[PATCH 1/2] drm/kms: Lock mode_config.mutex consistently from the sysfs handling code.

[Francisco Jerez]

Among other potential issues, this fixes a race between output polling
and status_show() that could cause a load detection false positive
with the nouveau driver.

Signed-off-by: Francisco Jerez <currojerez at riseup.net>
---
 drivers/gpu/drm/drm_sysfs.c |   71 ++++++++++++++++++++++++++++---------------
 1 files changed, 46 insertions(+), 25 deletions(-)

diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index 85da4c4..25a9d9e 100644
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -157,9 +157,13 @@ static ssize_t status_show(struct device *device,
 			   char *buf)
 {
 	struct drm_connector *connector = to_drm_connector(device);
+	struct drm_device *dev = connector->dev;
 	enum drm_connector_status status;
 
+	mutex_lock(&dev->mode_config.mutex);
 	status = connector->funcs->detect(connector, true);
+	mutex_unlock(&dev->mode_config.mutex);
+
 	return snprintf(buf, PAGE_SIZE, "%s\n",
 			drm_get_connector_status_name(status));
 }
@@ -173,9 +177,11 @@ static ssize_t dpms_show(struct device *device,
 	uint64_t dpms_status;
 	int ret;
 
+	mutex_lock(&dev->mode_config.mutex);
 	ret = drm_connector_property_get_value(connector,
 					    dev->mode_config.dpms_property,
 					    &dpms_status);
+	mutex_unlock(&dev->mode_config.mutex);
 	if (ret)
 		return 0;
 
@@ -199,25 +205,27 @@ static ssize_t edid_show(struct file *filp, struct kobject *kobj,
 {
 	struct device *connector_dev = container_of(kobj, struct device, kobj);
 	struct drm_connector *connector = to_drm_connector(connector_dev);
+	struct drm_device *dev = connector->dev;
 	unsigned char *edid;
-	size_t size;
+	size_t size, n = 0;
 
+	mutex_lock(&dev->mode_config.mutex);
 	if (!connector->edid_blob_ptr)
-		return 0;
+		goto out;
 
 	edid = connector->edid_blob_ptr->data;
 	size = connector->edid_blob_ptr->length;
 	if (!edid)
-		return 0;
+		goto out;
 
 	if (off >= size)
-		return 0;
-
-	if (off + count > size)
-		count = size - off;
-	memcpy(buf, edid + off, count);
+		goto out;
 
-	return count;
+	n = min(count, size - (size_t)off);
+	memcpy(buf, edid + off, n);
+out:
+	mutex_unlock(&dev->mode_config.mutex);
+	return n;
 }
 
 static ssize_t modes_show(struct device *device,
@@ -225,13 +233,16 @@ static ssize_t modes_show(struct device *device,
 			   char *buf)
 {
 	struct drm_connector *connector = to_drm_connector(device);
+	struct drm_device *dev = connector->dev;
 	struct drm_display_mode *mode;
 	int written = 0;
 
+	mutex_lock(&dev->mode_config.mutex);
 	list_for_each_entry(mode, &connector->modes, head) {
 		written += snprintf(buf + written, PAGE_SIZE - written, "%s\n",
 				    mode->name);
 	}
+	mutex_unlock(&dev->mode_config.mutex);
 
 	return written;
 }
@@ -245,7 +256,9 @@ static ssize_t subconnector_show(struct device *device,
 	struct drm_property *prop = NULL;
 	uint64_t subconnector;
 	int is_tv = 0;
-	int ret;
+	int ret = 0;
+
+	mutex_lock(&dev->mode_config.mutex);
 
 	switch (connector->connector_type) {
 		case DRM_MODE_CONNECTOR_DVII:
@@ -260,21 +273,24 @@ static ssize_t subconnector_show(struct device *device,
 			break;
 		default:
 			DRM_ERROR("Wrong connector type for this property\n");
-			return 0;
+			goto out;
 	}
 
 	if (!prop) {
 		DRM_ERROR("Unable to find subconnector property\n");
-		return 0;
+		goto out;
 	}
 
 	ret = drm_connector_property_get_value(connector, prop, &subconnector);
 	if (ret)
-		return 0;
+		goto out;
 
-	return snprintf(buf, PAGE_SIZE, "%s", is_tv ?
-			drm_get_tv_subconnector_name((int)subconnector) :
-			drm_get_dvi_i_subconnector_name((int)subconnector));
+	ret = snprintf(buf, PAGE_SIZE, "%s", is_tv ?
+		       drm_get_tv_subconnector_name((int)subconnector) :
+		       drm_get_dvi_i_subconnector_name((int)subconnector));
+out:
+	mutex_unlock(&dev->mode_config.mutex);
+	return ret;
 }
 
 static ssize_t select_subconnector_show(struct device *device,
@@ -286,7 +302,9 @@ static ssize_t select_subconnector_show(struct device *device,
 	struct drm_property *prop = NULL;
 	uint64_t subconnector;
 	int is_tv = 0;
-	int ret;
+	int ret = 0;
+
+	mutex_lock(&dev->mode_config.mutex);
 
 	switch (connector->connector_type) {
 		case DRM_MODE_CONNECTOR_DVII:
@@ -301,21 +319,24 @@ static ssize_t select_subconnector_show(struct device *device,
 			break;
 		default:
 			DRM_ERROR("Wrong connector type for this property\n");
-			return 0;
+			goto out;
 	}
 
 	if (!prop) {
 		DRM_ERROR("Unable to find select subconnector property\n");
-		return 0;
+		goto out;
 	}
 
 	ret = drm_connector_property_get_value(connector, prop, &subconnector);
 	if (ret)
-		return 0;
+		goto out;
 
-	return snprintf(buf, PAGE_SIZE, "%s", is_tv ?
-			drm_get_tv_select_name((int)subconnector) :
-			drm_get_dvi_i_select_name((int)subconnector));
+	ret = snprintf(buf, PAGE_SIZE, "%s", is_tv ?
+		       drm_get_tv_select_name((int)subconnector) :
+		       drm_get_dvi_i_select_name((int)subconnector));
+out:
+	mutex_unlock(&dev->mode_config.mutex);
+	return ret;
 }
 
 static struct device_attribute connector_attrs[] = {
-- 
1.6.4.4