Re: [PATCH] iommu/dart: add missing put_device() call in apple_dart_of_xlate

[Will Deacon <will@kernel.org>]

On Sun, Jul 13, 2025 at 12:16:24AM +0800, Zhang Shurong wrote:
> The apple_dart_of_xlate() function obtains a platform device reference
> via of_find_device_by_node() but doesn't release it with put_device().
> This patch adds proper device reference handling to prevent memory
> leaks.
> 
> Fixes: 46d1fb072e76 ("iommu/dart: Add DART iommu driver")
> Signed-off-by: Zhang Shurong <zhang_shurong@foxmail.com>
> ---
>  drivers/iommu/apple-dart.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
> index 190f28d76615..811bf5176568 100644
> --- a/drivers/iommu/apple-dart.c
> +++ b/drivers/iommu/apple-dart.c
> @@ -796,8 +796,10 @@ static int apple_dart_of_xlate(struct device *dev,
>  
>  	if (!cfg) {
>  		cfg = kzalloc(sizeof(*cfg), GFP_KERNEL);
> -		if (!cfg)
> +		if (!cfg)  {
> +			put_device(&iommu_pdev->dev);
>  			return -ENOMEM;
> +		}
>  		/* Will be ANDed with DART capabilities */
>  		cfg->supports_bypass = true;
>  	}
> @@ -805,8 +807,10 @@ static int apple_dart_of_xlate(struct device *dev,
>  
>  	cfg_dart = cfg->stream_maps[0].dart;
>  	if (cfg_dart) {
> -		if (cfg_dart->pgsize != dart->pgsize)
> +		if (cfg_dart->pgsize != dart->pgsize) {
> +			put_device(&iommu_pdev->dev);
>  			return -EINVAL;
> +		}
>  	}
>  
>  	cfg->supports_bypass &= dart->supports_bypass;
> @@ -825,6 +829,8 @@ static int apple_dart_of_xlate(struct device *dev,
>  		}
>  	}
>  
> +
> +	put_device(&iommu_pdev->dev);
>  	return -EINVAL;

Why is it correct to retain the reference on the device in the cases
where this function returns 0?

Will