drm: Simplify GETRESOURCES ioctl

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)

v4:
- Use u64_to_user_ptr (Chris)
- Don't forget to copy the last connector (Chris)

v5: Chris was right ...

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161211192019.29603-1-daniel.vetter@ffwll.ch

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 +99,62 @@ 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;
+	count = 0;
+	fb_id = u64_to_user_ptr(card_res->fb_id_ptr);
 	list_for_each_entry(fb, &file_priv->fbs, filp_head) {
-			if (put_user(fb->base.id, fb_id + copied)) {
+		if (count < card_res->count_fbs &&
+		    put_user(fb->base.id, fb_id + count)) {
 			mutex_unlock(&file_priv->fbs_lock);
 			return -EFAULT;
 		}
-			copied++;
-		}
+		count++;
 	}
-	card_res->count_fbs = fb_count;
+	card_res->count_fbs = count;
 	mutex_unlock(&file_priv->fbs_lock);
 
 	/* mode_config.mutex protects the connector list against e.g. DP MST
 	 * connector hot-adding. CRTC/Plane lists are invariant. */
 	mutex_lock(&dev->mode_config.mutex);
-	drm_for_each_crtc(crtc, dev)
-		crtc_count++;
-
-	drm_for_each_connector(connector, dev)
-		connector_count++;
-
-	drm_for_each_encoder(encoder, dev)
-		encoder_count++;
-
 	card_res->max_height = dev->mode_config.max_height;
 	card_res->min_height = dev->mode_config.min_height;
 	card_res->max_width = dev->mode_config.max_width;
 	card_res->min_width = dev->mode_config.min_width;
 
-	/* CRTCs */
-	if (card_res->count_crtcs >= crtc_count) {
-		copied = 0;
-		crtc_id = (uint32_t __user *)(unsigned long)card_res->crtc_id_ptr;
+	count = 0;
+	crtc_id = u64_to_user_ptr(card_res->crtc_id_ptr);
 	drm_for_each_crtc(crtc, dev) {
-			if (put_user(crtc->base.id, crtc_id + copied)) {
+		if (count < card_res->count_crtcs &&
+		    put_user(crtc->base.id, crtc_id + count)) {
 			ret = -EFAULT;
 			goto out;
 		}
-			copied++;
+		count++;
 	}
-	}
-	card_res->count_crtcs = crtc_count;
+	card_res->count_crtcs = count;
 
-	/* Encoders */
-	if (card_res->count_encoders >= encoder_count) {
-		copied = 0;
-		encoder_id = (uint32_t __user *)(unsigned long)card_res->encoder_id_ptr;
+	count = 0;
+	encoder_id = u64_to_user_ptr(card_res->encoder_id_ptr);
 	drm_for_each_encoder(encoder, dev) {
-			if (put_user(encoder->base.id, encoder_id +
-				     copied)) {
+		if (count < card_res->count_encoders &&
+		    put_user(encoder->base.id, encoder_id + count)) {
 			ret = -EFAULT;
 			goto out;
 		}
-			copied++;
-		}
+		count++;
 	}
-	card_res->count_encoders = encoder_count;
+	card_res->count_encoders = count;
 
-	/* Connectors */
-	if (card_res->count_connectors >= connector_count) {
-		copied = 0;
-		connector_id = (uint32_t __user *)(unsigned long)card_res->connector_id_ptr;
+	count = 0;
+	connector_id = u64_to_user_ptr(card_res->connector_id_ptr);
 	drm_for_each_connector(connector, dev) {
-			if (put_user(connector->base.id,
-				     connector_id + copied)) {
+		if (count < card_res->count_connectors &&
+		    put_user(connector->base.id, connector_id + count)) {
 			ret = -EFAULT;
 			goto out;
 		}
-			copied++;
-		}
+		count++;
 	}
-	card_res->count_connectors = connector_count;
+	card_res->count_connectors = count;
 
 out:
 	mutex_unlock(&dev->mode_config.mutex);