1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * fs/verity/measure.c: ioctl to get a verity file's measurement 4 * 5 * Copyright 2019 Google LLC 6 */ 7 8 #include "fsverity_private.h" 9 10 #include <linux/uaccess.h> 11 12 /** 13 * fsverity_ioctl_measure() - get a verity file's measurement 14 * @filp: file to get measurement of 15 * @_uarg: user pointer to fsverity_digest 16 * 17 * Retrieve the file measurement that the kernel is enforcing for reads from a 18 * verity file. See the "FS_IOC_MEASURE_VERITY" section of 19 * Documentation/filesystems/fsverity.rst for the documentation. 20 * 21 * Return: 0 on success, -errno on failure 22 */ 23 int fsverity_ioctl_measure(struct file *filp, void __user *_uarg) 24 { 25 const struct inode *inode = file_inode(filp); 26 struct fsverity_digest __user *uarg = _uarg; 27 const struct fsverity_info *vi; 28 const struct fsverity_hash_alg *hash_alg; 29 struct fsverity_digest arg; 30 31 vi = fsverity_get_info(inode); 32 if (!vi) 33 return -ENODATA; /* not a verity file */ 34 hash_alg = vi->tree_params.hash_alg; 35 36 /* 37 * The user specifies the digest_size their buffer has space for; we can 38 * return the digest if it fits in the available space. We write back 39 * the actual size, which may be shorter than the user-specified size. 40 */ 41 42 if (get_user(arg.digest_size, &uarg->digest_size)) 43 return -EFAULT; 44 if (arg.digest_size < hash_alg->digest_size) 45 return -EOVERFLOW; 46 47 memset(&arg, 0, sizeof(arg)); 48 arg.digest_algorithm = hash_alg - fsverity_hash_algs; 49 arg.digest_size = hash_alg->digest_size; 50 51 if (copy_to_user(uarg, &arg, sizeof(arg))) 52 return -EFAULT; 53 54 if (copy_to_user(uarg->digest, vi->measurement, hash_alg->digest_size)) 55 return -EFAULT; 56 57 return 0; 58 } 59 EXPORT_SYMBOL_GPL(fsverity_ioctl_measure); 60