linux-kernel - [PATCH 1/3] rtc: mt6397: fix possible race condition

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Date:   Sun,  9 Sep 2018 22:38:46 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     linux-rtc@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Eddie Huang <eddie.huang@...iatek.com>,
        Sean Wang <sean.wang@...iatek.com>
Subject: [PATCH 1/3] rtc: mt6397: fix possible race condition

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.

Cc: Eddie Huang <eddie.huang@...iatek.com>
Cc: Sean Wang <sean.wang@...iatek.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
---
 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 385f8303bb41..e9a25ec4d434 100644
--- a/drivers/rtc/rtc-mt6397.c
+++ b/drivers/rtc/rtc-mt6397.c
@@ -332,6 +332,10 @@ 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,
@@ -344,11 +348,11 @@ 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;
 	}
 
@@ -365,7 +369,6 @@ 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);
 
-- 
2.19.0.rc2