When using ptrace(2), push the point where we suspend into exec_cmnd().

This should reduce the amount of time the child has to wait for
the parent to use PTRACE_SEIZE to seize control and then PTRACE_CONT
to continue the child.

src/exec.c

@@ -48,6 +48,14 @@
 #include "sudo_plugin.h"
 #include "sudo_plugin_int.h"
 
+#ifdef HAVE_PTRACE_INTERCEPT
+static void
+handler(int signo)
+{
+    /* just return */
+}
+#endif /* HAVE_PTRACE_INTERCEPT */
+
 static void
 close_fds(struct command_details *details, int errfd, int intercept_fd)
 {
@@ -245,10 +253,35 @@ done:
  * If the exec fails, cstat is filled in with the value of errno.
  */
 void
-exec_cmnd(struct command_details *details, int intercept_fd, int errfd)
+exec_cmnd(struct command_details *details, sigset_t *mask,
+    int intercept_fd, int errfd)
 {
     debug_decl(exec_cmnd, SUDO_DEBUG_EXEC);
 
+#ifdef HAVE_PTRACE_INTERCEPT
+    if (ISSET(details->flags, CD_USE_PTRACE)) {
+	struct sigaction sa;
+	sigset_t set;
+
+	/* Tracer will send us SIGUSR1 when it is time to proceed. */
+	memset(&sa, 0, sizeof(sa));
+	sigemptyset(&sa.sa_mask);
+	sa.sa_flags = SA_RESTART;
+	sa.sa_handler = handler;
+	if (sudo_sigaction(SIGUSR1, &sa, NULL) != 0) {
+	    sudo_warn(U_("unable to set handler for signal %d"),
+		SIGUSR1);
+	}
+
+	/* Suspend child until tracer seizes control and sends SIGUSR1. */
+	sigfillset(&set);
+	sigdelset(&set, SIGUSR1);
+	sigsuspend(&set);
+    }
+#endif /* HAVE_PTRACE_INTERCEPT */
+
+    if (mask != NULL)
+	sigprocmask(SIG_SETMASK, mask, NULL);
     restore_signals();
     if (exec_setup(details, intercept_fd, errfd) == true) {
 	/* headed for execve() */
@@ -440,7 +473,7 @@ sudo_execute(struct command_details *details, struct command_status *cstat)
      */
     if (direct_exec_allowed(details)) {
 	if (!sudo_terminated(cstat)) {
-	    exec_cmnd(details, -1, -1);
+	    exec_cmnd(details, NULL, -1, -1);
 	    cstat->type = CMD_ERRNO;
 	    cstat->val = errno;
 	}

src/exec_monitor.c

@@ -386,8 +386,8 @@ mon_backchannel_cb(int fd, int what, void *v)
  * Returns only if execve() fails.
  */
 static void
-exec_cmnd_pty(struct command_details *details, bool foreground,
-    int intercept_fd, int errfd)
+exec_cmnd_pty(struct command_details *details, sigset_t *mask,
+    bool foreground, int intercept_fd, int errfd)
 {
     volatile pid_t self = getpid();
     debug_decl(exec_cmnd_pty, SUDO_DEBUG_EXEC);
@@ -430,7 +430,7 @@ exec_cmnd_pty(struct command_details *details, bool foreground,
     /* Execute command; only returns on error. */
     sudo_debug_printf(SUDO_DEBUG_INFO, "executing %s in the %s",
 	details->command, foreground ? "foreground" : "background");
-    exec_cmnd(details, intercept_fd, errfd);
+    exec_cmnd(details, mask, intercept_fd, errfd);
 
     debug_return;
 }
@@ -536,14 +536,6 @@ fill_exec_closure_monitor(struct monitor_closure *mc,
     debug_return;
 }
 
-#ifdef HAVE_PTRACE_INTERCEPT
-static void
-handler(int signo)
-{
-    /* just return */
-}
-#endif /* HAVE_PTRACE_INTERCEPT */
-
 /*
  * Monitor process that creates a new session with the controlling tty,
  * resets signal handlers and forks a child to call exec_cmnd_pty().
@@ -638,28 +630,8 @@ exec_monitor(struct command_details *details, sigset_t *oset,
 	close(errpipe[0]);
 	if (io_fds[SFD_USERTTY] != -1)
 	    close(io_fds[SFD_USERTTY]);
-#ifdef HAVE_PTRACE_INTERCEPT
-	if (ISSET(details->flags, CD_USE_PTRACE)) {
-	    sigset_t set;
-
-	    /* Tracer will send us SIGUSR1 when it is time to proceed. */
-	    sa.sa_handler = handler;
-	    if (sudo_sigaction(SIGUSR1, &sa, NULL) != 0) {
-		sudo_warn(U_("unable to set handler for signal %d"),
-		    SIGUSR1);
-	    }
-
-	    /* Suspend child until tracer seizes control and sends SIGUSR1. */
-	    sigfillset(&set);
-	    sigdelset(&set, SIGUSR1);
-	    sigsuspend(&set);
-	}
-#endif /* HAVE_PTRACE_INTERCEPT */
-	sigprocmask(SIG_SETMASK, oset, NULL);
-	restore_signals();
-
 	/* setup tty and exec command */
-	exec_cmnd_pty(details, foreground, intercept_fd, errpipe[1]);
+	exec_cmnd_pty(details, oset, foreground, intercept_fd, errpipe[1]);
 	if (write(errpipe[1], &errno, sizeof(int)) == -1)
 	    sudo_warn(U_("unable to execute %s"), details->command);
 	_exit(EXIT_FAILURE);

src/exec_nopty.c

@@ -348,14 +348,6 @@ free_exec_closure_nopty(struct exec_closure_nopty *ec)
     debug_return;
 }
 
-#ifdef HAVE_PTRACE_INTERCEPT
-static void
-handler(int signo)
-{
-    /* just return */
-}
-#endif /* HAVE_PTRACE_INTERCEPT */
-
 /*
  * Execute a command and wait for it to finish.
  */
@@ -426,27 +418,7 @@ exec_nopty(struct command_details *details, struct command_status *cstat)
 	close(errpipe[0]);
 	if (intercept_sv[0] != -1)
 	    close(intercept_sv[0]);
-#ifdef HAVE_PTRACE_INTERCEPT
-	if (ISSET(details->flags, CD_USE_PTRACE)) {
-	    struct sigaction sa;
-
-	    /* Tracer will send us SIGUSR1 when it is time to proceed. */
-	    memset(&sa, 0, sizeof(sa));
-	    sigemptyset(&sa.sa_mask);
-	    sa.sa_flags = SA_RESTART;
-	    sa.sa_handler = handler;
-	    if (sudo_sigaction(SIGUSR1, &sa, NULL) != 0) {
-		sudo_warn(U_("unable to set handler for signal %d"),
-		    SIGUSR1);
-	    }
-
-	    /* Suspend child until tracer seizes control and sends SIGUSR1. */
-	    sigdelset(&set, SIGUSR1);
-	    sigsuspend(&set);
-	}
-#endif /* HAVE_PTRACE_INTERCEPT */
-	sigprocmask(SIG_SETMASK, &oset, NULL);
-	exec_cmnd(details, intercept_sv[1], errpipe[1]);
+	exec_cmnd(details, &oset, intercept_sv[1], errpipe[1]);
 	while (write(errpipe[1], &errno, sizeof(int)) == -1) {
 	    if (errno != EINTR)
 		break;

src/sudo_exec.h

@@ -113,7 +113,7 @@ struct sudo_event_base;
 struct stat;
 
 /* exec.c */
-void exec_cmnd(struct command_details *details, int intercept_fd, int errfd);
+void exec_cmnd(struct command_details *details, sigset_t *mask, int intercept_fd, int errfd);
 void terminate_command(pid_t pid, bool use_pgrp);
 bool sudo_terminated(struct command_status *cstat);