2019-10-04 14:27:33

by Nick Crews

Subject: [PATCH v4] rtc: wilco-ec: Handle reading invalid times

If the RTC HW returns an invalid time, the rtc_year_days()
call would crash. This patch adds error logging in this
situation, and removes the tm_yday and tm_wday calculations.
These fields should not be relied upon by userspace
according to man rtc, and thus we don't need to calculate
them.

Signed-off-by: Nick Crews <[email protected]>
---
drivers/rtc/rtc-wilco-ec.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/rtc/rtc-wilco-ec.c b/drivers/rtc/rtc-wilco-ec.c
index 8ad4c4e6d557..ff46066a68a4 100644
--- a/drivers/rtc/rtc-wilco-ec.c
+++ b/drivers/rtc/rtc-wilco-ec.c
@@ -110,10 +110,12 @@ static int wilco_ec_rtc_read(struct device *dev, struct rtc_time *tm)
tm->tm_mday = rtc.day;
tm->tm_mon = rtc.month - 1;
tm->tm_year = rtc.year + (rtc.century * 100) - 1900;
- tm->tm_yday = rtc_year_days(tm->tm_mday, tm->tm_mon, tm->tm_year);
+ /* Ignore other tm fields, man rtc says userspace shouldn't use them. */

- /* Don't compute day of week, we don't need it. */
- tm->tm_wday = -1;
+ if (rtc_valid_tm(tm)) {
+ dev_err(dev, "Time from RTC is invalid: %ptRr\n", tm);
+ return -EIO;
+ }

return 0;
}
--
2.21.0

2019-10-08 22:27:33

by Daniel Campello

Subject: Re: [PATCH v4] rtc: wilco-ec: Handle reading invalid times

LGTM.
Reviewed-by: Daniel Campello <[email protected]>

2019-10-14 16:26:27

by Alexandre Belloni

Subject: Re: [PATCH v4] rtc: wilco-ec: Handle reading invalid times

On 04/10/2019 08:26:08-0600, Nick Crews wrote:
> If the RTC HW returns an invalid time, the rtc_year_days()
> call would crash. This patch adds error logging in this
> situation, and removes the tm_yday and tm_wday calculations.
> These fields should not be relied upon by userspace
> according to man rtc, and thus we don't need to calculate
> them.
>
> Signed-off-by: Nick Crews <[email protected]>
> ---
> drivers/rtc/rtc-wilco-ec.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
Applied, thanks.

--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com