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

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Message-Id: <20190416083045.13924-1-alexandre.belloni@bootlin.com>
Date:   Tue, 16 Apr 2019 10:30:43 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     linux-rtc@...r.kernel.org
Cc:     Fabio Estevam <fabio.estevam@....com>,
        Anson Huang <Anson.Huang@....com>,
        linux-kernel@...r.kernel.org,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Subject: [PATCH 1/3] rtc: mxc: 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
struct before requesting the IRQ.

Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
---
 drivers/rtc/rtc-mxc.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/rtc/rtc-mxc.c b/drivers/rtc/rtc-mxc.c
index 708b9e9b86a6..d9a038afedf0 100644
--- a/drivers/rtc/rtc-mxc.c
+++ b/drivers/rtc/rtc-mxc.c
@@ -340,6 +340,13 @@ static int mxc_rtc_probe(struct platform_device *pdev)
 	if (IS_ERR(pdata->ioaddr))
 		return PTR_ERR(pdata->ioaddr);
 
+	rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	pdata->rtc = rtc;
+	rtc->ops = &mxc_rtc_ops;
+
 	pdata->clk_ipg = devm_clk_get(&pdev->dev, "ipg");
 	if (IS_ERR(pdata->clk_ipg)) {
 		dev_err(&pdev->dev, "unable to get ipg clock!\n");
@@ -402,14 +409,9 @@ static int mxc_rtc_probe(struct platform_device *pdev)
 			dev_err(&pdev->dev, "failed to enable irq wake\n");
 	}
 
-	rtc = devm_rtc_device_register(&pdev->dev, pdev->name, &mxc_rtc_ops,
-				  THIS_MODULE);
-	if (IS_ERR(rtc)) {
-		ret = PTR_ERR(rtc);
+	ret = rtc_register_device(rtc);
+	if (ret)
 		goto exit_put_clk_ref;
-	}
-
-	pdata->rtc = rtc;
 
 	return 0;
 
-- 
2.20.1