linux-kernel - [tip:timers/urgent] tick/broadcast: Prevent NULL pointer dereference

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Message-ID: <tip-c1a9eeb938b5433947e5ea22f89baff3182e7075@git.kernel.org>
Date:   Thu, 15 Dec 2016 03:31:11 -0800
From:   tip-bot for Thomas Gleixner <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     sf84@...oste.net, anna-maria@...utronix.de, bigeasy@...utronix.de,
        slash.tmp@...e.fr, thibaud_cornic@...madesigns.com,
        linux-kernel@...r.kernel.org, mark.rutland@....com,
        mingo@...nel.org, rcochran@...utronix.de, hpa@...or.com,
        robin.murphy@....com, tglx@...utronix.de, daniel.lezcano@...aro.org
Subject: [tip:timers/urgent] tick/broadcast: Prevent NULL pointer
 dereference

Commit-ID:  c1a9eeb938b5433947e5ea22f89baff3182e7075
Gitweb:     http://git.kernel.org/tip/c1a9eeb938b5433947e5ea22f89baff3182e7075
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Thu, 15 Dec 2016 12:10:37 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Thu, 15 Dec 2016 12:25:13 +0100

tick/broadcast: Prevent NULL pointer dereference

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@...e.fr>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Anna-Maria Gleixner <anna-maria@...utronix.de>
Cc: Richard Cochran <rcochran@...utronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Peter Zijlstra <peterz@...radead.org>,
Cc: Sebastian Frias <sf84@...oste.net>
Cc: Thibaud Cornic <thibaud_cornic@...madesigns.com>
Cc: Robin Murphy <robin.murphy@....com>
Link: http://lkml.kernel.org/r/1147ef90-7877-e4d2-bb2b-5c4fa8d3144b@free.fr
---
 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 f6aae79..d2a20e8 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -871,6 +871,9 @@ 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 = clockevent_state_periodic(bc);