[PATCH AUTOSEL 4.14 060/103] rtc: mt6397: fix possible race condition

Sasha Levin
2019-11-08T11:44:45Z

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

[ Upstream commit babab2f86440352d24e76118fdd7d40cab5fd7bf ]

The IRQ is requested before the struct rtc is allocated and registered, but
this struct is used in the IRQ handler. This may lead to a NULL pointer
dereference.

Switch to devm_rtc_allocate_device/rtc_register_device to allocate the rtc
before requesting the IRQ.

Acked-by: Eddie Huang <eddie.huang@mediatek.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/rtc/rtc-mt6397.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/rtc/rtc-mt6397.c b/drivers/rtc/rtc-mt6397.c
index 1a61fa56f3ad7..e82df43e5ca28 100644
--- a/drivers/rtc/rtc-mt6397.c
+++ b/drivers/rtc/rtc-mt6397.c
@@ -333,6 +333,10 @@ static int mtk_rtc_probe(struct platform_device *pdev)

platform_set_drvdata(pdev, rtc);

+ rtc->rtc_dev = devm_rtc_allocate_device(rtc->dev);
+ if (IS_ERR(rtc->rtc_dev))
+ return PTR_ERR(rtc->rtc_dev);
+
ret = request_threaded_irq(rtc->irq, NULL,
mtk_rtc_irq_handler_thread,
IRQF_ONESHOT | IRQF_TRIGGER_HIGH,
@@ -345,11 +349,11 @@ static int mtk_rtc_probe(struct platform_device *pdev)

device_init_wakeup(&pdev->dev, 1);

- rtc->rtc_dev = rtc_device_register("mt6397-rtc", &pdev->dev,
- &mtk_rtc_ops, THIS_MODULE);
- if (IS_ERR(rtc->rtc_dev)) {
+ rtc->rtc_dev->ops = &mtk_rtc_ops;
+
+ ret = rtc_register_device(rtc->rtc_dev);
+ if (ret) {
dev_err(&pdev->dev, "register rtc device failed\n");
- ret = PTR_ERR(rtc->rtc_dev);
goto out_free_irq;
}

@@ -366,7 +370,6 @@ static int mtk_rtc_remove(struct platform_device *pdev)
{
struct mt6397_rtc *rtc = platform_get_drvdata(pdev);

- rtc_device_unregister(rtc->rtc_dev);
free_irq(rtc->irq, rtc->rtc_dev);
irq_dispose_mapping(rtc->irq);

--
2.20.1