linux-kernel - [PATCH 1/3] rtc: ds1374: fix possible race condition

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Message-Id: <20200306073404.56921-1-alexandre.belloni@bootlin.com>
Date:   Fri,  6 Mar 2020 08:34:01 +0100
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] rtc: ds1374: fix possible race condition

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.

Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
---
 drivers/rtc/rtc-ds1374.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/rtc/rtc-ds1374.c b/drivers/rtc/rtc-ds1374.c
index 6e9ddcd03992..cb18a11a3c76 100644
--- a/drivers/rtc/rtc-ds1374.c
+++ b/drivers/rtc/rtc-ds1374.c
@@ -620,6 +620,10 @@ static int ds1374_probe(struct i2c_client *client,
 	if (!ds1374)
 		return -ENOMEM;
 
+	ds1374->rtc = devm_rtc_allocate_device(&client->dev);
+	if (IS_ERR(ds1374->rtc))
+		return PTR_ERR(ds1374->rtc);
+
 	ds1374->client = client;
 	i2c_set_clientdata(client, ds1374);
 
@@ -641,12 +645,11 @@ static int ds1374_probe(struct i2c_client *client,
 		device_set_wakeup_capable(&client->dev, 1);
 	}
 
-	ds1374->rtc = devm_rtc_device_register(&client->dev, client->name,
-						&ds1374_rtc_ops, THIS_MODULE);
-	if (IS_ERR(ds1374->rtc)) {
-		dev_err(&client->dev, "unable to register the class device\n");
-		return PTR_ERR(ds1374->rtc);
-	}
+	ds1374->rtc->ops = &ds1374_rtc_ops;
+
+	ret = rtc_register_device(ds1374->rtc);
+	if (ret)
+		return ret;
 
 #ifdef CONFIG_RTC_DRV_DS1374_WDT
 	save_client = client;
-- 
2.24.1