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authorMiroslav Lichvar <mlichvar@redhat.com>2019-06-18 17:47:13 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-08-04 09:34:47 +0200
commit41164dd56336bcccab95f0f0077bbbefa7891246 (patch)
tree3a0cff6f585d73903ab2bb1ce9831bc3fc7446dc /kernel
parentb4a4a5610104a0f69dceb156b19c2df9b218776e (diff)
ntp: Limit TAI-UTC offset
[ 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>
Diffstat (limited to 'kernel')
-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 0e0dc5d89911..bbe767b1f454 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -39,6 +39,7 @@ 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
@@ -633,7 +634,8 @@ 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)