Re: [PATCH][V2][next] rtc: ds1307: check for failed memory allocation on wdt

Guenter Roeck
2020-04-02T14:39:58Z

On 4/2/20 6:52 AM, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.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@canonical.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)

What exactly is the point of returning an error just to ignore it ?

Guenter

> {
> 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;
> }
>