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- // SPDX-License-Identifier: GPL-2.0
- /*
- * Ioctl to get a verity file's digest
- *
- * Copyright 2019 Google LLC
- */
- #include "fsverity_private.h"
- #include <linux/uaccess.h>
- /**
- * fsverity_ioctl_measure() - get a verity file's digest
- * @filp: file to get digest of
- * @_uarg: user pointer to fsverity_digest
- *
- * Retrieve the file digest 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->file_digest, hash_alg->digest_size))
- return -EFAULT;
- return 0;
- }
- EXPORT_SYMBOL_GPL(fsverity_ioctl_measure);
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