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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
---
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;
--
2.10.2
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