Messages in this thread Patch in this message | | | From | John Stultz <> | Subject | [PATCH] time: Limit time values that would overflow ktime_t | Date | Wed, 1 Aug 2012 19:21:16 -0400 |
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Thomas, Ingo, This is against tip/timers/urgent. Let me know if you'd like to see any further changes
-john
Unexpected behavior could occur 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> Cc: stable@vger.kernel.org Reported-by: CAI Qian <caiqian@redhat.com> Signed-off-by: John Stultz <john.stultz@linaro.org> --- kernel/time/timekeeping.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 2988bc8..6a31968 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -88,6 +88,8 @@ __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) + static inline void tk_normalize_xtime(struct timekeeper *tk) { while (tk->xtime_nsec >= ((u64)NSEC_PER_SEC << tk->shift)) { @@ -430,6 +432,9 @@ 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(&tk->lock, flags); timekeeping_forward_now(tk); @@ -463,6 +468,8 @@ int timekeeping_inject_offset(struct timespec *ts) { struct timekeeper *tk = &timekeeper; unsigned long flags; + long long tmp; + int ret = 0; if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC) return -EINVAL; @@ -471,10 +478,17 @@ int timekeeping_inject_offset(struct timespec *ts) timekeeping_forward_now(tk); + /* Make sure the increased value won't cause ktime_t trouble */ + tmp = tk->xtime_sec + ts->tv_sec; + if (tmp >= KTIME_SEC_MAX) { + ret = -EINVAL; + goto error; + } tk_xtime_add(tk, ts); tk_set_wall_to_mono(tk, timespec_sub(tk->wall_to_monotonic, *ts)); +error: /* even if we error out, we forwarded the time, so call update */ timekeeping_update(tk, true); write_sequnlock_irqrestore(&tk->lock, flags); @@ -482,7 +496,7 @@ int timekeeping_inject_offset(struct timespec *ts) /* signal hrtimers about time change */ clock_was_set(); - return 0; + return ret; } EXPORT_SYMBOL(timekeeping_inject_offset); @@ -651,6 +665,16 @@ 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)) { + pr_warn("WARNING: Persistent clock returned > year 2242!\n" + " Check your CMOS/BIOS settings.\n"); + now.tv_sec = KTIME_SEC_MAX - TWENTY_YEARS; + } + seqlock_init(&tk->lock); ntp_init(); -- 1.7.9.5
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