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); 102