[Spice-devel] [PATCH spice-server v3] red-worker: Fix leak processing update commands

[Frediano Ziglio]

Is possible to have a leak processing update commands if
the update command is synchronous and the rectangle list
is empty. Note that Qemu always pass an empty list.

If the list is empty display_channel_update fill the list.
This is used to send back the list in case of asynchronous
requests. But in handle_dev_update_async (the callback that
handle the asynchronous case) the list is correctly freed.

This was discovered by accident looking at the code.

Reproduced with a Windows recording file using GCC address
sanitizer and this patch to spice-server-replay:

  --- a/server/red-replay-qxl.c
  +++ b/server/red-replay-qxl.c
  @@ -1280,7 +1280,13 @@ static void replay_handle_dev_input(QXLWorker *worker, SpiceReplay *replay,
           replay->created_primary = FALSE;
           worker->destroy_surfaces(worker);
           break;
  -    case RED_WORKER_MESSAGE_UPDATE:
  +    case RED_WORKER_MESSAGE_UPDATE: {
  +        static uint8_t count = 0;
  +        QXLRect dummy;
  +        QXLRect update = { 0, 0, 100, 100 };
  +        count ^= 1;
  +        worker->update_area(worker, 0, &update, count ? &dummy : NULL, count ? 1 : 0, 0);
  +        } break;
           // XXX do anything? we record the correct bitmaps already.
       case RED_WORKER_MESSAGE_DISPLAY_CONNECT:
           // we want to ignore this one - it is sent on client connection, we

Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
---
 server/red-worker.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Changes since v2:
- better check for leak (thanks Christophe);
- more complete test patch in comment.

Changes since v1:
- indented patch in comment to avoid am problems.

diff --git a/server/red-worker.c b/server/red-worker.c
index 4d8566be..675c232e 100644
--- a/server/red-worker.c
+++ b/server/red-worker.c
@@ -437,13 +437,17 @@ static void handle_dev_update(void *opaque, void *payload)
 {
     RedWorker *worker = opaque;
     RedWorkerMessageUpdate *msg = payload;
+    QXLRect *qxl_dirty_rects = msg->qxl_dirty_rects;
 
     spice_return_if_fail(worker->running);
 
     flush_display_commands(worker);
     display_channel_update(worker->display_channel,
                            msg->surface_id, msg->qxl_area, msg->clear_dirty_region,
-                           &msg->qxl_dirty_rects, &msg->num_dirty_rects);
+                           &qxl_dirty_rects, &msg->num_dirty_rects);
+    if (msg->qxl_dirty_rects == NULL) {
+        free(qxl_dirty_rects);
+    }
 }
 
 static void handle_dev_del_memslot(void *opaque, void *payload)
-- 
2.13.5