linux-kernel - Re: [PATCH] iommu/sun50i: check return value of of_find_device_by_node() in sun50i_iommu_of

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Message-ID: <2c2669d1-7f19-5be4-b6df-7cf896015336@arm.com>
Date:   Thu, 29 Oct 2020 10:21:19 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Yu Kuai <yukuai3@...wei.com>, joro@...tes.org, mripard@...nel.org,
        wens@...e.org
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, yi.zhang@...wei.com
Subject: Re: [PATCH] iommu/sun50i: check return value of
 of_find_device_by_node() in sun50i_iommu_of_xlate()

On 2020-10-29 09:22, Yu Kuai wrote:
> If of_find_device_by_node() failed in sun50i_iommu_of_xlate(), null
> pointer dereference will be triggered. Thus return error code if
> of_find_device_by_node() failed.

Again, by what means can that ever actually happen?

Robin.

> Fixes: 4100b8c229b3("iommu: Add Allwinner H6 IOMMU driver")
> Signed-off-by: Yu Kuai <yukuai3@...wei.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 ea6db1341916..ce94ffa15215 100644
> --- a/drivers/iommu/sun50i-iommu.c
> +++ b/drivers/iommu/sun50i-iommu.c
> @@ -764,6 +764,9 @@ static int sun50i_iommu_of_xlate(struct device *dev,
>   	struct platform_device *iommu_pdev = of_find_device_by_node(args->np);
>   	unsigned id = args->args[0];
>   
> +	if (!iommu_pdev)
> +		return -ENODEV;
> +
>   	dev_iommu_priv_set(dev, platform_get_drvdata(iommu_pdev));
>   
>   	return iommu_fwspec_add_ids(dev, &id, 1);
>