drivers/acpi/custom_method.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * custom_method.c - debugfs interface for customizing ACPI control method
0004  */
0005
0006 #include <linux/init.h>
0007 #include <linux/module.h>
0008 #include <linux/kernel.h>
0009 #include <linux/uaccess.h>
0010 #include <linux/debugfs.h>
0011 #include <linux/acpi.h>
0012 #include <linux/security.h>
0013
0014 #include "internal.h"
0015
0016 MODULE_LICENSE("GPL");
0017
0018 static struct dentry *cm_dentry;
0019
0020 /* /sys/kernel/debug/acpi/custom_method */
0021
0022 static ssize_t cm_write(struct file *file, const char __user *user_buf,
0023             size_t count, loff_t *ppos)
0024 {
0025     static char *buf;
0026     static u32 max_size;
0027     static u32 uncopied_bytes;
0028
0029     struct acpi_table_header table;
0030     acpi_status status;
0031     int ret;
0032
0033     ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
0034     if (ret)
0035         return ret;
0036
0037     if (!(*ppos)) {
0038         /* parse the table header to get the table length */
0039         if (count <= sizeof(struct acpi_table_header))
0040             return -EINVAL;
0041         if (copy_from_user(&table, user_buf,
0042                    sizeof(struct acpi_table_header)))
0043             return -EFAULT;
0044         uncopied_bytes = max_size = table.length;
0045         /* make sure the buf is not allocated */
0046         kfree(buf);
0047         buf = kzalloc(max_size, GFP_KERNEL);
0048         if (!buf)
0049             return -ENOMEM;
0050     }
0051
0052     if (buf == NULL)
0053         return -EINVAL;
0054
0055     if ((*ppos > max_size) ||
0056         (*ppos + count > max_size) ||
0057         (*ppos + count < count) ||
0058         (count > uncopied_bytes)) {
0059         kfree(buf);
0060         buf = NULL;
0061         return -EINVAL;
0062     }
0063
0064     if (copy_from_user(buf + (*ppos), user_buf, count)) {
0065         kfree(buf);
0066         buf = NULL;
0067         return -EFAULT;
0068     }
0069
0070     uncopied_bytes -= count;
0071     *ppos += count;
0072
0073     if (!uncopied_bytes) {
0074         status = acpi_install_method(buf);
0075         kfree(buf);
0076         buf = NULL;
0077         if (ACPI_FAILURE(status))
0078             return -EINVAL;
0079         add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
0080     }
0081
0082     return count;
0083 }
0084
0085 static const struct file_operations cm_fops = {
0086     .write = cm_write,
0087     .llseek = default_llseek,
0088 };
0089
0090 static int __init acpi_custom_method_init(void)
0091 {
0092     cm_dentry = debugfs_create_file("custom_method", S_IWUSR,
0093                     acpi_debugfs_dir, NULL, &cm_fops);
0094     return 0;
0095 }
0096
0097 static void __exit acpi_custom_method_exit(void)
0098 {
0099     debugfs_remove(cm_dentry);
0100 }
0101
0102 module_init(acpi_custom_method_init);
0103 module_exit(acpi_custom_method_exit);