linux-kernel - 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.

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Message-ID: <ad58db6e-7c1d-42c4-8039-0d7f0f057726@arm.com>
Date: Wed, 25 Jun 2025 11:41:35 +0100
From: Robin Murphy <robin.murphy@....com>
To: Zhang Shurong <zhang_shurong@...mail.com>, joro@...tes.org
Cc: will@...nel.org, wens@...e.org, jernej.skrabec@...il.com,
 samuel@...lland.org, iommu@...ts.linux.dev,
 linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: 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.

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@...mail.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));