[PATCH 4/4] drm: Simplify GETRESOURCES ioctl

[Chris Wilson]

On Sat, Dec 10, 2016 at 10:52:55PM +0100, Daniel Vetter wrote:
> Looping twice when we can do it once is silly. Also use a consistent
> style. Note that there's a good race with the connector list walking,
> since that is no longer protected by mode_config.mutex. But that's for
> a later patch to fix.
> 
> v2: Actually try to not blow up, somehow I lost the hunk that checks
> we don't copy too much. Noticed by Chris.
> 
> v3:
> - squash all drm_mode_getresources cleanups into one
> - use consistent style for walking objects (Chris)
> 
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
>  drivers/gpu/drm/drm_mode_config.c | 119 +++++++++++++++-----------------------
>  1 file changed, 47 insertions(+), 72 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> index 2735a5847ffa..54e371dac694 100644
> --- a/drivers/gpu/drm/drm_mode_config.c
> +++ b/drivers/gpu/drm/drm_mode_config.c
> @@ -84,17 +84,11 @@ int drm_mode_getresources(struct drm_device *dev, void *data,
>  			  struct drm_file *file_priv)
>  {
>  	struct drm_mode_card_res *card_res = data;
> -	struct list_head *lh;
>  	struct drm_framebuffer *fb;
>  	struct drm_connector *connector;
>  	struct drm_crtc *crtc;
>  	struct drm_encoder *encoder;
> -	int ret = 0;
> -	int connector_count = 0;
> -	int crtc_count = 0;
> -	int fb_count = 0;
> -	int encoder_count = 0;
> -	int copied = 0;
> +	int count, ret = 0;
>  	uint32_t __user *fb_id;
>  	uint32_t __user *crtc_id;
>  	uint32_t __user *connector_id;
> @@ -105,89 +99,70 @@ int drm_mode_getresources(struct drm_device *dev, void *data,
>  
>  
>  	mutex_lock(&file_priv->fbs_lock);
> -	/*
> -	 * For the non-control nodes we need to limit the list of resources
> -	 * by IDs in the group list for this node
> -	 */
> -	list_for_each(lh, &file_priv->fbs)
> -		fb_count++;
> -
> -	/* handle this in 4 parts */
> -	/* FBs */
> -	if (card_res->count_fbs >= fb_count) {
> -		copied = 0;
> -		fb_id = (uint32_t __user *)(unsigned long)card_res->fb_id_ptr;
> -		list_for_each_entry(fb, &file_priv->fbs, filp_head) {
> -			if (put_user(fb->base.id, fb_id + copied)) {
> -				mutex_unlock(&file_priv->fbs_lock);
> -				return -EFAULT;
> -			}
> -			copied++;
> +	count = 0;
> +	fb_id = (uint32_t __user *)(unsigned long)card_res->fb_id_ptr;

u64_to_user_ptr() please :)

> +	list_for_each_entry(fb, &file_priv->fbs, filp_head) {
> +		count++;
> +		if (count > card_res->count_fbs)
> +			continue;
> +
> +		if (put_user(fb->base.id, fb_id + count)) {

In this style increment of count has to happen after the copy.

i.e.
	if (count < card_res->count_fbs &&
	    put_user(fb->base.id, fb_id + count) {
	    mutex_unlock()
	    return -EFAULT;
	}
	count++;
 

> +			mutex_unlock(&file_priv->fbs_lock);
> +			return -EFAULT;
>  		}
>  	}
> -	card_res->count_fbs = fb_count;
> +	card_res->count_fbs = count;
>  	mutex_unlock(&file_priv->fbs_lock);

-- 
Chris Wilson, Intel Open Source Technology Centre