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authorMiroslav Lichvar <mlichvar@redhat.com>2019-06-18 17:47:13 +0200
committerThomas Gleixner <tglx@linutronix.de>2019-06-22 11:28:53 +0200
commitd897a4ab11dc8a9fda50d2eccc081a96a6385998 (patch)
treefade4e9ee1de5f30818462dc1f36e3d75dfd6e9b
parent141e1ecda356bb0034027a9acb949e97a963ba16 (diff)
ntp: Limit TAI-UTC offset
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
-rw-r--r--kernel/time/ntp.c4
1 files changed, 3 insertions, 1 deletions
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)