[ Upstream commit d897a4ab11dc8a9fda50d2eccc081a96a6385998 ]
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.
Reported-by: Weikang shi swkhack@gmail.com Signed-off-by: Miroslav Lichvar mlichvar@redhat.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: John Stultz john.stultz@linaro.org Cc: Prarit Bhargava prarit@redhat.com Cc: Richard Cochran richardcochran@gmail.com Cc: Stephen Boyd sboyd@kernel.org Link: https://lkml.kernel.org/r/20190618154713.20929-1-mlichvar@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 f43d47c8c3b6..98b3678fd48e 100644 --- a/kernel/time/ntp.c +++ b/kernel/time/ntp.c @@ -42,6 +42,7 @@ 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 @@ -690,7 +691,8 @@ 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)