[linux-2.6-block.git] / fs / ext4 / verity.c

// SPDX-License-Identifier: GPL-2.0
/*
 * fs/ext4/verity.c: fs-verity support for ext4
 *
 * Copyright 2019 Google LLC
 */

/*
 * Implementation of fsverity_operations for ext4.
 *
 * ext4 stores the verity metadata (Merkle tree and fsverity_descriptor) past
 * the end of the file, starting at the first 64K boundary beyond i_size.  This
 * approach works because (a) verity files are readonly, and (b) pages fully
 * beyond i_size aren't visible to userspace but can be read/written internally
 * by ext4 with only some relatively small changes to ext4.  This approach
 * avoids having to depend on the EA_INODE feature and on rearchitecturing
 * ext4's xattr support to support paging multi-gigabyte xattrs into memory, and
 * to support encrypting xattrs.  Note that the verity metadata *must* be
 * encrypted when the file is, since it contains hashes of the plaintext data.
 *
 * Using a 64K boundary rather than a 4K one keeps things ready for
 * architectures with 64K pages, and it doesn't necessarily waste space on-disk
 * since there can be a hole between i_size and the start of the Merkle tree.
 */

#include <linux/quotaops.h>

#include "ext4.h"
#include "ext4_extents.h"
#include "ext4_jbd2.h"

static inline loff_t ext4_verity_metadata_pos(const struct inode *inode)
{
	return round_up(inode->i_size, 65536);
}

/*
 * Read some verity metadata from the inode.  __vfs_read() can't be used because
 * we need to read beyond i_size.
 */
static int pagecache_read(struct inode *inode, void *buf, size_t count,
			  loff_t pos)
{
	while (count) {
		struct folio *folio;
		size_t n;

		folio = read_mapping_folio(inode->i_mapping, pos >> PAGE_SHIFT,
					 NULL);
		if (IS_ERR(folio))
			return PTR_ERR(folio);

		n = memcpy_from_file_folio(buf, folio, pos, count);
		folio_put(folio);

		buf += n;
		pos += n;
		count -= n;
	}
	return 0;
}

/*
 * Write some verity metadata to the inode for FS_IOC_ENABLE_VERITY.
 * kernel_write() can't be used because the file descriptor is readonly.
 */
static int pagecache_write(struct inode *inode, const void *buf, size_t count,
			   loff_t pos)
{
	struct address_space *mapping = inode->i_mapping;
	const struct address_space_operations *aops = mapping->a_ops;

	if (pos + count > inode->i_sb->s_maxbytes)
		return -EFBIG;

	while (count) {
		size_t n = min_t(size_t, count,
				 PAGE_SIZE - offset_in_page(pos));
		struct page *page;
		void *fsdata = NULL;
		int res;

		res = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);
		if (res)
			return res;

		memcpy_to_page(page, offset_in_page(pos), buf, n);

		res = aops->write_end(NULL, mapping, pos, n, n, page, fsdata);
		if (res < 0)
			return res;
		if (res != n)
			return -EIO;

		buf += n;
		pos += n;
		count -= n;
	}
	return 0;
}

static int ext4_begin_enable_verity(struct file *filp)
{
	struct inode *inode = file_inode(filp);
	const int credits = 2; /* superblock and inode for ext4_orphan_add() */
	handle_t *handle;
	int err;

	if (IS_DAX(inode) || ext4_test_inode_flag(inode, EXT4_INODE_DAX))
		return -EINVAL;

	if (ext4_verity_in_progress(inode))
		return -EBUSY;

	/*
	 * Since the file was opened readonly, we have to initialize the jbd
	 * inode and quotas here and not rely on ->open() doing it.  This must
	 * be done before evicting the inline data.
	 */

	err = ext4_inode_attach_jinode(inode);
	if (err)
		return err;

	err = dquot_initialize(inode);
	if (err)
		return err;

	err = ext4_convert_inline_data(inode);
	if (err)
		return err;

	if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
		ext4_warning_inode(inode,
				   "verity is only allowed on extent-based files");
		return -EOPNOTSUPP;
	}

	/*
	 * ext4 uses the last allocated block to find the verity descriptor, so
	 * we must remove any other blocks past EOF which might confuse things.
	 */
	err = ext4_truncate(inode);
	if (err)
		return err;

	handle = ext4_journal_start(inode, EXT4_HT_INODE, credits);
	if (IS_ERR(handle))
		return PTR_ERR(handle);

	err = ext4_orphan_add(handle, inode);
	if (err == 0)
		ext4_set_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);

	ext4_journal_stop(handle);
	return err;
}

/*
 * ext4 stores the verity descriptor beginning on the next filesystem block
 * boundary after the Merkle tree.  Then, the descriptor size is stored in the
 * last 4 bytes of the last allocated filesystem block --- which is either the
 * block in which the descriptor ends, or the next block after that if there
 * weren't at least 4 bytes remaining.
 *
 * We can't simply store the descriptor in an xattr because it *must* be
 * encrypted when ext4 encryption is used, but ext4 encryption doesn't encrypt
 * xattrs.  Also, if the descriptor includes a large signature blob it may be
 * too large to store in an xattr without the EA_INODE feature.
 */
static int ext4_write_verity_descriptor(struct inode *inode, const void *desc,
					size_t desc_size, u64 merkle_tree_size)
{
	const u64 desc_pos = round_up(ext4_verity_metadata_pos(inode) +
				      merkle_tree_size, i_blocksize(inode));
	const u64 desc_end = desc_pos + desc_size;
	const __le32 desc_size_disk = cpu_to_le32(desc_size);
	const u64 desc_size_pos = round_up(desc_end + sizeof(desc_size_disk),
					   i_blocksize(inode)) -
				  sizeof(desc_size_disk);
	int err;

	err = pagecache_write(inode, desc, desc_size, desc_pos);
	if (err)
		return err;

	return pagecache_write(inode, &desc_size_disk, sizeof(desc_size_disk),
			       desc_size_pos);
}

static int ext4_end_enable_verity(struct file *filp, const void *desc,
				  size_t desc_size, u64 merkle_tree_size)
{
	struct inode *inode = file_inode(filp);
	const int credits = 2; /* superblock and inode for ext4_orphan_del() */
	handle_t *handle;
	struct ext4_iloc iloc;
	int err = 0;

	/*
	 * If an error already occurred (which fs/verity/ signals by passing
	 * desc == NULL), then only clean-up is needed.
	 */
	if (desc == NULL)
		goto cleanup;

	/* Append the verity descriptor. */
	err = ext4_write_verity_descriptor(inode, desc, desc_size,
					   merkle_tree_size);
	if (err)
		goto cleanup;

	/*
	 * Write all pages (both data and verity metadata).  Note that this must
	 * happen before clearing EXT4_STATE_VERITY_IN_PROGRESS; otherwise pages
	 * beyond i_size won't be written properly.  For crash consistency, this
	 * also must happen before the verity inode flag gets persisted.
	 */
	err = filemap_write_and_wait(inode->i_mapping);
	if (err)
		goto cleanup;

	/*
	 * Finally, set the verity inode flag and remove the inode from the
	 * orphan list (in a single transaction).
	 */

	handle = ext4_journal_start(inode, EXT4_HT_INODE, credits);
	if (IS_ERR(handle)) {
		err = PTR_ERR(handle);
		goto cleanup;
	}

	err = ext4_orphan_del(handle, inode);
	if (err)
		goto stop_and_cleanup;

	err = ext4_reserve_inode_write(handle, inode, &iloc);
	if (err)
		goto stop_and_cleanup;

	ext4_set_inode_flag(inode, EXT4_INODE_VERITY);
	ext4_set_inode_flags(inode, false);
	err = ext4_mark_iloc_dirty(handle, inode, &iloc);
	if (err)
		goto stop_and_cleanup;

	ext4_journal_stop(handle);

	ext4_clear_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
	return 0;

stop_and_cleanup:
	ext4_journal_stop(handle);
cleanup:
	/*
	 * Verity failed to be enabled, so clean up by truncating any verity
	 * metadata that was written beyond i_size (both from cache and from
	 * disk), removing the inode from the orphan list (if it wasn't done
	 * already), and clearing EXT4_STATE_VERITY_IN_PROGRESS.
	 */
	truncate_inode_pages(inode->i_mapping, inode->i_size);
	ext4_truncate(inode);
	ext4_orphan_del(NULL, inode);
	ext4_clear_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
	return err;
}

static int ext4_get_verity_descriptor_location(struct inode *inode,
					       size_t *desc_size_ret,
					       u64 *desc_pos_ret)
{
	struct ext4_ext_path *path;
	struct ext4_extent *last_extent;
	u32 end_lblk;
	u64 desc_size_pos;
	__le32 desc_size_disk;
	u32 desc_size;
	u64 desc_pos;
	int err;

	/*
	 * Descriptor size is in last 4 bytes of last allocated block.
	 * See ext4_write_verity_descriptor().
	 */

	if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
		EXT4_ERROR_INODE(inode, "verity file doesn't use extents");
		return -EFSCORRUPTED;
	}

	path = ext4_find_extent(inode, EXT_MAX_BLOCKS - 1, NULL, 0);
	if (IS_ERR(path))
		return PTR_ERR(path);

	last_extent = path[path->p_depth].p_ext;
	if (!last_extent) {
		EXT4_ERROR_INODE(inode, "verity file has no extents");
		ext4_free_ext_path(path);
		return -EFSCORRUPTED;
	}

	end_lblk = le32_to_cpu(last_extent->ee_block) +
		   ext4_ext_get_actual_len(last_extent);
	desc_size_pos = (u64)end_lblk << inode->i_blkbits;
	ext4_free_ext_path(path);

	if (desc_size_pos < sizeof(desc_size_disk))
		goto bad;
	desc_size_pos -= sizeof(desc_size_disk);

	err = pagecache_read(inode, &desc_size_disk, sizeof(desc_size_disk),
			     desc_size_pos);
	if (err)
		return err;
	desc_size = le32_to_cpu(desc_size_disk);

	/*
	 * The descriptor is stored just before the desc_size_disk, but starting
	 * on a filesystem block boundary.
	 */

	if (desc_size > INT_MAX || desc_size > desc_size_pos)
		goto bad;

	desc_pos = round_down(desc_size_pos - desc_size, i_blocksize(inode));
	if (desc_pos < ext4_verity_metadata_pos(inode))
		goto bad;

	*desc_size_ret = desc_size;
	*desc_pos_ret = desc_pos;
	return 0;

bad:
	EXT4_ERROR_INODE(inode, "verity file corrupted; can't find descriptor");
	return -EFSCORRUPTED;
}

static int ext4_get_verity_descriptor(struct inode *inode, void *buf,
				      size_t buf_size)
{
	size_t desc_size = 0;
	u64 desc_pos = 0;
	int err;

	err = ext4_get_verity_descriptor_location(inode, &desc_size, &desc_pos);
	if (err)
		return err;

	if (buf_size) {
		if (desc_size > buf_size)
			return -ERANGE;
		err = pagecache_read(inode, buf, desc_size, desc_pos);
		if (err)
			return err;
	}
	return desc_size;
}

static struct page *ext4_read_merkle_tree_page(struct inode *inode,
					       pgoff_t index,
					       unsigned long num_ra_pages)
{
	struct folio *folio;

	index += ext4_verity_metadata_pos(inode) >> PAGE_SHIFT;

	folio = __filemap_get_folio(inode->i_mapping, index, FGP_ACCESSED, 0);
	if (IS_ERR(folio) || !folio_test_uptodate(folio)) {
		DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);

		if (!IS_ERR(folio))
			folio_put(folio);
		else if (num_ra_pages > 1)
			page_cache_ra_unbounded(&ractl, num_ra_pages, 0);
		folio = read_mapping_folio(inode->i_mapping, index, NULL);
		if (IS_ERR(folio))
			return ERR_CAST(folio);
	}
	return folio_file_page(folio, index);
}

static int ext4_write_merkle_tree_block(struct inode *inode, const void *buf,
					u64 pos, unsigned int size)
{
	pos += ext4_verity_metadata_pos(inode);

	return pagecache_write(inode, buf, size, pos);
}

const struct fsverity_operations ext4_verityops = {
	.begin_enable_verity	= ext4_begin_enable_verity,
	.end_enable_verity	= ext4_end_enable_verity,
	.get_verity_descriptor	= ext4_get_verity_descriptor,
	.read_merkle_tree_page	= ext4_read_merkle_tree_page,
	.write_merkle_tree_block = ext4_write_merkle_tree_block,
};
Commit	Line	Data
c93d8f88 EB	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* fs/ext4/verity.c: fs-verity support for ext4
	4	*
	5	* Copyright 2019 Google LLC
	6	*/
	7
	8	/*
	9	* Implementation of fsverity_operations for ext4.
	10	*
	11	* ext4 stores the verity metadata (Merkle tree and fsverity_descriptor) past
	12	* the end of the file, starting at the first 64K boundary beyond i_size. This
	13	* approach works because (a) verity files are readonly, and (b) pages fully
	14	* beyond i_size aren't visible to userspace but can be read/written internally
	15	* by ext4 with only some relatively small changes to ext4. This approach
	16	* avoids having to depend on the EA_INODE feature and on rearchitecturing
	17	* ext4's xattr support to support paging multi-gigabyte xattrs into memory, and
	18	* to support encrypting xattrs. Note that the verity metadata must be
	19	* encrypted when the file is, since it contains hashes of the plaintext data.
	20	*
	21	* Using a 64K boundary rather than a 4K one keeps things ready for
	22	* architectures with 64K pages, and it doesn't necessarily waste space on-disk
	23	* since there can be a hole between i_size and the start of the Merkle tree.
	24	*/
	25
	26	#include <linux/quotaops.h>
	27
	28	#include "ext4.h"
	29	#include "ext4_extents.h"
	30	#include "ext4_jbd2.h"
	31
	32	static inline loff_t ext4_verity_metadata_pos(const struct inode *inode)
	33	{
	34	return round_up(inode->i_size, 65536);
	35	}
	36
	37	/*
	38	* Read some verity metadata from the inode. __vfs_read() can't be used because
	39	* we need to read beyond i_size.
	40	*/
	41	static int pagecache_read(struct inode inode, void buf, size_t count,
	42	loff_t pos)
	43	{
	44	while (count) {
b23fb762 MW	45	struct folio *folio;
b23fb762 MW	46	size_t n;
c93d8f88	47
b23fb762	48	folio = read_mapping_folio(inode->i_mapping, pos >> PAGE_SHIFT,
c93d8f88	49	NULL);
b23fb762 MW	50	if (IS_ERR(folio))
b23fb762 MW	51	return PTR_ERR(folio);
c93d8f88	52
b23fb762 MW	53	n = memcpy_from_file_folio(buf, folio, pos, count);
b23fb762 MW	54	folio_put(folio);
c93d8f88 EB	55
	56	buf += n;
	57	pos += n;
	58	count -= n;
	59	}
	60	return 0;
	61	}
	62
	63	/*
	64	* Write some verity metadata to the inode for FS_IOC_ENABLE_VERITY.
	65	* kernel_write() can't be used because the file descriptor is readonly.
	66	*/
	67	static int pagecache_write(struct inode inode, const void buf, size_t count,
	68	loff_t pos)
	69	{
1b0aa444 MWO	70	struct address_space *mapping = inode->i_mapping;
	71	const struct address_space_operations *aops = mapping->a_ops;
	72
c93d8f88 EB	73	if (pos + count > inode->i_sb->s_maxbytes)
	74	return -EFBIG;
	75
	76	while (count) {
	77	size_t n = min_t(size_t, count,
	78	PAGE_SIZE - offset_in_page(pos));
	79	struct page *page;
956510c0	80	void *fsdata = NULL;
c93d8f88 EB	81	int res;
c93d8f88 EB	82
1b0aa444	83	res = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);
c93d8f88 EB	84	if (res)
	85	return res;
	86
bd256fda	87	memcpy_to_page(page, offset_in_page(pos), buf, n);
c93d8f88	88
1b0aa444	89	res = aops->write_end(NULL, mapping, pos, n, n, page, fsdata);
c93d8f88 EB	90	if (res < 0)
	91	return res;
	92	if (res != n)
	93	return -EIO;
	94
	95	buf += n;
	96	pos += n;
	97	count -= n;
	98	}
	99	return 0;
	100	}
	101
	102	static int ext4_begin_enable_verity(struct file *filp)
	103	{
	104	struct inode *inode = file_inode(filp);
	105	const int credits = 2; /* superblock and inode for ext4_orphan_add() */
	106	handle_t *handle;
	107	int err;
	108
b383a73f	109	if (IS_DAX(inode) \|\| ext4_test_inode_flag(inode, EXT4_INODE_DAX))
6c0d077f IW	110	return -EINVAL;
6c0d077f IW	111
c93d8f88 EB	112	if (ext4_verity_in_progress(inode))
	113	return -EBUSY;
	114
	115	/*
	116	* Since the file was opened readonly, we have to initialize the jbd
	117	* inode and quotas here and not rely on ->open() doing it. This must
	118	* be done before evicting the inline data.
	119	*/
	120
	121	err = ext4_inode_attach_jinode(inode);
	122	if (err)
	123	return err;
	124
	125	err = dquot_initialize(inode);
	126	if (err)
	127	return err;
	128
	129	err = ext4_convert_inline_data(inode);
	130	if (err)
	131	return err;
	132
	133	if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
	134	ext4_warning_inode(inode,
	135	"verity is only allowed on extent-based files");
	136	return -EOPNOTSUPP;
	137	}
	138
	139	/*
	140	* ext4 uses the last allocated block to find the verity descriptor, so
	141	* we must remove any other blocks past EOF which might confuse things.
	142	*/
	143	err = ext4_truncate(inode);
	144	if (err)
	145	return err;
	146
	147	handle = ext4_journal_start(inode, EXT4_HT_INODE, credits);
	148	if (IS_ERR(handle))
	149	return PTR_ERR(handle);
	150
	151	err = ext4_orphan_add(handle, inode);
	152	if (err == 0)
	153	ext4_set_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
	154
	155	ext4_journal_stop(handle);
	156	return err;
	157	}
	158
	159	/*
	160	* ext4 stores the verity descriptor beginning on the next filesystem block
	161	* boundary after the Merkle tree. Then, the descriptor size is stored in the
	162	* last 4 bytes of the last allocated filesystem block --- which is either the
	163	* block in which the descriptor ends, or the next block after that if there
	164	* weren't at least 4 bytes remaining.
	165	*
	166	* We can't simply store the descriptor in an xattr because it must be
	167	* encrypted when ext4 encryption is used, but ext4 encryption doesn't encrypt
	168	* xattrs. Also, if the descriptor includes a large signature blob it may be
	169	* too large to store in an xattr without the EA_INODE feature.
	170	*/
	171	static int ext4_write_verity_descriptor(struct inode inode, const void desc,
	172	size_t desc_size, u64 merkle_tree_size)
	173	{
	174	const u64 desc_pos = round_up(ext4_verity_metadata_pos(inode) +
	175	merkle_tree_size, i_blocksize(inode));
176	const u64 desc_end = desc_pos + desc_size;
177	const __le32 desc_size_disk = cpu_to_le32(desc_size);
178	const u64 desc_size_pos = round_up(desc_end + sizeof(desc_size_disk),
179	i_blocksize(inode)) -
180	sizeof(desc_size_disk);
181	int err;
182
183	err = pagecache_write(inode, desc, desc_size, desc_pos);
184	if (err)
185	return err;
186
187	return pagecache_write(inode, &desc_size_disk, sizeof(desc_size_disk),
188	desc_size_pos);
189	}
190
191	static int ext4_end_enable_verity(struct file filp, const void desc,
192	size_t desc_size, u64 merkle_tree_size)
193	{
194	struct inode *inode = file_inode(filp);
195	const int credits = 2; /* superblock and inode for ext4_orphan_del() */
196	handle_t *handle;
f053cf7a	197	struct ext4_iloc iloc;
c93d8f88	198	int err = 0;
c93d8f88	199
f053cf7a EB	200	/*
	201	* If an error already occurred (which fs/verity/ signals by passing
	202	* desc == NULL), then only clean-up is needed.
	203	*/
	204	if (desc == NULL)
	205	goto cleanup;
c93d8f88	206
f053cf7a EB	207	/* Append the verity descriptor. */
	208	err = ext4_write_verity_descriptor(inode, desc, desc_size,
	209	merkle_tree_size);
	210	if (err)
	211	goto cleanup;
c93d8f88 EB	212
c93d8f88 EB	213	/*
f053cf7a EB	214	* Write all pages (both data and verity metadata). Note that this must
	215	* happen before clearing EXT4_STATE_VERITY_IN_PROGRESS; otherwise pages
	216	* beyond i_size won't be written properly. For crash consistency, this
	217	* also must happen before the verity inode flag gets persisted.
c93d8f88	218	*/
f053cf7a EB	219	err = filemap_write_and_wait(inode->i_mapping);
	220	if (err)
	221	goto cleanup;
c93d8f88	222
f053cf7a EB	223	/*
	224	* Finally, set the verity inode flag and remove the inode from the
	225	* orphan list (in a single transaction).
	226	*/
c93d8f88 EB	227
	228	handle = ext4_journal_start(inode, EXT4_HT_INODE, credits);
	229	if (IS_ERR(handle)) {
f053cf7a EB	230	err = PTR_ERR(handle);
f053cf7a EB	231	goto cleanup;
c93d8f88 EB	232	}
c93d8f88 EB	233
f053cf7a EB	234	err = ext4_orphan_del(handle, inode);
	235	if (err)
	236	goto stop_and_cleanup;
	237
	238	err = ext4_reserve_inode_write(handle, inode, &iloc);
	239	if (err)
	240	goto stop_and_cleanup;
c93d8f88	241
f053cf7a EB	242	ext4_set_inode_flag(inode, EXT4_INODE_VERITY);
	243	ext4_set_inode_flags(inode, false);
	244	err = ext4_mark_iloc_dirty(handle, inode, &iloc);
	245	if (err)
	246	goto stop_and_cleanup;
c93d8f88	247
c93d8f88	248	ext4_journal_stop(handle);
f053cf7a EB	249
	250	ext4_clear_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
	251	return 0;
	252
	253	stop_and_cleanup:
	254	ext4_journal_stop(handle);
	255	cleanup:
	256	/*
	257	* Verity failed to be enabled, so clean up by truncating any verity
	258	* metadata that was written beyond i_size (both from cache and from
	259	* disk), removing the inode from the orphan list (if it wasn't done
	260	* already), and clearing EXT4_STATE_VERITY_IN_PROGRESS.
	261	*/
	262	truncate_inode_pages(inode->i_mapping, inode->i_size);
	263	ext4_truncate(inode);
	264	ext4_orphan_del(NULL, inode);
	265	ext4_clear_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
	266	return err;
c93d8f88 EB	267	}
	268
	269	static int ext4_get_verity_descriptor_location(struct inode *inode,
	270	size_t *desc_size_ret,
	271	u64 *desc_pos_ret)
	272	{
	273	struct ext4_ext_path *path;
	274	struct ext4_extent *last_extent;
	275	u32 end_lblk;
	276	u64 desc_size_pos;
	277	__le32 desc_size_disk;
	278	u32 desc_size;
	279	u64 desc_pos;
	280	int err;
	281
	282	/*
	283	* Descriptor size is in last 4 bytes of last allocated block.
	284	* See ext4_write_verity_descriptor().
	285	*/
	286
	287	if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
	288	EXT4_ERROR_INODE(inode, "verity file doesn't use extents");
	289	return -EFSCORRUPTED;
	290	}
	291
	292	path = ext4_find_extent(inode, EXT_MAX_BLOCKS - 1, NULL, 0);
	293	if (IS_ERR(path))
	294	return PTR_ERR(path);
	295
	296	last_extent = path[path->p_depth].p_ext;
	297	if (!last_extent) {
	298	EXT4_ERROR_INODE(inode, "verity file has no extents");
7ff5fdda	299	ext4_free_ext_path(path);
c93d8f88 EB	300	return -EFSCORRUPTED;
	301	}
	302
	303	end_lblk = le32_to_cpu(last_extent->ee_block) +
	304	ext4_ext_get_actual_len(last_extent);
	305	desc_size_pos = (u64)end_lblk << inode->i_blkbits;
7ff5fdda	306	ext4_free_ext_path(path);
c93d8f88 EB	307
	308	if (desc_size_pos < sizeof(desc_size_disk))
	309	goto bad;
	310	desc_size_pos -= sizeof(desc_size_disk);
	311
	312	err = pagecache_read(inode, &desc_size_disk, sizeof(desc_size_disk),
	313	desc_size_pos);
	314	if (err)
	315	return err;
	316	desc_size = le32_to_cpu(desc_size_disk);
	317
	318	/*
	319	* The descriptor is stored just before the desc_size_disk, but starting
	320	* on a filesystem block boundary.
	321	*/
	322
	323	if (desc_size > INT_MAX \|\| desc_size > desc_size_pos)
	324	goto bad;
	325
	326	desc_pos = round_down(desc_size_pos - desc_size, i_blocksize(inode));
	327	if (desc_pos < ext4_verity_metadata_pos(inode))
	328	goto bad;
	329
	330	*desc_size_ret = desc_size;
	331	*desc_pos_ret = desc_pos;
	332	return 0;
	333
	334	bad:
	335	EXT4_ERROR_INODE(inode, "verity file corrupted; can't find descriptor");
	336	return -EFSCORRUPTED;
	337	}
	338
	339	static int ext4_get_verity_descriptor(struct inode inode, void buf,
	340	size_t buf_size)
	341	{
	342	size_t desc_size = 0;
	343	u64 desc_pos = 0;
	344	int err;
	345
	346	err = ext4_get_verity_descriptor_location(inode, &desc_size, &desc_pos);
	347	if (err)
	348	return err;
	349
	350	if (buf_size) {
	351	if (desc_size > buf_size)
	352	return -ERANGE;
	353	err = pagecache_read(inode, buf, desc_size, desc_pos);
	354	if (err)
	355	return err;
	356	}
	357	return desc_size;
	358	}
	359
	360	static struct page ext4_read_merkle_tree_page(struct inode inode,
fd39073d EB	361	pgoff_t index,
fd39073d EB	362	unsigned long num_ra_pages)
c93d8f88	363	{
e9ebecf2	364	struct folio *folio;
fd39073d	365
c93d8f88 EB	366	index += ext4_verity_metadata_pos(inode) >> PAGE_SHIFT;
c93d8f88 EB	367
e9ebecf2	368	folio = __filemap_get_folio(inode->i_mapping, index, FGP_ACCESSED, 0);
7fa8a8ee	369	if (IS_ERR(folio) \|\| !folio_test_uptodate(folio)) {
4fa0e3ff MWO	370	DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
4fa0e3ff MWO	371
7fa8a8ee	372	if (!IS_ERR(folio))
e9ebecf2	373	folio_put(folio);
fd39073d	374	else if (num_ra_pages > 1)
73bb49da	375	page_cache_ra_unbounded(&ractl, num_ra_pages, 0);
e9ebecf2	376	folio = read_mapping_folio(inode->i_mapping, index, NULL);
7fa8a8ee LT	377	if (IS_ERR(folio))
7fa8a8ee LT	378	return ERR_CAST(folio);
fd39073d	379	}
e9ebecf2	380	return folio_file_page(folio, index);
c93d8f88 EB	381	}
	382
	383	static int ext4_write_merkle_tree_block(struct inode inode, const void buf,
72ea15f0	384	u64 pos, unsigned int size)
c93d8f88	385	{
72ea15f0	386	pos += ext4_verity_metadata_pos(inode);
c93d8f88	387
72ea15f0	388	return pagecache_write(inode, buf, size, pos);
c93d8f88 EB	389	}
	390
	391	const struct fsverity_operations ext4_verityops = {
	392	.begin_enable_verity = ext4_begin_enable_verity,
	393	.end_enable_verity = ext4_end_enable_verity,
	394	.get_verity_descriptor = ext4_get_verity_descriptor,
	395	.read_merkle_tree_page = ext4_read_merkle_tree_page,
	396	.write_merkle_tree_block = ext4_write_merkle_tree_block,
	397	};