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// SPDX-License-Identifier: GPL-2.0
/*
* 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
* @filp: file to get measurement of
* @_uarg: user pointer to fsverity_digest
*
* 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);
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