If execve fails in logging mode, pass the errno directly to the grandparent

on the backchannel and exit.  The immediate parent will get SIGCHLD and
try to report that status but its parent will no longer be listening.
It would probably be cleaner to pass this over a pipe in script_child().

src/script.c

@@ -599,6 +599,9 @@ script_execve(struct command_details *details, char *argv[], char *envp[],
 		break;
 	    }
 	}
+	if (!log_io)
+	    continue;
+
 	if (FD_ISSET(sv[0], fdsw)) {
 	    for (n = 0; n < NSIG; n++) {
 		if (!recvsig[n])
@@ -616,9 +619,6 @@ script_execve(struct command_details *details, char *argv[], char *envp[],
 		}
 	    }
 	}
-	if (!log_io)
-	    continue;
-
 	if (FD_ISSET(script_fds[SFD_USERTTY], fdsr)) {
 	    n = read(script_fds[SFD_USERTTY], input.buf + input.len,
 		sizeof(input.buf) - input.len);
@@ -836,7 +836,10 @@ script_child(const char *path, char *argv[], char *envp[], int backchannel, int
 	/* setup tty and exec command */
 	script_run(path, argv, envp, rbac);
 	warning("unable to execute %s", path); /* XXX - leave this to plugin? */
-	goto bad;
+	cstat.type = CMD_ERRNO;
+	cstat.val = errno;
+	send(backchannel, &cstat, sizeof(cstat), 0);
+	_exit(1);
     }
 
     /*
@@ -874,9 +877,17 @@ script_child(const char *path, char *argv[], char *envp[], int backchannel, int
 		do {
 		    n = send(backchannel, &cstat, sizeof(cstat), 0);
 		} while (n == -1 && errno == EINTR);
-		if (n != sizeof(cstat))
-		    break; /* XXX - error, kill child and exit */
-		sudo_debug(8, "sent wait status to parent");
+		if (n != sizeof(cstat)) {
+		    /*
+		     * If child failed to exec it sends its own status
+		     * which will result in ECONNRERFUSED here.
+		     * XXX - treat other errno as fatal
+		     */
+		    sudo_debug(8, "unable to send wait status: %s",
+			strerror(errno));
+		} else {
+		    sudo_debug(8, "sent wait status to parent");
+		}
 		if (!WIFSTOPPED(status)) {
 		    /* XXX */
 		    _exit(1); /* child dead */