Re: [PATCH] drm: Use kvzalloc for allocating blob property memory

[Ville Syrjälä]

On Fri, Jun 29, 2018 at 04:27:10PM +0200, Michel Dänzer wrote:
> From: Michel Dänzer <michel.daenzer@xxxxxxx>
> 
> The property size may be controlled by userspace, can be large (I've
> seen failure with order 4, i.e. 16 pages / 64 KB) and doesn't need to be
> physically contiguous.

I wonder if we should enforce some kind of reasonable limit
on the blob size. Looks like we allow anything up to
ULONG_MAX currently. We can't tell at createblob time how
the thing is going to be used, so can't have any kind
of property specific limit unfortunately.

> 
> Signed-off-by: Michel Dänzer <michel.daenzer@xxxxxxx>
> ---
>  drivers/gpu/drm/drm_property.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_property.c b/drivers/gpu/drm/drm_property.c
> index 1f8031e30f53..cdb10f885a4f 100644
> --- a/drivers/gpu/drm/drm_property.c
> +++ b/drivers/gpu/drm/drm_property.c
> @@ -532,7 +532,7 @@ static void drm_property_free_blob(struct kref *kref)
>  
>  	drm_mode_object_unregister(blob->dev, &blob->base);
>  
> -	kfree(blob);
> +	kvfree(blob);
>  }
>  
>  /**
> @@ -559,7 +559,7 @@ drm_property_create_blob(struct drm_device *dev, size_t length,
>  	if (!length || length > ULONG_MAX - sizeof(struct drm_property_blob))
>  		return ERR_PTR(-EINVAL);
>  
> -	blob = kzalloc(sizeof(struct drm_property_blob)+length, GFP_KERNEL);
> +	blob = kvzalloc(sizeof(struct drm_property_blob)+length, GFP_KERNEL);
>  	if (!blob)
>  		return ERR_PTR(-ENOMEM);
>  
> @@ -576,7 +576,7 @@ drm_property_create_blob(struct drm_device *dev, size_t length,
>  	ret = __drm_mode_object_add(dev, &blob->base, DRM_MODE_OBJECT_BLOB,
>  				    true, drm_property_free_blob);
>  	if (ret) {
> -		kfree(blob);
> +		kvfree(blob);
>  		return ERR_PTR(-EINVAL);
>  	}
>  
> -- 
> 2.18.0
> 
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-- 
Ville Syrjälä
Intel