drivers/acpi/custom_method.c

   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(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                 buf = kzalloc(max_size, GFP_KERNEL);
  46                 if (!buf)
  47                         return -ENOMEM;
  48         }
  49
  50         if (buf == NULL)
  51                 return -EINVAL;
  52
  53         if ((*ppos > max_size) ||
  54             (*ppos + count > max_size) ||
  55             (*ppos + count < count) ||
  56             (count > uncopied_bytes)) {
  57                 kfree(buf);
  58                 return -EINVAL;
  59         }
  60
  61         if (copy_from_user(buf + (*ppos), user_buf, count)) {
  62                 kfree(buf);
  63                 buf = NULL;
  64                 return -EFAULT;
  65         }
  66
  67         uncopied_bytes -= count;
  68         *ppos += count;
  69
  70         if (!uncopied_bytes) {
  71                 status = acpi_install_method(buf);
  72                 kfree(buf);
  73                 buf = NULL;
  74                 if (ACPI_FAILURE(status))
  75                         return -EINVAL;
  76                 add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
  77         }
  78
  79         kfree(buf);
  80         return count;
  81 }
  82
  83 static const struct file_operations cm_fops = {
  84         .write = cm_write,
  85         .llseek = default_llseek,
  86 };
  87
  88 static int __init acpi_custom_method_init(void)
  89 {
  90         cm_dentry = debugfs_create_file("custom_method", S_IWUSR,
  91                                         acpi_debugfs_dir, NULL, &cm_fops);
  92         return 0;
  93 }
  94
  95 static void __exit acpi_custom_method_exit(void)
  96 {
  97         debugfs_remove(cm_dentry);
  98 }
  99
 100 module_init(acpi_custom_method_init);
 101 module_exit(acpi_custom_method_exit);