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 #define _COMPONENT              ACPI_SYSTEM_COMPONENT
  17 ACPI_MODULE_NAME("custom_method");
  18 MODULE_LICENSE("GPL");
  19
  20 static struct dentry *cm_dentry;
  21
  22 /* /sys/kernel/debug/acpi/custom_method */
  23
  24 static ssize_t cm_write(struct file *file, const char __user * user_buf,
  25                         size_t count, loff_t *ppos)
  26 {
  27         static char *buf;
  28         static u32 max_size;
  29         static u32 uncopied_bytes;
  30
  31         struct acpi_table_header table;
  32         acpi_status status;
  33         int ret;
  34
  35         ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
  36         if (ret)
  37                 return ret;
  38
  39         if (!(*ppos)) {
  40                 /* parse the table header to get the table length */
  41                 if (count <= sizeof(struct acpi_table_header))
  42                         return -EINVAL;
  43                 if (copy_from_user(&table, user_buf,
  44                                    sizeof(struct acpi_table_header)))
  45                         return -EFAULT;
  46                 uncopied_bytes = max_size = table.length;
  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                 return -EINVAL;
  61         }
  62
  63         if (copy_from_user(buf + (*ppos), user_buf, count)) {
  64                 kfree(buf);
  65                 buf = NULL;
  66                 return -EFAULT;
  67         }
  68
  69         uncopied_bytes -= count;
  70         *ppos += count;
  71
  72         if (!uncopied_bytes) {
  73                 status = acpi_install_method(buf);
  74                 kfree(buf);
  75                 buf = NULL;
  76                 if (ACPI_FAILURE(status))
  77                         return -EINVAL;
  78                 add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
  79         }
  80
  81         kfree(buf);
  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("custom_method", S_IWUSR,
  93                                         acpi_debugfs_dir, NULL, &cm_fops);
  94         return 0;
  95 }
  96
  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);