From: John Stultz Date: Tue, 25 Nov 2014 04:35:45 +0000 (-0800) Subject: time: Fix sign bug in NTP mult overflow warning X-Git-Tag: v3.19-rc1~157^2~1 X-Git-Url: http://git.cascardo.info/?p=cascardo%2Flinux.git;a=commitdiff_plain;h=cb2aa63469f81426c7406227be70b628b42f7a05 time: Fix sign bug in NTP mult overflow warning In commit 6067dc5a8c2b ("time: Avoid possible NTP adjustment mult overflow") a new check was added to watch for adjustments that could cause a mult overflow. Unfortunately the check compares a signed with unsigned value and ignored the case where the adjustment was negative, which causes spurious warn-ons on some systems (and seems like it would result in problematic time adjustments there as well, due to the early return). Thus this patch adds a check to make sure the adjustment is positive before we check for an overflow, and resovles the issue in my testing. Reported-by: Fengguang Wu Debugged-by: pang.xunlei Signed-off-by: John Stultz Link: http://lkml.kernel.org/r/1416890145-30048-1-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar --- diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 29a7d6709da1..2dc0646258ae 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1330,7 +1330,7 @@ static __always_inline void timekeeping_apply_adjustment(struct timekeeper *tk, * * XXX - TODO: Doc ntp_error calculation. */ - if (tk->tkr.mult + mult_adj < mult_adj) { + if ((mult_adj > 0) && (tk->tkr.mult + mult_adj < mult_adj)) { /* NTP adjustment caused clocksource mult overflow */ WARN_ON_ONCE(1); return;