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Subject[PATCH 3/3] Use get_online_cpus to avoid races involving for_each_online_cpu
via_cputemp_init in drivers/hwmon/via-cputemp.c 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 platform devices with the same ID.

This fix surrounds for_each_online_cpu and register_hotcpu_notifier
with get_online_cpus+put_online_cpus.

Build tested.

Signed-off-by: Silas Boyd-Wickizer <sbw@mit.edu>
---
drivers/hwmon/via-cputemp.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/hwmon/via-cputemp.c b/drivers/hwmon/via-cputemp.c
index 8689664..9ad07c3 100644
--- a/drivers/hwmon/via-cputemp.c
+++ b/drivers/hwmon/via-cputemp.c
@@ -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
--
1.7.10.4


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