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Date: Thu, 11 Oct 2018 15:28:37 +0200
Subject: [PATCH] posix-timer: Properly check sigevent->sigev_notify
commit cef31d9af908243421258f1df35a4a644604efbe upstream.
timer_create() specifies via sigevent->sigev_notify the signal delivery for
the new timer. The valid modes are SIGEV_NONE, SIGEV_SIGNAL, SIGEV_THREAD
and (SIGEV_SIGNAL | SIGEV_THREAD_ID).
The sanity check in good_sigevent() is only checking the valid combination
for the SIGEV_THREAD_ID bit, i.e. SIGEV_SIGNAL, but if SIGEV_THREAD_ID is
not set it accepts any random value.
This has no real effects on the posix timer and signal delivery code, but
it affects show_timer() which handles the output of /proc/$PID/timers. That
function uses a string array to pretty print sigev_notify. The access to
that array has no bound checks, so random sigev_notify cause access beyond
the array bounds.
Add proper checks for the valid notify modes and remove the SIGEV_THREAD_ID
masking from various code pathes as SIGEV_NONE can never be set in
combination with SIGEV_THREAD_ID.
CVE: CVE-2017-18344
Upstream-Status: Backport
Reported-by: Eric Biggers <ebiggers3@gmail.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Reported-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
---
kernel/time/posix-timers.c | 33 +++++++++++++++++++--------------
1 file changed, 19 insertions(+), 14 deletions(-)
diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index f2826c3..72c40d3 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -507,17 +507,22 @@ static struct pid *good_sigevent(sigevent_t * event)
{
struct task_struct *rtn = current->group_leader;
- if ((event->sigev_notify & SIGEV_THREAD_ID ) &&
- (!(rtn = find_task_by_vpid(event->sigev_notify_thread_id)) ||
- !same_thread_group(rtn, current) ||
- (event->sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_SIGNAL))
+ switch (event->sigev_notify) {
+ case SIGEV_SIGNAL | SIGEV_THREAD_ID:
+ rtn = find_task_by_vpid(event->sigev_notify_thread_id);
+ if (!rtn || !same_thread_group(rtn, current))
+ return NULL;
+ /* FALLTHRU */
+ case SIGEV_SIGNAL:
+ case SIGEV_THREAD:
+ if (event->sigev_signo <= 0 || event->sigev_signo > SIGRTMAX)
+ return NULL;
+ /* FALLTHRU */
+ case SIGEV_NONE:
+ return task_pid(rtn);
+ default:
return NULL;
-
- if (((event->sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE) &&
- ((event->sigev_signo <= 0) || (event->sigev_signo > SIGRTMAX)))
- return NULL;
-
- return task_pid(rtn);
+ }
}
void posix_timers_register_clock(const clockid_t clock_id,
@@ -746,7 +751,7 @@ common_timer_get(struct k_itimer *timr, struct itimerspec *cur_setting)
if (iv.tv64)
cur_setting->it_interval = ktime_to_timespec(iv);
else if (!hrtimer_active(timer) &&
- (timr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE)
+ timr->it_sigev_notify != SIGEV_NONE)
return;
now = timer->base->get_time();
@@ -757,7 +762,7 @@ common_timer_get(struct k_itimer *timr, struct itimerspec *cur_setting)
* expiry is > now.
*/
if (iv.tv64 && (timr->it_requeue_pending & REQUEUE_PENDING ||
- (timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE))
+ timr->it_sigev_notify == SIGEV_NONE))
timr->it_overrun += (unsigned int) hrtimer_forward(timer, now, iv);
remaining = __hrtimer_expires_remaining_adjusted(timer, now);
@@ -767,7 +772,7 @@ common_timer_get(struct k_itimer *timr, struct itimerspec *cur_setting)
* A single shot SIGEV_NONE timer must return 0, when
* it is expired !
*/
- if ((timr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE)
+ if (timr->it_sigev_notify != SIGEV_NONE)
cur_setting->it_value.tv_nsec = 1;
} else
cur_setting->it_value = ktime_to_timespec(remaining);
@@ -865,7 +870,7 @@ common_timer_set(struct k_itimer *timr, int flags,
timr->it.real.interval = timespec_to_ktime(new_setting->it_interval);
/* SIGEV_NONE timers are not queued ! See common_timer_get */
- if (((timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE)) {
+ if (timr->it_sigev_notify == SIGEV_NONE) {
/* Setup correct expiry time for relative timers */
if (mode == HRTIMER_MODE_REL) {
hrtimer_add_expires(timer, timer->base->get_time());
--
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