[ 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@xxxxxxxxx> Signed-off-by: Miroslav Lichvar <mlichvar@xxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: John Stultz <john.stultz@xxxxxxxxxx> Cc: Prarit Bhargava <prarit@xxxxxxxxxx> Cc: Richard Cochran <richardcochran@xxxxxxxxx> Cc: Stephen Boyd <sboyd@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20190618154713.20929-1-mlichvar@xxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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 4bb9b66338be..9288532f73c8 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 @@ -640,7 +641,8 @@ static inline void process_adjtimex_modes(struct 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) -- 2.20.1
