linux-kernel - Re: [PATCH for-4.5] vfio: fix ioctl error handling

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Date:	Sun, 28 Feb 2016 07:23:22 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	Dan Carpenter <dan.carpenter@...cle.com>,
	stable@...r.kernel.org,
	Baptiste Reynal <b.reynal@...tualopensystems.com>,
	Eric Auger <eric.auger@...aro.org>,
	Antonios Motakis <a.motakis@...tualopensystems.com>,
	Julia Lawall <Julia.Lawall@...6.fr>, kvm@...r.kernel.org
Subject: Re: [PATCH for-4.5] vfio: fix ioctl error handling

On Thu, 25 Feb 2016 13:34:43 +0200
"Michael S. Tsirkin" <mst@...hat.com> wrote:

> Calling return copy_to_user(...) in an ioctl will not
> do the right thing if there's a pagefault:
> copy_to_user returns the number of bytes not copied
> in this case.
> 
> Fix up vfio to do
> 	if (copy_to_user(...))
> 		return -EFAULT;
> 
> everywhere.
> 
> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> Cc: stable@...r.kernel.org
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
>  drivers/vfio/pci/vfio_pci.c                  | 9 ++++++---
>  drivers/vfio/platform/vfio_platform_common.c | 9 ++++++---
>  drivers/vfio/vfio_iommu_type1.c              | 6 ++++--
>  3 files changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index 2760a7b..27a727a 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -446,7 +446,8 @@ static long vfio_pci_ioctl(void *device_data,
>  		info.num_regions = VFIO_PCI_NUM_REGIONS;
>  		info.num_irqs = VFIO_PCI_NUM_IRQS;
>  
> -		return copy_to_user((void __user *)arg, &info, minsz);
> +		if (copy_to_user((void __user *)arg, &info, minsz))
> +			return -EFAULT;

Ok, but where do we return 0 on success now?

>  
>  	} else if (cmd == VFIO_DEVICE_GET_REGION_INFO) {
>  		struct pci_dev *pdev = vdev->pdev;
> @@ -520,7 +521,8 @@ static long vfio_pci_ioctl(void *device_data,
>  			return -EINVAL;
>  		}
>  
> -		return copy_to_user((void __user *)arg, &info, minsz);
> +		if (copy_to_user((void __user *)arg, &info, minsz))
> +			return -EFAULT;
>  
>  	} else if (cmd == VFIO_DEVICE_GET_IRQ_INFO) {
>  		struct vfio_irq_info info;
> @@ -555,7 +557,8 @@ static long vfio_pci_ioctl(void *device_data,
>  		else
>  			info.flags |= VFIO_IRQ_INFO_NORESIZE;
>  
> -		return copy_to_user((void __user *)arg, &info, minsz);
> +		if (copy_to_user((void __user *)arg, &info, minsz))
> +			return -EFAULT;
>  
>  	} else if (cmd == VFIO_DEVICE_SET_IRQS) {
>  		struct vfio_irq_set hdr;
> diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
> index 418cdd9..eea367f 100644
> --- a/drivers/vfio/platform/vfio_platform_common.c
> +++ b/drivers/vfio/platform/vfio_platform_common.c
> @@ -219,7 +219,8 @@ static long vfio_platform_ioctl(void *device_data,
>  		info.num_regions = vdev->num_regions;
>  		info.num_irqs = vdev->num_irqs;
>  
> -		return copy_to_user((void __user *)arg, &info, minsz);
> +		if (copy_to_user((void __user *)arg, &info, minsz))
> +			return -EFAULT;
>  
>  	} else if (cmd == VFIO_DEVICE_GET_REGION_INFO) {
>  		struct vfio_region_info info;
> @@ -240,7 +241,8 @@ static long vfio_platform_ioctl(void *device_data,
>  		info.size = vdev->regions[info.index].size;
>  		info.flags = vdev->regions[info.index].flags;
>  
> -		return copy_to_user((void __user *)arg, &info, minsz);
> +		if (copy_to_user((void __user *)arg, &info, minsz))
> +			return -EFAULT;
>  
>  	} else if (cmd == VFIO_DEVICE_GET_IRQ_INFO) {
>  		struct vfio_irq_info info;
> @@ -259,7 +261,8 @@ static long vfio_platform_ioctl(void *device_data,
>  		info.flags = vdev->irqs[info.index].flags;
>  		info.count = vdev->irqs[info.index].count;
>  
> -		return copy_to_user((void __user *)arg, &info, minsz);
> +		if (copy_to_user((void __user *)arg, &info, minsz))
> +			return -EFAULT;
>  
>  	} else if (cmd == VFIO_DEVICE_SET_IRQS) {
>  		struct vfio_irq_set hdr;
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 6f1ea3d..62614f7 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -999,7 +999,8 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>  
>  		info.iova_pgsizes = vfio_pgsize_bitmap(iommu);
>  
> -		return copy_to_user((void __user *)arg, &info, minsz);
> +		if (copy_to_user((void __user *)arg, &info, minsz))
> +			return -EFAULT;
>  
>  	} else if (cmd == VFIO_IOMMU_MAP_DMA) {
>  		struct vfio_iommu_type1_dma_map map;
> @@ -1032,7 +1033,8 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>  		if (ret)
>  			return ret;
>  
> -		return copy_to_user((void __user *)arg, &unmap, minsz);
> +		if (copy_to_user((void __user *)arg, &unmap, minsz))
> +			return -EFAULT;
>  	}
>  
>  	return -ENOTTY;

All successes now land here in their respective files.  Thanks,

Alex