Re: [PATCH] can: c_can: Use platform id data when OF data is absent

[Vincent Mailhol <mailhol@kernel.org>]

On 24/06/2026 at 11:53, Vincent Mailhol wrote:
> On 24/06/2026 at 07:49, Pengpeng Hou wrote:
>> The platform driver keeps controller metadata in both the OF match table
>> and the platform id table.  Probe reads the metadata with
>> device_get_match_data(), which does not fall back to platform id-table
>> driver_data.
>>
>> When the device is matched through the platform id table, drvdata can
>> therefore be NULL before it is dereferenced for msg_obj_num and the
>> controller type.  Fall back to platform_get_device_id() when firmware
>> match data is not available.
> 
> So, you are telling me that this patch fixes a NULL pointer
> dereference? In that case, it needs to be backported. Please add a
> Fixes: tag.

Also, were you able to trigger that NULL pointer dereference?

> Fixes: 5e6c3454b405 ("net: can: Use device_get_match_data()")
> 
>> Signed-off-by: Pengpeng Hou <pengpeng@iscas.ac.cn>
>> ---
>>  drivers/net/can/c_can/c_can_platform.c | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/drivers/net/can/c_can/c_can_platform.c b/drivers/net/can/c_can/c_can_platform.c
>> index 19c86b94a40e..564c9e5b4c2c 100644
>> --- a/drivers/net/can/c_can/c_can_platform.c
>> +++ b/drivers/net/can/c_can/c_can_platform.c
>> @@ -263,9 +263,17 @@ static int c_can_plat_probe(struct platform_device *pdev)
>>  	int irq;
>>  	struct clk *clk;
>>  	const struct c_can_driver_data *drvdata;
>> +	const struct platform_device_id *id;
>>  	struct device_node *np = pdev->dev.of_node;
>>  
>>  	drvdata = device_get_match_data(&pdev->dev);
>> +	if (!drvdata) {
>> +		id = platform_get_device_id(pdev);
>> +		if (!id)
>> +			return -ENODEV;
>> +
>> +		drvdata = (const struct c_can_driver_data *)id->driver_data;
>> +	}
> 
> Reduce the visibility of id:
> 
> 	if (!drvdata) {
> 		const struct platform_device_id *id;
> 
> 		id = platform_get_device_id(pdev);
> 		if (!id)
> 			return -ENODEV;
> 
> 		drvdata = (const struct c_can_driver_data *)id->driver_data;
> 	}
> 
>>  
>>  	/* get the appropriate clk */
>>  	clk = devm_clk_get(&pdev->dev, NULL);
> 
> With the Fixes: tag added and above nitpick addressed:
> 
> Reviewed-by: Vincent Mailhol <mailhol@kernel.org>


Yours sincerely,
Vincent Mailhol