diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c
index b097ef209313..dfe097d07202 100644
--- a/drivers/acpi/custom_method.c
+++ b/drivers/acpi/custom_method.c
@@ -57,6 +57,7 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf,
 	    (*ppos + count < count) ||
 	    (count > uncopied_bytes)) {
 		kfree(buf);
+		buf = NULL;
 		return -EINVAL;
 	}
 
@@ -78,7 +79,6 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf,
 		add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
 	}
 
-	kfree(buf);
 	return count;
 }