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Message-Id: <20181220085743.708124630@linuxfoundation.org>
Date: Thu, 20 Dec 2018 10:18:40 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Team OWL337 <icytxw@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
John Stultz <john.stultz@...aro.org>,
Peter Zijlstra <peterz@...radead.org>,
Michael Kerrisk <mtk.manpages@...il.com>,
Florian Fainelli <f.fainelli@...il.com>,
Sasha Levin <sashal@...nel.org>,
Ben Hutchings <ben.hutchings@...ethink.co.uk>
Subject: [PATCH 3.18 28/31] posix-timers: Sanitize overrun handling
3.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: Thomas Gleixner <tglx@...utronix.de>
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@...il.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: John Stultz <john.stultz@...aro.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Michael Kerrisk <mtk.manpages@...il.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@...il.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
Signed-off-by: Ben Hutchings <ben.hutchings@...ethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
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(-)
--- 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/time/posix-cpu-timers.c
+++ b/kernel/time/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/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -348,6 +348,17 @@ 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;
@@ -355,12 +366,11 @@ 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);
}
@@ -389,7 +399,7 @@ 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)
@@ -484,8 +494,7 @@ static enum hrtimer_restart posix_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;
@@ -626,7 +635,7 @@ 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))) {
@@ -755,7 +764,7 @@ common_timer_get(struct k_itimer *timr,
*/
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 = ktime_sub(hrtimer_get_expires(timer), now);
/* Return 0 only, when the timer is expired and not pending */
@@ -817,7 +826,7 @@ 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;
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