[PATCH AUTOSEL 5.4 175/330] rtc: sa1100: fix possible race condition

Sasha Levin
2020-09-18T03:04:34Z

From: Alexandre Belloni <alexandre.belloni@bootlin.com>

[ Upstream commit f2997775b111c6d660c32a18d5d44d37cb7361b1 ]

Both RTC IRQs are requested before the struct rtc_device is allocated,
this may lead to a NULL pointer dereference in the IRQ handler.

To fix this issue, allocating the rtc_device struct before requesting
the IRQs using devm_rtc_allocate_device, and use rtc_register_device
to register the RTC device.

Link: https://lore.kernel.org/r/20200306010146.39762-1-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/rtc/rtc-sa1100.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/rtc/rtc-sa1100.c b/drivers/rtc/rtc-sa1100.c
index 86fa723b3b762..795273269d58e 100644
--- a/drivers/rtc/rtc-sa1100.c
+++ b/drivers/rtc/rtc-sa1100.c
@@ -182,7 +182,6 @@ static const struct rtc_class_ops sa1100_rtc_ops = {

int sa1100_rtc_init(struct platform_device *pdev, struct sa1100_rtc *info)
{
- struct rtc_device *rtc;
int ret;

spin_lock_init(&info->lock);
@@ -211,15 +210,14 @@ int sa1100_rtc_init(struct platform_device *pdev, struct sa1100_rtc *info)
writel_relaxed(0, info->rcnr);
}

- rtc = devm_rtc_device_register(&pdev->dev, pdev->name, &sa1100_rtc_ops,
- THIS_MODULE);
- if (IS_ERR(rtc)) {
+ info->rtc->ops = &sa1100_rtc_ops;
+ info->rtc->max_user_freq = RTC_FREQ;
+
+ ret = rtc_register_device(info->rtc);
+ if (ret) {
clk_disable_unprepare(info->clk);
- return PTR_ERR(rtc);
+ return ret;
}
- info->rtc = rtc;
-
- rtc->max_user_freq = RTC_FREQ;

/* Fix for a nasty initialization problem the in SA11xx RTSR register.
* See also the comments in sa1100_rtc_interrupt().
@@ -268,6 +266,10 @@ static int sa1100_rtc_probe(struct platform_device *pdev)
info->irq_1hz = irq_1hz;
info->irq_alarm = irq_alarm;

+ info->rtc = devm_rtc_allocate_device(&pdev->dev);
+ if (IS_ERR(info->rtc))
+ return PTR_ERR(info->rtc);
+
ret = devm_request_irq(&pdev->dev, irq_1hz, sa1100_rtc_interrupt, 0,
"rtc 1Hz", &pdev->dev);
if (ret) {
--
2.25.1