[PATCH] drm/ttm: add a WARN_ON in ttm_set_driver_manager when array bounds (v2)

[Chen, Guchun]

[Public]

Thanks for your suggestion, Robin. Do you agree with this as well, Christian and Xinhui?

Regards,
Guchun

-----Original Message-----
From: Robin Murphy <robin.murphy at arm.com> 
Sent: Saturday, September 11, 2021 2:25 AM
To: Chen, Guchun <Guchun.Chen at amd.com>; amd-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org; Koenig, Christian <Christian.Koenig at amd.com>; Pan, Xinhui <Xinhui.Pan at amd.com>; Deucher, Alexander <Alexander.Deucher at amd.com>
Cc: Shi, Leslie <Yuliang.Shi at amd.com>
Subject: Re: [PATCH] drm/ttm: add a WARN_ON in ttm_set_driver_manager when array bounds (v2)

On 2021-09-10 11:09, Guchun Chen wrote:
> Vendor will define their own memory types on top of TTM_PL_PRIV, but 
> call ttm_set_driver_manager directly without checking mem_type value 
> when setting up memory manager. So add such check to aware the case 
> when array bounds.
> 
> v2: lower check level to WARN_ON
> 
> Signed-off-by: Leslie Shi <Yuliang.Shi at amd.com>
> Signed-off-by: Guchun Chen <guchun.chen at amd.com>
> ---
>   include/drm/ttm/ttm_device.h | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/include/drm/ttm/ttm_device.h 
> b/include/drm/ttm/ttm_device.h index 07d722950d5b..aa79953c807c 100644
> --- a/include/drm/ttm/ttm_device.h
> +++ b/include/drm/ttm/ttm_device.h
> @@ -291,6 +291,7 @@ ttm_manager_type(struct ttm_device *bdev, int mem_type)
>   static inline void ttm_set_driver_manager(struct ttm_device *bdev, int type,
>   					  struct ttm_resource_manager *manager)
>   {
> +	WARN_ON(type >= TTM_NUM_MEM_TYPES);

Nit: I know nothing about this code, but from the context alone it would seem sensible to do

	if (WARN_ON(type >= TTM_NUM_MEM_TYPES))
		return;

to avoid making the subsequent assignment when we *know* it's invalid and likely to corrupt memory.

Robin.

>   	bdev->man_drv[type] = manager;
>   }
>   
>