linux-stable.git/kernel/time, branch linux-6.10.y

timekeeping: Fix bogus clock_was_set() invocation in do_adjtimex()

2024-08-14T13:34:30+00:00

commit 5916be8a53de6401871bdd953f6c60237b47d6d3 upstream.

The addition of the bases argument to clock_was_set() fixed up all call
sites correctly except for do_adjtimex(). This uses CLOCK_REALTIME
instead of CLOCK_SET_WALL as argument. CLOCK_REALTIME is 0.

As a result the effect of that clock_was_set() notification is incomplete
and might result in timers expiring late because the hrtimer code does
not re-evaluate the affected clock bases.

Use CLOCK_SET_WALL instead of CLOCK_REALTIME to tell the hrtimers code
which clock bases need to be re-evaluated.

Fixes: 17a1b8826b45 ("hrtimer: Add bases argument to clock_was_set()")
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/877ccx7igo.ffs@tglx
Signed-off-by: Greg Kroah-Hartman

ntp: Safeguard against time_constant overflow

2024-08-14T13:34:30+00:00

commit 06c03c8edce333b9ad9c6b207d93d3a5ae7c10c0 upstream.

Using syzkaller with the recently reintroduced signed integer overflow
sanitizer produces this UBSAN report:

UBSAN: signed-integer-overflow in ../kernel/time/ntp.c:738:18
9223372036854775806 + 4 cannot be represented in type 'long'
Call Trace:
 handle_overflow+0x171/0x1b0
 __do_adjtimex+0x1236/0x1440
 do_adjtimex+0x2be/0x740

The user supplied time_constant value is incremented by four and then
clamped to the operating range.

Before commit eea83d896e31 ("ntp: NTP4 user space bits update") the user
supplied value was sanity checked to be in the operating range. That change
removed the sanity check and relied on clamping after incrementing which
does not work correctly when the user supplied value is in the overflow
zone of the '+ 4' operation.

The operation requires CAP_SYS_TIME and the side effect of the overflow is
NTP getting out of sync.

Similar to the fixups for time_maxerror and time_esterror, clamp the user
space supplied value to the operating range.

[ tglx: Switch to clamping ]

Fixes: eea83d896e31 ("ntp: NTP4 user space bits update")
Signed-off-by: Justin Stitt 
Signed-off-by: Thomas Gleixner 
Cc: Miroslav Lichvar 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20240517-b4-sio-ntp-c-v2-1-f3a80096f36f@google.com
Closes: https://github.com/KSPP/linux/issues/352
Signed-off-by: Greg Kroah-Hartman

ntp: Clamp maxerror and esterror to operating range

2024-08-14T13:34:29+00:00

[ Upstream commit 87d571d6fb77ec342a985afa8744bb9bb75b3622 ]

Using syzkaller alongside the newly reintroduced signed integer overflow
sanitizer spits out this report:

UBSAN: signed-integer-overflow in ../kernel/time/ntp.c:461:16
9223372036854775807 + 500 cannot be represented in type 'long'
Call Trace:
 handle_overflow+0x171/0x1b0
 second_overflow+0x2d6/0x500
 accumulate_nsecs_to_secs+0x60/0x160
 timekeeping_advance+0x1fe/0x890
 update_wall_time+0x10/0x30

time_maxerror is unconditionally incremented and the result is checked
against NTP_PHASE_LIMIT, but the increment itself can overflow, resulting
in wrap-around to negative space.

Before commit eea83d896e31 ("ntp: NTP4 user space bits update") the user
supplied value was sanity checked to be in the operating range. That change
removed the sanity check and relied on clamping in handle_overflow() which
does not work correctly when the user supplied value is in the overflow
zone of the '+ 500' operation.

The operation requires CAP_SYS_TIME and the side effect of the overflow is
NTP getting out of sync.

Miroslav confirmed that the input value should be clamped to the operating
range and the same applies to time_esterror. The latter is not used by the
kernel, but the value still should be in the operating range as it was
before the sanity check got removed.

Clamp them to the operating range.

[ tglx: Changed it to clamping and included time_esterror ]

Fixes: eea83d896e31 ("ntp: NTP4 user space bits update")
Signed-off-by: Justin Stitt 
Signed-off-by: Thomas Gleixner 
Cc: Miroslav Lichvar 
Link: https://lore.kernel.org/all/20240517-b4-sio-ntp-usec-v2-1-d539180f2b79@google.com
Closes: https://github.com/KSPP/linux/issues/354
Signed-off-by: Sasha Levin

tick/broadcast: Move per CPU pointer access into the atomic section

2024-08-14T13:34:29+00:00

commit 6881e75237a84093d0986f56223db3724619f26e upstream.

The recent fix for making the take over of the broadcast timer more
reliable retrieves a per CPU pointer in preemptible context.

This went unnoticed as compilers hoist the access into the non-preemptible
region where the pointer is actually used. But of course it's valid that
the compiler keeps it at the place where the code puts it which rightfully
triggers:

  BUG: using smp_processor_id() in preemptible [00000000] code:
       caller is hotplug_cpu__broadcast_tick_pull+0x1c/0xc0

Move it to the actual usage site which is in a non-preemptible region.

Fixes: f7d43dd206e7 ("tick/broadcast: Make takeover of broadcast hrtimer reliable")
Reported-by: David Wang <00107082@163.com>
Signed-off-by: Thomas Gleixner 
Tested-by: Yu Liao 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/87ttg56ers.ffs@tglx
Signed-off-by: Greg Kroah-Hartman

clocksource: Fix brown-bag boolean thinko in cs_watchdog_read()

2024-08-14T13:34:17+00:00

commit f2655ac2c06a15558e51ed6529de280e1553c86e upstream.

The current "nretries > 1 || nretries >= max_retries" check in
cs_watchdog_read() will always evaluate to true, and thus pr_warn(), if
nretries is greater than 1.  The intent is instead to never warn on the
first try, but otherwise warn if the successful retry was the last retry.

Therefore, change that "||" to "&&".

Fixes: db3a34e17433 ("clocksource: Retry clock read if long delays detected")
Reported-by: Borislav Petkov 
Signed-off-by: Paul E. McKenney 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20240802154618.4149953-2-paulmck@kernel.org
Signed-off-by: Greg Kroah-Hartman

timers/migration: Do not rely always on group->parent

2024-08-03T07:01:06+00:00

[ Upstream commit facd40aa5c4699f94014012e4e58414c082f2c01 ]

When reading group->parent without holding the group lock it is racy
against CPUs coming online the first time and thereby creating another
level of the hierarchy. This is not a problem when this value is read once
to decide whether to abort a propagation or not. The worst outcome is an
unnecessary/early CPU wake up. But it is racy when reading it several times
during a single 'action' (like activation, deactivation, checking for
remote timer expiry,...) and relying on the consitency of this value
without holding the lock. This happens at the moment e.g. in
tmigr_inactive_up() which is also calling tmigr_udpate_events(). Code relys
on group->parent not to change during this 'action'.

Update parent struct member description to explain the above only
once. Remove parent pointer checks when they are not mandatory (like update
of data->childmask). Remove a warning, which would be nice but the trigger
of this warning is not reliable and add expand the data structure member
description instead. Expand a comment, why it is safe to rely on parent
pointer here (inside hierarchy update).

Fixes: 7ee988770326 ("timers: Implement the hierarchical pull model")
Reported-by: Borislav Petkov 
Signed-off-by: Anna-Maria Behnsen 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Frederic Weisbecker 
Link: https://lore.kernel.org/r/20240716-tmigr-fixes-v4-1-757baa7803fe@linutronix.de
Signed-off-by: Sasha Levin

tick/broadcast: Make takeover of broadcast hrtimer reliable

2024-08-03T07:00:30+00:00

commit f7d43dd206e7e18c182f200e67a8db8c209907fa upstream.

Running the LTP hotplug stress test on a aarch64 machine results in
rcu_sched stall warnings when the broadcast hrtimer was owned by the
un-plugged CPU. The issue is the following:

CPU1 (owns the broadcast hrtimer)	CPU2

				tick_broadcast_enter()
				  // shutdown local timer device
				  broadcast_shutdown_local()
				...
				tick_broadcast_exit()
				  clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT)
				  // timer device is not programmed
				  cpumask_set_cpu(cpu, tick_broadcast_force_mask)

				initiates offlining of CPU1
take_cpu_down()
/*
 * CPU1 shuts down and does not
 * send broadcast IPI anymore
 */
				takedown_cpu()
				  hotplug_cpu__broadcast_tick_pull()
				    // move broadcast hrtimer to this CPU
				    clockevents_program_event()
				      bc_set_next()
					hrtimer_start()
					/*
					 * timer device is not programmed
					 * because only the first expiring
					 * timer will trigger clockevent
					 * device reprogramming
					 */

What happens is that CPU2 exits broadcast mode with force bit set, then the
local timer device is not reprogrammed and CPU2 expects to receive the
expired event by the broadcast IPI. But this does not happen because CPU1
is offlined by CPU2. CPU switches the clockevent device to ONESHOT state,
but does not reprogram the device.

The subsequent reprogramming of the hrtimer broadcast device does not
program the clockevent device of CPU2 either because the pending expiry
time is already in the past and the CPU expects the event to be delivered.
As a consequence all CPUs which wait for a broadcast event to be delivered
are stuck forever.

Fix this issue by reprogramming the local timer device if the broadcast
force bit of the CPU is set so that the broadcast hrtimer is delivered.

[ tglx: Massage comment and change log. Add Fixes tag ]

Fixes: 989dcb645ca7 ("tick: Handle broadcast wakeup of multiple cpus")
Signed-off-by: Yu Liao 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240711124843.64167-1-liaoyu15@huawei.com
Signed-off-by: Greg Kroah-Hartman

hrtimer: Prevent queuing of hrtimer without a function callback

2024-06-25T14:54:27+00:00

The hrtimer function callback must not be NULL. It has to be specified by
the call side but it is not validated by the hrtimer code. When a hrtimer
is queued without a function callback, the kernel crashes with a null
pointer dereference when trying to execute the callback in __run_hrtimer().

Introduce a validation before queuing the hrtimer in
hrtimer_start_range_ns().

[anna-maria: Rephrase commit message]

Signed-off-by: Phil Chang 
Signed-off-by: Anna-Maria Behnsen 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Anna-Maria Behnsen

tick/nohz_full: Don't abuse smp_call_function_single() in tick_setup_device()

2024-06-10T18:18:13+00:00

After the recent commit 5097cbcb38e6 ("sched/isolation: Prevent boot crash
when the boot CPU is nohz_full") the kernel no longer crashes, but there is
another problem.

In this case tick_setup_device() calls tick_take_do_timer_from_boot() to
update tick_do_timer_cpu and this triggers the WARN_ON_ONCE(irqs_disabled)
in smp_call_function_single().

Kill tick_take_do_timer_from_boot() and just use WRITE_ONCE(), the new
comment explains why this is safe (thanks Thomas!).

Fixes: 08ae95f4fd3b ("nohz_full: Allow the boot CPU to be nohz_full")
Signed-off-by: Oleg Nesterov 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240528122019.GA28794@redhat.com
Link: https://lore.kernel.org/all/20240522151742.GA10400@redhat.com

Merge tag 'sysctl-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl

2024-05-18T00:31:24+00:00

Pull sysctl updates from Joel Granados:

 - Remove sentinel elements from ctl_table structs in kernel/*

   Removing sentinels in ctl_table arrays reduces the build time size
   and runtime memory consumed by ~64 bytes per array. Removals for
   net/, io_uring/, mm/, ipc/ and security/ are set to go into mainline
   through their respective subsystems making the next release the most
   likely place where the final series that removes the check for
   proc_name == NULL will land.

   This adds to removals already in arch/, drivers/ and fs/.

 - Adjust ctl_table definitions and references to allow constification
     - Remove unused ctl_table function arguments
     - Move non-const elements from ctl_table to ctl_table_header
     - Make ctl_table pointers const in ctl_table_root structure

   Making the static ctl_table structs const will increase safety by
   keeping the pointers to proc_handler functions in .rodata. Though no
   ctl_tables where made const in this PR, the ground work for making
   that possible has started with these changes sent by Thomas
   Weißschuh.

* tag 'sysctl-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl:
  sysctl: drop now unnecessary out-of-bounds check
  sysctl: move sysctl type to ctl_table_header
  sysctl: drop sysctl_is_perm_empty_ctl_table
  sysctl: treewide: constify argument ctl_table_root::permissions(table)
  sysctl: treewide: drop unused argument ctl_table_root::set_ownership(table)
  bpf: Remove the now superfluous sentinel elements from ctl_table array
  delayacct: Remove the now superfluous sentinel elements from ctl_table array
  kprobes: Remove the now superfluous sentinel elements from ctl_table array
  printk: Remove the now superfluous sentinel elements from ctl_table array
  scheduler: Remove the now superfluous sentinel elements from ctl_table array
  seccomp: Remove the now superfluous sentinel elements from ctl_table array
  timekeeping: Remove the now superfluous sentinel elements from ctl_table array
  ftrace: Remove the now superfluous sentinel elements from ctl_table array
  umh: Remove the now superfluous sentinel elements from ctl_table array
  kernel misc: Remove the now superfluous sentinel elements from ctl_table array