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Re: [dm-devel] [PATCH] dm: remake of the verity target




On Tue, 20 Mar 2012, Mandeep Singh Baines wrote:

> Hi Mikulas,
> 
> Can you please resend this patch with a proper commit message.
> We'd really like to see this merged. Alasdair, other than that,
> what work is remaining for verity to be merged?
> 
> Regards,
> Mandeep

Hi

I'm sending this new version of dm-verity to be merged. I've made some 
last changes in the format, hopefully no more changes will be needed. This 
changes make it incompatible with the original Google code (but the 
original code can be trivially changed to support these modifications).

Changes:

* Salt is hashed before the block (it used to be hased after). The reason 
is that if random salt is hashed before the block, it makes the process 
resilient to hash function collisions - so you can safely use md5, even if 
there's a collision attach for it.

* Argument line was simplified, there are no optional arguments.

* There is new argument specifying the size of the data device.

Mikulas

---

Remake of the google dm-verity patch.

Signed-off-by: Mikulas Patocka <mpatocka redhat com>

---
 drivers/md/Kconfig     |   17 
 drivers/md/Makefile    |    1 
 drivers/md/dm-verity.c |  849 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 867 insertions(+)

Index: linux-3.3-fast/drivers/md/Kconfig
===================================================================
--- linux-3.3-fast.orig/drivers/md/Kconfig	2012-03-19 13:46:54.000000000 +0100
+++ linux-3.3-fast/drivers/md/Kconfig	2012-03-19 13:46:55.000000000 +0100
@@ -404,4 +404,21 @@ config DM_VERITY2
 
           If unsure, say N.
 
+config DM_VERITY
+	tristate "Verity target support"
+	depends on BLK_DEV_DM
+	select CRYPTO
+	select CRYPTO_HASH
+	select DM_BUFIO
+	---help---
+	  This device-mapper target allows you to create a device that
+	  transparently integrity checks the data on it. You'll need to
+	  activate the digests you're going to use in the cryptoapi
+	  configuration.
+
+	  To compile this code as a module, choose M here: the module will
+	  be called dm-verity.
+
+	  If unsure, say N.
+
 endif # MD
Index: linux-3.3-fast/drivers/md/Makefile
===================================================================
--- linux-3.3-fast.orig/drivers/md/Makefile	2012-03-19 13:46:54.000000000 +0100
+++ linux-3.3-fast/drivers/md/Makefile	2012-03-19 13:46:55.000000000 +0100
@@ -29,6 +29,7 @@ obj-$(CONFIG_MD_FAULTY)		+= faulty.o
 obj-$(CONFIG_BLK_DEV_MD)	+= md-mod.o
 obj-$(CONFIG_BLK_DEV_DM)	+= dm-mod.o
 obj-$(CONFIG_DM_BUFIO)		+= dm-bufio.o
+obj-$(CONFIG_DM_VERITY)		+= dm-verity.o
 obj-$(CONFIG_DM_CRYPT)		+= dm-crypt.o
 obj-$(CONFIG_DM_DELAY)		+= dm-delay.o
 obj-$(CONFIG_DM_FLAKEY)		+= dm-flakey.o
Index: linux-3.3-fast/drivers/md/dm-verity.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-3.3-fast/drivers/md/dm-verity.c	2012-03-20 22:03:53.000000000 +0100
@@ -0,0 +1,849 @@
+/*
+ * Copyright (C) 2012 Red Hat, Inc.
+ *
+ * Author: Mikulas Patocka <mpatocka redhat com>
+ *
+ * Based on Chromium dm-verity driver (C) 2011 The Chromium OS Authors
+ *
+ * This file is released under the GPLv2.
+ *
+ * Device mapper target parameters:
+ *	<version>		0
+ *	<data device>
+ *	<hash device>
+ *	<data block size>
+ *	<hash block size>
+ *	<the number of data blocks>
+ *	<hash start block>
+ *	<algorithm>
+ *	<digest>
+ *	<salt>			(hex bytes or "-" for no salt)
+ *
+ * In the file "/sys/module/dm_verity/parameters/prefetch_cluster" you can set
+ * default prefetch value. Data are read in "prefetch_cluster" chunks from the
+ * hash device. Prefetch cluster greatly improves performance when data and hash
+ * are on the same disk on different partitions on devices with poor random
+ * access behavior.
+ */
+
+#include <linux/module.h>
+#include <linux/device-mapper.h>
+#include <crypto/hash.h>
+#include "dm-bufio.h"
+
+#define DM_MSG_PREFIX			"verity"
+
+#define DM_VERITY_IO_VEC_INLINE		16
+#define DM_VERITY_MEMPOOL_SIZE		4
+#define DM_VERITY_DEFAULT_PREFETCH_SIZE	262144
+
+#define DM_VERITY_MAX_LEVELS		63
+
+static unsigned prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE;
+
+module_param_named(prefetch_cluster, prefetch_cluster, uint, S_IRUGO | S_IWUSR);
+
+struct dm_verity {
+	struct dm_dev *data_dev;
+	struct dm_dev *hash_dev;
+	struct dm_target *ti;
+	struct dm_bufio_client *bufio;
+	char *alg_name;
+	struct crypto_shash *tfm;
+	u8 *root_digest;	/* digest of the root block */
+	u8 *salt;		/* salt, its size is salt_size */
+	unsigned salt_size;
+	sector_t data_start;	/* data offset in 512-byte sectors */
+	sector_t hash_start;	/* hash start in blocks */
+	sector_t data_blocks;	/* the number of data blocks */
+	sector_t hash_blocks;	/* the number of hash blocks */
+	unsigned char data_dev_block_bits;	/* log2(data blocksize) */
+	unsigned char hash_dev_block_bits;	/* log2(hash blocksize) */
+	unsigned char hash_per_block_bits;	/* log2(hashes in hash block) */
+	unsigned char levels;	/* the number of tree levels */
+	unsigned digest_size;	/* digest size for the current hash algorithm */
+	unsigned shash_descsize;/* the size of temporary space for crypto */
+
+	mempool_t *io_mempool;	/* mempool of struct dm_verity_io */
+	mempool_t *vec_mempool;	/* mempool of bio vector */
+
+	struct workqueue_struct *verify_wq;
+
+	/* starting blocks for each tree level. 0 is the lowest level. */
+	sector_t hash_level_block[DM_VERITY_MAX_LEVELS];
+};
+
+struct dm_verity_io {
+	struct dm_verity *v;
+	struct bio *bio;
+
+	/* original values of bio->bi_end_io and bio->bi_private */
+	bio_end_io_t *orig_bi_end_io;
+	void *orig_bi_private;
+
+	sector_t block;
+	unsigned n_blocks;
+
+	/* saved bio vector */
+	struct bio_vec *io_vec;
+	unsigned io_vec_size;
+
+	struct work_struct work;
+
+	/* a space for short vectors; longer vectors are allocated separately */
+	struct bio_vec io_vec_inline[DM_VERITY_IO_VEC_INLINE];
+
+	/* variable-size fields, accessible with functions
+		io_hash_desc, io_real_digest, io_want_digest */
+	/* u8 hash_desc[v->shash_descsize]; */
+	/* u8 real_digest[v->digest_size]; */
+	/* u8 want_digest[v->digest_size]; */
+};
+
+static struct shash_desc *io_hash_desc(struct dm_verity *v, struct dm_verity_io *io)
+{
+	return (struct shash_desc *)(io + 1);
+}
+
+static u8 *io_real_digest(struct dm_verity *v, struct dm_verity_io *io)
+{
+	return (u8 *)(io + 1) + v->shash_descsize;
+}
+
+static u8 *io_want_digest(struct dm_verity *v, struct dm_verity_io *io)
+{
+	return (u8 *)(io + 1) + v->shash_descsize + v->digest_size;
+}
+
+/*
+ * Auxiliary structure appended to each dm-bufio buffer. If the value
+ * hash_verified is nonzero, hash of the block has been verified.
+ *
+ * The variable hash_verified is set to 0 when allocating the buffer, then
+ * it can be changed to 1 and it is never reset to 0 again.
+ *
+ * There is no lock around this value, a race condition can at worst cause
+ * that multiple processes verify the hash of the same buffer simultaneously
+ * and write 1 to hash_verified simultaneously.
+ * This condition is harmless, so we don't need locking.
+ */
+struct buffer_aux {
+	int hash_verified;
+};
+
+/*
+ * Initialize struct buffer_aux for a freshly created buffer.
+ */
+static void dm_bufio_alloc_callback(struct dm_buffer *buf)
+{
+	struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
+	aux->hash_verified = 0;
+}
+
+/*
+ * Translate input sector number to the sector number on the target device.
+ */
+static sector_t verity_map_sector(struct dm_verity *v, sector_t bi_sector)
+{
+	return v->data_start + dm_target_offset(v->ti, bi_sector);
+}
+
+/*
+ * Return hash position of a specified block at a specified tree level
+ * (0 is the lowest level).
+ * The lowest "hash_per_block_bits"-bits of the result denote hash position
+ * inside a hash block. The remaining bits denote location of the hash block.
+ */
+static sector_t verity_position_at_level(struct dm_verity *v, sector_t block,
+					 int level)
+{
+	return block >> (level * v->hash_per_block_bits);
+}
+
+static void verity_hash_at_level(struct dm_verity *v, sector_t block, int level,
+				 sector_t *hash_block, unsigned *offset)
+{
+	sector_t position = verity_position_at_level(v, block, level);
+
+	*hash_block = v->hash_level_block[level] + (position >> v->hash_per_block_bits);
+	if (offset)
+		*offset = (position & ((1 << v->hash_per_block_bits) - 1)) << (v->hash_dev_block_bits - v->hash_per_block_bits);
+}
+
+/*
+ * Verify hash of a metadata block pertaining to the specified data block
+ * ("block" argument) at a specified level ("level" argument).
+ *
+ * On successful return, io_want_digest(v, io) contains the hash value for
+ * a lower tree level or for the data block (if we're at the lowest leve).
+ *
+ * If "skip_unverified" is true, unverified buffer is skipped an 1 is returned.
+ * If "skip_unverified" is false, unverified buffer is hashed and verified
+ * against current value of io_want_digest(v, io).
+ */
+static int verity_verify_level(struct dm_verity_io *io, sector_t block,
+			       int level, bool skip_unverified)
+{
+	struct dm_verity *v = io->v;
+	struct dm_buffer *buf;
+	struct buffer_aux *aux;
+	u8 *data;
+	int r;
+	sector_t hash_block;
+	unsigned offset;
+
+	verity_hash_at_level(v, block, level, &hash_block, &offset);
+
+	data = dm_bufio_read(v->bufio, hash_block, &buf);
+	if (unlikely(IS_ERR(data)))
+		return PTR_ERR(data);
+
+	aux = dm_bufio_get_aux_data(buf);
+
+	if (!aux->hash_verified) {
+		struct shash_desc *desc;
+		u8 *result;
+
+		if (skip_unverified) {
+			r = 1;
+			goto release_ret_r;
+		}
+
+		desc = io_hash_desc(v, io);
+		desc->tfm = v->tfm;
+		desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
+		r = crypto_shash_init(desc);
+		if (r < 0) {
+			DMERR("crypto_shash_init failed: %d", r);
+			goto release_ret_r;
+		}
+
+		r = crypto_shash_update(desc, v->salt, v->salt_size);
+		if (r < 0) {
+			DMERR("crypto_shash_update failed: %d", r);
+			goto release_ret_r;
+		}
+
+		r = crypto_shash_update(desc, data, 1 << v->hash_dev_block_bits);
+		if (r < 0) {
+			DMERR("crypto_shash_update failed: %d", r);
+			goto release_ret_r;
+		}
+
+		result = io_real_digest(v, io);
+		r = crypto_shash_final(desc, result);
+		if (r < 0) {
+			DMERR("crypto_shash_final failed: %d", r);
+			goto release_ret_r;
+		}
+		if (unlikely(memcmp(result, io_want_digest(v, io), v->digest_size))) {
+			DMERR_LIMIT("metadata block %llu is corrupted",
+				(unsigned long long)hash_block);
+			r = -EIO;
+			goto release_ret_r;
+		} else
+			aux->hash_verified = 1;
+	}
+
+	data += offset;
+
+	memcpy(io_want_digest(v, io), data, v->digest_size);
+
+	dm_bufio_release(buf);
+	return 0;
+
+release_ret_r:
+	dm_bufio_release(buf);
+	return r;
+}
+
+/*
+ * Verify one "dm_verity_io" structure.
+ */
+static int verity_verify_io(struct dm_verity_io *io)
+{
+	struct dm_verity *v = io->v;
+	unsigned b;
+	int i;
+	unsigned vector = 0, offset = 0;
+	for (b = 0; b < io->n_blocks; b++) {
+		struct shash_desc *desc;
+		u8 *result;
+		int r;
+		unsigned todo;
+
+		if (likely(v->levels)) {
+			/*
+			 * First, we try to get the requested hash for
+			 * the current block. If the hash block itself is
+			 * verified, zero is returned. If it isn't, this
+			 * function returns 0 and we fall back to whole
+			 * chain verification.
+			 */
+			int r = verity_verify_level(io, io->block + b, 0, true);
+			if (likely(!r))
+				goto test_block_hash;
+			if (r < 0)
+				return r;
+		}
+
+		memcpy(io_want_digest(v, io), v->root_digest, v->digest_size);
+
+		for (i = v->levels - 1; i >= 0; i--) {
+			int r = verity_verify_level(io, io->block + b, i, false);
+			if (unlikely(r))
+				return r;
+		}
+
+test_block_hash:
+		desc = io_hash_desc(v, io);
+		desc->tfm = v->tfm;
+		desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
+		r = crypto_shash_init(desc);
+		if (r < 0) {
+			DMERR("crypto_shash_init failed: %d", r);
+			return r;
+		}
+
+		r = crypto_shash_update(desc, v->salt, v->salt_size);
+		if (r < 0) {
+			DMERR("crypto_shash_update failed: %d", r);
+			return r;
+		}
+
+		todo = 1 << v->data_dev_block_bits;
+		do {
+			struct bio_vec *bv;
+			u8 *page;
+			unsigned len;
+
+			BUG_ON(vector >= io->io_vec_size);
+			bv = &io->io_vec[vector];
+			page = kmap_atomic(bv->bv_page, KM_USER0);
+			len = bv->bv_len - offset;
+			if (likely(len >= todo))
+				len = todo;
+			r = crypto_shash_update(desc,
+					page + bv->bv_offset + offset, len);
+			kunmap_atomic(page, KM_USER0);
+			if (r < 0) {
+				DMERR("crypto_shash_update failed: %d", r);
+				return r;
+			}
+			offset += len;
+			if (likely(offset == bv->bv_len)) {
+				offset = 0;
+				vector++;
+			}
+			todo -= len;
+		} while (todo);
+
+		result = io_real_digest(v, io);
+		r = crypto_shash_final(desc, result);
+		if (r < 0) {
+			DMERR("crypto_shash_final failed: %d", r);
+			return r;
+		}
+		if (unlikely(memcmp(result, io_want_digest(v, io), v->digest_size))) {
+			DMERR_LIMIT("data block %llu is corrupted",
+				(unsigned long long)(io->block + b));
+			return -EIO;
+		}
+	}
+	BUG_ON(vector != io->io_vec_size);
+	BUG_ON(offset);
+	return 0;
+}
+
+/*
+ * End one "io" structure with a given error.
+ */
+static void verity_finish_io(struct dm_verity_io *io, int error)
+{
+	struct bio *bio = io->bio;
+	struct dm_verity *v = io->v;
+
+	bio->bi_end_io = io->orig_bi_end_io;
+	bio->bi_private = io->orig_bi_private;
+
+	if (io->io_vec != io->io_vec_inline)
+		mempool_free(io->io_vec, v->vec_mempool);
+	mempool_free(io, v->io_mempool);
+
+	bio_endio(bio, error);
+}
+
+static void verity_work(struct work_struct *w)
+{
+	struct dm_verity_io *io = container_of(w, struct dm_verity_io, work);
+
+	verity_finish_io(io, verity_verify_io(io));
+}
+
+static void verity_end_io(struct bio *bio, int error)
+{
+	struct dm_verity_io *io = bio->bi_private;
+	if (error) {
+		verity_finish_io(io, error);
+		return;
+	}
+
+	INIT_WORK(&io->work, verity_work);
+	queue_work(io->v->verify_wq, &io->work);
+}
+
+/*
+ * Prefetch buffers for the specified io.
+ * The root buffer is not prefetched, it is assumed that it will be cached
+ * all the time.
+ */
+static void verity_prefetch_io(struct dm_verity *v, struct dm_verity_io *io)
+{
+	int i;
+	for (i = v->levels - 2; i >= 0; i--) {
+		sector_t hash_block_start;
+		sector_t hash_block_end;
+		verity_hash_at_level(v, io->block, i, &hash_block_start, NULL);
+		verity_hash_at_level(v, io->block + io->n_blocks - 1, i, &hash_block_end, NULL);
+		if (!i) {
+			unsigned cluster = *(volatile unsigned *)&prefetch_cluster;
+			cluster >>= v->data_dev_block_bits;
+			if (unlikely(!cluster))
+				goto no_prefetch_cluster;
+			if (unlikely(cluster & (cluster - 1)))
+				cluster = 1 << (fls(cluster) - 1);
+
+			hash_block_start &= ~(sector_t)(cluster - 1);
+			hash_block_end |= cluster - 1;
+			if (unlikely(hash_block_end >= v->hash_blocks))
+				hash_block_end = v->hash_blocks - 1;
+		}
+no_prefetch_cluster:
+		dm_bufio_prefetch(v->bufio, hash_block_start,
+					hash_block_end - hash_block_start + 1);
+	}
+}
+
+/*
+ * Bio map function. It allocates dm_verity_io structure and bio vector and
+ * fills them. Then it issues prefetches and the I/O.
+ */
+static int verity_map(struct dm_target *ti, struct bio *bio,
+		      union map_info *map_context)
+{
+	struct dm_verity *v = ti->private;
+	struct dm_verity_io *io;
+
+	bio->bi_bdev = v->data_dev->bdev;
+	bio->bi_sector = verity_map_sector(v, bio->bi_sector);
+
+	if (((unsigned)bio->bi_sector | bio_sectors(bio)) &
+	    ((1 << (v->data_dev_block_bits - SECTOR_SHIFT)) - 1)) {
+		DMERR_LIMIT("unaligned io");
+		return -EIO;
+	}
+
+	if ((bio->bi_sector + bio_sectors(bio)) >>
+	    (v->data_dev_block_bits - SECTOR_SHIFT) > v->data_blocks) {
+		DMERR_LIMIT("io out of range");
+		return -EIO;
+	}
+
+	if (bio_data_dir(bio) == WRITE)
+		return -EIO;
+
+	io = mempool_alloc(v->io_mempool, GFP_NOIO);
+	io->v = v;
+	io->bio = bio;
+	io->orig_bi_end_io = bio->bi_end_io;
+	io->orig_bi_private = bio->bi_private;
+	io->block = bio->bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
+	io->n_blocks = bio->bi_size >> v->data_dev_block_bits;
+
+	bio->bi_end_io = verity_end_io;
+	bio->bi_private = io;
+	io->io_vec_size = bio->bi_vcnt - bio->bi_idx;
+	if (io->io_vec_size < DM_VERITY_IO_VEC_INLINE)
+		io->io_vec = io->io_vec_inline;
+	else
+		io->io_vec = mempool_alloc(v->vec_mempool, GFP_NOIO);
+	memcpy(io->io_vec, bio_iovec(bio),
+	       io->io_vec_size * sizeof(struct bio_vec));
+
+	verity_prefetch_io(v, io);
+
+	generic_make_request(bio);
+
+	return DM_MAPIO_SUBMITTED;
+}
+
+static int verity_status(struct dm_target *ti, status_type_t type,
+			 char *result, unsigned maxlen)
+{
+	struct dm_verity *v = ti->private;
+	unsigned sz = 0;
+	unsigned x;
+
+	switch (type) {
+	case STATUSTYPE_INFO:
+		result[0] = 0;
+		break;
+	case STATUSTYPE_TABLE:
+		DMEMIT("%u %s %s %u %u %llu %llu %s ",
+			0,
+			v->data_dev->name,
+			v->hash_dev->name,
+			1 << v->data_dev_block_bits,
+			1 << v->hash_dev_block_bits,
+			(unsigned long long)v->data_blocks,
+			(unsigned long long)v->hash_start,
+			v->alg_name
+			);
+		for (x = 0; x < v->digest_size; x++)
+			DMEMIT("%02x", v->root_digest[x]);
+		DMEMIT(" ");
+		if (!v->salt_size)
+			DMEMIT("-");
+		else
+			for (x = 0; x < v->salt_size; x++)
+				DMEMIT("%02x", v->salt[x]);
+		break;
+	}
+	return 0;
+}
+
+static int verity_ioctl(struct dm_target *ti, unsigned cmd,
+			unsigned long arg)
+{
+	struct dm_verity *v = ti->private;
+	int r = 0;
+
+	if (v->data_start ||
+	    ti->len != i_size_read(v->data_dev->bdev->bd_inode) >> SECTOR_SHIFT)
+		r = scsi_verify_blk_ioctl(NULL, cmd);
+
+	return r ? : __blkdev_driver_ioctl(v->data_dev->bdev, v->data_dev->mode,
+				     cmd, arg);
+}
+
+static int verity_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
+			struct bio_vec *biovec, int max_size)
+{
+	struct dm_verity *v = ti->private;
+	struct request_queue *q = bdev_get_queue(v->data_dev->bdev);
+
+	if (!q->merge_bvec_fn)
+		return max_size;
+
+	bvm->bi_bdev = v->data_dev->bdev;
+	bvm->bi_sector = verity_map_sector(v, bvm->bi_sector);
+
+	return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
+}
+
+static int verity_iterate_devices(struct dm_target *ti,
+				  iterate_devices_callout_fn fn, void *data)
+{
+	struct dm_verity *v = ti->private;
+	return fn(ti, v->data_dev, v->data_start, ti->len, data);
+}
+
+static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
+{
+	struct dm_verity *v = ti->private;
+
+	if (limits->logical_block_size < 1 << v->data_dev_block_bits)
+		limits->logical_block_size = 1 << v->data_dev_block_bits;
+	if (limits->physical_block_size < 1 << v->data_dev_block_bits)
+		limits->physical_block_size = 1 << v->data_dev_block_bits;
+	blk_limits_io_min(limits, limits->logical_block_size);
+}
+
+static void verity_dtr(struct dm_target *ti);
+
+static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
+{
+	struct dm_verity *v;
+	unsigned num;
+	unsigned long long num_ll;
+	int r;
+	int i;
+	sector_t hash_position;
+	char dummy;
+
+	v = kzalloc(sizeof(struct dm_verity), GFP_KERNEL);
+	if (!v) {
+		ti->error = "Cannot allocate verity structure";
+		return -ENOMEM;
+	}
+	ti->private = v;
+	v->ti = ti;
+
+	if ((dm_table_get_mode(ti->table) & ~FMODE_READ) != 0) {
+		ti->error = "Device must be readonly";
+		r = -EINVAL;
+		goto bad;
+	}
+
+	if (argc != 10) {
+		ti->error = "Invalid argument count";
+		r = -EINVAL;
+		goto bad;
+	}
+
+	if (sscanf(argv[0], "%d%c", &num, &dummy) != 1 ||
+	    num != 0) {
+		ti->error = "Invalid version";
+		r = -EINVAL;
+		goto bad;
+	}
+
+	r = dm_get_device(ti, argv[1], FMODE_READ, &v->data_dev);
+	if (r) {
+		ti->error = "Data device lookup failed";
+		goto bad;
+	}
+
+	r = dm_get_device(ti, argv[2], FMODE_READ, &v->hash_dev);
+	if (r) {
+		ti->error = "Data device lookup failed";
+		goto bad;
+	}
+
+	if (sscanf(argv[3], "%u%c", &num, &dummy) != 1 ||
+	    !num || (num & (num - 1)) ||
+	    num < bdev_logical_block_size(v->data_dev->bdev) ||
+	    num > PAGE_SIZE) {
+		ti->error = "Invalid data device block size";
+		r = -EINVAL;
+		goto bad;
+	}
+	v->data_dev_block_bits = ffs(num) - 1;
+
+	if (sscanf(argv[4], "%u%c", &num, &dummy) != 1 ||
+	    !num || (num & (num - 1)) ||
+	    num < bdev_logical_block_size(v->hash_dev->bdev) ||
+	    num > INT_MAX) {
+		ti->error = "Invalid hash device block size";
+		r = -EINVAL;
+		goto bad;
+	}
+	v->hash_dev_block_bits = ffs(num) - 1;
+
+	if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
+	    num_ll << (v->data_dev_block_bits - SECTOR_SHIFT) !=
+	    (sector_t)num_ll << (v->data_dev_block_bits - SECTOR_SHIFT)) {
+		ti->error = "Invalid data blocks";
+		r = -EINVAL;
+		goto bad;
+	}
+	v->data_blocks = num_ll;
+
+	if (ti->len > (v->data_blocks << (v->data_dev_block_bits - SECTOR_SHIFT))) {
+		ti->error = "Data device is too small";
+		r = -EINVAL;
+		goto bad;
+	}
+
+	if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||
+	    num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT) !=
+	    (sector_t)num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT)) {
+		ti->error = "Invalid hash start";
+		r = -EINVAL;
+		goto bad;
+	}
+	v->hash_start = num_ll;
+
+	v->alg_name = kstrdup(argv[7], GFP_KERNEL);
+	if (!v->alg_name) {
+		ti->error = "Cannot allocate algorithm name";
+		r = -ENOMEM;
+		goto bad;
+	}
+
+	v->tfm = crypto_alloc_shash(v->alg_name, 0, 0);
+	if (IS_ERR(v->tfm)) {
+		ti->error = "Cannot initialize hash function";
+		r = PTR_ERR(v->tfm);
+		v->tfm = NULL;
+		goto bad;
+	}
+	v->digest_size = crypto_shash_digestsize(v->tfm);
+	if ((1 << v->hash_dev_block_bits) < v->digest_size * 2) {
+		ti->error = "Digest size too big";
+		r = -EINVAL;
+		goto bad;
+	}
+	v->shash_descsize =
+		sizeof(struct shash_desc) + crypto_shash_descsize(v->tfm);
+
+	v->root_digest = kmalloc(v->digest_size, GFP_KERNEL);
+	if (!v->root_digest) {
+		ti->error = "Cannot allocate root digest";
+		r = -ENOMEM;
+		goto bad;
+	}
+	if (strlen(argv[8]) != v->digest_size * 2 ||
+	    hex2bin(v->root_digest, argv[8], v->digest_size)) {
+		ti->error = "Invalid root digest";
+		r = -EINVAL;
+		goto bad;
+	}
+
+	if (strcmp(argv[9], "-")) {
+		v->salt_size = strlen(argv[9]) / 2;
+		v->salt = kmalloc(v->salt_size, GFP_KERNEL);
+		if (!v->salt) {
+			ti->error = "Cannot allocate salt";
+			r = -ENOMEM;
+			goto bad;
+		}
+		if (strlen(argv[9]) != v->salt_size * 2 ||
+		    hex2bin(v->salt, argv[9], v->salt_size)) {
+			ti->error = "Invalid salt";
+			r = -EINVAL;
+			goto bad;
+		}
+	}
+
+	v->hash_per_block_bits =
+		fls((1 << v->hash_dev_block_bits) / v->digest_size) - 1;
+
+	v->levels = 0;
+	if (v->data_blocks)
+		while (v->hash_per_block_bits * v->levels < 64 &&
+		       (unsigned long long)(v->data_blocks - 1) >>
+		       (v->hash_per_block_bits * v->levels))
+			v->levels++;
+
+	if (v->levels > DM_VERITY_MAX_LEVELS) {
+		ti->error = "Too many tree levels";
+		r = -E2BIG;
+		goto bad;
+	}
+
+	hash_position = v->hash_start;
+	for (i = v->levels - 1; i >= 0; i--) {
+		sector_t s;
+		v->hash_level_block[i] = hash_position;
+		s = verity_position_at_level(v, v->data_blocks, i);
+		s = (s >> v->hash_per_block_bits) +
+		    !!(s & ((1 << v->hash_per_block_bits) - 1));
+		if (hash_position + s < hash_position) {
+			ti->error = "Hash device offset overflow";
+			r = -E2BIG;
+			goto bad;
+		}
+		hash_position += s;
+	}
+	v->hash_blocks = hash_position;
+
+	v->bufio = dm_bufio_client_create(v->hash_dev->bdev,
+		1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux),
+		dm_bufio_alloc_callback, NULL);
+	if (IS_ERR(v->bufio)) {
+		ti->error = "Cannot initialize dm-bufio";
+		r = PTR_ERR(v->bufio);
+		v->bufio = NULL;
+		goto bad;
+	}
+
+	if (dm_bufio_get_device_size(v->bufio) < v->hash_blocks) {
+		ti->error = "Hash device is too small";
+		r = -E2BIG;
+		goto bad;
+	}
+
+	v->io_mempool = mempool_create_kmalloc_pool(DM_VERITY_MEMPOOL_SIZE,
+	  sizeof(struct dm_verity_io) + v->shash_descsize + v->digest_size * 2);
+	if (!v->io_mempool) {
+		ti->error = "Cannot allocate io mempool";
+		r = -ENOMEM;
+		goto bad;
+	}
+
+	v->vec_mempool = mempool_create_kmalloc_pool(DM_VERITY_MEMPOOL_SIZE,
+					BIO_MAX_PAGES * sizeof(struct bio_vec));
+	if (!v->vec_mempool) {
+		ti->error = "Cannot allocate vector mempool";
+		r = -ENOMEM;
+		goto bad;
+	}
+
+	/*v->verify_wq = alloc_workqueue("verityd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM, 1);*/
+	/* WQ_UNBOUND greatly improves performance when running on ramdisk */
+	v->verify_wq = alloc_workqueue("verityd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND, num_online_cpus());
+	if (!v->verify_wq) {
+		ti->error = "Cannot allocate workqueue";
+		r = -ENOMEM;
+		goto bad;
+	}
+
+	return 0;
+
+bad:
+	verity_dtr(ti);
+	return r;
+}
+
+static void verity_dtr(struct dm_target *ti)
+{
+	struct dm_verity *v = ti->private;
+
+	if (v->verify_wq)
+		destroy_workqueue(v->verify_wq);
+	if (v->vec_mempool)
+		mempool_destroy(v->vec_mempool);
+	if (v->io_mempool)
+		mempool_destroy(v->io_mempool);
+	if (v->bufio)
+		dm_bufio_client_destroy(v->bufio);
+	kfree(v->salt);
+	kfree(v->root_digest);
+	if (v->tfm)
+		crypto_free_shash(v->tfm);
+	kfree(v->alg_name);
+	if (v->hash_dev)
+		dm_put_device(ti, v->hash_dev);
+	if (v->data_dev)
+		dm_put_device(ti, v->data_dev);
+	kfree(v);
+}
+
+static struct target_type verity_target = {
+	.name		= "verity",
+	.version	= {1, 0, 0},
+	.module		= THIS_MODULE,
+	.ctr		= verity_ctr,
+	.dtr		= verity_dtr,
+	.map		= verity_map,
+	.status		= verity_status,
+	.ioctl		= verity_ioctl,
+	.merge		= verity_merge,
+	.iterate_devices = verity_iterate_devices,
+	.io_hints	= verity_io_hints,
+};
+
+static int __init dm_verity_init(void)
+{
+	int r;
+	r = dm_register_target(&verity_target);
+	if (r < 0)
+		DMERR("register failed %d", r);
+	return r;
+}
+
+static void __exit dm_verity_exit(void)
+{
+	dm_unregister_target(&verity_target);
+}
+
+module_init(dm_verity_init);
+module_exit(dm_verity_exit);
+
+MODULE_AUTHOR("Mikulas Patocka <mpatocka redhat com>");
+MODULE_AUTHOR("Mandeep Baines <msb chromium org>");
+MODULE_AUTHOR("Will Drewry <wad chromium org>");
+MODULE_DESCRIPTION(DM_NAME " target for transparent disk integrity checking");
+MODULE_LICENSE("GPL");
+


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