Commit 1ec3ddfd authored Sep 23, 2012 by Silas Boyd-Wickizer Committed by Jean Delvare Sep 23, 2012

hwmon: (via-cputemp) Use get_online_cpus to avoid races involving CPU hotplug



via_cputemp_init loops with for_each_online_cpu, adding
platform_devices, then calls register_hotcpu_notifier.  If a CPU is
offlined between the loop and register_hotcpu_notifier, then later
onlined, via_cputemp_device_add will attempt to add platform devices
with the same ID.  A similar race occurs during via_cputemp_exit,
after the module calls unregister_hotcpu_notifier, a CPU might offline
and a device will exist for a CPU that is offline.

This fix surrounds for_each_online_cpu and register_hotcpu_notifier
with get_online_cpus+put_online_cpus; and surrounds
unregister_hotcpu_notifier and device unregistering with
get_online_cpus+put_online_cpus.

Build tested.

Signed-off-by: Silas Boyd-Wickizer <sbw@mit.edu>
Acked-by: Harald Welte <laforge@gnumonks.org>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

parent e5e77cf9

drivers/hwmon/via-cputemp.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -328,6 +328,7 @@ static int __init via_cputemp_init(void)
		if (err)
		goto exit;

		get_online_cpus();
		for_each_online_cpu(i) {
		struct cpuinfo_x86 *c = &cpu_data(i);

		@@ -347,12 +348,14 @@ static int __init via_cputemp_init(void)

		#ifndef CONFIG_HOTPLUG_CPU
		if (list_empty(&pdev_list)) {
		put_online_cpus();
		err = -ENODEV;
		goto exit_driver_unreg;
		}
		#endif

		register_hotcpu_notifier(&via_cputemp_cpu_notifier);
		put_online_cpus();
		return 0;

		#ifndef CONFIG_HOTPLUG_CPU
		@@ -367,6 +370,7 @@ static void __exit via_cputemp_exit(void)
		{
		struct pdev_entry p, n;

		get_online_cpus();
		unregister_hotcpu_notifier(&via_cputemp_cpu_notifier);
		mutex_lock(&pdev_list_mutex);
		list_for_each_entry_safe(p, n, &pdev_list, list) {
		@@ -375,6 +379,7 @@ static void __exit via_cputemp_exit(void)
		kfree(p);
		}
		mutex_unlock(&pdev_list_mutex);
		put_online_cpus();
		platform_driver_unregister(&via_cputemp_driver);
		}