server: make a copy of exit messages when filtering fields

We encountered another segfault similar to the one fixed in #1432. This time, it's related
to the pid field in exit events. Fix this by making a copy of the exit event before
filtering.

Signed-off-by: William Findlay <will@isovalent.com>

pkg/server/server.go

@@ -166,14 +166,12 @@ func (s *Server) GetEventsWG(request *tetragon.GetEventsRequest, server tetragon
 			// Filter the GetEventsResponse fields
 			filters := filters.FieldFiltersFromGetEventsRequest(request)
 			filterEvent := event
-			if len(filters) > 0 && filterEvent.GetProcessExec() != nil { // this is an exec event and we have fieldFilters
-				// We need a copy of the exec event as modifing the original message
+			if len(filters) > 0 && (filterEvent.GetProcessExec() != nil || filterEvent.GetProcessExit() != nil) { // this is an exec or exit event and we have fieldFilters
+				// We need a copy of the exec or exit event as modifing the original message
 				// can cause issues in the process cache (we keep a copy of that message there).
 				filterEvent = proto.Clone(event).(*tetragon.GetEventsResponse)
 			}
 			for _, filter := range filters {
-				// we need not to change res
-				// maybe only for exec events
 				filter.Filter(filterEvent)
 			}