[src/trunk]: src/sys/kern kernel: Avoid arithmetic overflow in ntp_adjtime.

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

details:   https://anonhg.NetBSD.org/src/rev/504795c1d2b4
branches:  trunk
changeset: 359982:504795c1d2b4
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sat Feb 05 15:29:50 2022 +0000

description:
kernel: Avoid arithmetic overflow in ntp_adjtime.

Reported-by: syzbot+f4343a1c91ddfe8bbe97%syzkaller.appspotmail.com@localhost

diffstat:

 sys/kern/kern_ntptime.c |  7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diffs (28 lines):

diff -r 4636f57e153f -r 504795c1d2b4 sys/kern/kern_ntptime.c
--- a/sys/kern/kern_ntptime.c   Sat Feb 05 15:17:40 2022 +0000
+++ b/sys/kern/kern_ntptime.c   Sat Feb 05 15:29:50 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_ntptime.c,v 1.60 2018/10/29 22:02:25 christos Exp $       */
+/*     $NetBSD: kern_ntptime.c,v 1.61 2022/02/05 15:29:50 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 1.60 2018/10/29 22:02:25 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_ntptime.c,v 1.61 2022/02/05 15:29:50 riastradh Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_ntp.h"
@@ -347,7 +347,8 @@
        if (modes & MOD_CLKA)
                time_status &= ~STA_CLK;
        if (modes & MOD_FREQUENCY) {
-               freq = (ntv->freq * 1000LL) >> 16;
+               freq = MIN(INT32_MAX, MAX(INT32_MIN, ntv->freq));
+               freq = (freq * (int64_t)1000) >> 16;
                if (freq > MAXFREQ)
                        L_LINT(time_freq, MAXFREQ);
                else if (freq < -MAXFREQ)