From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755129Ab3LCQAS (ORCPT ); Tue, 3 Dec 2013 11:00:18 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:41878 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754545Ab3LCQAO (ORCPT ); Tue, 3 Dec 2013 11:00:14 -0500 From: Konrad Rzeszutek Wilk To: rjw@rjwysocki.net, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: xen-devel@lists.xenproject.org, Konrad Rzeszutek Wilk , Daniel Lezcano Subject: [PATCH] cpuidle: Check for dev before deregistering it. Date: Tue, 3 Dec 2013 10:59:58 -0500 Message-Id: <1386086398-3686-1-git-send-email-konrad.wilk@oracle.com> X-Mailer: git-send-email 1.8.3.1 X-Source-IP: acsinet22.oracle.com [141.146.126.238] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If not, we could end up in the unfortunate situation where we dereference a NULL pointer b/c we have cpuidle disabled. This is the case when booting under Xen (which uses the ACPI P/C states but disables the CPU idle driver) - and can be easily reproduced when booting with cpuidle.off=1. BUG: unable to handle kernel NULL pointer dereference at (null) IP: [] cpuidle_unregister_device+0x2a/0x90 .. snip.. Call Trace: [] acpi_processor_power_exit+0x3c/0x5c [] acpi_processor_stop+0x61/0xb6 [] __device_release_driver+0fffff81421653>] device_release_driver+0x23/0x30 [] bus_remove_device+0x108/0x180 [] device_del+0x129/0x1c0 [] ? unregister_xenbus_watch+0x1f0/0x1f0 [] device_unregister+0x1e/0x60 [] unregister_cpu+0x39/0x60 [] arch_unregister_cpu+0x23/0x30 [] handle_vcpu_hotplug_event+0xc1/0xe0 [] xenwatch_thread+0x45/0x120 [] ? abort_exclusive_wait+0xb0/0xb0 [] kthread+0xd2/0xf0 [] ? kthread_create_on_node+0x180/0x180 [] ret_from_fork+0x7c/0xb0 [] ? kthread_create_on_node+0x180/0x180 This problem also appears in 3.12 and could be a candidate for backport. CC: "Rafael J. Wysocki" CC: Daniel Lezcano CC: linux-pm@vger.kernel.org Signed-off-by: Konrad Rzeszutek Wilk --- drivers/cpuidle/cpuidle.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 2a991e4..a55e68f 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -400,7 +400,7 @@ EXPORT_SYMBOL_GPL(cpuidle_register_device); */ void cpuidle_unregister_device(struct cpuidle_device *dev) { - if (dev->registered == 0) + if (!dev || dev->registered == 0) return; cpuidle_pause_and_lock(); -- 1.8.3.1