Skip to content
Browse files

rtc: Add an option to invalidate dates in 2038

hctosys is setting the system time from the kernel. This means that 32bit
system can get their time set to a date after the 31bit time_t overflow.

This is currently an issue as userspace is not yet ready to handle those
dates and may break. For example systemd's usage of timerfd shows that the
timerfd will always fire immediately because it can't be set at a date
after the current date.

The new RTC_INVALID_2038 option will make sure that date after 03:09:07 on
Jan 19 2038 are invalid. This is 5 minutes before the 31bit overflow. This
leaves enough time for userspace to react and is short enough to make the
issue visible.

Signed-off-by: Alexandre Belloni <>
  • Loading branch information...
alexandrebelloni committed Feb 20, 2016
1 parent 66aac38 commit b7048bfbba7633b9858b10094e2e7b0eaffa6483
Showing with 14 additions and 1 deletion.
  1. +10 −0 drivers/rtc/Kconfig
  2. +4 −1 drivers/rtc/rtc-lib.c
@@ -73,6 +73,16 @@ config RTC_DEBUG
Say yes here to enable debugging support in the RTC framework
and individual RTC drivers.

config RTC_INVALID_2038
bool "Invalidate dates after 2038"
depends on !64BIT
default y
Saying yes here will make any date after 03:09:07 on Jan 19 2038
invalid (this is 5 minutes before the 31 bits overflow of a time_t).
This is useful if your userspace is not yet ready to handle 64 bits

comment "RTC interfaces"

@@ -107,7 +107,10 @@ int rtc_valid_tm(struct rtc_time *tm)
|| ((unsigned)tm->tm_min) >= 60
|| ((unsigned)tm->tm_sec) >= 60)
return -EINVAL;

if (rtc_tm_to_time64(tm) > 0x7FFFFED4) /* 5 minutes before overflow */
return -EINVAL;
return 0;

1 comment on commit b7048bf


This comment has been minimized.

Copy link

rzr commented on b7048bf Feb 20, 2016

let me crosslink this patch to this bug report :


Please sign in to comment.
You can’t perform that action at this time.