On 10/04, Mathias Krause wrote: > > If userland creates a timer without specifying a sigevent info, we'll > create one ourself, using a stack local variable. Particularly will we > use the timer ID as sival_int. But as sigev_value is a union containing > a pointer and an int, that assignment will only partially initialize > sigev_value on systems where the size of a pointer is bigger than the > size of an int. On such systems we'll copy the uninitialized stack bytes > from the timer_create() call to userland when the timer actually fires > and we're going to deliver the signal.
So we have a minor information leak, > Cc: <[email protected]> # v2.6.28+ not sure this is -stable material but I won't really argue. > --- a/kernel/time/posix-timers.c > +++ b/kernel/time/posix-timers.c > @@ -636,6 +636,7 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, > which_clock, > goto out; > } > } else { > + memset(&event.sigev_value, 0, sizeof(event.sigev_value)); > event.sigev_notify = SIGEV_SIGNAL; > event.sigev_signo = SIGALRM; > event.sigev_value.sival_int = new_timer->it_id; How about - event.sigev_value.sival_int = new_timer->it_id; + event.sigev_value = (sigval_t) { .sival_int = new_timer_id }; ? (btw, new_timer->sigq->info.si_tid initialization can use new_timer_id too) this makes the initialization more explicit and can help gcc to optimize this assignment although this is minor. In any case this all looks confusing to me. sys_timer_create() does new_timer->sigq->info.si_value = event.sigev_value; new_timer->sigq->info.si_tid = new_timer->it_id; later, this writes to the differents members (_rt and _timer) in the same union. But the comment in struct siginfo says that we should use _timer. And copy_siginfo_to_user() reports si_tid and si_ptr, this again reads _timer and _rt. This should actually work, _sigval should have the same offset in both struct's, still it looks confusing imho. Perhaps we should change #define si_value _sifields._rt._sigval #define si_int _sifields._rt._sigval.sival_int #define si_ptr _sifields._rt._sigval.sival_ptr to use _timer instead. Nevermind, this is off-topic. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
