drm/vmwgfx: Allow dropped masters render-node like access on legacy nodes v2

Applications like gnome-shell may try to render after dropping master
privileges. Since the driver should now be safe against this scenario,
allow those applications to use their legacy node like a render node.

v2: Add missing return statement.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>

2 files changed, 12 insertions, 1 deletions

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
index 03854d606d58..e13b20bd9908 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
@@ -1052,10 +1052,15 @@ static struct vmw_master *vmw_master_check(struct drm_device *dev,
         }
 
         /*
-         * Check if we were previously master, but now dropped.
+         * Check if we were previously master, but now dropped. In that
+         * case, allow at least render node functionality.
          */
         if (vmw_fp->locked_master) {
                 mutex_unlock(&dev->master_mutex);
+
+                if (flags & DRM_RENDER_ALLOW)
+                        return NULL;
+
                 DRM_ERROR("Dropped master trying to access ioctl that "
                           "requires authentication.\n");
                 return ERR_PTR(-EACCES);
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
index 5b8595b78429..3361769842f4 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
@@ -911,6 +911,12 @@ vmw_surface_handle_reference(struct vmw_private *dev_priv,
                                   "surface reference.\n");
                         return -EACCES;
                 }
+                if (ACCESS_ONCE(vmw_fpriv(file_priv)->locked_master)) {
+                        DRM_ERROR("Locked master refused legacy "
+                                  "surface reference.\n");
+                        return -EACCES;
+                }
+
                 handle = u_handle;
         }