revert last two commits. vfork cannot be used in subroutine,

it trashes stack on return

networking/ifupdown.c

@@ -1008,9 +1008,12 @@ static int popen2(FILE **in, FILE **out, char *command, char *param)
 	xpiped_pair(outfd);
 
 	fflush(NULL);
-	pid = xvfork();
+	pid = vfork();
 
-	if (pid == 0) { /* child */
+	switch (pid) {
+	case -1:  /* failure */
+		bb_perror_msg_and_die("vfork");
+	case 0:  /* child */
 		/* NB: close _first_, then move fds! */
 		close(infd.wr);
 		close(outfd.rd);

networking/inetd.c

@@ -1303,7 +1303,7 @@ int inetd_main(int argc ATTRIBUTE_UNUSED, char **argv)
 					pid = vfork();
 
 				if (pid < 0) { /* fork error */
-					bb_perror_msg(BB_MMU ? "vfork" + 1 : "vfork");
+					bb_perror_msg("fork");
 					sleep(1);
 					restore_sigmask(&omask);
 					maybe_close(accepted_fd);

networking/sendmail.c

@@ -120,6 +120,15 @@ static void signal_handler(int signo)
 #undef err
 }
 
+/* libbb candidate */
+static pid_t vfork_or_die(void)
+{
+	pid_t pid = vfork();
+	if (pid < 0)
+		bb_perror_msg_and_die("vfork");
+	return pid;
+}
+
 static void launch_helper(const char **argv)
 {
 	// setup vanilla unidirectional pipes interchange
@@ -128,7 +137,7 @@ static void launch_helper(const char **argv)
 
 	xpipe(pipes);
 	xpipe(pipes+2);
-	helper_pid = xvfork();
+	helper_pid = vfork_or_die();
 	idx = (!helper_pid) * 2;
 	xdup2(pipes[idx], STDIN_FILENO);
 	xdup2(pipes[3-idx], STDOUT_FILENO);