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); 104