[race] : Move the installation of the SIGCHLD handler before fork

Author: deshaw-bawangad

src/exec_monitor.c

@@ -616,6 +616,13 @@ exec_monitor(struct command_details *details, sigset_t *oset,
 	selinux_audit_role_change();
     }
 #endif
+    /*
+     * Create new event base and register read events for the
+     * signal pipe, error pipe, and backchannel.
+     */
+     init_exec_events_monitor(&mc, errsock[0]);
+     /* Restore signal mask now that signal handlers are setup. */
+     sigprocmask(SIG_SETMASK, oset, NULL);
 
     mc.cmnd_pid = sudo_debug_fork();
     switch (mc.cmnd_pid) {
@@ -654,15 +661,6 @@ exec_monitor(struct command_details *details, sigset_t *oset,
     cstat.val = mc.cmnd_pid;
     send_status(backchannel, &cstat);
 
-    /*
-     * Create new event base and register read events for the
-     * signal pipe, error pipe, and backchannel.
-     */
-    init_exec_events_monitor(&mc, errsock[0]);
-
-    /* Restore signal mask now that signal handlers are setup. */
-    sigprocmask(SIG_SETMASK, oset, NULL);
-
     /* If any of stdin/stdout/stderr are pipes, close them in parent. */
     if (io_fds[SFD_STDIN] != io_fds[SFD_FOLLOWER])
 	close(io_fds[SFD_STDIN]);

src/exec_nopty.c

@@ -606,6 +606,10 @@ exec_nopty(struct command_details *details,
     }
 #endif
 
+    /* Allocate and set signal events and the error pipe event.*/
+    init_exec_events(&ec, evbase, errpipe[0]);
+    /* Restore signal mask now that signal handlers are setup. */
+    sigprocmask(SIG_SETMASK, &oset, NULL);
     ec.cmnd_pid = sudo_debug_fork();
     switch (ec.cmnd_pid) {
     case -1:
@@ -667,9 +671,6 @@ exec_nopty(struct command_details *details,
     if (ISSET(details->flags, CD_SET_TIMEOUT))
 	alarm(details->timeout);
 
-    /* Allocate and set signal events and the error pipe event.  */
-    init_exec_events(&ec, evbase, errpipe[0]);
-
     if (ISSET(details->flags, CD_INTERCEPT|CD_LOG_SUBCMDS)) {
 	int rc = 1;
 
@@ -692,9 +693,6 @@ exec_nopty(struct command_details *details,
     /* Enable any I/O log events. */
     add_io_events(&ec);
 
-    /* Restore signal mask now that signal handlers are setup. */
-    sigprocmask(SIG_SETMASK, &oset, NULL);
-
     /*
      * Non-pty event loop.
      * Wait for command to exit, handles signals and the error pipe.

src/exec_pty.c

@@ -1335,6 +1335,10 @@ exec_pty(struct command_details *details,
 	debug_return_bool(true);
     }
 
+    /* Allocate and set signal events and the backchannel event. */
+    init_exec_events(ec, evbase, sv[0]);
+    /* Restore signal mask now that signal handlers are setup. */
+    sigprocmask(SIG_SETMASK, &oset, NULL);
     ec->monitor_pid = sudo_debug_fork();
     switch (ec->monitor_pid) {
     case -1:
@@ -1408,9 +1412,6 @@ exec_pty(struct command_details *details,
     if (ISSET(details->flags, CD_SET_TIMEOUT))
 	alarm(details->timeout);
 
-    /* Allocate and set signal events and the backchannel event.  */
-    init_exec_events(ec, evbase, sv[0]);
-
     /* Create event and closure for intercept mode. */
     if (ISSET(details->flags, CD_INTERCEPT|CD_LOG_SUBCMDS)) {
 	ec->intercept = intercept_setup(intercept_sv[0], ec->evbase, details);
@@ -1422,9 +1423,6 @@ exec_pty(struct command_details *details,
     cstat->type = CMD_INVALID;
     cstat->val = 0;
 
-    /* Restore signal mask now that signal handlers are setup. */
-    sigprocmask(SIG_SETMASK, &oset, NULL);
-
     /*
      * I/O logging must be in the C locale for floating point numbers
      * to be logged consistently.