drm: Make control nodes master-less v3

Like for render-nodes, there is no point in maintaining the master concept
for control nodes, so set the struct drm_file::master pointer to NULL.

At the same time, make sure DRM_MASTER | DRM_CONTROL_ALLOW ioctls are always
allowed when called through the control node. Previously the caller also
needed to be master.

v2: Adapt to refactoring of ioctl permission check.
v3: Formatting of logical expression. Use drm_is_control_client() instead of
    drm_is_control().

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>

3 files changed, 13 insertions, 5 deletions

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 05e30530c025..cf2dfb790bf1 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -306,13 +306,14 @@ static int drm_ioctl_permit(u32 flags, struct drm_file *file_priv)
                      !file_priv->authenticated))
                 return -EACCES;
 
-        /* MASTER is only for master */
-        if (unlikely((flags & DRM_MASTER) && !file_priv->is_master))
+        /* MASTER is only for master or control clients */
+        if (unlikely((flags & DRM_MASTER) && !file_priv->is_master &&
+                     !drm_is_control_client(file_priv)))
                 return -EACCES;
 
         /* Control clients must be explicitly allowed */
         if (unlikely(!(flags & DRM_CONTROL_ALLOW) &&
-                     file_priv->minor->type == DRM_MINOR_CONTROL))
+                     drm_is_control_client(file_priv)))
                 return -EACCES;
 
         /* Render clients must be explicitly allowed */
diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
index 9b02f126fb0d..5432a1a61c15 100644
--- a/drivers/gpu/drm/drm_fops.c
+++ b/drivers/gpu/drm/drm_fops.c
@@ -232,7 +232,8 @@ static int drm_open_helper(struct inode *inode, struct file *filp,
         /* if there is no current master make this fd it, but do not create
          * any master object for render clients */
         mutex_lock(&dev->struct_mutex);
-        if (!priv->minor->master && !drm_is_render_client(priv)) {
+        if (!priv->minor->master && !drm_is_render_client(priv) &&
+            !drm_is_control_client(priv)) {
                 /* create a new master */
                 priv->minor->master = drm_master_create(priv->minor);
                 if (!priv->minor->master) {
@@ -270,7 +271,8 @@ static int drm_open_helper(struct inode *inode, struct file *filp,
                                 goto out_close;
                         }
                 }
-        } else if (!drm_is_render_client(priv)) {
+        } else if (!drm_is_render_client(priv) &&
+                   !drm_is_control_client(priv)) {
                 /* get a reference to the master */
                 priv->master = drm_master_get(priv->minor->master);
         }
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 2242968e7deb..3cf9f46ce2e6 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1207,6 +1207,11 @@ static inline bool drm_is_render_client(struct drm_file *file_priv)
         return file_priv->minor->type == DRM_MINOR_RENDER;
 }
 
+static inline bool drm_is_control_client(const struct drm_file *file_priv)
+{
+        return file_priv->minor->type == DRM_MINOR_CONTROL;
+}
+
 /******************************************************************/
 /** \name Internal function definitions */
 /*@{*/