linux-stable.git/drivers/rtc/class.c, branch linux-5.17.y

rtc: fix use-after-free on device removal

2022-05-25T07:58:58+00:00

[ Upstream commit c8fa17d9f08a448184f03d352145099b5beb618e ]

If the irqwork is still scheduled or running while the RTC device is
removed, a use-after-free occurs in rtc_timer_do_work().  Cleanup the
timerqueue and ensure the work is stopped to fix this.

 BUG: KASAN: use-after-free in mutex_lock+0x94/0x110
 Write of size 8 at addr ffffff801d846338 by task kworker/3:1/41

 Workqueue: events rtc_timer_do_work
 Call trace:
  mutex_lock+0x94/0x110
  rtc_timer_do_work+0xec/0x630
  process_one_work+0x5fc/0x1344
  ...

 Allocated by task 551:
  kmem_cache_alloc_trace+0x384/0x6e0
  devm_rtc_allocate_device+0xf0/0x574
  devm_rtc_device_register+0x2c/0x12c
  ...

 Freed by task 572:
  kfree+0x114/0x4d0
  rtc_device_release+0x64/0x80
  device_release+0x8c/0x1f4
  kobject_put+0x1c4/0x4b0
  put_device+0x20/0x30
  devm_rtc_release_device+0x1c/0x30
  devm_action_release+0x54/0x90
  release_nodes+0x124/0x310
  devres_release_group+0x170/0x240
  i2c_device_remove+0xd8/0x314
  ...

 Last potentially related work creation:
  insert_work+0x5c/0x330
  queue_work_on+0xcc/0x154
  rtc_set_time+0x188/0x5bc
  rtc_dev_ioctl+0x2ac/0xbd0
  ...

Signed-off-by: Vincent Whitchurch 
Signed-off-by: Alexandre Belloni 
Link: https://lore.kernel.org/r/20211210160951.7718-1-vincent.whitchurch@axis.com
Signed-off-by: Sasha Levin

rtc: expose RTC_FEATURE_UPDATE_INTERRUPT

2021-10-18T15:25:52+00:00

Set RTC_FEATURE_UPDATE_INTERRUPT by default and clear it when it is not
supported.

Signed-off-by: Alexandre Belloni 
Link: https://lore.kernel.org/r/20211018152337.78732-1-alexandre.belloni@bootlin.com

rtc: expose correction feature

2021-10-18T15:20:50+00:00

Add a new feature for RTCs able to correct the oscillator imprecision. This
is also called offset or trimming. Such drivers have a .set_offset callback,
use that to set the feature bit from the core.

Signed-off-by: Alexandre Belloni 
Link: https://lore.kernel.org/r/20211018151933.76865-4-alexandre.belloni@bootlin.com

rtc: class: check return value when calling dev_set_name()

2021-10-15T19:06:10+00:00

I got a null-ptr-deref report when doing fault injection test:

BUG: kernel NULL pointer dereference, address: 0000000000000000
RIP: 0010:strcmp+0xc/0x20
Call Trace:
 __devm_rtc_register_device.cold.7+0x16a/0x2df
 rv3029_probe+0x4b1/0x770 [rtc_rv3029c2]
 rv3029_i2c_probe+0x141/0x180 [rtc_rv3029c2]
 i2c_device_probe+0xa07/0xbb0
 really_probe+0x285/0xc30

If dev_set_name() fails, dev_name() is null, it causes null-ptr-deref,
we need check the return value of dev_set_name().

Reported-by: Hulk Robot 
Signed-off-by: Yang Yingliang 
Signed-off-by: Alexandre Belloni 
Link: https://lore.kernel.org/r/20211012041629.2504158-1-yangyingliang@huawei.com

rtc: class: don't call cdev_device_del() when cdev_device_add() failed

2021-10-15T19:05:33+00:00

I got a null-ptr-deref report when doing fault injection test:

general protection fault, probably for non-canonical address 0xdffffc0000000022: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000110-0x0000000000000117]
RIP: 0010:device_del+0x132/0xdc0
Call Trace:
 cdev_device_del+0x1a/0x80
 devm_rtc_unregister_device+0x37/0x80
 release_nodes+0xc3/0x3b0

If cdev_device_add() fails, 'dev->p' is not set, it causes
null-ptr-deref when calling cdev_device_del(). Registering
character device is optional, we don't return error code
here, so introduce a new flag 'RTC_NO_CDEV' to indicate
if it has character device, cdev_device_del() is called
when this bit is not set.

Reported-by: Hulk Robot 
Signed-off-by: Yang Yingliang 
Signed-off-by: Alexandre Belloni 
Link: https://lore.kernel.org/r/20211011132114.3663509-1-yangyingliang@huawei.com

rtc: class: remove bogus documentation

2021-02-05T23:58:24+00:00

rtc_device_unregister is gone since commit fdcfd854333b ("rtc: rework
rtc_register_device() resource management"). Remove its documentation.

Signed-off-by: Alexandre Belloni 
Link: https://lore.kernel.org/r/20210202112219.3610853-2-alexandre.belloni@bootlin.com

rtc: introduce features bitfield

2021-01-16T22:19:26+00:00

Introduce a bitfield to allow the drivers to announce the available
features for an RTC.

The main use case would be to better handle alarms, that could be present
or not or have a minute resolution or may need a correct week day to be set.

Use the newly introduced RTC_FEATURE_ALARM bit to then test whether alarms
are available instead of relying on the presence of ops->set_alarm.

Signed-off-by: Alexandre Belloni 
Link: https://lore.kernel.org/r/20210110231752.1418816-2-alexandre.belloni@bootlin.com

Merge tag 'rtc-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux

2020-12-20T18:12:06+00:00

Pull RTC updates from Alexandre Belloni:
 "Subsystem:

   - Remove nvram ABI. There was no complaints about the deprecation for
     the last 3 years.

   - Improve RTC device allocation and registration

   - Now available for ARCH=um

  Drivers:

   - at91rm9200: correction and sam9x60 support

   - ds1307: improve ACPI support

   - mxc: now DT only

   - pcf2127: watchdog support now needs the reset-source property

   - pcf8523: set range

   - rx6110: i2c support"

* tag 'rtc-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux: (43 commits)
  rtc: pcf2127: only use watchdog when explicitly available
  dt-bindings: rtc: add reset-source property
  rtc: fix RTC removal
  rtc: s3c: Remove dead code related to periodic tick handling
  rtc: s3c: Disable all enable (RTC, tick) bits in the probe
  rtc: ep93xx: Fix NULL pointer dereference in ep93xx_rtc_read_time
  rtc: test: remove debug message
  rtc: mxc{,_v2}: enable COMPILE_TEST
  rtc: enable RTC framework on ARCH=um
  rtc: pcf8523: use BIT
  rtc: pcf8523: set range
  rtc: pcf8523: switch to devm_rtc_allocate_device
  rtc: destroy mutex when releasing the device
  rtc: shrink devm_rtc_allocate_device()
  rtc: rework rtc_register_device() resource management
  rtc: nvmem: emit an error message when nvmem registration fails
  rtc: add devm_ prefix to rtc_nvmem_register()
  rtc: nvmem: remove nvram ABI
  Documentation: list RTC devres helpers in devres.rst
  rtc: omap: use devm_pinctrl_register()
  ...

rtc: fix RTC removal

2020-12-15T23:33:33+00:00

Since the rtc_register_device, removing an RTC device will end with a
refcount_t: underflow; use-after-free warning since put_device is called
twice in the device tear down path.

Fixes: fdcfd854333b ("rtc: rework rtc_register_device() resource management")
Signed-off-by: Alexandre Belloni 
Reviewed-by: Bartosz Golaszewski 
Link: https://lore.kernel.org/r/20201205231449.610980-1-alexandre.belloni@bootlin.com

ntp: Make the RTC sync offset less obscure

2020-12-11T09:40:53+00:00

The current RTC set_offset_nsec value is not really intuitive to
understand. 

  tsched       twrite(t2.tv_sec - 1) 	 t2 (seconds increment)

The offset is calculated from twrite based on the assumption that t2 -
twrite == 1s. That means for the MC146818 RTC the offset needs to be
negative so that the write happens 500ms before t2.

It's easier to understand when the whole calculation is based on t2. That
avoids negative offsets and the meaning is obvious:

 t2 - twrite:     The time defined by the chip when seconds increment
      		  after the write.

 twrite - tsched: The time for the transport to the point where the chip
 	  	  is updated. 

==> set_offset_nsec =  t2 - tsched
    ttransport      =  twrite - tsched
    tRTCinc         =  t2 - twrite
==> set_offset_nsec =  ttransport + tRTCinc

tRTCinc is a chip property and can be obtained from the data sheet.

ttransport depends on how the RTC is connected. It is close to 0 for
directly accessible RTCs. For RTCs behind a slow bus, e.g. i2c, it's the
time required to send the update over the bus. This can be estimated or
even calibrated, but that's a different problem.

Adjust the implementation and update comments accordingly.

Signed-off-by: Thomas Gleixner 
Acked-by: Alexandre Belloni 
Link: https://lore.kernel.org/r/20201206220542.263204937@linutronix.de