[PATCH AUTOSEL 4.9 44/68] ACPI / SBS: Fix rare oops when removing modules

Sasha Levin
2019-11-13T02:06:48Z

From: Ronald Tschalär <ronald@innovation.ch>

[ Upstream commit 757c968c442397f1249bb775a7c8c03842e3e0c7 ]

There was a small race when removing the sbshc module where
smbus_alarm() had queued acpi_smbus_callback() for deferred execution
but it hadn't been run yet, so that when it did run hc had been freed
and the module unloaded, resulting in an invalid paging request.

A similar race existed when removing the sbs module with regards to
acpi_sbs_callback() (which is called from acpi_smbus_callback()).

We therefore need to ensure no callbacks are pending or executing before
the cleanups are done and the modules are removed.

Signed-off-by: Ronald TschalÃ¤r <ronald@innovation.ch>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/acpi/osl.c | 1 +
drivers/acpi/sbshc.c | 2 ++
2 files changed, 3 insertions(+)

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 416953a425109..b9fade7a3bcf4 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -1126,6 +1126,7 @@ void acpi_os_wait_events_complete(void)
flush_workqueue(kacpid_wq);
flush_workqueue(kacpi_notify_wq);
}
+EXPORT_SYMBOL(acpi_os_wait_events_complete);

struct acpi_hp_work {
struct work_struct work;
diff --git a/drivers/acpi/sbshc.c b/drivers/acpi/sbshc.c
index 7a3431018e0ab..5008ead4609a4 100644
--- a/drivers/acpi/sbshc.c
+++ b/drivers/acpi/sbshc.c
@@ -196,6 +196,7 @@ int acpi_smbus_unregister_callback(struct acpi_smb_hc *hc)
hc->callback = NULL;
hc->context = NULL;
mutex_unlock(&hc->lock);
+ acpi_os_wait_events_complete();
return 0;
}

@@ -292,6 +293,7 @@ static int acpi_smbus_hc_remove(struct acpi_device *device)

hc = acpi_driver_data(device);
acpi_ec_remove_query_handler(hc->ec, hc->query_bit);
+ acpi_os_wait_events_complete();
kfree(hc);
device->driver_data = NULL;
return 0;
--
2.20.1