent(mmc_dev(cq_host->mmc), cq_host->data_size,
>> +				   cq_host->trans_desc_base,
>> +				   cq_host->trans_desc_dma_base);
>> +		cq_host->trans_desc_base = NULL;
>> +		cq_host->trans_desc_dma_base = 0;
>> +	}
>> +
>> +	return -ENOMEM;
>>  }
>>  
>>  static void __cqhci_enable(struct cqhci_host *cq_host)
>>
> 
> Normally, error handling is done step-by-step e.g.
> 
> diff --git a/drivers/mmc/host/cqhci.c b/drivers/mmc/host/cqhci.c
> index 26d63594b7ea..d015b465ade4 100644
> --- a/drivers/mmc/host/cqhci.c
> +++ b/drivers/mmc/host/cqhci.c
> @@ -217,12 +217,15 @@ static int cqhci_host_alloc_tdl(struct cqhci_host *cq_host)
>  						 cq_host->desc_size,
>  						 &cq_host->desc_dma_base,
>  						 GFP_KERNEL);
> +	if (!cq_host->desc_base)
> +		return -ENOMEM;
> +
>  	cq_host->trans_desc_base = dmam_alloc_coherent(mmc_dev(cq_host->mmc),
>  					      cq_host->data_size,
>  					      &cq_host->trans_desc_dma_base,
>  					      GFP_KERNEL);
> -	if (!cq_host->desc_base || !cq_host->trans_desc_base)
> -		return -ENOMEM;
> +	if (!cq_host->trans_desc_base)
> +		goto err_free_dma;
>  
>  	pr_debug("%s: cqhci: desc-base: 0x%p trans-base: 0x%p\n desc_dma 0x%llx trans_dma: 0x%llx\n",
>  		 mmc_hostname(cq_host->mmc), cq_host->desc_base, cq_host->trans_desc_base,
> @@ -233,6 +236,13 @@ static int cqhci_host_alloc_tdl(struct cqhci_host *cq_host)
>  		setup_trans_desc(cq_host, i);
>  
>  	return 0;
> +
> +err_free_dma:
> +	dmam_free_coherent(mmc_dev(cq_host->mmc), cq_host->desc_size,
> +			   cq_host->desc_base, cq_host->desc_dma_base);
> +	cq_host->desc_base = NULL;
> +	cq_host->desc_dma_base = 0;
> +	return NULL;

That should be
	return -ENOMEM;

>  }
>  
>  static void __cqhci_enable(struct cqhci_host *cq_host)
>