[src/trunk]: src/sys/kern ntp(9): Clamp ntv->offset to avoid arithmetic overf...

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/be13e56854e0
branches:  trunk
changeset: 363475:be13e56854e0
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sun Mar 13 12:30:47 2022 +0000

description:
ntp(9): Clamp ntv->offset to avoid arithmetic overflow on adjtime.

Reported-by: syzbot+b8406db60db88650652e%syzkaller.appspotmail.com@localhost

diffstat:

 sys/kern/kern_ntptime.c |  14 +++++++++-----
 1 files changed, 9 insertions(+), 5 deletions(-)

diffs (36 lines):

diff -r f445e820ad51 -r be13e56854e0 sys/kern/kern_ntptime.c
--- a/sys/kern/kern_ntptime.c   Sun Mar 13 12:21:28 2022 +0000
+++ b/sys/kern/kern_ntptime.c   Sun Mar 13 12:30:47 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_ntptime.c,v 1.61 2022/02/05 15:29:50 riastradh Exp $      */
+/*     $NetBSD: kern_ntptime.c,v 1.62 2022/03/13 12:30:47 riastradh Exp $      */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -60,7 +60,7 @@
 
 #include <sys/cdefs.h>
 /* __FBSDID("$FreeBSD: src/sys/kern/kern_ntptime.c,v 1.59 2005/05/28 14:34:41 rwatson Exp $"); */
-__KERNEL_RCSID(0, "$NetBSD: kern_ntptime.c,v 1.61 2022/02/05 15:29:50 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_ntptime.c,v 1.62 2022/03/13 12:30:47 riastradh Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_ntp.h"
@@ -365,10 +365,14 @@
 #endif /* PPS_SYNC */
        }
        if (modes & MOD_OFFSET) {
-               if (time_status & STA_NANO)
+               if (time_status & STA_NANO) {
                        hardupdate(ntv->offset);
-               else
-                       hardupdate(ntv->offset * 1000);
+               } else {
+                       long offset = ntv->offset;
+                       offset = MIN(offset, MAXPHASE/1000);
+                       offset = MAX(offset, -MAXPHASE/1000);
+                       hardupdate(offset * 1000);
+               }
        }
 
        /*