On 11/1/18 1:02 PM, Florian Fainelli wrote: > From: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > [ Upstream commit 78c9c4dfbf8c04883941445a195276bb4bb92c76 ] > > The posix timer overrun handling is broken because the forwarding functions > can return a huge number of overruns which does not fit in an int. As a > consequence timer_getoverrun(2) and siginfo::si_overrun can turn into > random number generators. > > The k_clock::timer_forward() callbacks return a 64 bit value now. Make > k_itimer::ti_overrun[_last] 64bit as well, so the kernel internal > accounting is correct. 3Remove the temporary (int) casts. > > Add a helper function which clamps the overrun value returned to user space > via timer_getoverrun(2) or siginfo::si_overrun limited to a positive value > between 0 and INT_MAX. INT_MAX is an indicator for user space that the > overrun value has been clamped. > > Reported-by: Team OWL337 <icytxw@xxxxxxxxx> > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Acked-by: John Stultz <john.stultz@xxxxxxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx> > Link: https://lkml.kernel.org/r/20180626132705.018623573@xxxxxxxxxxxxx > [florian: Make patch apply to v4.9.135] > Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx> > --- > Thomas, can you review for correctness? Thanks! Thomas, John, does that look like a reasonable backport for 4.9? > > include/linux/posix-timers.h | 4 ++-- > kernel/time/posix-cpu-timers.c | 2 +- > kernel/time/posix-timers.c | 29 +++++++++++++++++++---------- > 3 files changed, 22 insertions(+), 13 deletions(-) > > diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h > index 62d44c176071..e4b8678183f5 100644 > --- a/include/linux/posix-timers.h > +++ b/include/linux/posix-timers.h > @@ -65,8 +65,8 @@ struct k_itimer { > spinlock_t it_lock; > clockid_t it_clock; /* which timer type */ > timer_t it_id; /* timer id */ > - int it_overrun; /* overrun on pending signal */ > - int it_overrun_last; /* overrun on last delivered signal */ > + s64 it_overrun; /* overrun on pending signal */ > + s64 it_overrun_last; /* overrun on last delivered signal */ > int it_requeue_pending; /* waiting to requeue this timer */ > #define REQUEUE_PENDING 1 > int it_sigev_notify; /* notify word of sigevent struct */ > diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c > index 39008d78927a..21a27bb73587 100644 > --- a/kernel/time/posix-cpu-timers.c > +++ b/kernel/time/posix-cpu-timers.c > @@ -103,7 +103,7 @@ static void bump_cpu_timer(struct k_itimer *timer, > continue; > > timer->it.cpu.expires += incr; > - timer->it_overrun += 1 << i; > + timer->it_overrun += 1LL << i; > delta -= incr; > } > } > diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c > index fc7c37ad90a0..0e6ed2e7d066 100644 > --- a/kernel/time/posix-timers.c > +++ b/kernel/time/posix-timers.c > @@ -355,6 +355,17 @@ static __init int init_posix_timers(void) > > __initcall(init_posix_timers); > > +/* > + * The siginfo si_overrun field and the return value of timer_getoverrun(2) > + * are of type int. Clamp the overrun value to INT_MAX > + */ > +static inline int timer_overrun_to_int(struct k_itimer *timr, int baseval) > +{ > + s64 sum = timr->it_overrun_last + (s64)baseval; > + > + return sum > (s64)INT_MAX ? INT_MAX : (int)sum; > +} > + > static void schedule_next_timer(struct k_itimer *timr) > { > struct hrtimer *timer = &timr->it.real.timer; > @@ -362,12 +373,11 @@ static void schedule_next_timer(struct k_itimer *timr) > if (timr->it.real.interval.tv64 == 0) > return; > > - timr->it_overrun += (unsigned int) hrtimer_forward(timer, > - timer->base->get_time(), > - timr->it.real.interval); > + timr->it_overrun += hrtimer_forward(timer, timer->base->get_time(), > + timr->it.real.interval); > > timr->it_overrun_last = timr->it_overrun; > - timr->it_overrun = -1; > + timr->it_overrun = -1LL; > ++timr->it_requeue_pending; > hrtimer_restart(timer); > } > @@ -396,7 +406,7 @@ void do_schedule_next_timer(struct siginfo *info) > else > schedule_next_timer(timr); > > - info->si_overrun += timr->it_overrun_last; > + info->si_overrun = timer_overrun_to_int(timr, info->si_overrun); > } > > if (timr) > @@ -491,8 +501,7 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer) > now = ktime_add(now, kj); > } > #endif > - timr->it_overrun += (unsigned int) > - hrtimer_forward(timer, now, > + timr->it_overrun += hrtimer_forward(timer, now, > timr->it.real.interval); > ret = HRTIMER_RESTART; > ++timr->it_requeue_pending; > @@ -633,7 +642,7 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock, > it_id_set = IT_ID_SET; > new_timer->it_id = (timer_t) new_timer_id; > new_timer->it_clock = which_clock; > - new_timer->it_overrun = -1; > + new_timer->it_overrun = -1LL; > > if (timer_event_spec) { > if (copy_from_user(&event, timer_event_spec, sizeof (event))) { > @@ -762,7 +771,7 @@ common_timer_get(struct k_itimer *timr, struct itimerspec *cur_setting) > */ > if (iv.tv64 && (timr->it_requeue_pending & REQUEUE_PENDING || > timr->it_sigev_notify == SIGEV_NONE)) > - timr->it_overrun += (unsigned int) hrtimer_forward(timer, now, iv); > + timr->it_overrun += hrtimer_forward(timer, now, iv); > > remaining = __hrtimer_expires_remaining_adjusted(timer, now); > /* Return 0 only, when the timer is expired and not pending */ > @@ -824,7 +833,7 @@ SYSCALL_DEFINE1(timer_getoverrun, timer_t, timer_id) > if (!timr) > return -EINVAL; > > - overrun = timr->it_overrun_last; > + overrun = timer_overrun_to_int(timr, 0); > unlock_timer(timr, flags); > > return overrun; > -- Florian
