2015-12-04 04:01:36

by Sasha Levin

Subject: [PATCH v2] rtc: fix overflow and incorrect calculation in rtc_time64_to_tm

At some point after humans go extinct and robots cotrol the world, dividing
he time64_t by 86400 to extract the days will overflow a 32bit integer,
leading to incorrect conversion into rtc_time in rtc_time64_to_tm().

Signed-off-by: Sasha Levin <[email protected]>
---
drivers/rtc/rtc-lib.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/rtc/rtc-lib.c b/drivers/rtc/rtc-lib.c
index e6bfb9c..cafae93 100644
--- a/drivers/rtc/rtc-lib.c
+++ b/drivers/rtc/rtc-lib.c
@@ -53,12 +53,11 @@ EXPORT_SYMBOL(rtc_year_days);
void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
{
unsigned int month, year;
- unsigned long secs;
- int days;
+ int secs;
+ time64_t days;

/* time must be positive */
- days = div_s64(time, 86400);
- secs = time - (unsigned int) days * 86400;
+ days = div_s64_rem(time, 86400, &secs);

/* day of the week, 1970-01-01 was a Thursday */
tm->tm_wday = (days + 4) % 7;
--
1.7.10.4

2015-12-13 13:51:47

by Alexandre Belloni

Subject: Re: [PATCH v2] rtc: fix overflow and incorrect calculation in rtc_time64_to_tm

On 03/12/2015 at 23:01:14 -0500, Sasha Levin wrote :
> At some point after humans go extinct and robots cotrol the world, dividing
> he time64_t by 86400 to extract the days will overflow a 32bit integer,
> leading to incorrect conversion into rtc_time in rtc_time64_to_tm().
>
> Signed-off-by: Sasha Levin <[email protected]>
> ---
> drivers/rtc/rtc-lib.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
Applied, thanks.

--
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com