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 * 15 * Retrieve the file measurement that the kernel is enforcing for reads from a 16 * verity file. See the "FS_IOC_MEASURE_VERITY" section of 17 * Documentation/filesystems/fsverity.rst for the documentation. 18 * 19 * Return: 0 on success, -errno on failure 20 */ 21 int fsverity_ioctl_measure(struct file *filp, void __user *_uarg) 22 { 23 const struct inode *inode = file_inode(filp); 24 struct fsverity_digest __user *uarg = _uarg; 25 const struct fsverity_info *vi; 26 const struct fsverity_hash_alg *hash_alg; 27 struct fsverity_digest arg; 28 29 vi = fsverity_get_info(inode); 30 if (!vi) 31 return -ENODATA; /* not a verity file */ 32 hash_alg = vi->tree_params.hash_alg; 33 34 /* 35 * The user specifies the digest_size their buffer has space for; we can 36 * return the digest if it fits in the available space. We write back 37 * the actual size, which may be shorter than the user-specified size. 38 */ 39 40 if (get_user(arg.digest_size, &uarg->digest_size)) 41 return -EFAULT; 42 if (arg.digest_size < hash_alg->digest_size) 43 return -EOVERFLOW; 44 45 memset(&arg, 0, sizeof(arg)); 46 arg.digest_algorithm = hash_alg - fsverity_hash_algs; 47 arg.digest_size = hash_alg->digest_size; 48 49 if (copy_to_user(uarg, &arg, sizeof(arg))) 50 return -EFAULT; 51 52 if (copy_to_user(uarg->digest, vi->measurement, hash_alg->digest_size)) 53 return -EFAULT; 54 55 return 0; 56 } 57 EXPORT_SYMBOL_GPL(fsverity_ioctl_measure); 58