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Date: Tue, 28 May 2024 10:25:28 +0100
From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>, Jason Gunthorpe <jgg@ziepe.ca>,
	Kevin Tian <kevin.tian@intel.com>, iommu@lists.linux.dev,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] iommu: Return right value in iommu_sva_bind_device()
Message-ID: <20240528092528.GA2482616@myrica>
References: <20240528042528.71396-1-baolu.lu@linux.intel.com>
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In-Reply-To: <20240528042528.71396-1-baolu.lu@linux.intel.com>

On Tue, May 28, 2024 at 12:25:28PM +0800, Lu Baolu wrote:
> iommu_sva_bind_device() should return either a sva bond handle or an
> ERR_PTR value in error cases. Existing drivers (idxd and uacce) only
> check the return value with IS_ERR(). This could potentially lead to
> a kernel NULL pointer dereference issue if the function returns NULL
> instead of an error pointer.
> 
> In reality, this doesn't cause any problems because iommu_sva_bind_device()
> only returns NULL when the kernel is not configured with CONFIG_IOMMU_SVA.
> In this case, iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) will
> return an error, and the device drivers won't call iommu_sva_bind_device()
> at all.
> 
> Fixes: 26b25a2b98e4 ("iommu: Bind process address spaces to devices")
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>

Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>

> ---
>  include/linux/iommu.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 7bc8dff7cf6d..17b3f36ad843 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -1533,7 +1533,7 @@ struct iommu_domain *iommu_sva_domain_alloc(struct device *dev,
>  static inline struct iommu_sva *
>  iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
>  {
> -	return NULL;
> +	return ERR_PTR(-ENODEV);
>  }
>  
>  static inline void iommu_sva_unbind_device(struct iommu_sva *handle)
> -- 
> 2.34.1
>