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authorThomas Gleixner <tglx@linutronix.de>2018-11-01 13:02:38 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-11-10 07:43:01 -0800
commit65cb24de03f1c8e00a4fedf416b80a4e8f8a6ef2 (patch)
tree9bf45e88c5bcd099ced62afc49e22f7633d2ffe7
parentb0b77fb6c9912d0b97a3c468c52b18d1447062c4 (diff)
posix-timers: Sanitize overrun handling
[ 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> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sasha Levin <sashal@kernel.org>
-rw-r--r--include/linux/posix-timers.h4
-rw-r--r--kernel/time/posix-cpu-timers.c2
-rw-r--r--kernel/time/posix-timers.c29
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;