[mutter/gnome-3-28] gpu-kms: Don't crash if drmModeGetResources returns NULL

[Jonas Ådahl <jadahl src gnome org>]

commit 62660bbd1526c6135d149df397b2470c6e71969d
Author: Aaron Plattner <aplattner nvidia com>
Date:   Thu Jul 19 10:51:34 2018 -0700

    gpu-kms: Don't crash if drmModeGetResources returns NULL
    
    DRM drivers can be opened by meta_launcher_open_restricted() even if they don't
    implement modesetting. However, drmModeGetResources() will return NULL.
    
    Check whether that happened in meta_gpu_kms_new() and return with an error
    instead of crashing.
    
    Fixes #223.

 src/backends/native/meta-gpu-kms.c | 7 +++++++
 1 file changed, 7 insertions(+)
---
diff --git a/src/backends/native/meta-gpu-kms.c b/src/backends/native/meta-gpu-kms.c
index 613a60705..259cd7122 100644
--- a/src/backends/native/meta-gpu-kms.c
+++ b/src/backends/native/meta-gpu-kms.c
@@ -801,6 +801,13 @@ meta_gpu_kms_new (MetaMonitorManagerKms  *monitor_manager_kms,
    */
   drm_resources = drmModeGetResources (kms_fd);
 
+  if (!drm_resources)
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED, "No resources");
+      meta_launcher_close_restricted (launcher, kms_fd);
+      return NULL;
+    }
+
   n_connectors = drm_resources->count_connectors;
 
   drmModeFreeResources (drm_resources);