[tip:timers/core] posix-timers: Zero out oldval itimerspec

[tip-bot for Thomas Gleixner <tipbot@zytor.com>]

Commit-ID:  5c7a3a3d20a4e175304c0e23809e3d70be8fed8a
Gitweb:     http://git.kernel.org/tip/5c7a3a3d20a4e175304c0e23809e3d70be8fed8a
Author:     Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Mon, 12 Jun 2017 19:44:09 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon, 12 Jun 2017 21:07:40 +0200

posix-timers: Zero out oldval itimerspec

The recent posix timer rework moved the clearing of the itimerspec to the
real syscall implementation, but forgot that the kclock->timer_get() is
used by timer_settime() as well. That results in an uninitialized variable
and bogus values returned to user space.

Add the missing memset to timer_settime().

Fixes: eabdec043853 ("posix-timers: Zero settings value in common code")
Reported-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Link: http://lkml.kernel.org/r/20170609201156.GB21491@outlook.office365.com
---
 kernel/time/posix-timers.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index b53a0b5..88517dc 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -828,6 +828,8 @@ SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
 	if (!timespec64_valid(&new_spec64.it_interval) ||
 	    !timespec64_valid(&new_spec64.it_value))
 		return -EINVAL;
+	if (rtn)
+		memset(rtn, 0, sizeof(*rtn));
 retry:
 	timr = lock_timer(timer_id, &flag);
 	if (!timr)