From: john stultz Date: Tue, 27 Mar 2007 05:32:26 +0000 (-0800) Subject: [PATCH] ntp: avoid time_offset overflows X-Git-Tag: v2.6.21-rc6~96 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=d62ac21aa075c8ddf3d02a98d28afce635e77e8e;p=platform%2Fkernel%2Flinux-3.10.git [PATCH] ntp: avoid time_offset overflows I've been seeing some odd NTP behavior recently on a few boxes and finally narrowed it down to time_offset overflowing when converted to SHIFT_UPDATE units (which was a side effect from my HZfreeNTP patch). This patch converts time_offset from a long to a s64 which resolves the issue. [tglx@linutronix.de: signedness fixes] Signed-off-by: John Stultz Cc: Roman Zippel Cc: john stultz Cc: Ingo Molnar Cc: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c index eb12509..cb25649 100644 --- a/kernel/time/ntp.c +++ b/kernel/time/ntp.c @@ -32,7 +32,7 @@ static u64 tick_length, tick_length_base; /* TIME_ERROR prevents overwriting the CMOS clock */ static int time_state = TIME_OK; /* clock synchronization status */ int time_status = STA_UNSYNC; /* clock status bits */ -static long time_offset; /* time adjustment (ns) */ +static s64 time_offset; /* time adjustment (ns) */ static long time_constant = 2; /* pll time constant */ long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */ long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */ @@ -196,7 +196,7 @@ void __attribute__ ((weak)) notify_arch_cmos_timer(void) */ int do_adjtimex(struct timex *txc) { - long ltemp, mtemp, save_adjust; + long mtemp, save_adjust, rem; s64 freq_adj, temp64; int result; @@ -277,14 +277,14 @@ int do_adjtimex(struct timex *txc) time_adjust = txc->offset; } else if (time_status & STA_PLL) { - ltemp = txc->offset * NSEC_PER_USEC; + time_offset = txc->offset * NSEC_PER_USEC; /* * Scale the phase adjustment and * clamp to the operating range. */ - time_offset = min(ltemp, MAXPHASE * NSEC_PER_USEC); - time_offset = max(time_offset, -MAXPHASE * NSEC_PER_USEC); + time_offset = min(time_offset, (s64)MAXPHASE * NSEC_PER_USEC); + time_offset = max(time_offset, (s64)-MAXPHASE * NSEC_PER_USEC); /* * Select whether the frequency is to be controlled @@ -297,11 +297,11 @@ int do_adjtimex(struct timex *txc) mtemp = xtime.tv_sec - time_reftime; time_reftime = xtime.tv_sec; - freq_adj = (s64)time_offset * mtemp; + freq_adj = time_offset * mtemp; freq_adj = shift_right(freq_adj, time_constant * 2 + (SHIFT_PLL + 2) * 2 - SHIFT_NSEC); if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { - temp64 = (s64)time_offset << (SHIFT_NSEC - SHIFT_FLL); + temp64 = time_offset << (SHIFT_NSEC - SHIFT_FLL); if (time_offset < 0) { temp64 = -temp64; do_div(temp64, mtemp); @@ -314,8 +314,10 @@ int do_adjtimex(struct timex *txc) freq_adj += time_freq; freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC); time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC); - time_offset = (time_offset / NTP_INTERVAL_FREQ) - << SHIFT_UPDATE; + time_offset = div_long_long_rem_signed(time_offset, + NTP_INTERVAL_FREQ, + &rem); + time_offset <<= SHIFT_UPDATE; } /* STA_PLL */ } /* txc->modes & ADJ_OFFSET */ if (txc->modes & ADJ_TICK) @@ -328,12 +330,12 @@ leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0) result = TIME_ERROR; if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) - txc->offset = save_adjust; + txc->offset = save_adjust; else - txc->offset = shift_right(time_offset, SHIFT_UPDATE) - * NTP_INTERVAL_FREQ / 1000; - txc->freq = (time_freq / NSEC_PER_USEC) - << (SHIFT_USEC - SHIFT_NSEC); + txc->offset = ((long)shift_right(time_offset, SHIFT_UPDATE)) * + NTP_INTERVAL_FREQ / 1000; + txc->freq = (time_freq / NSEC_PER_USEC) << + (SHIFT_USEC - SHIFT_NSEC); txc->maxerror = time_maxerror; txc->esterror = time_esterror; txc->status = time_status;