From eb10f49cb5004439aeb1da4de58d46ffb6569ecf Mon Sep 17 00:00:00 2001
From: cheloha <cheloha@openbsd.org>
Date: Wed, 31 Jan 2018 15:57:44 +0000
Subject: [PATCH] Check GETTY_SPACING against the monotonic clock.

Ensures that we can use the check if the system clock is set backwards.

While here, move time retrieval into the child process in start_getty(),
and only get the time if se_started has been set.

ok millert@ tb@
---
 sbin/init/init.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/sbin/init/init.c b/sbin/init/init.c
index 5440d13dbc4..16e12c220cd 100644
--- a/sbin/init/init.c
+++ b/sbin/init/init.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: init.c,v 1.66 2018/01/06 16:26:12 millert Exp $	*/
+/*	$OpenBSD: init.c,v 1.67 2018/01/31 15:57:44 cheloha Exp $	*/
 /*	$NetBSD: init.c,v 1.22 1996/05/15 23:29:33 jtc Exp $	*/
 
 /*-
@@ -143,7 +143,7 @@ void setctty(char *);
 typedef struct init_session {
 	int	se_index;		/* index of entry in ttys file */
 	pid_t	se_process;		/* controlling process */
-	time_t	se_started;		/* used to avoid thrashing */
+	struct	timespec se_started;	/* used to avoid thrashing */
 	int	se_flags;		/* status of session */
 #define	SE_SHUTDOWN	0x1		/* session won't be restarted */
 #define	SE_PRESENT	0x2		/* session is in /etc/ttys */
@@ -1007,7 +1007,7 @@ start_getty(session_t *sp)
 {
 	pid_t pid;
 	sigset_t mask;
-	time_t current_time = time(NULL);
+	struct timespec current_time, elapsed;
 	int p[2], new = 1;
 
 	if (sp->se_flags & SE_DEVEXISTS)
@@ -1060,11 +1060,15 @@ start_getty(session_t *sp)
 		sleep(1);
 	}
 
-	if (current_time > sp->se_started &&
-	    current_time - sp->se_started < GETTY_SPACING) {
-		warning("getty repeating too quickly on port %s, sleeping",
-		    sp->se_device);
-		sleep(GETTY_SLEEP);
+	if (timespecisset(&sp->se_started)) {
+		clock_gettime(CLOCK_MONOTONIC, &current_time);
+		timespecsub(&current_time, &sp->se_started, &elapsed);
+		if (elapsed.tv_sec < GETTY_SPACING) {
+			warning(
+			    "getty repeating too quickly on port %s, sleeping",
+			    sp->se_device);
+			sleep(GETTY_SLEEP);
+		}
 	}
 
 	if (sp->se_window) {
@@ -1121,7 +1125,7 @@ collect_child(pid_t pid)
 	}
 
 	sp->se_process = pid;
-	sp->se_started = time(NULL);
+	clock_gettime(CLOCK_MONOTONIC, &sp->se_started);
 	add_session(sp);
 }
 
@@ -1188,7 +1192,7 @@ f_multi_user(void)
 			break;
 		}
 		sp->se_process = pid;
-		sp->se_started = time(NULL);
+		clock_gettime(CLOCK_MONOTONIC, &sp->se_started);
 		add_session(sp);
 	}
 
-- 
2.20.1