Fix bug where the parent handlers were leaked to the moniton

Author: pvdrz

sudo/lib/exec/event.rs

@@ -200,4 +200,11 @@ impl<T: EventClosure> EventDispatcher<T> {
             }
         }
     }
+
+    /// Unregister all the handlers created by the dispatcher.
+    pub(super) fn unregister_handlers(self) {
+        for handler in self.signal_handlers {
+            handler.unregister();
+        }
+    }
 }

sudo/lib/exec/parent.rs

@@ -54,6 +54,8 @@ pub(super) fn exec_pty(
     // enabled or if sudo is running in background.
     // FIXME (ogsudo): Copy terminal settings from `/dev/tty` to the pty.
     // FIXME (ogsudo): Start in raw mode unless we're part of a pipeline
+    // FIXME: it would be better if we didn't create the dispatcher before the fork and managed
+    // to block all the signals instead.
     let mut dispatcher = EventDispatcher::<ParentClosure>::new()?;
 
     let monitor_pid = fork().map_err(|err| {
@@ -66,6 +68,10 @@ pub(super) fn exec_pty(
         drop(pty.leader);
         drop(backchannels.parent);
 
+        // Unregister all the handlers so `exec_monitor` can register new ones for the monitor
+        // process.
+        dispatcher.unregister_handlers();
+
         // If `exec_monitor` returns, it means we failed to execute the command somehow.
         if let Err(err) = exec_monitor(pty.follower, command, &mut backchannels.monitor) {
             if let Err(err) = backchannels.monitor.send(&err.into()) {