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                 /* 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
  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);