tick/broadcast: Prevent NULL pointer dereference

Dan reported that the recent changes to the broadcast code introduced
a potential NULL dereference.

Add the proper check.

Fixes: e0454311903d "tick/broadcast: Sanity check the shutdown of the local clock_event"
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 10 insertions, 8 deletions

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index ee3cf942d6eb..52b9e199b5ac 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -409,14 +409,16 @@ void tick_broadcast_control(enum tick_broadcast_mode mode)
                 break;
         }
 
-        if (cpumask_empty(tick_broadcast_mask)) {
-                if (!bc_stopped)
-                        clockevents_shutdown(bc);
-        } else if (bc_stopped) {
-                if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
-                        tick_broadcast_start_periodic(bc);
-                else
-                        tick_broadcast_setup_oneshot(bc);
+        if (bc) {
+                if (cpumask_empty(tick_broadcast_mask)) {
+                        if (!bc_stopped)
+                                clockevents_shutdown(bc);
+                } else if (bc_stopped) {
+                        if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
+                                tick_broadcast_start_periodic(bc);
+                        else
+                                tick_broadcast_setup_oneshot(bc);
+                }
         }
         raw_spin_unlock(&tick_broadcast_lock);
 }