Shells typically change their process group when they start up so

that they can implement job control.  Most well-behaved shells
change the pgrp back to its original value before suspending so we
must not try to restore in that case, lest we race with the child
upon resume, potentially stopping sudo with SIGTTOU while the command
continues to run.  Some shells, such as pdksh, just suspend the
shell by sending SIGSTOP to themselves without restoring the pgrp.
In this case we need to change the pgrp back for them.
Should fix bug #568

--HG--
branch : 1.7

diff --git a/exec.c b/exec.c
index 7f49926006e6b61c6fc37c28833d751ecdd4f5e1..65d505b02650e860af813865c87d7e0a2912417a 100644 (file)
--- a/exec.c
+++ b/exec.c
@@ -79,6 +79,7 @@ struct sigforward {
 };
 TQ_DECLARE(sigforward)
 static struct sigforward_list sigfwd_list;
+static pid_t ppgrp = -1;
 static void forward_signals __P((int fd));
 static void schedule_signal __P((int signo));
 static int log_io;
@@ -126,6 +127,12 @@ static int fork_cmnd(path, argv, envp, sv, rbac_enabled)
     struct command_status cstat;
     sigaction_t sa;
 
+    ppgrp = getpgrp(); /* parent's process group */
+
+    /*
+     * XXX - should only send SIGCONT when command pgrp != parent pgrp 
+     *       OR we were suspended by a user (not kernel or tty) signal.
+     */
     zero_bytes(&sa, sizeof(sa));
     sigemptyset(&sa.sa_mask);
     sa.sa_flags = SA_INTERRUPT; /* do not restart syscalls */
@@ -566,18 +573,29 @@ handle_signals(sv, child, cstat)
                    if (WIFSTOPPED(status)) {
                        /*
                         * Save the controlling terminal's process group
-                        * so we can restore it after we resume.
+                        * so we can restore it after we resume, if needed.
+                        * Most well-behaved shells change the pgrp back to
+                        * its original value before suspending so we must
+                        * not try to restore in that case, lest we race with
+                        * the child upon resume, potentially stopping sudo
+                        * with SIGTTOU while the command continues to run.
                         */
 #ifdef HAVE_TCSETPGRP
                        pid_t saved_pgrp = (pid_t)-1;
                        int fd = open(_PATH_TTY, O_RDWR|O_NOCTTY, 0);
-                       if (fd != -1)
-                           saved_pgrp = tcgetpgrp(fd);
+                       if (fd != -1) {
+                           if ((saved_pgrp = tcgetpgrp(fd)) == ppgrp)
+                               saved_pgrp = -1;
+                       }
 #endif /* HAVE_TCSETPGRP */
                        if (kill(getpid(), WSTOPSIG(status)) != 0)
                            warning("kill(%d, %d)", getpid(), WSTOPSIG(status));
 #ifdef HAVE_TCSETPGRP
                        if (fd != -1) {
+                           /*
+                            * Restore command's process group if different.
+                            * Otherwise, we cannot resume some shells.
+                            */
                            if (saved_pgrp != (pid_t)-1)
                                (void)tcsetpgrp(fd, saved_pgrp);
                            close(fd);