rtc: mt6397: fix possible race condition

BugLink: https://bugs.launchpad.net/bugs/1853915
[ 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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/rtc/rtc-mt6397.c b/drivers/rtc/rtc-mt6397.c
index 1a61fa56f3ad77bad999d234778e8d953fc1ad5a..e82df43e5ca289add3059605e4b41fb417f57cc4 100644 (file)
--- 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);