[PATCH AUTOSEL 5.4 176/330] rtc: ds1374: fix possible race condition

Sasha Levin
2020-09-18T02:04:53Z

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

[ Upstream commit c11af8131a4e7ba1960faed731ee7e84c2c13c94 ]

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.

Link: https://lore.kernel.org/r/20200306073404.56921-1-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 367497914c100..28eb96cbaf98b 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;
--
2.25.1