Looping when we keep track of this is silly. Only thing we have to be careful is with sampling the connector count. To avoid inconsisten results due to gcc re-computing this, use READ_ONCE.
And to avoid surprising userspace, make sure we don't copy more connectors than planned, and report the actual number of connectors copied. That way any racing hot-add/remove will be handled.
v2: Actually try to not blow up, somehow I lost the hunk that checks we don't copy too much. Noticed by Chris.
Cc: Chris Wilson chris@chris-wilson.co.uk Signed-off-by: Daniel Vetter daniel.vetter@ffwll.ch --- drivers/gpu/drm/drm_mode_config.c | 19 +++++++------------ 1 file changed, 7 insertions(+), 12 deletions(-)
diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c index 2735a5847ffa..64c2971478db 100644 --- a/drivers/gpu/drm/drm_mode_config.c +++ b/drivers/gpu/drm/drm_mode_config.c @@ -90,10 +90,10 @@ int drm_mode_getresources(struct drm_device *dev, void *data, struct drm_crtc *crtc; struct drm_encoder *encoder; int ret = 0; - int connector_count = 0; - int crtc_count = 0; + int connector_count = READ_ONCE(dev->mode_config.num_connector); + int crtc_count = dev->mode_config.num_crtc; int fb_count = 0; - int encoder_count = 0; + int encoder_count = dev->mode_config.num_encoder; int copied = 0; uint32_t __user *fb_id; uint32_t __user *crtc_id; @@ -131,15 +131,6 @@ int drm_mode_getresources(struct drm_device *dev, void *data, /* 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; @@ -179,6 +170,9 @@ int drm_mode_getresources(struct drm_device *dev, void *data, copied = 0; connector_id = (uint32_t __user *)(unsigned long)card_res->connector_id_ptr; drm_for_each_connector(connector, dev) { + if (copied >= connector_count) + break; + if (put_user(connector->base.id, connector_id + copied)) { ret = -EFAULT; @@ -186,6 +180,7 @@ int drm_mode_getresources(struct drm_device *dev, void *data, } copied++; } + connector_count = copied; } card_res->count_connectors = connector_count;