[GIT pull] timer fix for 4.15

[Thomas Gleixner <tglx@linutronix.de>]

Linus,

please pull the latest timers-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers-urgent-for-linus

A single bugfix which prevents arbitrary sigev_notify values in
posix-timers.

Thanks,

	tglx

------------------>
Thomas Gleixner (1):
      posix-timer: Properly check sigevent->sigev_notify


 kernel/time/posix-timers.c | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 13d6881f908b..ec999f32c840 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -434,17 +434,22 @@ 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);
+	}
 }
 
 static struct k_itimer * alloc_posix_timer(void)
@@ -669,7 +674,7 @@ void common_timer_get(struct k_itimer *timr, struct itimerspec64 *cur_setting)
 	struct timespec64 ts64;
 	bool sig_none;
 
-	sig_none = (timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE;
+	sig_none = timr->it_sigev_notify == SIGEV_NONE;
 	iv = timr->it_interval;
 
 	/* interval timer ? */
@@ -856,7 +861,7 @@ int common_timer_set(struct k_itimer *timr, int flags,
 
 	timr->it_interval = timespec64_to_ktime(new_setting->it_interval);
 	expires = timespec64_to_ktime(new_setting->it_value);
-	sigev_none = (timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE;
+	sigev_none = timr->it_sigev_notify == SIGEV_NONE;
 
 	kc->timer_arm(timr, expires, flags & TIMER_ABSTIME, sigev_none);
 	timr->it_active = !sigev_none;