fix(libsinsp): purge O_CLOEXEC fds on execve

O_CLOEXEC file descriptors should be removed when processing
a successful execve (execveat etc.), otherwise we end up with
bloating the fd tables with bogus fds.

Signed-off-by: Grzegorz Nosek <grzegorz.nosek@sysdig.com>

Author: gnosek

userspace/libsinsp/fdinfo.h

@@ -267,6 +267,22 @@ class SINSP_PUBLIC sinsp_fdinfo : public libsinsp::state::extensible_struct {
 		return (m_flags & FLAGS_OVERLAY_LOWER) == FLAGS_OVERLAY_LOWER;
 	}
 
+	inline bool is_close_on_exec() const {
+		if((m_openflags & PPM_O_CLOEXEC) == PPM_O_CLOEXEC) {
+			return true;
+		}
+
+		if(m_type == SCAP_FD_EVENTPOLL && (m_openflags & PPM_EPOLL_CLOEXEC) == PPM_EPOLL_CLOEXEC) {
+			return true;
+		}
+
+		if(m_type == SCAP_FD_MEMFD && (m_openflags & PPM_MFD_CLOEXEC) == PPM_MFD_CLOEXEC) {
+			return true;
+		}
+
+		return false;
+	}
+
 	void add_filename_raw(std::string_view rawpath);
 
 	void add_filename(std::string_view fullpath);

userspace/libsinsp/parsers.cpp

@@ -1745,11 +1745,12 @@ void sinsp_parser::parse_execve_exit(sinsp_evt &evt, sinsp_parser_verdict &verdi
 	                               evt.get_tinfo()->m_gid,
 	                               must_notify_thread_group_update());
 	//
-	// execve starts with a clean fd list, so we get rid of the fd list that clone
-	// copied from the parent
-	// XXX validate this
+	// Purge CLOEXEC FDs on successful execve/execveat
 	//
-	//  scap_fd_free_table(tinfo);
+	if(auto *fd_table = evt.get_tinfo()->get_fd_table(); fd_table != nullptr) {
+		fd_table->retain(
+		        [&](int64_t fd, const sinsp_fdinfo &info) { return !info.is_close_on_exec(); });
+	}
 
 	//
 	// Clear the flags for this thread, making sure to propagate the inverted