Messages in this thread | | | Date | Mon, 08 Apr 2013 13:20:03 -0700 | From | John Stultz <> | Subject | Re: [PATCH] ktime_add_ns() may overflow on 32bit architectures |
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On 03/19/2013 05:29 AM, David Engraf wrote: > Hello, > > I've triggered an overflow when using ktime_add_ns() on a 32bit > architecture not supporting CONFIG_KTIME_SCALAR. > > When passing a very high value for u64 nsec, e.g. 7881299347898368000 > the do_div() function converts this value to seconds (7881299347) > which is still to high to pass to the ktime_set() function as long. > The result in my case is a negative value. > > The problem on my system occurs in the tick-sched.c, > tick_nohz_stop_sched_tick() when time_delta is set to > timekeeping_max_deferment(). The check for time_delta < KTIME_MAX is > valid, thus ktime_add_ns() is called with a too large value resulting > in a negative expire value. This leads to an endless loop in the > ticker code: > > time_delta: 7881299347898368000 > expires = ktime_add_ns(last_update, time_delta) > expires: negative value > > This error doesn't occurs on 64bit or architectures supporting > CONFIG_KTIME_SCALAR (e.g. ARM, x86-32).
Sorry, this fell through the cracks. I see Andrew caught it, but I've queued for 3.10 in my tree as well.
This should be tagged for -stable as well, no?
thanks -john
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