From: Thomas Gleixner tglx@linutronix.de
[ 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@gmail.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Acked-by: John Stultz john.stultz@linaro.org Cc: Peter Zijlstra peterz@infradead.org Cc: Michael Kerrisk mtk.manpages@gmail.com Link: https://lkml.kernel.org/r/20180626132705.018623573@linutronix.de [florian: Make patch apply to v4.9.135] Signed-off-by: Florian Fainelli f.fainelli@gmail.com --- Thomas, can you review for correctness? Thanks!
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;