From 269e9d112639ab6c54645de217c46ef75617d780 Mon Sep 17 00:00:00 2001
From: Frediano Ziglio <fziglio@redhat.com>
Date: Wed, 9 Sep 2015 12:45:06 +0100
Subject: [PATCH 2/2] worker: avoid double free or double create of surfaces

A driver can overwrite surface state creating a surface with the same
id of a previous one.
Also can try to destroy surfaces that are not created.
Both requests cause invalid internal states that could lead to crashes
or memory corruptions.

Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
---
 server/red_worker.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/server/red_worker.c b/server/red_worker.c
index c62dbcb..a7eaab9 100644
--- a/server/red_worker.c
+++ b/server/red_worker.c
@@ -4320,6 +4320,10 @@ static inline void red_process_surface(RedWorker *worker, RedSurfaceCmd *surface
         int32_t stride = surface->u.surface_create.stride;
         int reloaded_surface = loadvm || (surface->flags & QXL_SURF_FLAG_KEEP_DATA);
 
+        if (red_surface->refs) {
+            spice_warning("avoiding creating a surface twice");
+            break;
+        }
         data = surface->u.surface_create.data;
         if (stride < 0) {
             data -= (int32_t)(stride * (height - 1));
@@ -4333,7 +4337,10 @@ static inline void red_process_surface(RedWorker *worker, RedSurfaceCmd *surface
         break;
     }
     case QXL_SURFACE_CMD_DESTROY:
-        spice_warn_if(!red_surface->context.canvas);
+        if (!red_surface->refs) {
+            spice_warning("avoiding destroying a surface twice");
+            break;
+        }
         set_surface_release_info(worker, surface_id, 0, surface->release_info, group_id);
         red_handle_depends_on_target_surface(worker, surface_id);
         /* note that red_handle_depends_on_target_surface must be called before red_current_clear.
-- 
2.4.3