From 78ea4639a7647f2fcc957c3a532bde49df9895c7 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Tue, 4 Feb 2014 00:43:05 +0100 Subject: ACPI / hotplug: Fix potential race in acpi_bus_notify() There is a slight possibility for the ACPI device object pointed to by adev in acpi_hotplug_notify_cb() to become invalid between the acpi_bus_get_device() that it comes from and the subsequent dereference of that pointer under get_device(). Namely, if acpi_scan_drop_device() runs in parallel with acpi_hotplug_notify_cb(), acpi_device_del_work_fn() queued up by it may delete the device object in question right after a successful execution of acpi_bus_get_device() in acpi_bus_notify(). An analogous problem is present in acpi_bus_notify() where the device pointer coming from acpi_bus_get_device() may become invalid before it subsequent dereference in the "if" block. To prevent that from happening, introduce a new function, acpi_bus_get_acpi_device(), working analogously to acpi_bus_get_device() except that it will grab a reference to the ACPI device object returned by it and it will do that under the ACPICA's namespace mutex. Then, make both acpi_hotplug_notify_cb() and acpi_bus_notify() use acpi_bus_get_acpi_device() instead of acpi_bus_get_device() so as to ensure that the pointers used by them will not become stale at one point. In addition to that, introduce acpi_bus_put_acpi_device() as a wrapper around put_device() to be used along with acpi_bus_get_acpi_device() and make the (new) users of the latter use acpi_bus_put_acpi_device() too. Signed-off-by: Rafael J. Wysocki Tested-by: Mika Westerberg --- include/acpi/acpi_bus.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/acpi/acpi_bus.h') diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h index 8256eb4ad057..94fd61a0456d 100644 --- a/include/acpi/acpi_bus.h +++ b/include/acpi/acpi_bus.h @@ -381,6 +381,8 @@ extern int unregister_acpi_notifier(struct notifier_block *); */ int acpi_bus_get_device(acpi_handle handle, struct acpi_device **device); +struct acpi_device *acpi_bus_get_acpi_device(acpi_handle handle); +void acpi_bus_put_acpi_device(struct acpi_device *adev); acpi_status acpi_bus_get_status_handle(acpi_handle handle, unsigned long long *sta); int acpi_bus_get_status(struct acpi_device *device); -- cgit v1.2.3