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Subject[PATCH] powercap: fix race condition in register_control_type
Date
The device becomes visible to userspace via device_register()
even before it fully initialized by idr_init(). If userspace
or another thread tries to register a zone immediately after
device_register(), the control_type_valid() will fail because
the control_type is not yet in the list. The IDR is not yet
initialized, so this race condition causes zone registration
failure.

Move idr_init() and list addition before device_register()
fix the race condition.

Signed-off-by: Sumeet Pawnikar <sumeet4linux@gmail.com>
---
drivers/powercap/powercap_sys.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/powercap/powercap_sys.c b/drivers/powercap/powercap_sys.c
index 4112a0097338..bdc65e040d17 100644
--- a/drivers/powercap/powercap_sys.c
+++ b/drivers/powercap/powercap_sys.c
@@ -625,17 +625,22 @@ struct powercap_control_type *powercap_register_control_type(
INIT_LIST_HEAD(&control_type->node);
control_type->dev.class = &powercap_class;
dev_set_name(&control_type->dev, "%s", name);
- result = device_register(&control_type->dev);
- if (result) {
- put_device(&control_type->dev);
- return ERR_PTR(result);
- }
idr_init(&control_type->idr);

mutex_lock(&powercap_cntrl_list_lock);
list_add_tail(&control_type->node, &powercap_cntrl_list);
mutex_unlock(&powercap_cntrl_list_lock);

+ result = device_register(&control_type->dev);
+ if (result) {
+ mutex_lock(&powercap_cntrl_list_lock);
+ list_del(&control_type->node);
+ mutex_unlock(&powercap_cntrl_list_lock);
+ idr_destroy(&control_type->idr);
+ put_device(&control_type->dev);
+ return ERR_PTR(result);
+ }
+
return control_type;
}
EXPORT_SYMBOL_GPL(powercap_register_control_type);
--
2.43.0

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