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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.

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>
[bwh: Backported to 3.16:
 - Add sig_none variable in common_timer_get(), added earlier upstream
 - Adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This commit is contained in:
Thomas Gleixner 2017-12-15 10:32:03 +01:00 committed by syphyr
parent d8bfd2f23b
commit 7116a83411
1 changed files with 21 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
kernel/posix-timers.c
View File

@ -498,17 +498,22 @@ 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,
@ -728,16 +733,17 @@ common_timer_get(struct k_itimer *timr, struct itimerspec *cur_setting)
{
ktime_t now, remaining, iv;
struct hrtimer *timer = &timr->it.real.timer;
bool sig_none;
memset(cur_setting, 0, sizeof(struct itimerspec));
sig_none = timr->it_sigev_notify == SIGEV_NONE;
iv = timr->it.real.interval;
/* interval timer ? */
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)
else if (!hrtimer_active(timer) && !sig_none)
return;
now = timer->base->get_time();
@ -747,8 +753,7 @@ common_timer_get(struct k_itimer *timr, struct itimerspec *cur_setting)
* timer move the expiry time forward by intervals, so
* expiry is > now.
*/
if (iv.tv64 && (timr->it_requeue_pending & REQUEUE_PENDING ||
(timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE))
if (iv.tv64 && (timr->it_requeue_pending & REQUEUE_PENDING || sig_none))
timr->it_overrun += (unsigned int) hrtimer_forward(timer, now, iv);
remaining = ktime_sub(hrtimer_get_expires(timer), now);
@ -758,7 +763,7 @@ 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 (!sig_none)
cur_setting->it_value.tv_nsec = 1;
} else
cur_setting->it_value = ktime_to_timespec(remaining);
@ -856,7 +861,7 @@ 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());