alarmtimer: Fix bug where relative alarm timers were treated as absolute

Sharvil noticed with the posix timer_settime interface, using the
CLOCK_REALTIME_ALARM or CLOCK_BOOTTIME_ALARM clockid, if the users
tried to specify a relative time timer, it would incorrectly be
treated as absolute regardless of the state of the flags argument.

This patch corrects this, properly checking the absolute/relative flag,
as well as adds further error checking that no invalid flag bits are set.

Reported-by: Sharvil Nanavati <sharvil@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Sharvil Nanavati <sharvil@google.com>
Cc: stable <stable@vger.kernel.org> #3.0+
Link: http://lkml.kernel.org/r/1404767171-6902-1-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 18 insertions, 2 deletions

diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index 88c9c65a430d..fe75444ae7ec 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -585,9 +585,14 @@ static int alarm_timer_set(struct k_itimer *timr, int flags,
                                 struct itimerspec *new_setting,
                                 struct itimerspec *old_setting)
 {
+        ktime_t exp;
+
         if (!rtcdev)
                 return -ENOTSUPP;
 
+        if (flags & ~TIMER_ABSTIME)
+                return -EINVAL;
+
         if (old_setting)
                 alarm_timer_get(timr, old_setting);
 
@@ -597,8 +602,16 @@ static int alarm_timer_set(struct k_itimer *timr, int flags,
 
         /* start the timer */
         timr->it.alarm.interval = timespec_to_ktime(new_setting->it_interval);
-        alarm_start(&timr->it.alarm.alarmtimer,
-                        timespec_to_ktime(new_setting->it_value));
+        exp = timespec_to_ktime(new_setting->it_value);
+        /* Convert (if necessary) to absolute time */
+        if (flags != TIMER_ABSTIME) {
+                ktime_t now;
+
+                now = alarm_bases[timr->it.alarm.alarmtimer.type].gettime();
+                exp = ktime_add(now, exp);
+        }
+
+        alarm_start(&timr->it.alarm.alarmtimer, exp);
         return 0;
 }
 
@@ -730,6 +743,9 @@ static int alarm_timer_nsleep(const clockid_t which_clock, int flags,
         if (!alarmtimer_get_rtcdev())
                 return -ENOTSUPP;
 
+        if (flags & ~TIMER_ABSTIME)
+                return -EINVAL;
+
         if (!capable(CAP_WAKE_ALARM))
                 return -EPERM;