[mutter] wayland/dma-buf: Handle lack of gbm_device gracefully

[Marge Bot <marge-bot src gnome org>]

commit a09b99261f44a9e90c7361245e671e027855a66c
Author: Jonas Ådahl <jadahl gmail com>
Date:   Fri Mar 4 18:06:26 2022 +0100

    wayland/dma-buf: Handle lack of gbm_device gracefully
    
    In some configurations (e.g. NVIDIA driver 470) Xwayland may use DMA
    buffer for passing buffers around. When this is done, we might attempt
    to scanout these buffers when they are fullscreen, and to do so we
    import them using gbm.
    
    However, for the mentioned configuration, there is no gbm device
    available for importing. This was not handled, and resulted in a crash;
    avoid this crash by checking whether we have a gbm device and fail
    gracefully if we don't.
    
    Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/2098
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2318>

 src/wayland/meta-wayland-dma-buf.c | 47 +++++++++++++++++++++++++++-----------
 1 file changed, 34 insertions(+), 13 deletions(-)
---
diff --git a/src/wayland/meta-wayland-dma-buf.c b/src/wayland/meta-wayland-dma-buf.c
index 4f516127cc..699c78eb32 100644
--- a/src/wayland/meta-wayland-dma-buf.c
+++ b/src/wayland/meta-wayland-dma-buf.c
@@ -468,14 +468,22 @@ meta_wayland_dma_buf_buffer_attach (MetaWaylandBuffer  *buffer,
 
 #ifdef HAVE_NATIVE_BACKEND
 static struct gbm_bo *
-import_scanout_gbm_bo (MetaWaylandDmaBufBuffer *dma_buf,
-                       MetaGpuKms              *gpu_kms,
-                       int                      n_planes,
-                       gboolean                *use_modifier)
+import_scanout_gbm_bo (MetaWaylandDmaBufBuffer  *dma_buf,
+                       MetaGpuKms               *gpu_kms,
+                       int                       n_planes,
+                       gboolean                 *use_modifier,
+                       GError                  **error)
 {
   struct gbm_device *gbm_device;
+  struct gbm_bo *gbm_bo;
 
   gbm_device = meta_gbm_device_from_gpu (gpu_kms);
+  if (!gbm_device)
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+                   "No gbm_device available");
+      return NULL;
+    }
 
   if (dma_buf->drm_modifier != DRM_FORMAT_MOD_INVALID ||
       n_planes > 1 ||
@@ -501,9 +509,10 @@ import_scanout_gbm_bo (MetaWaylandDmaBufBuffer *dma_buf,
               sizeof (import_with_modifier.offsets));
 
       *use_modifier = TRUE;
-      return gbm_bo_import (gbm_device, GBM_BO_IMPORT_FD_MODIFIER,
-                            &import_with_modifier,
-                            GBM_BO_USE_SCANOUT);
+
+      gbm_bo = gbm_bo_import (gbm_device, GBM_BO_IMPORT_FD_MODIFIER,
+                              &import_with_modifier,
+                              GBM_BO_USE_SCANOUT);
     }
   else
     {
@@ -518,10 +527,19 @@ import_scanout_gbm_bo (MetaWaylandDmaBufBuffer *dma_buf,
       };
 
       *use_modifier = FALSE;
-      return gbm_bo_import (gbm_device, GBM_BO_IMPORT_FD,
-                            &import_legacy,
-                            GBM_BO_USE_SCANOUT);
+      gbm_bo = gbm_bo_import (gbm_device, GBM_BO_IMPORT_FD,
+                              &import_legacy,
+                              GBM_BO_USE_SCANOUT);
+    }
+
+  if (!gbm_bo)
+    {
+      g_set_error (error, G_IO_ERROR, g_io_error_from_errno (errno),
+                   "gbm_bo_import failed: %s", g_strerror (errno));
+      return NULL;
     }
+
+  return gbm_bo;
 }
 #endif
 
@@ -550,10 +568,12 @@ meta_wayland_dma_buf_try_acquire_scanout (MetaWaylandDmaBufBuffer *dma_buf,
 
   device_file = meta_renderer_native_get_primary_device_file (renderer_native);
   gpu_kms = meta_renderer_native_get_primary_gpu (renderer_native);
-  gbm_bo = import_scanout_gbm_bo (dma_buf, gpu_kms, n_planes, &use_modifier);
+  gbm_bo = import_scanout_gbm_bo (dma_buf, gpu_kms, n_planes, &use_modifier,
+                                  &error);
   if (!gbm_bo)
     {
-      g_debug ("Failed to import scanout gbm_bo: %s", g_strerror (errno));
+      meta_topic (META_DEBUG_WAYLAND,
+                  "Failed to import scanout gbm_bo: %s", error->message);
       return NULL;
     }
 
@@ -564,7 +584,8 @@ meta_wayland_dma_buf_try_acquire_scanout (MetaWaylandDmaBufBuffer *dma_buf,
   fb = meta_drm_buffer_gbm_new_take (device_file, gbm_bo, flags, &error);
   if (!fb)
     {
-      g_debug ("Failed to create scanout buffer: %s", error->message);
+      meta_topic (META_DEBUG_WAYLAND,
+                  "Failed to create scanout buffer: %s", error->message);
       gbm_bo_destroy (gbm_bo);
       return NULL;
     }