[PATCH AUTOSEL 5.17 04/31] rtc: fix use-after-free on device removal

Sasha Levin
2022-04-07T01:10:52Z

From: Vincent Whitchurch <vincent.whitchurch@axis.com>

[ 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 <vincent.whitchurch@axis.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20211210160951.7718-1-vincent.whitchurch@axis.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/rtc/class.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 4b460c61f1d8..40d504dac1a9 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -26,6 +26,15 @@ struct class *rtc_class;
static void rtc_device_release(struct device *dev)
{
struct rtc_device *rtc = to_rtc_device(dev);
+ struct timerqueue_head *head = &rtc->timerqueue;
+ struct timerqueue_node *node;
+
+ mutex_lock(&rtc->ops_lock);
+ while ((node = timerqueue_getnext(head)))
+ timerqueue_del(head, node);
+ mutex_unlock(&rtc->ops_lock);
+
+ cancel_work_sync(&rtc->irqwork);

ida_simple_remove(&rtc_ida, rtc->id);
mutex_destroy(&rtc->ops_lock);
--
2.35.1