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 | |
16 | MODULE_LICENSE("GPL" ); |
17 | |
18 | static struct dentry *cm_dentry; |
19 | |
20 | /* /sys/kernel/debug/acpi/custom_method */ |
21 | |
22 | static 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(what: 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(to: &table, from: user_buf, |
42 | n: 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(objp: buf); |
47 | buf = kzalloc(size: 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(objp: buf); |
60 | buf = NULL; |
61 | return -EINVAL; |
62 | } |
63 | |
64 | if (copy_from_user(to: buf + (*ppos), from: user_buf, n: count)) { |
65 | kfree(objp: 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(buffer: buf); |
75 | kfree(objp: 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 | |
85 | static const struct file_operations cm_fops = { |
86 | .write = cm_write, |
87 | .llseek = default_llseek, |
88 | }; |
89 | |
90 | static int __init acpi_custom_method_init(void) |
91 | { |
92 | cm_dentry = debugfs_create_file(name: "custom_method" , S_IWUSR, |
93 | parent: acpi_debugfs_dir, NULL, fops: &cm_fops); |
94 | return 0; |
95 | } |
96 | |
97 | static void __exit acpi_custom_method_exit(void) |
98 | { |
99 | debugfs_remove(dentry: cm_dentry); |
100 | } |
101 | |
102 | module_init(acpi_custom_method_init); |
103 | module_exit(acpi_custom_method_exit); |
104 | |