[PATCH 1/1] drm/hyperv: Fix address space leak when Hyper-V DRM device is removed

[Saurabh Singh Sengar]

On Mon, Feb 10, 2025 at 11:34:41AM -0800, mhkelley58 at gmail.com wrote:
> From: Michael Kelley <mhklinux at outlook.com>
> 
> When a Hyper-V DRM device is probed, the driver allocates MMIO space for
> the vram, and maps it cacheable. If the device removed, or in the error
> path for device probing, the MMIO space is released but no unmap is done.
> Consequently the kernel address space for the mapping is leaked.
> 
> Fix this by adding iounmap() calls in the device removal path, and in the
> error path during device probing.
> 
> Fixes: f1f63cbb705d ("drm/hyperv: Fix an error handling path in hyperv_vmbus_probe()")
> Fixes: a0ab5abced55 ("drm/hyperv : Removing the restruction of VRAM allocation with PCI bar size")
> Signed-off-by: Michael Kelley <mhklinux at outlook.com>
> ---
>  drivers/gpu/drm/hyperv/hyperv_drm_drv.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_drv.c b/drivers/gpu/drm/hyperv/hyperv_drm_drv.c
> index e0953777a206..b491827941f1 100644
> --- a/drivers/gpu/drm/hyperv/hyperv_drm_drv.c
> +++ b/drivers/gpu/drm/hyperv/hyperv_drm_drv.c
> @@ -156,6 +156,7 @@ static int hyperv_vmbus_probe(struct hv_device *hdev,
>  	return 0;
>  
>  err_free_mmio:
> +	iounmap(hv->vram);
>  	vmbus_free_mmio(hv->mem->start, hv->fb_size);
>  err_vmbus_close:
>  	vmbus_close(hdev->channel);
> @@ -174,6 +175,7 @@ static void hyperv_vmbus_remove(struct hv_device *hdev)
>  	vmbus_close(hdev->channel);
>  	hv_set_drvdata(hdev, NULL);
>  
> +	iounmap(hv->vram);
>  	vmbus_free_mmio(hv->mem->start, hv->fb_size);
>  }
>  
> -- 
> 2.25.1
> 

Thanks for the fix. May I know how do you find such issues ?

Reviewed-by: Saurabh Sengar <ssengar at linux.microsoft.com>
Tested-by: Saurabh Sengar <ssengar at linux.microsoft.com>

- Saurabh