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Updates for time keeping:

Browse Source 
- Fix a couple of issues in the NTP code where user supplied values are
     neither sanity checked nor clamped to the operating range. This results
     in integer overflows and eventualy NTP getting out of sync.
 
     According to the history the sanity checks had been removed in favor of
     clamping the values, but the clamping never worked correctly under all
     circumstances. The NTP people asked to not bring the sanity checks back
     as it might break existing applications.
 
     Make the clamping work correctly and add it where it's missing
 
   - If adjtimex() sets the clock it has to trigger the hrtimer subsystem so
     it can adjust and if the clock was set into the future expire timers if
     needed. The caller should provide a bitmask to tell hrtimers which
     clocks have been adjusted. adjtimex() uses not the proper constant and
     uses CLOCK_REALTIME instead, which is 0. So hrtimers adjusts only the
     clocks, but does not check for expired timers, which might make them
     expire really late. Use the proper bitmask constant instead.
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Merge tag 'timers-urgent-2024-08-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull time keeping fixes from Thomas Gleixner:

 - Fix a couple of issues in the NTP code where user supplied values are
   neither sanity checked nor clamped to the operating range. This
   results in integer overflows and eventualy NTP getting out of sync.

   According to the history the sanity checks had been removed in favor
   of clamping the values, but the clamping never worked correctly under
   all circumstances. The NTP people asked to not bring the sanity
   checks back as it might break existing applications.

   Make the clamping work correctly and add it where it's missing

 - If adjtimex() sets the clock it has to trigger the hrtimer subsystem
   so it can adjust and if the clock was set into the future expire
   timers if needed. The caller should provide a bitmask to tell
   hrtimers which clocks have been adjusted.

   adjtimex() uses not the proper constant and uses CLOCK_REALTIME
   instead, which is 0. So hrtimers adjusts only the clocks, but does
   not check for expired timers, which might make them expire really
   late. Use the proper bitmask constant instead.

* tag 'timers-urgent-2024-08-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  timekeeping: Fix bogus clock_was_set() invocation in do_adjtimex()
  ntp: Safeguard against time_constant overflow
  ntp: Clamp maxerror and esterror to operating range
This commit is contained in:
Linus Torvalds 2024-08-11 10:15:34 -07:00
commit 7270e931b5
2 changed files with 5 additions and 6 deletions
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9
kernel/time/ntp.c
View File

@ -727,17 +727,16 @@ static inline void process_adjtimex_modes(const struct __kernel_timex *txc,
}
if (txc->modes & ADJ_MAXERROR)
time_maxerror = txc->maxerror;
time_maxerror = clamp(txc->maxerror, 0, NTP_PHASE_LIMIT);
if (txc->modes & ADJ_ESTERROR)
time_esterror = txc->esterror;
time_esterror = clamp(txc->esterror, 0, NTP_PHASE_LIMIT);
if (txc->modes & ADJ_TIMECONST) {
time_constant = txc->constant;
time_constant = clamp(txc->constant, 0, MAXTC);
if (!(time_status & STA_NANO))
time_constant += 4;
time_constant = min(time_constant, (long)MAXTC);
time_constant = max(time_constant, 0l);
time_constant = clamp(time_constant, 0, MAXTC);
}
if (txc->modes & ADJ_TAI &&

2
kernel/time/timekeeping.c
View File

@ -2606,7 +2606,7 @@ int do_adjtimex(struct __kernel_timex *txc)
clock_set |= timekeeping_advance(TK_ADV_FREQ);
if (clock_set)
clock_was_set(CLOCK_REALTIME);
clock_was_set(CLOCK_SET_WALL);
ntp_notify_cmos_timer();