drm: Protect master->unique with dev->master_mutex

No one looks at the major/minor versions except the unique/busid
stuff. If we protect that with the master_mutex (since it also affects
the unique of each master, oh well) we can mark these two IOCTL with
DRM_UNLOCKED.

While doing this I realized that the comment for the magic_map is
outdated, I've forgotten to update it in:

commit d2b34ee6
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Fri Jun 17 09:33:21 2016 +0200

    drm: Protect authmagic with master_mutex

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161210215255.7765-1-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_ioctl.c

@@ -115,11 +115,15 @@ static int drm_getunique(struct drm_device *dev, void *data,
 	struct drm_unique *u = data;
 	struct drm_master *master = file_priv->master;
 
+	mutex_lock(&master->dev->master_mutex);
 	if (u->unique_len >= master->unique_len) {
-		if (copy_to_user(u->unique, master->unique, master->unique_len))
+		if (copy_to_user(u->unique, master->unique, master->unique_len)) {
+			mutex_unlock(&master->dev->master_mutex);
 			return -EFAULT;
 		}
+	}
 	u->unique_len = master->unique_len;
+	mutex_unlock(&master->dev->master_mutex);
 
 	return 0;
 }
@@ -340,6 +344,7 @@ static int drm_setversion(struct drm_device *dev, void *data, struct drm_file *f
 	struct drm_set_version *sv = data;
 	int if_version, retcode = 0;
 
+	mutex_lock(&dev->master_mutex);
 	if (sv->drm_di_major != -1) {
 		if (sv->drm_di_major != DRM_IF_MAJOR ||
 		    sv->drm_di_minor < 0 || sv->drm_di_minor > DRM_IF_MINOR) {
@@ -374,6 +379,7 @@ static int drm_setversion(struct drm_device *dev, void *data, struct drm_file *f
 	sv->drm_di_minor = DRM_IF_MINOR;
 	sv->drm_dd_major = dev->driver->major;
 	sv->drm_dd_minor = dev->driver->minor;
+	mutex_unlock(&dev->master_mutex);
 
 	return retcode;
 }
@@ -528,7 +534,7 @@ EXPORT_SYMBOL(drm_ioctl_permit);
 static const struct drm_ioctl_desc drm_ioctls[] = {
 	DRM_IOCTL_DEF(DRM_IOCTL_VERSION, drm_version,
 		      DRM_UNLOCKED|DRM_RENDER_ALLOW|DRM_CONTROL_ALLOW),
-	DRM_IOCTL_DEF(DRM_IOCTL_GET_UNIQUE, drm_getunique, 0),
+	DRM_IOCTL_DEF(DRM_IOCTL_GET_UNIQUE, drm_getunique, DRM_UNLOCKED),
 	DRM_IOCTL_DEF(DRM_IOCTL_GET_MAGIC, drm_getmagic, DRM_UNLOCKED),
 	DRM_IOCTL_DEF(DRM_IOCTL_IRQ_BUSID, drm_irq_by_busid, DRM_MASTER|DRM_ROOT_ONLY),
 	DRM_IOCTL_DEF(DRM_IOCTL_GET_MAP, drm_legacy_getmap_ioctl, DRM_UNLOCKED),
@@ -536,7 +542,7 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
 	DRM_IOCTL_DEF(DRM_IOCTL_GET_STATS, drm_getstats, DRM_UNLOCKED),
 	DRM_IOCTL_DEF(DRM_IOCTL_GET_CAP, drm_getcap, DRM_UNLOCKED|DRM_RENDER_ALLOW),
 	DRM_IOCTL_DEF(DRM_IOCTL_SET_CLIENT_CAP, drm_setclientcap, 0),
-	DRM_IOCTL_DEF(DRM_IOCTL_SET_VERSION, drm_setversion, DRM_MASTER),
+	DRM_IOCTL_DEF(DRM_IOCTL_SET_VERSION, drm_setversion, DRM_UNLOCKED | DRM_MASTER),
 
 	DRM_IOCTL_DEF(DRM_IOCTL_SET_UNIQUE, drm_invalid_op, DRM_AUTH|DRM_MASTER|DRM_ROOT_ONLY),
 	DRM_IOCTL_DEF(DRM_IOCTL_BLOCK, drm_noop, DRM_AUTH|DRM_MASTER|DRM_ROOT_ONLY),

include/drm/drm_auth.h

@@ -33,10 +33,7 @@
  *
  * @refcount: Refcount for this master object.
  * @dev: Link back to the DRM device
- * @unique: Unique identifier: e.g. busid. Protected by drm_global_mutex.
- * @unique_len: Length of unique field. Protected by drm_global_mutex.
- * @magic_map: Map of used authentication tokens. Protected by struct_mutex.
- * @lock: DRI lock information.
+ * @lock: DRI1 lock information.
  * @driver_priv: Pointer to driver-private information.
  *
  * Note that master structures are only relevant for the legacy/primary device
@@ -45,8 +42,20 @@
 struct drm_master {
 	struct kref refcount;
 	struct drm_device *dev;
+	/**
+	 * @unique: Unique identifier: e.g. busid. Protected by struct
+	 * &drm_device master_mutex.
+	 */
 	char *unique;
+	/**
+	 * @unique_len: Length of unique field. Protected by struct &drm_device
+	 * master_mutex.
+	 */
 	int unique_len;
+	/**
+	 * @magic_map: Map of used authentication tokens. Protected by struct
+	 * &drm_device master_mutex.
+	 */
 	struct idr magic_map;
 	struct drm_lock_data lock;
 	void *driver_priv;