[PATCH 3.10 083/268] tick/broadcast: Prevent NULL pointer dereference

Willy Tarreau
2017-06-19T18:37:33Z

From: Thomas Gleixner <tglx@linutronix.de>

commit c1a9eeb938b5433947e5ea22f89baff3182e7075 upstream.

When a disfunctional timer, e.g. dummy timer, is installed, the tick core
tries to setup the broadcast timer.

If no broadcast device is installed, the kernel crashes with a NULL pointer
dereference in tick_broadcast_setup_oneshot() because the function has no
sanity check.

Reported-by: Mason <slash.tmp@free.fr>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Richard Cochran <rcochran@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Cc: Sebastian Frias <sf84@laposte.net>
Cc: Thibaud Cornic <thibaud_cornic@sigmadesigns.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Link: http://lkml.kernel.org/r/1147ef90-7877-e4d2-bb2b-5c4fa8d3144b@free.fr
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
kernel/time/tick-broadcast.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 19ee339..6f27814 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -775,6 +775,9 @@ void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
{
int cpu = smp_processor_id();

+ if (!bc)
+ return;
+
/* Set it up only once ! */
if (bc->event_handler != tick_handle_oneshot_broadcast) {
int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC;
--
2.8.0.rc2.1.gbe9624a