[tracker-miners/wip/carlosg/invalid-reads] libtracker-miner: Add missing ref to SPARQL buffer task

[Carlos Garnacho <carlosg src gnome org>]

commit d5ba6f69a02b710a470109cb466698baee3b0ce8
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun Oct 11 14:23:21 2020 +0200

    libtracker-miner: Add missing ref to SPARQL buffer task
    
    On error paths, we let tracker_sparql_buffer_push_finish() still return
    the underlying TrackerTask, together with the error, so we can detach
    it properly.
    
    However, in this situation we are not adding an extra task ref, while
    the callback expects to own a reference. This causes refcounting issues
    and eventually invalid reads.
    
    Fixes: https://gitlab.gnome.org/GNOME/tracker-miners/-/issues/130

 src/libtracker-miner/tracker-sparql-buffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/libtracker-miner/tracker-sparql-buffer.c b/src/libtracker-miner/tracker-sparql-buffer.c
index d5a538d41..7afa12dde 100644
--- a/src/libtracker-miner/tracker-sparql-buffer.c
+++ b/src/libtracker-miner/tracker-sparql-buffer.c
@@ -522,7 +522,7 @@ tracker_sparql_buffer_push_finish (TrackerSparqlBuffer  *buffer,
        task = g_task_propagate_pointer (G_TASK (res), error);
 
        if (!task)
-               task = g_task_get_task_data (G_TASK (res));
+               task = g_object_ref (g_task_get_task_data (G_TASK (res)));
 
        return task;
 }