platform/loongarch: laptop: Fix possible UAF and simplify generic_acpi_laptop_init()

Currently the return value of 'sub_driver->init' is not checked. If
sparse_keymap_setup() called in the init function fails, 'generic_
inputdev' is freed, then it will lead a UAF when using it in generic_
acpi_laptop_init(). Fix it by checking the return value and setting
generic_inputdev to NULL after free, so as to avoid double free it.

The error code in generic_subdriver_init() is always negative, so the
return of generic_subdriver_init() can be simplified.

Fixes: 6246ed09 ("LoongArch: Add ACPI-based generic laptop driver")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

drivers/platform/loongarch/loongson-laptop.c

@@ -448,6 +448,7 @@ static int __init event_init(struct generic_sub_driver *sub_driver)
 	if (ret < 0) {
 		pr_err("Failed to setup input device keymap\n");
 		input_free_device(generic_inputdev);
+		generic_inputdev = NULL;
 
 		return ret;
 	}
@@ -502,8 +503,11 @@ static int __init generic_subdriver_init(struct generic_sub_driver *sub_driver)
 	if (ret)
 		return -EINVAL;
 
-	if (sub_driver->init)
-		sub_driver->init(sub_driver);
+	if (sub_driver->init) {
+		ret = sub_driver->init(sub_driver);
+		if (ret)
+			goto err_out;
+	}
 
 	if (sub_driver->notify) {
 		ret = setup_acpi_notify(sub_driver);
@@ -519,7 +523,7 @@ static int __init generic_subdriver_init(struct generic_sub_driver *sub_driver)
 
 err_out:
 	generic_subdriver_exit(sub_driver);
-	return (ret < 0) ? ret : 0;
+	return ret;
 }
 
 static void generic_subdriver_exit(struct generic_sub_driver *sub_driver)