platform/x86: think-lmi: mutex protection around multiple WMI calls

When an attribute is being changed if the Admin account is enabled, or if
a password is being updated then multiple WMI calls are needed.
Add mutex protection to ensure no race conditions are introduced.

Fixes: b49f72e7 ("platform/x86: think-lmi: Certificate authentication support")
Signed-off-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20230601200552.4396-1-mpearson-lenovo@squebb.caSigned-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/think-lmi.c

@@ -14,6 +14,7 @@
 #include <linux/acpi.h>
 #include <linux/errno.h>
 #include <linux/fs.h>
+#include <linux/mutex.h>
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/dmi.h>
@@ -195,6 +196,7 @@ static const char * const level_options[] = {
 };
 static struct think_lmi tlmi_priv;
 static struct class *fw_attr_class;
+static DEFINE_MUTEX(tlmi_mutex);
 
 /* ------ Utility functions ------------*/
 /* Strip out CR if one is present */
@@ -437,6 +439,9 @@ static ssize_t new_password_store(struct kobject *kobj,
 	/* Strip out CR if one is present, setting password won't work if it is present */
 	strip_cr(new_pwd);
 
+	/* Use lock in case multiple WMI operations needed */
+	mutex_lock(&tlmi_mutex);
+
 	pwdlen = strlen(new_pwd);
 	/* pwdlen == 0 is allowed to clear the password */
 	if (pwdlen && ((pwdlen < setting->minlen) || (pwdlen > setting->maxlen))) {
@@ -493,6 +498,7 @@ static ssize_t new_password_store(struct kobject *kobj,
 		kfree(auth_str);
 	}
 out:
+	mutex_unlock(&tlmi_mutex);
 	kfree(new_pwd);
 	return ret ?: count;
 }
@@ -981,6 +987,9 @@ static ssize_t current_value_store(struct kobject *kobj,
 	/* Strip out CR if one is present */
 	strip_cr(new_setting);
 
+	/* Use lock in case multiple WMI operations needed */
+	mutex_lock(&tlmi_mutex);
+
 	/* Check if certificate authentication is enabled and active */
 	if (tlmi_priv.certificate_support && tlmi_priv.pwd_admin->cert_installed) {
 		if (!tlmi_priv.pwd_admin->signature || !tlmi_priv.pwd_admin->save_signature) {
@@ -1039,6 +1048,7 @@ static ssize_t current_value_store(struct kobject *kobj,
 		kobject_uevent(&tlmi_priv.class_dev->kobj, KOBJ_CHANGE);
 	}
 out:
+	mutex_unlock(&tlmi_mutex);
 	kfree(auth_str);
 	kfree(set_str);
 	kfree(new_setting);