From 813e8e3d6aaa0b511126cce15c16a931afffe768 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Tue, 3 Dec 2013 10:59:58 -0500 Subject: [PATCH] cpuidle: Check for dev before deregistering it. 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. Signed-off-by: Konrad Rzeszutek Wilk Cc: All applicable Signed-off-by: Rafael J. Wysocki --- 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(); -- 2.7.4