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>
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@ -328,6 +328,7 @@ static int __init via_cputemp_init(void)
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if (err)
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goto exit;
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get_online_cpus();
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for_each_online_cpu(i) {
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struct cpuinfo_x86 *c = &cpu_data(i);
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@ -347,12 +348,14 @@ static int __init via_cputemp_init(void)
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#ifndef CONFIG_HOTPLUG_CPU
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if (list_empty(&pdev_list)) {
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put_online_cpus();
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err = -ENODEV;
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goto exit_driver_unreg;
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}
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#endif
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register_hotcpu_notifier(&via_cputemp_cpu_notifier);
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put_online_cpus();
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return 0;
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#ifndef CONFIG_HOTPLUG_CPU
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@ -367,6 +370,7 @@ static void __exit via_cputemp_exit(void)
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{
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struct pdev_entry *p, *n;
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get_online_cpus();
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unregister_hotcpu_notifier(&via_cputemp_cpu_notifier);
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mutex_lock(&pdev_list_mutex);
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list_for_each_entry_safe(p, n, &pdev_list, list) {
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@ -375,6 +379,7 @@ static void __exit via_cputemp_exit(void)
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kfree(p);
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}
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mutex_unlock(&pdev_list_mutex);
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put_online_cpus();
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platform_driver_unregister(&via_cputemp_driver);
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}
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