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

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Message-ID: <20250211033326.GA17799@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
Date: Mon, 10 Feb 2025 19:33:26 -0800
From: Saurabh Singh Sengar <ssengar@...ux.microsoft.com>
To: mhklinux@...look.com
Cc: drawat.floss@...il.com, maarten.lankhorst@...ux.intel.com,
	mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com,
	simona@...ll.ch, christophe.jaillet@...adoo.fr, wei.liu@...nel.org,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-hyperv@...r.kernel.org
Subject: Re: [PATCH 1/1] drm/hyperv: Fix address space leak when Hyper-V DRM
 device is removed

On Mon, Feb 10, 2025 at 11:34:41AM -0800, mhkelley58@...il.com wrote:
> From: Michael Kelley <mhklinux@...look.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@...look.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@...ux.microsoft.com>
Tested-by: Saurabh Sengar <ssengar@...ux.microsoft.com>

- Saurabh