3.16.62-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner <tglx@xxxxxxxxxxxxx> commit 78c9c4dfbf8c04883941445a195276bb4bb92c76 upstream. 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 [bwh: Backported to 3.16: adjust filenames, context] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- include/linux/posix-timers.h | 4 ++-- kernel/posix-cpu-timers.c | 2 +- kernel/posix-timers.c | 31 ++++++++++++++++++++----------- 3 files changed, 23 insertions(+), 14 deletions(-) --- 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 */ --- a/kernel/posix-cpu-timers.c +++ b/kernel/posix-cpu-timers.c @@ -103,7 +103,7 @@ static void bump_cpu_timer(struct k_itim continue; timer->it.cpu.expires += incr; - timer->it_overrun += 1 << i; + timer->it_overrun += 1LL << i; delta -= incr; } } --- a/kernel/posix-timers.c +++ b/kernel/posix-timers.c @@ -347,6 +347,17 @@ 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; @@ -354,12 +365,11 @@ static void schedule_next_timer(struct k 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); } @@ -388,7 +398,7 @@ void do_schedule_next_timer(struct sigin 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) @@ -483,9 +493,8 @@ static enum hrtimer_restart posix_timer_ now = ktime_add(now, kj); } #endif - timr->it_overrun += (unsigned int) - hrtimer_forward(timer, now, - timr->it.real.interval); + 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 cloc 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))) { @@ -763,7 +772,7 @@ common_timer_get(struct k_itimer *timr, * expiry is > now. */ if (iv.tv64 && (timr->it_requeue_pending & REQUEUE_PENDING || sig_none)) - timr->it_overrun += (unsigned int) hrtimer_forward(timer, now, iv); + timr->it_overrun += hrtimer_forward(timer, now, iv); remaining = ktime_sub(hrtimer_get_expires(timer), now); /* Return 0 only, when the timer is expired and not pending */ @@ -825,7 +834,7 @@ SYSCALL_DEFINE1(timer_getoverrun, timer_ if (!timr) return -EINVAL; - overrun = timr->it_overrun_last; + overrun = timer_overrun_to_int(timr, 0); unlock_timer(timr, flags); return overrun;
