linux-kernel - [PATCH 1/7] rtc: xgene: fix possible race condition

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Message-Id: <20190320123233.13519-1-alexandre.belloni@bootlin.com>
Date:   Wed, 20 Mar 2019 13:32:27 +0100
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     linux-rtc@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Subject: [PATCH 1/7] rtc: xgene: 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-xgene.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/rtc/rtc-xgene.c b/drivers/rtc/rtc-xgene.c
index 153820876a82..2f741f455c30 100644
--- a/drivers/rtc/rtc-xgene.c
+++ b/drivers/rtc/rtc-xgene.c
@@ -168,6 +168,10 @@ static int xgene_rtc_probe(struct platform_device *pdev)
 	if (IS_ERR(pdata->csr_base))
 		return PTR_ERR(pdata->csr_base);
 
+	pdata->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(pdata->rtc))
+		return PTR_ERR(pdata->rtc);
+
 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0) {
 		dev_err(&pdev->dev, "No IRQ resource\n");
@@ -198,15 +202,15 @@ static int xgene_rtc_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	pdata->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
-					 &xgene_rtc_ops, THIS_MODULE);
-	if (IS_ERR(pdata->rtc)) {
-		clk_disable_unprepare(pdata->clk);
-		return PTR_ERR(pdata->rtc);
-	}
-
 	/* HW does not support update faster than 1 seconds */
 	pdata->rtc->uie_unsupported = 1;
+	pdata->rtc->ops = &xgene_rtc_ops;
+
+	ret = rtc_register_device(pdata->rtc);
+	if (ret) {
+		clk_disable_unprepare(pdata->clk);
+		return ret;
+	}
 
 	return 0;
 }
-- 
2.20.1