linux-kernel - Re: [PATCH][next] dmaengine: ti: omap-dma: don't allow a null od->plat pointer to be dereferenced

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Date:   Wed, 8 Jan 2020 09:20:37 +0200
From:   Peter Ujfalusi <peter.ujfalusi@...com>
To:     Colin King <colin.king@...onical.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Tony Lindgren <tony@...mide.com>, <dmaengine@...r.kernel.org>
CC:     <kernel-janitors@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][next] dmaengine: ti: omap-dma: don't allow a null
 od->plat pointer to be dereferenced

Colin, Tony,

On 07/01/2020 13.59, Peter Ujfalusi wrote:
> Colin,
> 
> On 06/01/2020 14.23, Colin King wrote:
>> From: Colin Ian King <colin.king@...onical.com>
>>
>> Currently when the call to dev_get_platdata returns null the driver issues
>> a warning and then later dereferences the null pointer.  Avoid this issue
>> by returning -EPROBE_DEFER errror rather when the platform data is null.
> 
> Thank you for noticing it!
> 
> Acked-by: Peter Ujfalusi <peter.ujfalusi@...com>
> 
>> Addresses-Coverity: ("Dereference after null check")
>> Fixes: 211010aeb097 ("dmaengine: ti: omap-dma: Pass sdma auxdata to driver and use it")
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>> ---
>>  drivers/dma/ti/omap-dma.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/dma/ti/omap-dma.c b/drivers/dma/ti/omap-dma.c
>> index fc8f7b2fc7b3..335c3fa7a3b1 100644
>> --- a/drivers/dma/ti/omap-dma.c
>> +++ b/drivers/dma/ti/omap-dma.c
>> @@ -1658,8 +1658,10 @@ static int omap_dma_probe(struct platform_device *pdev)
>>  	if (conf) {
>>  		od->cfg = conf;
>>  		od->plat = dev_get_platdata(&pdev->dev);
>> -		if (!od->plat)
>> +		if (!od->plat) {
>>  			dev_warn(&pdev->dev, "no sdma auxdata needed?\n");
>> +			return -EPROBE_DEFER;

I think we should make the print as dev_err("&pdev->dev,
"omap_system_dma_plat_info is missing") and return with -ENODEV. The
omap_system_dma_plat_info is _needed_ and if we have booted with device
tree it is not going to appear later.

Tony, what do you think?

>> +		}
>>  	} else {
>>  		od->cfg = &default_cfg;
>>  
>>

- Péter

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