From patchwork Mon Jul 1 15:32:29 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 11026349 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3ABE913A4 for ; Mon, 1 Jul 2019 15:34:25 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2CCF1285A7 for ; Mon, 1 Jul 2019 15:34:25 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2169B28707; Mon, 1 Jul 2019 15:34:25 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2D70C28703 for ; Mon, 1 Jul 2019 15:34:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729464AbfGAPeK (ORCPT ); Mon, 1 Jul 2019 11:34:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:42776 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729426AbfGAPeI (ORCPT ); Mon, 1 Jul 2019 11:34:08 -0400 Received: from sol.localdomain (c-24-5-143-220.hsd1.ca.comcast.net [24.5.143.220]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8982D21841; Mon, 1 Jul 2019 15:34:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561995247; bh=q2bNNfDrSB6IlDzdKadNl6E8aicCMy8qKBraqwEuAAQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=m5QatE4nelCK/IWk/yBuDVUbmmKTznNPgMbVSeUcApxEr8ZnUonpoSULBCmxUP3Ck 32QsploS2IIT/uzBhI6ZNKjG6C+kukdhy/ZLsxz2YYjQxAovJINN2HfcTR7ILSUZ61 430MMIUZwoReMZ7dgj0Mtj0Qbbx3/fesoxtYIQw4= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-integrity@vger.kernel.org, Jaegeuk Kim , "Theodore Y . Ts'o" , Victor Hsieh , Chandan Rajendra , Dave Chinner , Christoph Hellwig , "Darrick J . Wong" , Linus Torvalds Subject: [PATCH v6 09/17] fs-verity: add data verification hooks for ->readpages() Date: Mon, 1 Jul 2019 08:32:29 -0700 Message-Id: <20190701153237.1777-10-ebiggers@kernel.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190701153237.1777-1-ebiggers@kernel.org> References: <20190701153237.1777-1-ebiggers@kernel.org> MIME-Version: 1.0 Sender: linux-fscrypt-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fscrypt@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Eric Biggers Add functions that verify data pages that have been read from a fs-verity file, against that file's Merkle tree. These will be called from filesystems' ->readpage() and ->readpages() methods. Since data verification can block, a workqueue is provided for these methods to enqueue verification work from their bio completion callback. See the "Verifying data" section of Documentation/filesystems/fsverity.rst for more information. Reviewed-by: Theodore Ts'o Reviewed-by: Jaegeuk Kim Signed-off-by: Eric Biggers --- fs/verity/Makefile | 3 +- fs/verity/fsverity_private.h | 5 + fs/verity/init.c | 8 + fs/verity/open.c | 6 + fs/verity/verify.c | 275 +++++++++++++++++++++++++++++++++++ include/linux/fsverity.h | 56 +++++++ 6 files changed, 352 insertions(+), 1 deletion(-) create mode 100644 fs/verity/verify.c diff --git a/fs/verity/Makefile b/fs/verity/Makefile index e6a8951c493a..7fa628cd5eba 100644 --- a/fs/verity/Makefile +++ b/fs/verity/Makefile @@ -2,4 +2,5 @@ obj-$(CONFIG_FS_VERITY) += hash_algs.o \ init.o \ - open.o + open.o \ + verify.o diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h index c79746ff335e..eaa2b3b93bbf 100644 --- a/fs/verity/fsverity_private.h +++ b/fs/verity/fsverity_private.h @@ -134,5 +134,10 @@ void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); void fsverity_free_info(struct fsverity_info *vi); int __init fsverity_init_info_cache(void); +void __init fsverity_exit_info_cache(void); + +/* verify.c */ + +int __init fsverity_init_workqueue(void); #endif /* _FSVERITY_PRIVATE_H */ diff --git a/fs/verity/init.c b/fs/verity/init.c index fff1fd634335..b593805aafcc 100644 --- a/fs/verity/init.c +++ b/fs/verity/init.c @@ -41,7 +41,15 @@ static int __init fsverity_init(void) if (err) return err; + err = fsverity_init_workqueue(); + if (err) + goto err_exit_info_cache; + pr_debug("Initialized fs-verity\n"); return 0; + +err_exit_info_cache: + fsverity_exit_info_cache(); + return err; } late_initcall(fsverity_init) diff --git a/fs/verity/open.c b/fs/verity/open.c index 2cb2fe8082bf..3636a1ed8e2c 100644 --- a/fs/verity/open.c +++ b/fs/verity/open.c @@ -337,3 +337,9 @@ int __init fsverity_init_info_cache(void) return -ENOMEM; return 0; } + +void __init fsverity_exit_info_cache(void) +{ + kmem_cache_destroy(fsverity_info_cachep); + fsverity_info_cachep = NULL; +} diff --git a/fs/verity/verify.c b/fs/verity/verify.c new file mode 100644 index 000000000000..62ab8f6a8ea1 --- /dev/null +++ b/fs/verity/verify.c @@ -0,0 +1,275 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * fs/verity/verify.c: data verification functions, i.e. hooks for ->readpages() + * + * Copyright 2019 Google LLC + */ + +#include "fsverity_private.h" + +#include +#include +#include + +static struct workqueue_struct *fsverity_read_workqueue; + +/** + * hash_at_level() - compute the location of the block's hash at the given level + * + * @params: (in) the Merkle tree parameters + * @dindex: (in) the index of the data block being verified + * @level: (in) the level of hash we want (0 is leaf level) + * @hindex: (out) the index of the hash block containing the wanted hash + * @hoffset: (out) the byte offset to the wanted hash within the hash block + */ +static void hash_at_level(const struct merkle_tree_params *params, + pgoff_t dindex, unsigned int level, pgoff_t *hindex, + unsigned int *hoffset) +{ + pgoff_t position; + + /* Offset of the hash within the level's region, in hashes */ + position = dindex >> (level * params->log_arity); + + /* Index of the hash block in the tree overall */ + *hindex = params->level_start[level] + (position >> params->log_arity); + + /* Offset of the wanted hash (in bytes) within the hash block */ + *hoffset = (position & ((1 << params->log_arity) - 1)) << + (params->log_blocksize - params->log_arity); +} + +/* Extract a hash from a hash page */ +static void extract_hash(struct page *hpage, unsigned int hoffset, + unsigned int hsize, u8 *out) +{ + void *virt = kmap_atomic(hpage); + + memcpy(out, virt + hoffset, hsize); + kunmap_atomic(virt); +} + +static inline int cmp_hashes(const struct fsverity_info *vi, + const u8 *want_hash, const u8 *real_hash, + pgoff_t index, int level) +{ + const unsigned int hsize = vi->tree_params.digest_size; + + if (memcmp(want_hash, real_hash, hsize) == 0) + return 0; + + fsverity_err(vi->inode, + "FILE CORRUPTED! index=%lu, level=%d, want_hash=%s:%*phN, real_hash=%s:%*phN", + index, level, + vi->tree_params.hash_alg->name, hsize, want_hash, + vi->tree_params.hash_alg->name, hsize, real_hash); + return -EBADMSG; +} + +/* + * Verify a single data page against the file's Merkle tree. + * + * In principle, we need to verify the entire path to the root node. However, + * for efficiency the filesystem may cache the hash pages. Therefore we need + * only ascend the tree until an already-verified page is seen, as indicated by + * the PageChecked bit being set; then verify the path to that page. + * + * This code currently only supports the case where the verity block size is + * equal to PAGE_SIZE. Doing otherwise would be possible but tricky, since we + * wouldn't be able to use the PageChecked bit. + * + * Note that multiple processes may race to verify a hash page and mark it + * Checked, but it doesn't matter; the result will be the same either way. + * + * Return: true if the page is valid, else false. + */ +static bool verify_page(struct inode *inode, const struct fsverity_info *vi, + struct ahash_request *req, struct page *data_page) +{ + const struct merkle_tree_params *params = &vi->tree_params; + const unsigned int hsize = params->digest_size; + const pgoff_t index = data_page->index; + int level; + u8 _want_hash[FS_VERITY_MAX_DIGEST_SIZE]; + const u8 *want_hash; + u8 real_hash[FS_VERITY_MAX_DIGEST_SIZE]; + struct page *hpages[FS_VERITY_MAX_LEVELS]; + unsigned int hoffsets[FS_VERITY_MAX_LEVELS]; + int err; + + if (WARN_ON_ONCE(!PageLocked(data_page) || PageUptodate(data_page))) + return false; + + pr_debug_ratelimited("Verifying data page %lu...\n", index); + + /* + * Starting at the leaf level, ascend the tree saving hash pages along + * the way until we find a verified hash page, indicated by PageChecked; + * or until we reach the root. + */ + for (level = 0; level < params->num_levels; level++) { + pgoff_t hindex; + unsigned int hoffset; + struct page *hpage; + + hash_at_level(params, index, level, &hindex, &hoffset); + + pr_debug_ratelimited("Level %d: hindex=%lu, hoffset=%u\n", + level, hindex, hoffset); + + hpage = inode->i_sb->s_vop->read_merkle_tree_page(inode, + hindex); + if (IS_ERR(hpage)) { + err = PTR_ERR(hpage); + fsverity_err(inode, + "Error %d reading Merkle tree page %lu", + err, hindex); + goto out; + } + + if (PageChecked(hpage)) { + extract_hash(hpage, hoffset, hsize, _want_hash); + want_hash = _want_hash; + put_page(hpage); + pr_debug_ratelimited("Hash page already checked, want %s:%*phN\n", + params->hash_alg->name, + hsize, want_hash); + goto descend; + } + pr_debug_ratelimited("Hash page not yet checked\n"); + hpages[level] = hpage; + hoffsets[level] = hoffset; + } + + want_hash = vi->root_hash; + pr_debug("Want root hash: %s:%*phN\n", + params->hash_alg->name, hsize, want_hash); +descend: + /* Descend the tree verifying hash pages */ + for (; level > 0; level--) { + struct page *hpage = hpages[level - 1]; + unsigned int hoffset = hoffsets[level - 1]; + + err = fsverity_hash_page(params, inode, req, hpage, real_hash); + if (err) + goto out; + err = cmp_hashes(vi, want_hash, real_hash, index, level - 1); + if (err) + goto out; + SetPageChecked(hpage); + extract_hash(hpage, hoffset, hsize, _want_hash); + want_hash = _want_hash; + put_page(hpage); + pr_debug("Verified hash page at level %d, now want %s:%*phN\n", + level - 1, params->hash_alg->name, hsize, want_hash); + } + + /* Finally, verify the data page */ + err = fsverity_hash_page(params, inode, req, data_page, real_hash); + if (err) + goto out; + err = cmp_hashes(vi, want_hash, real_hash, index, -1); +out: + for (; level > 0; level--) + put_page(hpages[level - 1]); + + return err == 0; +} + +/** + * fsverity_verify_page() - verify a data page + * + * Verify a page that has just been read from a verity file. The page must be a + * pagecache page that is still locked and not yet uptodate. + * + * Return: true if the page is valid, else false. + */ +bool fsverity_verify_page(struct page *page) +{ + struct inode *inode = page->mapping->host; + const struct fsverity_info *vi = inode->i_verity_info; + struct ahash_request *req; + bool valid; + + req = ahash_request_alloc(vi->tree_params.hash_alg->tfm, GFP_NOFS); + if (unlikely(!req)) + return false; + + valid = verify_page(inode, vi, req, page); + + ahash_request_free(req); + + return valid; +} +EXPORT_SYMBOL_GPL(fsverity_verify_page); + +#ifdef CONFIG_BLOCK +/** + * fsverity_verify_bio() - verify a 'read' bio that has just completed + * + * Verify a set of pages that have just been read from a verity file. The pages + * must be pagecache pages that are still locked and not yet uptodate. Pages + * that fail verification are set to the Error state. Verification is skipped + * for pages already in the Error state, e.g. due to fscrypt decryption failure. + * + * This is a helper function for use by the ->readpages() method of filesystems + * that issue bios to read data directly into the page cache. Filesystems that + * populate the page cache without issuing bios (e.g. non block-based + * filesystems) must instead call fsverity_verify_page() directly on each page. + * All filesystems must also call fsverity_verify_page() on holes. + */ +void fsverity_verify_bio(struct bio *bio) +{ + struct inode *inode = bio_first_page_all(bio)->mapping->host; + const struct fsverity_info *vi = inode->i_verity_info; + struct ahash_request *req; + struct bio_vec *bv; + struct bvec_iter_all iter_all; + + req = ahash_request_alloc(vi->tree_params.hash_alg->tfm, GFP_NOFS); + if (unlikely(!req)) { + bio_for_each_segment_all(bv, bio, iter_all) + SetPageError(bv->bv_page); + return; + } + + bio_for_each_segment_all(bv, bio, iter_all) { + struct page *page = bv->bv_page; + + if (!PageError(page) && !verify_page(inode, vi, req, page)) + SetPageError(page); + } + + ahash_request_free(req); +} +EXPORT_SYMBOL_GPL(fsverity_verify_bio); +#endif /* CONFIG_BLOCK */ + +/** + * fsverity_enqueue_verify_work() - enqueue work on the fs-verity workqueue + * + * Enqueue verification work for asynchronous processing. + */ +void fsverity_enqueue_verify_work(struct work_struct *work) +{ + queue_work(fsverity_read_workqueue, work); +} +EXPORT_SYMBOL_GPL(fsverity_enqueue_verify_work); + +int __init fsverity_init_workqueue(void) +{ + /* + * Use an unbound workqueue to allow bios to be verified in parallel + * even when they happen to complete on the same CPU. This sacrifices + * locality, but it's worthwhile since hashing is CPU-intensive. + * + * Also use a high-priority workqueue to prioritize verification work, + * which blocks reads from completing, over regular application tasks. + */ + fsverity_read_workqueue = alloc_workqueue("fsverity_read_queue", + WQ_UNBOUND | WQ_HIGHPRI, + num_online_cpus()); + if (!fsverity_read_workqueue) + return -ENOMEM; + return 0; +} diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h index cbd0f84e1620..95c257cd7ff0 100644 --- a/include/linux/fsverity.h +++ b/include/linux/fsverity.h @@ -33,6 +33,23 @@ struct fsverity_operations { */ int (*get_verity_descriptor)(struct inode *inode, void *buf, size_t bufsize); + + /** + * Read a Merkle tree page of the given inode. + * + * @inode: the inode + * @index: 0-based index of the page within the Merkle tree + * + * This can be called at any time on an open verity file, as well as + * between ->begin_enable_verity() and ->end_enable_verity(). It may be + * called by multiple processes concurrently, even with the same page. + * + * Note that this must retrieve a *page*, not necessarily a *block*. + * + * Return: the page on success, ERR_PTR() on failure + */ + struct page *(*read_merkle_tree_page)(struct inode *inode, + pgoff_t index); }; #ifdef CONFIG_FS_VERITY @@ -49,6 +66,12 @@ extern int fsverity_file_open(struct inode *inode, struct file *filp); extern int fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr); extern void fsverity_cleanup_inode(struct inode *inode); +/* verify.c */ + +extern bool fsverity_verify_page(struct page *page); +extern void fsverity_verify_bio(struct bio *bio); +extern void fsverity_enqueue_verify_work(struct work_struct *work); + #else /* !CONFIG_FS_VERITY */ static inline struct fsverity_info *fsverity_get_info(const struct inode *inode) @@ -73,6 +96,39 @@ static inline void fsverity_cleanup_inode(struct inode *inode) { } +/* verify.c */ + +static inline bool fsverity_verify_page(struct page *page) +{ + WARN_ON(1); + return false; +} + +static inline void fsverity_verify_bio(struct bio *bio) +{ + WARN_ON(1); +} + +static inline void fsverity_enqueue_verify_work(struct work_struct *work) +{ + WARN_ON(1); +} + #endif /* !CONFIG_FS_VERITY */ +/** + * fsverity_active() - do reads from the inode need to go through fs-verity? + * + * This checks whether ->i_verity_info has been set. + * + * Filesystems call this from ->readpages() to check whether the pages need to + * be verified or not. Don't use IS_VERITY() for this purpose; it's subject to + * a race condition where the file is being read concurrently with + * FS_IOC_ENABLE_VERITY completing. (S_VERITY is set before ->i_verity_info.) + */ +static inline bool fsverity_active(const struct inode *inode) +{ + return fsverity_get_info(inode) != NULL; +} + #endif /* _LINUX_FSVERITY_H */