Don't allow the TAI-UTC offset of the system clock to be set by
adjtimex() to a value larger than 100000 seconds.
This prevents an overflow in the conversion to int, prevents the
CLOCK_TAI clock from getting too far ahead of the CLOCK_REALTIME clock,
and it is still large enough to allow leap seconds to be inserted at the
maximum rate currently supported by the kernel (once per day) for the
next ~270 years, however unlikely it is that someone can survive a
catastrophic event which slowed down the rotation of the Earth so much.
Cc: John Stultz <john.stu...@linaro.org>
Cc: Prarit Bhargava <pra...@redhat.com>
Cc: Richard Cochran <richardcoch...@gmail.com>
Cc: Stephen Boyd <sb...@kernel.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Signed-off-by: Miroslav Lichvar <mlich...@redhat.com>
---
kernel/time/ntp.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 8de4f789dc1b..65eb796610dc 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -43,6 +43,7 @@ static u64 tick_length_base;
#define MAX_TICKADJ 500LL /* usecs */
#define MAX_TICKADJ_SCALED \
(((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
+#define MAX_TAI_OFFSET 100000
/*
* phase-lock loop variables
@@ -691,7 +692,8 @@ static inline void process_adjtimex_modes(const struct
__kernel_timex *txc,
time_constant = max(time_constant, 0l);
}
- if (txc->modes & ADJ_TAI && txc->constant >= 0)
+ if (txc->modes & ADJ_TAI &&
+ txc->constant >= 0 && txc->constant <= MAX_TAI_OFFSET)
*time_tai = txc->constant;
if (txc->modes & ADJ_OFFSET)
--
2.17.2
