gdbus: Fix crash when watch is toggled or disconnected

This partially reverts 510b32b7156625b9df737c916b7a7a5c6fb285b9 since it
still necessary to take a reference before calling dbus_watch_handle
since internally it can call watch_info_free as in the following trace:

 Invalid read of size 8
   at 0x121085: watch_func (mainloop.c:105)
   by 0x4C72694: g_main_context_dispatch (gmain.c:2539)
   by 0x4C729C7: g_main_context_iterate.isra.23 (gmain.c:3146)
   by 0x4C72DC1: g_main_loop_run (gmain.c:3340)
   by 0x120541: main (main.c:551)
 Address 0x5bbcd90 is 16 bytes inside a block of size 24 free'd
   at 0x4A079AE: free (vg_replace_malloc.c:427)
   by 0x4C7837E: g_free (gmem.c:252)
   by 0x4F708BF: dbus_watch_set_data (dbus-watch.c:614)
   by 0x4F70938: _dbus_watch_unref (dbus-watch.c:132)
   by 0x4F6E9A7: _dbus_transport_handle_watch (dbus-transport.c:884)
   by 0x4F59AFB: _dbus_connection_handle_watch (dbus-connection.c:1497)
   by 0x4F70AF9: dbus_watch_handle (dbus-watch.c:683)
   by 0x121084: watch_func (mainloop.c:103)
   by 0x4C72694: g_main_context_dispatch (gmain.c:2539)
   by 0x4C729C7: g_main_context_iterate.isra.23 (gmain.c:3146)
   by 0x4C72DC1: g_main_loop_run (gmain.c:3340)
   by 0x120541: main (main.c:551)

diff --git a/gdbus/mainloop.c b/gdbus/mainloop.c
index 435fb93bb1c12c6e31c78e761f13f91eedec3c4b..3e88eac8627e4224b00790bfe61a78830e225be4 100644 (file)
--- a/gdbus/mainloop.c
+++ b/gdbus/mainloop.c
@@ -88,16 +88,22 @@ static gboolean watch_func(GIOChannel *chan, GIOCondition cond, gpointer data)
        struct watch_info *info = data;
        unsigned int flags = 0;
        DBusDispatchStatus status;
+       DBusConnection *conn;
 
        if (cond & G_IO_IN)  flags |= DBUS_WATCH_READABLE;
        if (cond & G_IO_OUT) flags |= DBUS_WATCH_WRITABLE;
        if (cond & G_IO_HUP) flags |= DBUS_WATCH_HANGUP;
        if (cond & G_IO_ERR) flags |= DBUS_WATCH_ERROR;
 
+       /* Protect connection from being destroyed by dbus_watch_handle */
+       conn = dbus_connection_ref(info->conn);
+
        dbus_watch_handle(info->watch, flags);
 
-       status = dbus_connection_get_dispatch_status(info->conn);
-       queue_dispatch(info->conn, status);
+       status = dbus_connection_get_dispatch_status(conn);
+       queue_dispatch(conn, status);
+
+       dbus_connection_unref(conn);
 
        return TRUE;
 }