[PATCH 08/13] drm/irq: Check for valid VBLANK before dereference

[Michel Dänzer]

On 17.12.2014 01:53, Thierry Reding wrote:
> From: Thierry Reding <treding at nvidia.com>
> 
> When accessing the array of per-CRTC VBLANK structures we must always
> check that the index into the array is valid before dereferencing to
> avoid crashing.
> 
> Signed-off-by: Thierry Reding <treding at nvidia.com>
> ---
>  drivers/gpu/drm/drm_irq.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> index a24658162284..cb207e047505 100644
> --- a/drivers/gpu/drm/drm_irq.c
> +++ b/drivers/gpu/drm/drm_irq.c
> @@ -1070,10 +1070,10 @@ void drm_vblank_put(struct drm_device *dev, int crtc)
>  {
>  	struct drm_vblank_crtc *vblank = &dev->vblank[crtc];
>  
> -	if (WARN_ON(atomic_read(&vblank->refcount) == 0))
> +	if (WARN_ON(crtc >= dev->num_crtcs))
>  		return;
>  
> -	if (WARN_ON(crtc >= dev->num_crtcs))
> +	if (WARN_ON(atomic_read(&vblank->refcount) == 0))
>  		return;
>  
>  	/* Last user schedules interrupt disable */
> @@ -1356,6 +1356,9 @@ void drm_vblank_post_modeset(struct drm_device *dev, int crtc)
>  	if (!dev->num_crtcs)
>  		return;
>  
> +	if (WARN_ON(crtc >= dev->num_crtcs))
> +		return;
> +
>  	if (vblank->inmodeset) {
>  		spin_lock_irqsave(&dev->vbl_lock, irqflags);
>  		dev->vblank_disable_allowed = true;
> 

It would probably be better to use WARN_ON_ONCE, otherwise any bugs
triggering these might flood dmesg.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer