| Message ID | a63f2b482281004df854d8345cb18368224880b6.1514200190.git.baolin.wang@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | rtc: Fix overflow when converting time64_t to rtc_time | expand |
Hi Alexandre, On 25 December 2017 at 19:10, Baolin Wang <baolin.wang@linaro.org> wrote: > If we convert one large time values to rtc_time, in the original formula > 'days * 86400' can be overflowed in 'unsigned int' type to make the formula > get one incorrect remain seconds value. Thus we can use div_s64_rem() > function to avoid this situation. > > Signed-off-by: Baolin Wang <baolin.wang@linaro.org> Could you apply this patch if there are no other comments? Thanks. > --- > drivers/rtc/rtc-lib.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/drivers/rtc/rtc-lib.c b/drivers/rtc/rtc-lib.c > index 1ae7da5..ad5bb21 100644 > --- a/drivers/rtc/rtc-lib.c > +++ b/drivers/rtc/rtc-lib.c > @@ -52,13 +52,11 @@ int rtc_year_days(unsigned int day, unsigned int month, unsigned int year) > */ > void rtc_time64_to_tm(time64_t time, struct rtc_time *tm) > { > - unsigned int month, year; > - unsigned long secs; > + unsigned int month, year, secs; > int 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; > -- > 1.7.9.5 > -- Baolin.wang Best Regards
On Fri, Jan 26, 2018 at 6:06 AM, Baolin Wang <baolin.wang@linaro.org> wrote: > If we convert one large time values to rtc_time, in the original formula > 'days * 86400' can be overflowed in 'unsigned int' type to make the formula > get one incorrect remain seconds value. Thus we can use div_s64_rem() > function to avoid this situation. > > Signed-off-by: Baolin Wang <baolin.wang@linaro.org> Acked-by: Arnd Bergmann <arnd@arndb.de>
Hi Alexandre, On 26 January 2018 at 17:24, Arnd Bergmann <arnd@arndb.de> wrote: > On Fri, Jan 26, 2018 at 6:06 AM, Baolin Wang <baolin.wang@linaro.org> wrote: >> If we convert one large time values to rtc_time, in the original formula >> 'days * 86400' can be overflowed in 'unsigned int' type to make the formula >> get one incorrect remain seconds value. Thus we can use div_s64_rem() >> function to avoid this situation. >> >> Signed-off-by: Baolin Wang <baolin.wang@linaro.org> > > Acked-by: Arnd Bergmann <arnd@arndb.de> Could you apply this patch? Since it was pending for a while and it is a bug fix. Thanks. -- Baolin.wang Best Regards
On 26/01/2018 at 13:06:01 +0800, Baolin Wang wrote: > If we convert one large time values to rtc_time, in the original formula > 'days * 86400' can be overflowed in 'unsigned int' type to make the formula > get one incorrect remain seconds value. Thus we can use div_s64_rem() > function to avoid this situation. > > Signed-off-by: Baolin Wang <baolin.wang@linaro.org> > --- > drivers/rtc/rtc-lib.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > Applied, thanks. -- Alexandre Belloni, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering http://bootlin.com
diff --git a/drivers/rtc/rtc-lib.c b/drivers/rtc/rtc-lib.c index 1ae7da5..ad5bb21 100644 --- a/drivers/rtc/rtc-lib.c +++ b/drivers/rtc/rtc-lib.c @@ -52,13 +52,11 @@ int rtc_year_days(unsigned int day, unsigned int month, unsigned int year) */ void rtc_time64_to_tm(time64_t time, struct rtc_time *tm) { - unsigned int month, year; - unsigned long secs; + unsigned int month, year, secs; int 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;
If we convert one large time values to rtc_time, in the original formula 'days * 86400' can be overflowed in 'unsigned int' type to make the formula get one incorrect remain seconds value. Thus we can use div_s64_rem() function to avoid this situation. Signed-off-by: Baolin Wang <baolin.wang@linaro.org> --- drivers/rtc/rtc-lib.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) -- 1.7.9.5