linux-kernel - [PATCH AUTOSEL 5.5 025/106] rtc: 88pm860x: fix possible race condition

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Message-Id: <20200415114226.13103-25-sashal@kernel.org>
Date:   Wed, 15 Apr 2020 07:41:05 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Sasha Levin <sashal@...nel.org>, linux-rtc@...r.kernel.org
Subject: [PATCH AUTOSEL 5.5 025/106] rtc: 88pm860x: fix possible race condition

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

[ Upstream commit 9cf4789e6e4673d0b2c96fa6bb0c35e81b43111a ]

The RTC IRQ is requested before the struct rtc_device is allocated,
this may lead to a NULL pointer dereference in the IRQ handler.

To fix this issue, allocating the rtc_device struct before requesting
the RTC IRQ using devm_rtc_allocate_device, and use rtc_register_device
to register the RTC device.

Also remove the unnecessary error message as the core already prints the
info.

Link: https://lore.kernel.org/r/20200311223956.51352-1-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/rtc/rtc-88pm860x.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/rtc/rtc-88pm860x.c b/drivers/rtc/rtc-88pm860x.c
index 4743b16a8d849..1526402e126b2 100644
--- a/drivers/rtc/rtc-88pm860x.c
+++ b/drivers/rtc/rtc-88pm860x.c
@@ -336,6 +336,10 @@ static int pm860x_rtc_probe(struct platform_device *pdev)
 	info->dev = &pdev->dev;
 	dev_set_drvdata(&pdev->dev, info);
 
+	info->rtc_dev = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(info->rtc_dev))
+		return PTR_ERR(info->rtc_dev);
+
 	ret = devm_request_threaded_irq(&pdev->dev, info->irq, NULL,
 					rtc_update_handler, IRQF_ONESHOT, "rtc",
 					info);
@@ -377,13 +381,11 @@ static int pm860x_rtc_probe(struct platform_device *pdev)
 		}
 	}
 
-	info->rtc_dev = devm_rtc_device_register(&pdev->dev, "88pm860x-rtc",
-					    &pm860x_rtc_ops, THIS_MODULE);
-	ret = PTR_ERR(info->rtc_dev);
-	if (IS_ERR(info->rtc_dev)) {
-		dev_err(&pdev->dev, "Failed to register RTC device: %d\n", ret);
+	info->rtc_dev->ops = &pm860x_rtc_ops;
+
+	ret = rtc_register_device(info->rtc_dev);
+	if (ret)
 		return ret;
-	}
 
 	/*
 	 * enable internal XO instead of internal 3.25MHz clock since it can
-- 
2.20.1