Hello, Andrew. On Wed, Feb 20, 2013 at 01:23:00PM -0800, Andrew Morton wrote: > > @@ -637,6 +637,9 @@ static struct k_itimer *__lock_timer(timer_t timer_id, > > unsigned long *flags) > > { > > struct k_itimer *timr; > > > > + if ((int)timer_id < 0) > > + return NULL; > > + > > rcu_read_lock(); > > timr = idr_find(&posix_timers_id, (int)timer_id); > > if (timr) { > > This is a bit risky - if some arch defines timer_t to be a u64 then we > will incorrectly treat 0x0000 0001 ffff ffff as a negative number. > (That's a lot of timers!) > > A fancy way of avoiding this is > > if (timer_id & ((typeof timer_id)1 << (sizeof(timer_id) - 1))) > > (approximately ;)) > > But I think casting to (long) should be good enough?
Sans WARN_ON_ONCE(), the code would behave the same as before, which in turn, from what I can tell, is the behavior the code intended to implement before idr_alloc() conversion. If timer_id is being allocated from idr, a valid id can never go over INT_MAX and returning NULL for any ID above that is the correct behavior, I think. If timer_t is larger than int, both (int) and (long) castings wouldn't be useful. Both will miss (1LU << 33) + 1 and idr_find() will end up looking for 1. If we want to be strict, we would have to do, I think, if ((unsigned long long)timer_t > INT_MAX) hopefully with some comments. That said, if I'm grepping it right, all archs define timer_t as int, so maybe we're just being paranoid. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/