Fix an issue reported by deraadt@: When hitting Ctrl-Backslash (= SIGQUIT)

in the less(1) spawned by man(1), man(1) died uncleanly, leaving behind
its temp files, and killed less(1) uncleanly as well with SIGPIPE,
leaving the terminal in the wrong state.

Fix this by giving less(1) its own process group and handing it
control of the terminal, but in such a way that Ctrl-z (= SIGSTOP)
still works: In that case, let man(1) stop itself, too, and let it
continue the pager when it continues itself.

Joint work with millert@ who contributed most of the expertise
required, and also most parts of the code.
OK deraadt@ millert@

1 files changed, 35 insertions, 5 deletions

diff --git a/usr.bin/mandoc/main.c b/usr.bin/mandoc/main.c
index 8268fb26118..b9d4b3fafa6 100644
--- a/usr.bin/mandoc/main.c
+++ b/usr.bin/mandoc/main.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: main.c,v 1.164 2015/11/07 17:58:52 schwarze Exp $ */
+/*	$OpenBSD: main.c,v 1.165 2015/11/14 23:56:41 schwarze Exp $ */
 /*
  * Copyright (c) 2008-2012 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2010-2012, 2014, 2015 Ingo Schwarze <schwarze@openbsd.org>
@@ -24,6 +24,7 @@
 #include <assert.h>
 #include <ctype.h>
 #include <err.h>
+#include <errno.h>
 #include <fcntl.h>
 #include <glob.h>
 #include <signal.h>
@@ -120,14 +121,16 @@ main(int argc, char *argv[])
 	int		 show_usage;
 	int		 options;
 	int		 use_pager;
+	int		 status;
 	int		 c;
+	pid_t		 pager_pid;
 
 	progname = getprogname();
 	if (strncmp(progname, "mandocdb", 8) == 0 ||
 	    strncmp(progname, "makewhatis", 10) == 0)
 		return mandocdb(argc, argv);
 
-	if (pledge("stdio rpath tmppath proc exec flock", NULL) == -1)
+	if (pledge("stdio rpath tmppath tty proc exec flock", NULL) == -1)
 		err((int)MANDOCLEVEL_SYSERR, "pledge");
 
 	/* Search options. */
@@ -387,7 +390,7 @@ main(int argc, char *argv[])
 
 	/* mandoc(1) */
 
-	if (pledge(use_pager ? "stdio rpath tmppath proc exec" :
+	if (pledge(use_pager ? "stdio rpath tmppath tty proc exec" :
 	    "stdio rpath", NULL) == -1)
 		err((int)MANDOCLEVEL_SYSERR, "pledge");
 
@@ -484,7 +487,29 @@ out:
 	if (tag_files != NULL) {
 		fclose(stdout);
 		tag_write();
-		waitpid(spawn_pager(tag_files), NULL, 0);
+		pager_pid = spawn_pager(tag_files);
+		for (;;) {
+			if (waitpid(pager_pid, &status, WUNTRACED) == -1) {
+				if (errno == EINTR)
+					continue;
+				warn("wait");
+				rc = MANDOCLEVEL_SYSERR;
+				break;
+			}
+			if (!WIFSTOPPED(status))
+				break;
+
+			(void)tcsetpgrp(STDIN_FILENO, getpgid(0));
+			kill(0, WSTOPSIG(status));
+	
+			/*
+			 * I'm now stopped.
+			 * When getting SIGCONT, continue here:
+			 */
+
+			(void)tcsetpgrp(STDIN_FILENO, pager_pid);
+			kill(pager_pid, SIGCONT);
+		}
 		tag_unlink();
 	}
 
@@ -971,9 +996,14 @@ spawn_pager(struct tag_files *tag_files)
 	case -1:
 		err((int)MANDOCLEVEL_SYSERR, "fork");
 	case 0:
+		/* Set pgrp in both parent and child to avoid racing exec. */
+		(void)setpgid(0, 0);
 		break;
 	default:
-		if (pledge("stdio rpath tmppath", NULL) == -1)
+		(void)setpgid(pager_pid, 0);
+		if (tcsetpgrp(STDIN_FILENO, pager_pid) == -1)
+			err((int)MANDOCLEVEL_SYSERR, "tcsetpgrp");
+		if (pledge("stdio rpath tmppath tty proc", NULL) == -1)
 			err((int)MANDOCLEVEL_SYSERR, "pledge");
 		return pager_pid;
 	}