[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 <johnstul@us.ibm.com> Cc: Roman Zippel <zippel@linux-m68k.org> Cc: john stultz <johnstul@us.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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kernel/time
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@ -32,7 +32,7 @@ static u64 tick_length, tick_length_base;
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/* TIME_ERROR prevents overwriting the CMOS clock */
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static int time_state = TIME_OK; /* clock synchronization status */
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int time_status = STA_UNSYNC; /* clock status bits */
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static long time_offset; /* time adjustment (ns) */
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static s64 time_offset; /* time adjustment (ns) */
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static long time_constant = 2; /* pll time constant */
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long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */
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long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */
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@ -196,7 +196,7 @@ void __attribute__ ((weak)) notify_arch_cmos_timer(void)
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*/
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int do_adjtimex(struct timex *txc)
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{
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long ltemp, mtemp, save_adjust;
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long mtemp, save_adjust, rem;
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s64 freq_adj, temp64;
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int result;
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@ -277,14 +277,14 @@ int do_adjtimex(struct timex *txc)
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time_adjust = txc->offset;
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}
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else if (time_status & STA_PLL) {
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ltemp = txc->offset * NSEC_PER_USEC;
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time_offset = txc->offset * NSEC_PER_USEC;
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/*
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* Scale the phase adjustment and
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* clamp to the operating range.
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*/
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time_offset = min(ltemp, MAXPHASE * NSEC_PER_USEC);
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time_offset = max(time_offset, -MAXPHASE * NSEC_PER_USEC);
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time_offset = min(time_offset, (s64)MAXPHASE * NSEC_PER_USEC);
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time_offset = max(time_offset, (s64)-MAXPHASE * NSEC_PER_USEC);
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/*
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* Select whether the frequency is to be controlled
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@ -297,11 +297,11 @@ int do_adjtimex(struct timex *txc)
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mtemp = xtime.tv_sec - time_reftime;
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time_reftime = xtime.tv_sec;
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freq_adj = (s64)time_offset * mtemp;
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freq_adj = time_offset * mtemp;
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freq_adj = shift_right(freq_adj, time_constant * 2 +
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(SHIFT_PLL + 2) * 2 - SHIFT_NSEC);
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if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {
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temp64 = (s64)time_offset << (SHIFT_NSEC - SHIFT_FLL);
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temp64 = time_offset << (SHIFT_NSEC - SHIFT_FLL);
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if (time_offset < 0) {
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temp64 = -temp64;
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do_div(temp64, mtemp);
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@ -314,8 +314,10 @@ int do_adjtimex(struct timex *txc)
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freq_adj += time_freq;
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freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC);
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time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC);
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time_offset = (time_offset / NTP_INTERVAL_FREQ)
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<< SHIFT_UPDATE;
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time_offset = div_long_long_rem_signed(time_offset,
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NTP_INTERVAL_FREQ,
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&rem);
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time_offset <<= SHIFT_UPDATE;
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} /* STA_PLL */
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} /* txc->modes & ADJ_OFFSET */
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if (txc->modes & ADJ_TICK)
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@ -328,12 +330,12 @@ leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)
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result = TIME_ERROR;
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if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
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txc->offset = save_adjust;
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txc->offset = save_adjust;
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else
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txc->offset = shift_right(time_offset, SHIFT_UPDATE)
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* NTP_INTERVAL_FREQ / 1000;
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txc->freq = (time_freq / NSEC_PER_USEC)
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<< (SHIFT_USEC - SHIFT_NSEC);
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txc->offset = ((long)shift_right(time_offset, SHIFT_UPDATE)) *
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NTP_INTERVAL_FREQ / 1000;
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txc->freq = (time_freq / NSEC_PER_USEC) <<
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(SHIFT_USEC - SHIFT_NSEC);
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txc->maxerror = time_maxerror;
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txc->esterror = time_esterror;
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txc->status = time_status;
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