[PATCH 07/13] intel_idle: Avoid a double free of the per-CPU data.

Len Brown
2016-04-06T21:01:46Z

The helper function, intel_idle_cpuidle_devices_uninit, frees the
globally allocated per-CPU data. However, this function is invoked
from the hot plug notifier callback at a time when freeing that data
is not safe.

If the call to cpuidle_register_driver() should fail (say, due to lack
of memory), then the driver will free its per-CPU region. On the
*next* CPU_ONLINE event, the driver will happily use the region again
and even free it again if the failure repeats.

This patch fixes the issue by moving the call to free_percpu() outside
of the helper function at the two call sites that actually need to
free the per-CPU data.

Signed-off-by: Richard Cochran <rcochran@linutronix.de>
Signed-off-by: Len Brown <len.brown@intel.com>
---
drivers/idle/intel_idle.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 085538a..04fe4df 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -1069,7 +1069,7 @@ static int __init intel_idle_probe(void)

/*
* intel_idle_cpuidle_devices_uninit()
- * unregister, free cpuidle_devices
+ * Unregisters the cpuidle devices.
*/
static void intel_idle_cpuidle_devices_uninit(void)
{
@@ -1080,9 +1080,6 @@ static void intel_idle_cpuidle_devices_uninit(void)
dev = per_cpu_ptr(intel_idle_cpuidle_devices, i);
cpuidle_unregister_device(dev);
}
-
- free_percpu(intel_idle_cpuidle_devices);
- return;
}

/*
@@ -1368,6 +1365,7 @@ static int __init intel_idle_init(void)
if (retval) {
cpu_notifier_register_done();
cpuidle_unregister_driver(&intel_idle_driver);
+ free_percpu(intel_idle_cpuidle_devices);
return retval;
}
}
@@ -1390,6 +1388,7 @@ static void __exit intel_idle_exit(void)
cpu_notifier_register_done();

cpuidle_unregister_driver(&intel_idle_driver);
+ free_percpu(intel_idle_cpuidle_devices);
}

module_init(intel_idle_init);
--
2.8.0.rc4.16.g56331f8