Messages in this thread | | | Date | Tue, 09 Apr 2013 09:08:08 +0200 | From | David Engraf <> | Subject | Re: [PATCH] ktime_add_ns() may overflow on 32bit architectures |
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Am 08.04.2013 22:20, schrieb John Stultz: > 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?
Yes, please tag it for -stable as well because I had the problem with kernel 3.0 and it can overflow on all current version.
Best regards - David
> thanks > -john >
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