linux-stable.git/drivers/rtc/interface.c, branch linux-5.4.y Linux kernel stable tree rtc: interface: Fix long-standing race when setting alarm 2025-10-29T12:59:53+00:00 Esben Haabendal esben@geanix.com 2025-05-16T07:23:35+00:00 524e37f7854171869ba725f3e5968790a8e18791 commit 795cda8338eab036013314dbc0b04aae728880ab upstream. As described in the old comment dating back to commit 6610e0893b8b ("RTC: Rework RTC code to use timerqueue for events") from 2010, we have been living with a race window when setting alarm with an expiry in the near future (i.e. next second). With 1 second resolution, it can happen that the second ticks after the check for the timer having expired, but before the alarm is actually set. When this happen, no alarm IRQ is generated, at least not with some RTC chips (isl12022 is an example of this). With UIE RTC timer being implemented on top of alarm irq, being re-armed every second, UIE will occasionally fail to work, as an alarm irq lost due to this race will stop the re-arming loop. For now, I have limited the additional expiry check to only be done for alarms set to next seconds. I expect it should be good enough, although I don't know if we can now for sure that systems with loads could end up causing the same problems for alarms set 2 seconds or even longer in the future. I haven't been able to reproduce the problem with this check in place. Cc: stable@vger.kernel.org Signed-off-by: Esben Haabendal <esben@geanix.com> Link: https://lore.kernel.org/r/20250516-rtc-uie-irq-fixes-v2-1-3de8e530a39e@geanix.com Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 795cda8338eab036013314dbc0b04aae728880ab upstream.

As described in the old comment dating back to
commit 6610e0893b8b ("RTC: Rework RTC code to use timerqueue for events")
from 2010, we have been living with a race window when setting alarm
with an expiry in the near future (i.e. next second).
With 1 second resolution, it can happen that the second ticks after the
check for the timer having expired, but before the alarm is actually set.
When this happen, no alarm IRQ is generated, at least not with some RTC
chips (isl12022 is an example of this).

With UIE RTC timer being implemented on top of alarm irq, being re-armed
every second, UIE will occasionally fail to work, as an alarm irq lost
due to this race will stop the re-arming loop.

For now, I have limited the additional expiry check to only be done for
alarms set to next seconds. I expect it should be good enough, although I
don't know if we can now for sure that systems with loads could end up
causing the same problems for alarms set 2 seconds or even longer in the
future.

I haven't been able to reproduce the problem with this check in place.

Cc: stable@vger.kernel.org
Signed-off-by: Esben Haabendal <esben@geanix.com>
Link: https://lore.kernel.org/r/20250516-rtc-uie-irq-fixes-v2-1-3de8e530a39e@geanix.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
rtc: interface: Ensure alarm irq is enabled when UIE is enabled 2025-10-29T12:59:53+00:00 Esben Haabendal esben@geanix.com 2025-05-16T07:23:39+00:00 755e5a8ffb40622fb6e87af0fb4909f61ca7b973 commit 9db26d5855d0374d4652487bfb5aacf40821c469 upstream. When setting a normal alarm, user-space is responsible for using RTC_AIE_ON/RTC_AIE_OFF to control if alarm irq should be enabled. But when RTC_UIE_ON is used, interrupts must be enabled so that the requested irq events are generated. When RTC_UIE_OFF is used, alarm irq is disabled if there are no other alarms queued, so this commit brings symmetry to that. Signed-off-by: Esben Haabendal <esben@geanix.com> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20250516-rtc-uie-irq-fixes-v2-5-3de8e530a39e@geanix.com Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 9db26d5855d0374d4652487bfb5aacf40821c469 upstream.

When setting a normal alarm, user-space is responsible for using
RTC_AIE_ON/RTC_AIE_OFF to control if alarm irq should be enabled.

But when RTC_UIE_ON is used, interrupts must be enabled so that the
requested irq events are generated.
When RTC_UIE_OFF is used, alarm irq is disabled if there are no other
alarms queued, so this commit brings symmetry to that.

Signed-off-by: Esben Haabendal <esben@geanix.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250516-rtc-uie-irq-fixes-v2-5-3de8e530a39e@geanix.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
rtc: check if __rtc_read_time was successful in rtc_timer_do_work() 2024-12-14T18:44:40+00:00 Yongliang Gao leonylgao@tencent.com 2024-10-11T04:31:53+00:00 44b3257ff705d63d5f00ef8ed314a0eeb7ec37f2 [ Upstream commit e8ba8a2bc4f60a1065f23d6a0e7cbea945a0f40d ] If the __rtc_read_time call fails,, the struct rtc_time tm; may contain uninitialized data, or an illegal date/time read from the RTC hardware. When calling rtc_tm_to_ktime later, the result may be a very large value (possibly KTIME_MAX). If there are periodic timers in rtc->timerqueue, they will continually expire, may causing kernel softlockup. Fixes: 6610e0893b8b ("RTC: Rework RTC code to use timerqueue for events") Signed-off-by: Yongliang Gao <leonylgao@tencent.com> Acked-by: Jingqun Li <jingqunli@tencent.com> Link: https://lore.kernel.org/r/20241011043153.3788112-1-leonylgao@gmail.com Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit e8ba8a2bc4f60a1065f23d6a0e7cbea945a0f40d ]

If the __rtc_read_time call fails,, the struct rtc_time tm; may contain
uninitialized data, or an illegal date/time read from the RTC hardware.

When calling rtc_tm_to_ktime later, the result may be a very large value
(possibly KTIME_MAX). If there are periodic timers in rtc->timerqueue,
they will continually expire, may causing kernel softlockup.

Fixes: 6610e0893b8b ("RTC: Rework RTC code to use timerqueue for events")
Signed-off-by: Yongliang Gao <leonylgao@tencent.com>
Acked-by: Jingqun Li <jingqunli@tencent.com>
Link: https://lore.kernel.org/r/20241011043153.3788112-1-leonylgao@gmail.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
rtc: interface: Add RTC offset to alarm after fix-up 2024-08-19T03:33:35+00:00 Csókás, Bence csokas.bence@prolan.hu 2024-06-19T14:04:52+00:00 84033790be84cdab758c638fdbb6313137fc98e5 [ Upstream commit 463927a8902a9f22c3633960119410f57d4c8920 ] `rtc_add_offset()` is called by `__rtc_read_time()` and `__rtc_read_alarm()` to add the RTC's offset to the raw read-outs from the device drivers. However, in the latter case, a fix-up algorithm is run if the RTC device does not report a full `struct rtc_time` alarm value. In that case, the offset was forgot to be added. Fixes: fd6792bb022e ("rtc: fix alarm read and set offset") Signed-off-by: Csókás, Bence <csokas.bence@prolan.hu> Link: https://lore.kernel.org/r/20240619140451.2800578-1-csokas.bence@prolan.hu Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 463927a8902a9f22c3633960119410f57d4c8920 ]

`rtc_add_offset()` is called by `__rtc_read_time()`
and `__rtc_read_alarm()` to add the RTC's offset to
the raw read-outs from the device drivers. However,
in the latter case, a fix-up algorithm is run if
the RTC device does not report a full `struct rtc_time`
alarm value. In that case, the offset was forgot to be
added.

Fixes: fd6792bb022e ("rtc: fix alarm read and set offset")

Signed-off-by: Csókás, Bence <csokas.bence@prolan.hu>
Link: https://lore.kernel.org/r/20240619140451.2800578-1-csokas.bence@prolan.hu
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
rtc: check if __rtc_read_time was successful 2022-04-15T12:18:28+00:00 Tom Rix trix@redhat.com 2022-03-26T19:42:36+00:00 8d67f67361c0c797c47593abbc0bd8de5b06f914 commit 915593a7a663b2ad08b895a5f3ba8b19d89d4ebf upstream. Clang static analysis reports this issue interface.c:810:8: warning: Passed-by-value struct argument contains uninitialized data now = rtc_tm_to_ktime(tm); ^~~~~~~~~~~~~~~~~~~ tm is set by a successful call to __rtc_read_time() but its return status is not checked. Check if it was successful before setting the enabled flag. Move the decl of err to function scope. Fixes: 2b2f5ff00f63 ("rtc: interface: ignore expired timers when enqueuing new timers") Signed-off-by: Tom Rix <trix@redhat.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20220326194236.2916310-1-trix@redhat.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 915593a7a663b2ad08b895a5f3ba8b19d89d4ebf upstream.

Clang static analysis reports this issue
interface.c:810:8: warning: Passed-by-value struct
  argument contains uninitialized data
  now = rtc_tm_to_ktime(tm);
      ^~~~~~~~~~~~~~~~~~~

tm is set by a successful call to __rtc_read_time()
but its return status is not checked.  Check if
it was successful before setting the enabled flag.
Move the decl of err to function scope.

Fixes: 2b2f5ff00f63 ("rtc: interface: ignore expired timers when enqueuing new timers")
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220326194236.2916310-1-trix@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
rtc: disable uie before setting time and enable after 2019-12-17T18:56:52+00:00 Alexandre Belloni alexandre.belloni@bootlin.com 2019-10-20T23:13:20+00:00 b44f9cd36bbc699d7dc71c99e4b7dabcd4fd55d8 commit 7e7c005b4b1f1f169bcc4b2c3a40085ecc663df2 upstream. When setting the time in the future with the uie timer enabled, rtc_timer_do_work will loop for a while because the expiration of the uie timer was way before the current RTC time and a new timer will be enqueued until the current rtc time is reached. If the uie timer is enabled, disable it before setting the time and enable it after expiring current timers (which may actually be an alarm). This is the safest thing to do to ensure the uie timer is still synchronized with the RTC, especially in the UIE emulation case. Reported-by: syzbot+08116743f8ad6f9a6de7@syzkaller.appspotmail.com Fixes: 6610e0893b8b ("RTC: Rework RTC code to use timerqueue for events") Link: https://lore.kernel.org/r/20191020231320.8191-1-alexandre.belloni@bootlin.com Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 7e7c005b4b1f1f169bcc4b2c3a40085ecc663df2 upstream.

When setting the time in the future with the uie timer enabled,
rtc_timer_do_work will loop for a while because the expiration of the uie
timer was way before the current RTC time and a new timer will be enqueued
until the current rtc time is reached.

If the uie timer is enabled, disable it before setting the time and enable
it after expiring current timers (which may actually be an alarm).

This is the safest thing to do to ensure the uie timer is still
synchronized with the RTC, especially in the UIE emulation case.

Reported-by: syzbot+08116743f8ad6f9a6de7@syzkaller.appspotmail.com
Fixes: 6610e0893b8b ("RTC: Rework RTC code to use timerqueue for events")
Link: https://lore.kernel.org/r/20191020231320.8191-1-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers: Introduce device lookup variants by name 2019-07-30T11:07:41+00:00 Suzuki K Poulose suzuki.poulose@arm.com 2019-07-23T22:18:32+00:00 6cda08a20dbde45b021091230c8a359fa08c5103 Add a helper to match the device name for device lookup. Also reuse this generic exported helper for the existing bus_find_device_by_name(). and add similar variants for driver/class. Cc: Alessandro Zummo <a.zummo@towertech.it> Cc: Alexander Aring <alex.aring@gmail.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Dan Murphy <dmurphy@ti.com> Cc: Harald Freudenberger <freude@linux.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com> Cc: Lee Jones <lee.jones@linaro.org> Cc: linux-leds@vger.kernel.org Cc: linux-rtc@vger.kernel.org Cc: linux-usb@vger.kernel.org Cc: linux-wpan@vger.kernel.org Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com> Cc: Pavel Machek <pavel@ucw.cz> Cc: Peter Oberparleiter <oberpar@linux.ibm.com> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: Stefan Schmidt <stefan@datenfreihafen.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20190723221838.12024-2-suzuki.poulose@arm.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
Add a helper to match the device name for device lookup. Also
reuse this generic exported helper for the existing bus_find_device_by_name().
and add similar variants for driver/class.

Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Alexander Aring <alex.aring@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dan Murphy <dmurphy@ti.com>
Cc: Harald Freudenberger <freude@linux.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: linux-leds@vger.kernel.org
Cc: linux-rtc@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Cc: linux-wpan@vger.kernel.org
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Stefan Schmidt <stefan@datenfreihafen.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20190723221838.12024-2-suzuki.poulose@arm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
rtc: interface: Change type of 'count' from int to u64 2019-07-13T11:53:22+00:00 Puranjay Mohan puranjay12@gmail.com 2019-06-18T04:23:51+00:00 3126790d1fd3f0dff11240c1bdb04a6f020a5a03 Callers of hrtimer_forward_now() should save the return value in u64. function rtc_pie_update_irq() stores it in variable 'count' of type int change type of count from unsigned long to u64 to solve the issue. Signed-off-by: Puranjay Mohan <puranjay12@gmail.com> Link: https://lore.kernel.org/r/20190618042351.9692-1-puranjay12@gmail.com Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> 
Callers of hrtimer_forward_now() should save the return value in u64.
function rtc_pie_update_irq() stores it in variable 'count' of type int
change type of count from unsigned long to u64 to solve the issue.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
Link: https://lore.kernel.org/r/20190618042351.9692-1-puranjay12@gmail.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
rtc: drop set_mms and set_mmss64 2019-05-08T20:14:36+00:00 Alexandre Belloni alexandre.belloni@bootlin.com 2019-04-30T14:16:51+00:00 a01ab0669ddf652f521630129e614c16542994b0 There are no users of set_mms and set_mmss64 as they have all been converted to set_time and are handling the tm to time conversion on their own. Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> 
There are no users of set_mms and set_mmss64 as they have all been
converted to set_time and are handling the tm to time conversion on their
own.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
rtc: don't reference bogus function pointer in kdoc 2019-04-04T08:07:11+00:00 Wolfram Sang wsa+renesas@sang-engineering.com 2019-04-03T15:19:52+00:00 c48cadf5bf4becefcd0751b97995d2350aa9bb57 The mentioned function pointer is long gone since early 2011. Remove the reference in the comment and reword it slightly. Fixes: 51ba60c5bb3b ("RTC: Cleanup rtc_class_ops->update_irq_enable()") Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> 
The mentioned function pointer is long gone since early 2011. Remove the
reference in the comment and reword it slightly.

Fixes: 51ba60c5bb3b ("RTC: Cleanup rtc_class_ops->update_irq_enable()")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>