Close all STDIO ports after fork os slurmstepd to get correct dup2

src/slurmd/slurmd/req.c

@@ -756,16 +756,20 @@ _forkexec_slurmstepd(slurmd_step_type_t type, void *req,
 			error("close write to_stepd in grandchild: %m");
 		if (close(to_slurmd[0]) < 0)
 			error("close read to_slurmd in parent: %m");
+
+		(void) close(STDIN_FILENO); /* ignore return */
 		if (dup2(to_stepd[0], STDIN_FILENO) == -1) {
 			error("dup2 over STDIN_FILENO: %m");
 			exit(1);
 		}
 		fd_set_close_on_exec(to_stepd[0]);
+		(void) close(STDOUT_FILENO); /* ignore return */
 		if (dup2(to_slurmd[1], STDOUT_FILENO) == -1) {
 			error("dup2 over STDOUT_FILENO: %m");
 			exit(1);
 		}
 		fd_set_close_on_exec(to_slurmd[1]);
+		(void) close(STDERR_FILENO); /* ignore return */
 		if (dup2(devnull, STDERR_FILENO) == -1) {
 			error("dup2 /dev/null to STDERR_FILENO: %m");
 			exit(1);