linux-toradex.git/kernel/time/ntp.c, branch v3.12.42

ntp: Fixup adjtimex freq validation on 32-bit systems

2015-04-09T12:13:23+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 
Cc: Christian Riesch 
Signed-off-by: Jiri Slaby

time: adjtimex: Validate the ADJ_FREQUENCY values

2015-01-29T14:45:01+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: Jiri Slaby

ntp: Make periodic RTC update more reliable

2013-12-08T15:29:16+00:00

commit a97ad0c4b447a132a322cedc3a5f7fa4cab4b304 upstream.

The current code requires that the scheduled update of the RTC happens
in the closest tick to the half of the second. This seems to be
difficult to achieve reliably. The scheduled work may be missing the
target time by a tick or two and be constantly rescheduled every second.

Relax the limit to 10 ticks. As a typical RTC drifts in the 11-minute
update interval by several milliseconds, this shouldn't affect the
overall accuracy of the RTC much.

Signed-off-by: Miroslav Lichvar 
Signed-off-by: John Stultz 
Cc: Josh Boyer 
Signed-off-by: Greg Kroah-Hartman

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

ntp: Remove unused variable flags in __hardpps

2013-05-28T20:45:19+00:00

kernel/time/ntp.c: In function ‘__hardpps’:
kernel/time/ntp.c:877: warning: unused variable ‘flags’

commit a076b2146fabb0894cae5e0189a8ba3f1502d737 ("ntp: Remove ntp_lock,
using the timekeeping locks to protect ntp state") removed its users,
but not the actual variable.

Signed-off-by: Geert Uytterhoeven 
Signed-off-by: John Stultz

ntp: Remove ntp_lock, using the timekeeping locks to protect ntp state

2013-04-04T20:18:17+00:00

In order to properly handle the NTP state in future changes to the
timekeeping lock management, this patch moves the management of
all of the ntp state under the timekeeping locks.

This allows us to remove the ntp_lock.

Cc: Thomas Gleixner 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Signed-off-by: John Stultz

timekeeping: Move ADJ_SETOFFSET to top level do_adjtimex()

2013-04-04T20:18:15+00:00

Since ADJ_SETOFFSET adjusts the timekeeping state, process
it as part of the top level do_adjtimex() function in
timekeeping.c.

This avoids deadlocks that could occur once we change the
ntp locking rules.

Cc: Thomas Gleixner 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Signed-off-by: John Stultz

ntp: Rework do_adjtimex to take timespec and tai arguments

2013-04-04T20:18:15+00:00

In order to change the locking rules, we need to provide
the timespec and tai values rather then having the ntp
logic acquire these values itself.

Cc: Thomas Gleixner 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Signed-off-by: John Stultz

ntp: Move timex validation to timekeeping do_adjtimex call.

2013-04-04T20:18:14+00:00

Move logic that does not need the ntp state to be done
in the timekeeping do_adjtimex() call.

Cc: Thomas Gleixner 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Signed-off-by: John Stultz

ntp: Move do_adjtimex() and hardpps() functions to timekeeping.c

2013-04-04T20:18:14+00:00

In preparation for changing the ntp locking rules, move
do_adjtimex and hardpps accessor functions to timekeeping.c,
but keep the code logic in ntp.c.

This patch also introduces a ntp_internal.h file so timekeeping
specific interfaces of ntp.c can be more limitedly shared with
timekeeping.c.

Cc: Thomas Gleixner 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Signed-off-by: John Stultz