platform/x86: asus-wmi: Fix racy registrations

asus_wmi_register_driver() may be called from multiple drivers
concurrently, which can lead to the racy list operations, eventually
corrupting the memory and hitting Oops on some ASUS machines.
Also, the error handling is missing, and it forgot to unregister ACPI
lps0 dev ops in the error case.

This patch covers those issues by introducing a simple mutex at
acpi_wmi_register_driver() & *_unregister_driver, and adding the
proper call of asus_s2idle_check_unregister() in the error path.

Fixes: feea7bd ("platform/x86: asus-wmi: Refactor Ally suspend/resume")
Link: https://bugzilla.suse.com/show_bug.cgi?id=1246924
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Takashi Iwai <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Ilpo Järvinen <[email protected]>
Signed-off-by: Ilpo Järvinen <[email protected]>

Author: tiwai

drivers/platform/x86/asus-wmi.c

@@ -5088,16 +5088,22 @@ static int asus_wmi_probe(struct platform_device *pdev)
 
 	asus_s2idle_check_register();
 
-	return asus_wmi_add(pdev);
+	ret = asus_wmi_add(pdev);
+	if (ret)
+		asus_s2idle_check_unregister();
+
+	return ret;
 }
 
 static bool used;
+static DEFINE_MUTEX(register_mutex);
 
 int __init_or_module asus_wmi_register_driver(struct asus_wmi_driver *driver)
 {
 	struct platform_driver *platform_driver;
 	struct platform_device *platform_device;
 
+	guard(mutex)(&register_mutex);
 	if (used)
 		return -EBUSY;
 
@@ -5120,6 +5126,7 @@ EXPORT_SYMBOL_GPL(asus_wmi_register_driver);
 
 void asus_wmi_unregister_driver(struct asus_wmi_driver *driver)
 {
+	guard(mutex)(&register_mutex);
 	asus_s2idle_check_unregister();
 
 	platform_device_unregister(driver->platform_device);