Thread exception channel shouldn't get the process

zircon-object/src/task/exception.rs

@@ -166,7 +166,7 @@ pub enum ExceptionType {
 }
 
 #[repr(u32)]
-#[derive(Copy, Clone)]
+#[derive(Copy, Clone,PartialEq)]
 pub enum ExceptionChannelType {
     None = 0,
     Debugger = 1,

zircon-syscall/src/exception.rs

@@ -73,6 +73,9 @@ impl Syscall<'_> {
         let proc = self.thread.proc();
         let exception =
             proc.get_object_with_rights::<ExceptionObject>(exception, Rights::default())?;
+        if exception.get_exception().get_current_channel_type() == ExceptionChannelType::Thread {
+            return Err(ZxError::ACCESS_DENIED)
+        }
         let (object, right) = exception.get_exception().get_process_and_rights();
         let handle = proc.add_handle(Handle::new(object, right));
         out.write(handle)?;