From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 16 Mar 2018 13:07:59 +0100
Subject: kernel/cpu_chill: use schedule_hrtimeout()
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
Git-commit: 6c20f578cbd5e291a4293b434351e5cc506e95fc
Patch-mainline: Queued in subsystem maintainer repository
References: SLE Realtime Extension

If a task calls cpu_chill() and gets woken up by a regular or spurious
wakeup and has a signal pending, then it exits the sleep loop in
do_nanosleep() and sets up the restart block. If restart->nanosleep.type is
not TI_NONE then this results in accessing a stale user pointer from a
previously interrupted syscall and a copy to user based on the stale
pointer or a BUG() when 'type' is not supported in nanosleep_copyout().

Instead all this trouble, use schedule_hrtimeout().

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
---
 kernel/time/hrtimer.c |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1856,14 +1856,13 @@ SYSCALL_DEFINE2(nanosleep, struct timesp
  */
 void cpu_chill(void)
 {
-	struct timespec64 tu = {
-		.tv_nsec = NSEC_PER_MSEC,
-	};
+	ktime_t chill_time;
 	unsigned int freeze_flag = current->flags & PF_NOFREEZE;
 
+	chill_time = ktime_set(0, NSEC_PER_MSEC);
+	set_current_state(TASK_UNINTERRUPTIBLE);
 	current->flags |= PF_NOFREEZE;
-	__hrtimer_nanosleep(&tu, NULL, HRTIMER_MODE_REL_HARD, CLOCK_MONOTONIC,
-			    TASK_UNINTERRUPTIBLE);
+	schedule_hrtimeout(&chill_time, HRTIMER_MODE_REL_HARD);
 	if (!freeze_flag)
 		current->flags &= ~PF_NOFREEZE;
 }