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
cm_write(struct file * file,const char __user * user_buf,size_t count,loff_t * ppos)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(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
85 static const struct file_operations cm_fops = {
86 .write = cm_write,
87 .llseek = default_llseek,
88 };
89
acpi_custom_method_init(void)90 static 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
acpi_custom_method_exit(void)97 static void __exit acpi_custom_method_exit(void)
98 {
99 debugfs_remove(cm_dentry);
100 }
101
102 module_init(acpi_custom_method_init);
103 module_exit(acpi_custom_method_exit);
104