linux-kernel - [PATCH][V2][next] rtc: ds1307: check for failed memory allocation on wdt

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Date:   Thu,  2 Apr 2020 14:52:01 +0100
From:   Colin King <colin.king@...onical.com>
To:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Chris Packham <chris.packham@...iedtelesis.co.nz>,
        linux-rtc@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][V2][next] rtc: ds1307: check for failed memory allocation on wdt

From: Colin Ian King <colin.king@...onical.com>

Currently a failed memory allocation will lead to a null pointer
dereference on point wdt.  Fix this by checking for a failed allocation
and adding error return handling to function ds1307_wdt_register.
Also move the error exit label "exit" to allow a return statement to
be removed.

Addresses-Coverity: ("Dereference null return")
Fixes: fd90d48db037 ("rtc: ds1307: add support for watchdog timer on ds1388")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
V2: move error exit label and remove a return statement, thanks to 
    Walter Harms for spotting this clean up.
---
 drivers/rtc/rtc-ds1307.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index fad042118862..c058b02efb4d 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -1665,14 +1665,16 @@ static const struct watchdog_ops ds1388_wdt_ops = {
 
 };
 
-static void ds1307_wdt_register(struct ds1307 *ds1307)
+static int ds1307_wdt_register(struct ds1307 *ds1307)
 {
 	struct watchdog_device	*wdt;
 
 	if (ds1307->type != ds_1388)
-		return;
+		return 0;
 
 	wdt = devm_kzalloc(ds1307->dev, sizeof(*wdt), GFP_KERNEL);
+	if (!wdt)
+		return -ENOMEM;
 
 	wdt->info = &ds1388_wdt_info;
 	wdt->ops = &ds1388_wdt_ops;
@@ -1683,10 +1685,13 @@ static void ds1307_wdt_register(struct ds1307 *ds1307)
 	watchdog_init_timeout(wdt, 0, ds1307->dev);
 	watchdog_set_drvdata(wdt, ds1307);
 	devm_watchdog_register_device(ds1307->dev, wdt);
+
+	return 0;
 }
 #else
-static void ds1307_wdt_register(struct ds1307 *ds1307)
+static int ds1307_wdt_register(struct ds1307 *ds1307)
 {
+	return 0;
 }
 #endif /* CONFIG_WATCHDOG_CORE */
 
@@ -1979,10 +1984,7 @@ static int ds1307_probe(struct i2c_client *client,
 
 	ds1307_hwmon_register(ds1307);
 	ds1307_clks_register(ds1307);
-	ds1307_wdt_register(ds1307);
-
-	return 0;
-
+	err = ds1307_wdt_register(ds1307);
 exit:
 	return err;
 }
-- 
2.25.1