linux-kernel - Re: [PATCH] iommu: Check dev->iommu in iommu_dev

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Date:   Tue, 26 Jan 2021 13:50:40 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
Cc:     <linux-kernel@...r.kernel.org>, <iommu@...ts.linux-foundation.org>,
        jean-philippe@...aro.org, will@...nel.org, linuxarm@...neuler.org,
        prime.zeng@...ilicon.com
Subject: Re: [PATCH] iommu: Check dev->iommu in iommu_dev_xxx functions

On Tue, 26 Jan 2021 13:06:29 +0000
Shameer Kolothum <shameerali.kolothum.thodi@...wei.com> wrote:

> The device iommu probe/attach might have failed leaving dev->iommu
> to NULL and device drivers may still invoke these functions resulting
> a crash in iommu vendor driver code. Hence make sure we check that.
> 
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
> ---
>  drivers/iommu/iommu.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index ffeebda8d6de..cb68153c5cc0 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2867,7 +2867,7 @@ bool iommu_dev_has_feature(struct device *dev,
> enum iommu_dev_features feat) {
>  	const struct iommu_ops *ops = dev->bus->iommu_ops;
>  
> -	if (ops && ops->dev_has_feat)
> +	if (dev->iommu && ops && ops->dev_has_feat)
>  		return ops->dev_has_feat(dev, feat);

Might make sense to make these more self-contained, e.g.:

	if (dev->iommu && dev->iommu->ops->foo)
		dev->iommu->ops->foo()

Robin.

 
>  	return false;
> @@ -2878,7 +2878,7 @@ int iommu_dev_enable_feature(struct device
> *dev, enum iommu_dev_features feat) {
>  	const struct iommu_ops *ops = dev->bus->iommu_ops;
>  
> -	if (ops && ops->dev_enable_feat)
> +	if (dev->iommu && ops && ops->dev_enable_feat)
>  		return ops->dev_enable_feat(dev, feat);
>  
>  	return -ENODEV;
> @@ -2894,7 +2894,7 @@ int iommu_dev_disable_feature(struct device
> *dev, enum iommu_dev_features feat) {
>  	const struct iommu_ops *ops = dev->bus->iommu_ops;
>  
> -	if (ops && ops->dev_disable_feat)
> +	if (dev->iommu && ops && ops->dev_disable_feat)
>  		return ops->dev_disable_feat(dev, feat);
>  
>  	return -EBUSY;
> @@ -2905,7 +2905,7 @@ bool iommu_dev_feature_enabled(struct device
> *dev, enum iommu_dev_features feat) {
>  	const struct iommu_ops *ops = dev->bus->iommu_ops;
>  
> -	if (ops && ops->dev_feat_enabled)
> +	if (dev->iommu && ops && ops->dev_feat_enabled)
>  		return ops->dev_feat_enabled(dev, feat);
>  
>  	return false;