Re: [PATCH] The sun50i_iommu_of_xlate() function didn't properly handle the case where of_find_device_by_node() returns NULL. This could lead to a NULL pointer dereference when accessing platform_get_drvdata(iommu_pdev) if the device node couldn't be found.

[Robin Murphy <robin.murphy@arm.com>]

On 2025-06-24 9:35 am, Zhang Shurong wrote:
> Add a WARN_ON() check to detect this condition and return -ENODEV when it
> occurs. This ensures proper error handling and helps diagnose incorrect
> device tree configurations at runtime.

Please look at how this op is called in of_iommu_xlate(), then at how 
the ops are registered by sun50i_iommu_probe(), and then clarify how you 
think the driver could ever be bound to a device which does not exist.

Thanks,
Robin.

> Fixes: 4100b8c229b3 ("iommu: Add Allwinner H6 IOMMU driver")
> Signed-off-by: Zhang Shurong <zhang_shurong@foxmail.com>
> ---
>   drivers/iommu/sun50i-iommu.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/iommu/sun50i-iommu.c b/drivers/iommu/sun50i-iommu.c
> index 76c9620af4bb..0f85850269ae 100644
> --- a/drivers/iommu/sun50i-iommu.c
> +++ b/drivers/iommu/sun50i-iommu.c
> @@ -833,6 +833,9 @@ static int sun50i_iommu_of_xlate(struct device *dev,
>   				 const struct of_phandle_args *args)
>   {
>   	struct platform_device *iommu_pdev = of_find_device_by_node(args->np);
> +	if (WARN_ON(!iommu_pdev))
> +		return -ENODEV;
> +
>   	unsigned id = args->args[0];
>   
>   	dev_iommu_priv_set(dev, platform_get_drvdata(iommu_pdev));