linux-stable.git/kernel/time/ntp.c, branch v3.16.78

ntp: Allow TAI-UTC offset to be set to zero

2019-09-23T20:12:03+00:00

commit fdc6bae940ee9eb869e493990540098b8c0fd6ab upstream.

The ADJ_TAI adjtimex mode sets the TAI-UTC offset of the system clock.
It is typically set by NTP/PTP implementations and it is automatically
updated by the kernel on leap seconds. The initial value is zero (which
applications may interpret as unknown), but this value cannot be set by
adjtimex. This limitation seems to go back to the original "nanokernel"
implementation by David Mills.

Change the ADJ_TAI check to accept zero as a valid TAI-UTC offset in
order to allow setting it back to the initial value.

Fixes: 153b5d054ac2 ("ntp: support for TAI")
Suggested-by: Ondrej Mosnacek 
Signed-off-by: Miroslav Lichvar 
Signed-off-by: Thomas Gleixner 
Cc: John Stultz 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Link: https://lkml.kernel.org/r/20190417084833.7401-1-mlichvar@redhat.com
Signed-off-by: Ben Hutchings

ntp: Fixup adjtimex freq validation on 32-bit systems

2015-03-02T15:04:31+00:00

commit 29183a70b0b828500816bd794b3fe192fce89f73 upstream.

Additional validation of adjtimex freq values to avoid
potential multiplication overflows were added in commit
5e5aeb4367b (time: adjtimex: Validate the ADJ_FREQUENCY values)

Unfortunately the patch used LONG_MAX/MIN instead of
LLONG_MAX/MIN, which was fine on 64-bit systems, but being
much smaller on 32-bit systems caused false positives
resulting in most direct frequency adjustments to fail w/
EINVAL.

ntpd only does direct frequency adjustments at startup, so
the issue was not as easily observed there, but other time
sync applications like ptpd and chrony were more effected by
the bug.

See bugs:

  https://bugzilla.kernel.org/show_bug.cgi?id=92481
  https://bugzilla.redhat.com/show_bug.cgi?id=1188074

This patch changes the checks to use LLONG_MAX for
clarity, and additionally the checks are disabled
on 32-bit systems since LLONG_MAX/PPM_SCALE is always
larger then the 32-bit long freq value, so multiplication
overflows aren't possible there.

Reported-by: Josh Boyer 
Reported-by: George Joseph 
Tested-by: George Joseph 
Signed-off-by: John Stultz 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Sasha Levin 
Link: http://lkml.kernel.org/r/1423553436-29747-1-git-send-email-john.stultz@linaro.org
[ Prettified the changelog and the comments a bit. ]
Signed-off-by: Ingo Molnar 
Signed-off-by: Luis Henriques

time: adjtimex: Validate the ADJ_FREQUENCY values

2015-03-02T15:04:31+00:00

commit 5e5aeb4367b450a28f447f6d5ab57d8f2ab16a5f upstream.

Verify that the frequency value from userspace is valid and makes sense.

Unverified values can cause overflows later on.

Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Signed-off-by: Sasha Levin 
[jstultz: Fix up bug for negative values and drop redunent cap check]
Signed-off-by: John Stultz 
Signed-off-by: Luis Henriques

Merge branch 'akpm' (patchbomb from Andrew) into next

2014-06-04T23:55:13+00:00

Merge misc updates from Andrew Morton:

 - a few fixes for 3.16.  Cc'ed to stable so they'll get there somehow.

 - various misc fixes and cleanups

 - most of the ocfs2 queue.  Review is slow...

 - most of MM.  The MM queue is pretty huge this time, but not much in
   the way of feature work.

 - some tweaks under kernel/

 - printk maintenance work

 - updates to lib/

 - checkpatch updates

 - tweaks to init/

* emailed patches from Andrew Morton : (276 commits)
  fs/autofs4/dev-ioctl.c: add __init to autofs_dev_ioctl_init
  fs/ncpfs/getopt.c: replace simple_strtoul by kstrtoul
  init/main.c: remove an ifdef
  kthreads: kill CLONE_KERNEL, change kernel_thread(kernel_init) to avoid CLONE_SIGHAND
  init/main.c: add initcall_blacklist kernel parameter
  init/main.c: don't use pr_debug()
  fs/binfmt_flat.c: make old_reloc() static
  fs/binfmt_elf.c: fix bool assignements
  fs/efs: convert printk(KERN_DEBUG to pr_debug
  fs/efs: add pr_fmt / use __func__
  fs/efs: convert printk to pr_foo()
  scripts/checkpatch.pl: device_initcall is not the only __initcall substitute
  checkpatch: check stable email address
  checkpatch: warn on unnecessary void function return statements
  checkpatch: prefer kstrto to sscanf(buf, "%", &bar);
  checkpatch: add warning for kmalloc/kzalloc with multiply
  checkpatch: warn on #defines ending in semicolon
  checkpatch: make --strict a default for files in drivers/net and net/
  checkpatch: always warn on missing blank line after variable declaration block
  checkpatch: fix wildcard DT compatible string checking
  ...

timekeeping: use printk_deferred when holding timekeeping seqlock

2014-06-04T23:54:17+00:00

Jiri Bohac pointed out that there are rare but potential deadlock
possibilities when calling printk while holding the timekeeping
seqlock.

This is due to printk() triggering console sem wakeup, which can
cause scheduling code to trigger hrtimers which may try to read
the time.

Specifically, as Jiri pointed out, that path is:
  printk
    vprintk_emit
      console_unlock
        up(&console_sem)
          __up
	    wake_up_process
	      try_to_wake_up
	        ttwu_do_activate
		  ttwu_activate
		    activate_task
		      enqueue_task
		        enqueue_task_fair
			  hrtick_update
			    hrtick_start_fair
			      hrtick_start_fair
			        get_time
				  ktime_get
				    --> endless loop on
				    read_seqcount_retry(&timekeeper_seq, ...)

This patch tries to avoid this issue by using printk_deferred (previously
named printk_sched) which should defer printing via a irq_work_queue.

Signed-off-by: John Stultz 
Reported-by: Jiri Bohac 
Reviewed-by: Steven Rostedt 
Cc: Jan Kara 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Steven Rostedt 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ntp: Make is_error_status() use its argument

2014-05-12T18:01:08+00:00

is_error_status() is an inline function always called with the
global time_status as an argument, so there's zero functional
difference with this change, but the non-CONFIG_NTP_PPS version
uses the passed-in argument, while the CONFIG_NTP_PPS one ignores
its argument and uses the global.

Looks like is_error_status was refactored out, but someone forgot
to change the logic to check the local argument value.

Thus this patch makes it use the argument always; shorter variable
names are good.

Signed-off-by: George Spelvin 
[jstultz: Tweaked commit message]
Signed-off-by: John Stultz

ntp: Convert simple_strtol to kstrtol

2014-05-12T17:09:25+00:00

Replace obsolete function simple_strtol w/ kstrtol

Inspired-By: Andrew Morton 
Cc: John Stultz 
Cc: Andrew Morton 
Signed-off-by: Fabian Frederick 
[jstultz: Tweak commit message]
Signed-off-by: John Stultz

timekeeping: Move clock sync work to power efficient workqueue

2014-02-07T14:34:28+00:00

For better use of CPU idle time, allow the scheduler to select the CPU
on which the CMOS clock sync work would be scheduled. This improves
idle residency time and conserver power.

This functionality is enabled when CONFIG_WQ_POWER_EFFICIENT is selected.

Signed-off-by: Shaibal Dutta 
[zoran.markovic@linaro.org: Added commit message. Aligned code.]
Signed-off-by: Zoran Markovic 
Cc: John Stultz 
Link: http://lkml.kernel.org/r/1391195904-12497-1-git-send-email-zoran.markovic@linaro.org
Signed-off-by: Thomas Gleixner

Merge tag 'v3.12-rc3' into timers/core

2013-10-03T05:52:21+00:00

Merge Linux 3.12-rc3 - refresh the tree with the latest fixes before merging new bits.

Signed-off-by: Ingo Molnar

timekeeping: Fix HRTICK related deadlock from ntp lock changes

2013-09-12T05:49:51+00:00

Gerlando Falauto reported that when HRTICK is enabled, it is
possible to trigger system deadlocks. These were hard to
reproduce, as HRTICK has been broken in the past, but seemed
to be connected to the timekeeping_seq lock.

Since seqlock/seqcount's aren't supported w/ lockdep, I added
some extra spinlock based locking and triggered the following
lockdep output:

[   15.849182] ntpd/4062 is trying to acquire lock:
[   15.849765]  (&(&pool->lock)->rlock){..-...}, at: [] __queue_work+0x145/0x480
[   15.850051]
[   15.850051] but task is already holding lock:
[   15.850051]  (timekeeper_lock){-.-.-.}, at: [] do_adjtimex+0x7f/0x100



[   15.850051] Chain exists of: &(&pool->lock)->rlock --> &p->pi_lock --> timekeeper_lock
[   15.850051]  Possible unsafe locking scenario:
[   15.850051]
[   15.850051]        CPU0                    CPU1
[   15.850051]        ----                    ----
[   15.850051]   lock(timekeeper_lock);
[   15.850051]                                lock(&p->pi_lock);
[   15.850051] lock(timekeeper_lock);
[   15.850051] lock(&(&pool->lock)->rlock);
[   15.850051]
[   15.850051]  *** DEADLOCK ***

The deadlock was introduced by 06c017fdd4dc48451a ("timekeeping:
Hold timekeepering locks in do_adjtimex and hardpps") in 3.10

This patch avoids this deadlock, by moving the call to
schedule_delayed_work() outside of the timekeeper lock
critical section.

Reported-by: Gerlando Falauto 
Tested-by: Lin Ming 
Signed-off-by: John Stultz 
Cc: Mathieu Desnoyers 
Cc: stable  #3.11, 3.10
Link: http://lkml.kernel.org/r/1378943457-27314-1-git-send-email-john.stultz@linaro.org
Signed-off-by: Ingo Molnar