// SPDX-License-Identifier: GPL-2.0 /* * fs/verity/measure.c: ioctl to get a verity file's measurement * * Copyright 2019 Google LLC */ #include "fsverity_private.h" #include <linux/uaccess.h> /** * fsverity_ioctl_measure() - get a verity file's measurement * * Retrieve the file measurement that the kernel is enforcing for reads from a * verity file. See the "FS_IOC_MEASURE_VERITY" section of * Documentation/filesystems/fsverity.rst for the documentation. * * Return: 0 on success, -errno on failure */ int fsverity_ioctl_measure(struct file *filp, void __user *_uarg) { const struct inode *inode = file_inode(filp); struct fsverity_digest __user *uarg = _uarg; const struct fsverity_info *vi; const struct fsverity_hash_alg *hash_alg; struct fsverity_digest arg; vi = fsverity_get_info(inode); if (!vi) return -ENODATA; /* not a verity file */ hash_alg = vi->tree_params.hash_alg; /* * The user specifies the digest_size their buffer has space for; we can * return the digest if it fits in the available space. We write back * the actual size, which may be shorter than the user-specified size. */ if (get_user(arg.digest_size, &uarg->digest_size)) return -EFAULT; if (arg.digest_size < hash_alg->digest_size) return -EOVERFLOW; memset(&arg, 0, sizeof(arg)); arg.digest_algorithm = hash_alg - fsverity_hash_algs; arg.digest_size = hash_alg->digest_size; if (copy_to_user(uarg, &arg, sizeof(arg))) return -EFAULT; if (copy_to_user(uarg->digest, vi->measurement, hash_alg->digest_size)) return -EFAULT; return 0; } EXPORT_SYMBOL_GPL(fsverity_ioctl_measure);