1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * custom_method.c - debugfs interface for customizing ACPI control method
4 */
5
6#include <linux/init.h>
7#include <linux/module.h>
8#include <linux/kernel.h>
9#include <linux/uaccess.h>
10#include <linux/debugfs.h>
11#include <linux/acpi.h>
12#include <linux/security.h>
13
14#include "internal.h"
15
16MODULE_LICENSE("GPL");
17
18static struct dentry *cm_dentry;
19
20/* /sys/kernel/debug/acpi/custom_method */
21
22static ssize_t cm_write(struct file *file, const char __user * user_buf,
23			size_t count, loff_t *ppos)
24{
25	static char *buf;
26	static u32 max_size;
27	static u32 uncopied_bytes;
28
29	struct acpi_table_header table;
30	acpi_status status;
31	int ret;
32
33	ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
34	if (ret)
35		return ret;
36
37	if (!(*ppos)) {
38		/* parse the table header to get the table length */
39		if (count <= sizeof(struct acpi_table_header))
40			return -EINVAL;
41		if (copy_from_user(&table, user_buf,
42				   sizeof(struct acpi_table_header)))
43			return -EFAULT;
44		uncopied_bytes = max_size = table.length;
45		/* make sure the buf is not allocated */
46		kfree(buf);
47		buf = kzalloc(max_size, GFP_KERNEL);
48		if (!buf)
49			return -ENOMEM;
50	}
51
52	if (buf == NULL)
53		return -EINVAL;
54
55	if ((*ppos > max_size) ||
56	    (*ppos + count > max_size) ||
57	    (*ppos + count < count) ||
58	    (count > uncopied_bytes)) {
59		kfree(buf);
60		buf = NULL;
61		return -EINVAL;
62	}
63
64	if (copy_from_user(buf + (*ppos), user_buf, count)) {
65		kfree(buf);
66		buf = NULL;
67		return -EFAULT;
68	}
69
70	uncopied_bytes -= count;
71	*ppos += count;
72
73	if (!uncopied_bytes) {
74		status = acpi_install_method(buf);
75		kfree(buf);
76		buf = NULL;
77		if (ACPI_FAILURE(status))
78			return -EINVAL;
79		add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
80	}
81
82	return count;
83}
84
85static const struct file_operations cm_fops = {
86	.write = cm_write,
87	.llseek = default_llseek,
88};
89
90static int __init acpi_custom_method_init(void)
91{
92	cm_dentry = debugfs_create_file("custom_method", S_IWUSR,
93					acpi_debugfs_dir, NULL, &cm_fops);
94	return 0;
95}
96
97static void __exit acpi_custom_method_exit(void)
98{
99	debugfs_remove(cm_dentry);
100}
101
102module_init(acpi_custom_method_init);
103module_exit(acpi_custom_method_exit);
104