[PATCH 6.11 773/817] rtc: check if __rtc_read_time was successful in rtc_timer_do_work()

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6.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yongliang Gao <leonylgao@xxxxxxxxxxx>

[ 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@xxxxxxxxxxx>
Acked-by: Jingqun Li <jingqunli@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20241011043153.3788112-1-leonylgao@xxxxxxxxx
Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/rtc/interface.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index cca650b2e0b94..aaf76406cd7d7 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -904,13 +904,18 @@ void rtc_timer_do_work(struct work_struct *work)
 	struct timerqueue_node *next;
 	ktime_t now;
 	struct rtc_time tm;
+	int err;
 
 	struct rtc_device *rtc =
 		container_of(work, struct rtc_device, irqwork);
 
 	mutex_lock(&rtc->ops_lock);
 again:
-	__rtc_read_time(rtc, &tm);
+	err = __rtc_read_time(rtc, &tm);
+	if (err) {
+		mutex_unlock(&rtc->ops_lock);
+		return;
+	}
 	now = rtc_tm_to_ktime(tm);
 	while ((next = timerqueue_getnext(&rtc->timerqueue))) {
 		if (next->expires > now)
-- 
2.43.0







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