Messages in this thread Patch in this message | | | From | John Stultz <> | Subject | [PATCH 2/2] [RFC] time: Limit time values that would overflow ktime_t | Date | Tue, 31 Jul 2012 02:35:48 -0400 |
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We could observe unexpected behavior if the time is set to a value large enough to overflow a 64bit ktime_t (which is something larger then the year 2264).
So check timekeeping inputs to make sure we don't set the time to a value that overflows ktime_t.
Note: This does not protect from setting the time close to overflowing ktime_t and then letting natural accumulation cause the overflow.
Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Zhouping Liu <zliu@redhat.com> Cc: CAI Qian <caiqian@redhat.com> Reported-by: CAI Qian <caiqian@redhat.com> Signed-off-by: John Stultz <john.stultz@linaro.org> --- kernel/time/timekeeping.c | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 96179ab..78bccd0 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -92,7 +92,7 @@ __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock); /* flag for if timekeeping is suspended */ int __read_mostly timekeeping_suspended; - +#define TWENTY_YEARS (20LL*365*24*60*60) /** * timekeeper_setup_internals - Set up internals to use clocksource clock. @@ -387,6 +387,9 @@ int do_settimeofday(const struct timespec *tv) if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC) return -EINVAL; + if ((unsigned long long)tv->tv_sec >= KTIME_SEC_MAX) + return -EINVAL; + write_seqlock_irqsave(&timekeeper.lock, flags); timekeeping_forward_now(); @@ -418,6 +421,8 @@ EXPORT_SYMBOL(do_settimeofday); int timekeeping_inject_offset(struct timespec *ts) { unsigned long flags; + struct timespec tmp; + int ret = 0; if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC) return -EINVAL; @@ -426,10 +431,17 @@ int timekeeping_inject_offset(struct timespec *ts) timekeeping_forward_now(); - timekeeper.xtime = timespec_add(timekeeper.xtime, *ts); + /* Make sure the increased value won't cause ktime_t trouble */ + tmp = timespec_add(timekeeper.xtime, *ts); + if ((unsigned long long)tmp.tv_sec >= KTIME_SEC_MAX) { + ret= -EINVAL; + goto error; + } + timekeeper.xtime = tmp; timekeeper.wall_to_monotonic = timespec_sub(timekeeper.wall_to_monotonic, *ts); +error: /* even if we error out, we forwarded the time, so call update */ timekeeping_update(true); write_sequnlock_irqrestore(&timekeeper.lock, flags); @@ -437,7 +449,7 @@ int timekeeping_inject_offset(struct timespec *ts) /* signal hrtimers about time change */ clock_was_set(); - return 0; + return ret; } EXPORT_SYMBOL(timekeeping_inject_offset); @@ -599,6 +611,16 @@ void __init timekeeping_init(void) read_persistent_clock(&now); read_boot_clock(&boot); + /* + * Check to make sure the persistent clock + * didn't return something crazy. + */ + if (now.tv_sec > (KTIME_SEC_MAX - TWENTY_YEARS)) { + printk("WARNING: Persistent clock returned a year greater then" + " 2242. Capping at 2242.\n"); + now.tv_sec = KTIME_SEC_MAX - TWENTY_YEARS; + } + seqlock_init(&timekeeper.lock); ntp_init(); -- 1.7.9.5
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