drm/vmwgfx: check master authentication in surface_ref ioctls

With later commit we'll rework DRM authentication handling. Namely
DRM_AUTH will not be a requirement for DRM_RENDER_ALLOW ioctls.

Since vmwgfx does isolation for primary clients in different master
realms, the DRM_AUTH can be dropped.

The only place where authentication matters, is surface_reference ioctls
whenever a legacy (non-prime) handle is used. For those ioctls we call
vmw_surface_handle_reference(), where we explicitly check if the client
is both a) master and b) unauthenticated - bailing out as result.

Otherwise the usual isolation path kicks in and we're all good.

v2: Reword commit message, since the isolation work has landed.

Cc: VMware Graphics <[e-mail]>
Cc: Thomas Hellstrom <[e-mail]>
Signed-off-by: Emil Velikov <[e-mail]>
Reviewed-by: Thomas Hellstrom <[e-mail]>
Signed-off-by: Thomas Hellstrom <[e-mail]>

drivers/gpu/drm/vmwgfx/vmwgfx_surface.c

···
 		user_srf = container_of(base, struct vmw_user_surface,
 					prime.base);
 
+		/* Error out if we are unauthenticated primary */
+		if (drm_is_primary_client(file_priv) &&
+		    !file_priv->authenticated) {
+			ret = -EACCES;
+			goto out_bad_resource;
+		}
+
 		/*
 		 * Make sure the surface creator has the same
 		 * authenticating master, or is already registered with us.