// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2012 Red Hat, Inc.
 *
 * Author: Mikulas Patocka <mpatocka@redhat.com>
 *
 * Based on Chromium dm-verity driver (C) 2011 The Chromium OS Authors
 *
 * 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. Setting this greatly improves performance when data and hash
 * are on the same disk on different partitions on devices with poor random
 * access behavior.
 */

#include "dm-verity.h"
#include "dm-verity-fec.h"
#include "dm-verity-verify-sig.h"
#include "dm-audit.h"
#include <linux/hex.h>
#include <linux/module.h>
#include <linux/reboot.h>
#include <linux/string.h>
#include <linux/jump_label.h>
#include <linux/security.h>

#define DM_MSG_PREFIX                   "verity"

#define DM_VERITY_ENV_LENGTH            42
#define DM_VERITY_ENV_VAR_NAME          "DM_VERITY_ERR_BLOCK_NR"

#define DM_VERITY_DEFAULT_PREFETCH_SIZE 262144
#define DM_VERITY_USE_BH_DEFAULT_BYTES  8192

#define DM_VERITY_MAX_CORRUPTED_ERRS    100

#define DM_VERITY_OPT_LOGGING           "ignore_corruption"
#define DM_VERITY_OPT_RESTART           "restart_on_corruption"
#define DM_VERITY_OPT_PANIC             "panic_on_corruption"
#define DM_VERITY_OPT_ERROR_RESTART     "restart_on_error"
#define DM_VERITY_OPT_ERROR_PANIC       "panic_on_error"
#define DM_VERITY_OPT_IGN_ZEROES        "ignore_zero_blocks"
#define DM_VERITY_OPT_AT_MOST_ONCE      "check_at_most_once"
#define DM_VERITY_OPT_TASKLET_VERIFY    "try_verify_in_tasklet"

#define DM_VERITY_OPTS_MAX              (5 + DM_VERITY_OPTS_FEC + \
                                         DM_VERITY_ROOT_HASH_VERIFICATION_OPTS)

static unsigned int dm_verity_prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE;

module_param_named(prefetch_cluster, dm_verity_prefetch_cluster, uint, 0644);

static unsigned int dm_verity_use_bh_bytes[4] = {
        DM_VERITY_USE_BH_DEFAULT_BYTES, // IOPRIO_CLASS_NONE
        DM_VERITY_USE_BH_DEFAULT_BYTES, // IOPRIO_CLASS_RT
        DM_VERITY_USE_BH_DEFAULT_BYTES, // IOPRIO_CLASS_BE
        0                               // IOPRIO_CLASS_IDLE
};

module_param_array_named(use_bh_bytes, dm_verity_use_bh_bytes, uint, NULL, 0644);

static DEFINE_STATIC_KEY_FALSE(use_bh_wq_enabled);

struct dm_verity_prefetch_work {
        struct work_struct work;
        struct dm_verity *v;
        unsigned short ioprio;
        sector_t block;
        unsigned int n_blocks;
};

/*
 * 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 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);
}

int verity_hash(struct dm_verity *v, struct dm_verity_io *io,
                const u8 *data, size_t len, u8 *digest)
{
        struct shash_desc *desc;
        int r;

        if (likely(v->use_sha256_lib)) {
                struct sha256_ctx *ctx = &io->hash_ctx.sha256;

                /*
                 * Fast path using SHA-256 library.  This is enabled only for
                 * verity version 1, where the salt is at the beginning.
                 */
                *ctx = *v->initial_hashstate.sha256;
                sha256_update(ctx, data, len);
                sha256_final(ctx, digest);
                return 0;
        }

        desc = &io->hash_ctx.shash;
        desc->tfm = v->shash_tfm;
        if (unlikely(v->initial_hashstate.shash == NULL)) {
                /* Version 0: salt at end */
                r = crypto_shash_init(desc) ?:
                    crypto_shash_update(desc, data, len) ?:
                    crypto_shash_update(desc, v->salt, v->salt_size) ?:
                    crypto_shash_final(desc, digest);
        } else {
                /* Version 1: salt at beginning */
                r = crypto_shash_import(desc, v->initial_hashstate.shash) ?:
                    crypto_shash_finup(desc, data, len, digest);
        }
        if (unlikely(r))
                DMERR("Error hashing block: %d", r);
        return r;
}

static void verity_hash_at_level(struct dm_verity *v, sector_t block, int level,
                                 sector_t *hash_block, unsigned int *offset)
{
        sector_t position = verity_position_at_level(v, block, level);
        unsigned int idx;

        *hash_block = v->hash_level_block[level] + (position >> v->hash_per_block_bits);

        if (!offset)
                return;

        idx = position & ((1 << v->hash_per_block_bits) - 1);
        if (!v->version)
                *offset = idx * v->digest_size;
        else
                *offset = idx << (v->hash_dev_block_bits - v->hash_per_block_bits);
}

/*
 * Handle verification errors.
 */
static int verity_handle_err(struct dm_verity *v, enum verity_block_type type,
                             unsigned long long block)
{
        char verity_env[DM_VERITY_ENV_LENGTH];
        char *envp[] = { verity_env, NULL };
        const char *type_str = "";
        struct mapped_device *md = dm_table_get_md(v->ti->table);

        /* Corruption should be visible in device status in all modes */
        v->hash_failed = true;

        if (v->corrupted_errs >= DM_VERITY_MAX_CORRUPTED_ERRS)
                goto out;

        v->corrupted_errs++;

        switch (type) {
        case DM_VERITY_BLOCK_TYPE_DATA:
                type_str = "data";
                break;
        case DM_VERITY_BLOCK_TYPE_METADATA:
                type_str = "metadata";
                break;
        default:
                BUG();
        }

        DMERR_LIMIT("%s: %s block %llu is corrupted", v->data_dev->name,
                    type_str, block);

        if (v->corrupted_errs == DM_VERITY_MAX_CORRUPTED_ERRS) {
                DMERR("%s: reached maximum errors", v->data_dev->name);
                dm_audit_log_target(DM_MSG_PREFIX, "max-corrupted-errors", v->ti, 0);
        }

        snprintf(verity_env, DM_VERITY_ENV_LENGTH, "%s=%d,%llu",
                DM_VERITY_ENV_VAR_NAME, type, block);

        kobject_uevent_env(&disk_to_dev(dm_disk(md))->kobj, KOBJ_CHANGE, envp);

out:
        if (v->mode == DM_VERITY_MODE_LOGGING)
                return 0;

        if (v->mode == DM_VERITY_MODE_RESTART)
                kernel_restart("dm-verity device corrupted");

        if (v->mode == DM_VERITY_MODE_PANIC)
                panic("dm-verity device corrupted");

        return 1;
}

/*
 * Verify hash of a metadata block pertaining to the specified data block
 * ("block" argument) at a specified level ("level" argument).
 *
 * On successful return, want_digest contains the hash value for a lower tree
 * level or for the data block (if we're at the lowest level).
 *
 * If "skip_unverified" is true, unverified buffer is skipped and 1 is returned.
 * If "skip_unverified" is false, unverified buffer is hashed and verified
 * against current value of want_digest.
 */
static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
                               sector_t block, int level, bool skip_unverified,
                               u8 *want_digest)
{
        struct dm_buffer *buf;
        struct buffer_aux *aux;
        u8 *data;
        int r;
        sector_t hash_block;
        unsigned int offset;
        struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);

        verity_hash_at_level(v, block, level, &hash_block, &offset);

        if (static_branch_unlikely(&use_bh_wq_enabled) && io->in_bh) {
                data = dm_bufio_get(v->bufio, hash_block, &buf);
                if (IS_ERR_OR_NULL(data)) {
                        /*
                         * In softirq and the hash was not in the bufio cache.
                         * Return early and resume execution from a kworker to
                         * read the hash from disk.
                         */
                        return -EAGAIN;
                }
        } else {
                data = dm_bufio_read_with_ioprio(v->bufio, hash_block,
                                                &buf, bio->bi_ioprio);
        }

        if (IS_ERR(data)) {
                if (skip_unverified)
                        return 1;
                r = PTR_ERR(data);
                data = dm_bufio_new(v->bufio, hash_block, &buf);
                if (IS_ERR(data))
                        return r;
                if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_METADATA,
                                      want_digest, hash_block, data) == 0) {
                        aux = dm_bufio_get_aux_data(buf);
                        aux->hash_verified = 1;
                        goto release_ok;
                } else {
                        dm_bufio_release(buf);
                        dm_bufio_forget(v->bufio, hash_block);
                        return r;
                }
        }

        aux = dm_bufio_get_aux_data(buf);

        if (!aux->hash_verified) {
                if (skip_unverified) {
                        r = 1;
                        goto release_ret_r;
                }

                r = verity_hash(v, io, data, 1 << v->hash_dev_block_bits,
                                io->tmp_digest);
                if (unlikely(r < 0))
                        goto release_ret_r;

                if (likely(memcmp(io->tmp_digest, want_digest,
                                  v->digest_size) == 0))
                        aux->hash_verified = 1;
                else if (static_branch_unlikely(&use_bh_wq_enabled) && io->in_bh) {
                        /*
                         * Error handling code (FEC included) cannot be run in a
                         * softirq since it may sleep, so fallback to a kworker.
                         */
                        r = -EAGAIN;
                        goto release_ret_r;
                } else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_METADATA,
                                             want_digest, hash_block, data) == 0)
                        aux->hash_verified = 1;
                else if (verity_handle_err(v,
                                           DM_VERITY_BLOCK_TYPE_METADATA,
                                           hash_block)) {
                        struct bio *bio;
                        io->had_mismatch = true;
                        bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
                        dm_audit_log_bio(DM_MSG_PREFIX, "verify-metadata", bio,
                                         block, 0);
                        r = -EIO;
                        goto release_ret_r;
                }
        }

release_ok:
        data += offset;
        memcpy(want_digest, data, v->digest_size);
        r = 0;

release_ret_r:
        dm_bufio_release(buf);
        return r;
}

/*
 * Find a hash for a given block, write it to digest and verify the integrity
 * of the hash tree if necessary.
 */
int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io,
                          sector_t block, u8 *digest, bool *is_zero)
{
        int r = 0, i;

        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 1 and we fall back to whole
                 * chain verification.
                 */
                r = verity_verify_level(v, io, block, 0, true, digest);
                if (likely(r <= 0))
                        goto out;
        }

        memcpy(digest, v->root_digest, v->digest_size);

        for (i = v->levels - 1; i >= 0; i--) {
                r = verity_verify_level(v, io, block, i, false, digest);
                if (unlikely(r))
                        goto out;
        }
out:
        if (!r && v->zero_digest)
                *is_zero = !memcmp(v->zero_digest, digest, v->digest_size);
        else
                *is_zero = false;

        return r;
}

static noinline int verity_recheck(struct dm_verity *v, struct dm_verity_io *io,
                                   const u8 *want_digest, sector_t cur_block,
                                   u8 *dest)
{
        struct page *page;
        void *buffer;
        int r;
        struct dm_io_request io_req;
        struct dm_io_region io_loc;

        page = mempool_alloc(&v->recheck_pool, GFP_NOIO);
        buffer = page_to_virt(page);

        io_req.bi_opf = REQ_OP_READ;
        io_req.mem.type = DM_IO_KMEM;
        io_req.mem.ptr.addr = buffer;
        io_req.notify.fn = NULL;
        io_req.client = v->io;
        io_loc.bdev = v->data_dev->bdev;
        io_loc.sector = cur_block << (v->data_dev_block_bits - SECTOR_SHIFT);
        io_loc.count = 1 << (v->data_dev_block_bits - SECTOR_SHIFT);
        r = dm_io(&io_req, 1, &io_loc, NULL, IOPRIO_DEFAULT);
        if (unlikely(r))
                goto free_ret;

        r = verity_hash(v, io, buffer, 1 << v->data_dev_block_bits,
                        io->tmp_digest);
        if (unlikely(r))
                goto free_ret;

        if (memcmp(io->tmp_digest, want_digest, v->digest_size)) {
                r = -EIO;
                goto free_ret;
        }

        memcpy(dest, buffer, 1 << v->data_dev_block_bits);
        r = 0;
free_ret:
        mempool_free(page, &v->recheck_pool);

        return r;
}

static int verity_handle_data_hash_mismatch(struct dm_verity *v,
                                            struct dm_verity_io *io,
                                            struct bio *bio,
                                            struct pending_block *block)
{
        const u8 *want_digest = block->want_digest;
        sector_t blkno = block->blkno;
        u8 *data = block->data;

        if (static_branch_unlikely(&use_bh_wq_enabled) && io->in_bh) {
                /*
                 * Error handling code (FEC included) cannot be run in a
                 * softirq since it may sleep, so fallback to a kworker.
                 */
                return -EAGAIN;
        }
        if (verity_recheck(v, io, want_digest, blkno, data) == 0) {
                if (v->validated_blocks)
                        set_bit(blkno, v->validated_blocks);
                return 0;
        }
        if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_DATA, want_digest,
                              blkno, data) == 0)
                return 0;
        if (bio->bi_status)
                return -EIO; /* Error correction failed; Just return error */

        if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA, blkno)) {
                io->had_mismatch = true;
                dm_audit_log_bio(DM_MSG_PREFIX, "verify-data", bio, blkno, 0);
                return -EIO;
        }
        return 0;
}

static void verity_clear_pending_blocks(struct dm_verity_io *io)
{
        int i;

        for (i = io->num_pending - 1; i >= 0; i--) {
                kunmap_local(io->pending_blocks[i].data);
                io->pending_blocks[i].data = NULL;
        }
        io->num_pending = 0;
}

static int verity_verify_pending_blocks(struct dm_verity *v,
                                        struct dm_verity_io *io,
                                        struct bio *bio)
{
        const unsigned int block_size = 1 << v->data_dev_block_bits;
        int i, r;

        if (io->num_pending == 2) {
                /* num_pending == 2 implies that the algorithm is SHA-256 */
                sha256_finup_2x(v->initial_hashstate.sha256,
                                io->pending_blocks[0].data,
                                io->pending_blocks[1].data, block_size,
                                io->pending_blocks[0].real_digest,
                                io->pending_blocks[1].real_digest);
        } else {
                for (i = 0; i < io->num_pending; i++) {
                        r = verity_hash(v, io, io->pending_blocks[i].data,
                                        block_size,
                                        io->pending_blocks[i].real_digest);
                        if (unlikely(r))
                                return r;
                }
        }

        for (i = 0; i < io->num_pending; i++) {
                struct pending_block *block = &io->pending_blocks[i];

                if (likely(memcmp(block->real_digest, block->want_digest,
                                  v->digest_size) == 0)) {
                        if (v->validated_blocks)
                                set_bit(block->blkno, v->validated_blocks);
                } else {
                        r = verity_handle_data_hash_mismatch(v, io, bio, block);
                        if (unlikely(r))
                                return r;
                }
        }
        verity_clear_pending_blocks(io);
        return 0;
}

/*
 * Verify one "dm_verity_io" structure.
 */
static int verity_verify_io(struct dm_verity_io *io)
{
        struct dm_verity *v = io->v;
        const unsigned int block_size = 1 << v->data_dev_block_bits;
        const int max_pending = v->use_sha256_finup_2x ? 2 : 1;
        struct bvec_iter iter_copy;
        struct bvec_iter *iter;
        struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
        unsigned int b;
        int r;

        io->num_pending = 0;

        if (static_branch_unlikely(&use_bh_wq_enabled) && io->in_bh) {
                /*
                 * Copy the iterator in case we need to restart verification in
                 * a kworker.
                 */
                iter_copy = io->iter;
                iter = &iter_copy;
        } else
                iter = &io->iter;

        for (b = 0; b < io->n_blocks;
             b++, bio_advance_iter_single(bio, iter, block_size)) {
                sector_t blkno = io->block + b;
                struct pending_block *block;
                bool is_zero;
                struct bio_vec bv;
                void *data;

                if (v->validated_blocks && bio->bi_status == BLK_STS_OK &&
                    likely(test_bit(blkno, v->validated_blocks)))
                        continue;

                block = &io->pending_blocks[io->num_pending];

                r = verity_hash_for_block(v, io, blkno, block->want_digest,
                                          &is_zero);
                if (unlikely(r < 0))
                        goto error;

                bv = bio_iter_iovec(bio, *iter);
                if (unlikely(bv.bv_len < block_size)) {
                        /*
                         * Data block spans pages.  This should not happen,
                         * since dm-verity sets dma_alignment to the data block
                         * size minus 1, and dm-verity also doesn't allow the
                         * data block size to be greater than PAGE_SIZE.
                         */
                        DMERR_LIMIT("unaligned io (data block spans pages)");
                        r = -EIO;
                        goto error;
                }

                data = bvec_kmap_local(&bv);

                if (is_zero) {
                        /*
                         * If we expect a zero block, don't validate, just
                         * return zeros.
                         */
                        memset(data, 0, block_size);
                        kunmap_local(data);
                        continue;
                }
                block->data = data;
                block->blkno = blkno;
                if (++io->num_pending == max_pending) {
                        r = verity_verify_pending_blocks(v, io, bio);
                        if (unlikely(r))
                                goto error;
                }
        }

        if (io->num_pending) {
                r = verity_verify_pending_blocks(v, io, bio);
                if (unlikely(r))
                        goto error;
        }

        return 0;

error:
        verity_clear_pending_blocks(io);
        return r;
}

/*
 * Skip verity work in response to I/O error when system is shutting down.
 */
static inline bool verity_is_system_shutting_down(void)
{
        return system_state == SYSTEM_HALT || system_state == SYSTEM_POWER_OFF
                || system_state == SYSTEM_RESTART;
}

static void restart_io_error(struct work_struct *w)
{
        kernel_restart("dm-verity device has I/O error");
}

/*
 * End one "io" structure with a given error.
 */
static void verity_finish_io(struct dm_verity_io *io, blk_status_t status)
{
        struct dm_verity *v = io->v;
        struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);

        bio->bi_end_io = io->orig_bi_end_io;
        bio->bi_status = status;

        verity_fec_finish_io(io);

        if (unlikely(status != BLK_STS_OK) &&
            unlikely(!(bio->bi_opf & REQ_RAHEAD)) &&
            !io->had_mismatch &&
            !verity_is_system_shutting_down()) {
                if (v->error_mode == DM_VERITY_MODE_PANIC) {
                        panic("dm-verity device has I/O error");
                }
                if (v->error_mode == DM_VERITY_MODE_RESTART) {
                        static DECLARE_WORK(restart_work, restart_io_error);
                        queue_work(v->verify_wq, &restart_work);
                        /*
                         * We deliberately don't call bio_endio here, because
                         * the machine will be restarted anyway.
                         */
                        return;
                }
        }

        bio_endio(bio);
}

static void verity_work(struct work_struct *w)
{
        struct dm_verity_io *io = container_of(w, struct dm_verity_io, work);

        io->in_bh = false;

        verity_finish_io(io, errno_to_blk_status(verity_verify_io(io)));
}

static void verity_bh_work(struct work_struct *w)
{
        struct dm_verity_io *io = container_of(w, struct dm_verity_io, work);
        int err;

        io->in_bh = true;
        err = verity_verify_io(io);
        if (err == -EAGAIN || err == -ENOMEM) {
                /* fallback to retrying in a kworker */
                INIT_WORK(&io->work, verity_work);
                queue_work(io->v->verify_wq, &io->work);
                return;
        }

        verity_finish_io(io, errno_to_blk_status(err));
}

static inline bool verity_use_bh(unsigned int bytes, unsigned short ioprio)
{
        return ioprio <= IOPRIO_CLASS_IDLE &&
                bytes <= READ_ONCE(dm_verity_use_bh_bytes[ioprio]) &&
                !need_resched();
}

static void verity_end_io(struct bio *bio)
{
        struct dm_verity_io *io = bio->bi_private;
        unsigned short ioprio = IOPRIO_PRIO_CLASS(bio->bi_ioprio);
        unsigned int bytes = io->n_blocks << io->v->data_dev_block_bits;

        if (bio->bi_status &&
            (!verity_fec_is_enabled(io->v) ||
             verity_is_system_shutting_down() ||
             (bio->bi_opf & REQ_RAHEAD))) {
                verity_finish_io(io, bio->bi_status);
                return;
        }

        if (static_branch_unlikely(&use_bh_wq_enabled) && io->v->use_bh_wq &&
                verity_use_bh(bytes, ioprio)) {
                if (in_hardirq() || irqs_disabled()) {
                        INIT_WORK(&io->work, verity_bh_work);
                        queue_work(system_bh_wq, &io->work);
                } else {
                        verity_bh_work(&io->work);
                }
        } else {
                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 work_struct *work)
{
        struct dm_verity_prefetch_work *pw =
                container_of(work, struct dm_verity_prefetch_work, work);
        struct dm_verity *v = pw->v;
        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, pw->block, i, &hash_block_start, NULL);
                verity_hash_at_level(v, pw->block + pw->n_blocks - 1, i, &hash_block_end, NULL);

                if (!i) {
                        unsigned int cluster = READ_ONCE(dm_verity_prefetch_cluster);

                        cluster >>= v->data_dev_block_bits;
                        if (unlikely(!cluster))
                                goto no_prefetch_cluster;

                        if (unlikely(cluster & (cluster - 1)))
                                cluster = 1 << __fls(cluster);

                        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_with_ioprio(v->bufio, hash_block_start,
                                        hash_block_end - hash_block_start + 1,
                                        pw->ioprio);
        }

        kfree(pw);
}

static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io,
                                   unsigned short ioprio)
{
        sector_t block = io->block;
        unsigned int n_blocks = io->n_blocks;
        struct dm_verity_prefetch_work *pw;

        if (v->validated_blocks) {
                while (n_blocks && test_bit(block, v->validated_blocks)) {
                        block++;
                        n_blocks--;
                }
                while (n_blocks && test_bit(block + n_blocks - 1,
                                            v->validated_blocks))
                        n_blocks--;
                if (!n_blocks)
                        return;
        }

        pw = kmalloc_obj(struct dm_verity_prefetch_work,
                         GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);

        if (!pw)
                return;

        INIT_WORK(&pw->work, verity_prefetch_io);
        pw->v = v;
        pw->block = block;
        pw->n_blocks = n_blocks;
        pw->ioprio = ioprio;
        queue_work(v->verify_wq, &pw->work);
}

/*
 * 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)
{
        struct dm_verity *v = ti->private;
        struct dm_verity_io *io;

        bio_set_dev(bio, v->data_dev->bdev);
        bio->bi_iter.bi_sector = verity_map_sector(v, bio->bi_iter.bi_sector);

        if (((unsigned int)bio->bi_iter.bi_sector | bio_sectors(bio)) &
            ((1 << (v->data_dev_block_bits - SECTOR_SHIFT)) - 1)) {
                DMERR_LIMIT("unaligned io");
                return DM_MAPIO_KILL;
        }

        if (bio_end_sector(bio) >>
            (v->data_dev_block_bits - SECTOR_SHIFT) > v->data_blocks) {
                DMERR_LIMIT("io out of range");
                return DM_MAPIO_KILL;
        }

        if (bio_data_dir(bio) == WRITE)
                return DM_MAPIO_KILL;

        io = dm_per_bio_data(bio, ti->per_io_data_size);
        io->v = v;
        io->orig_bi_end_io = bio->bi_end_io;
        io->block = bio->bi_iter.bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
        io->n_blocks = bio->bi_iter.bi_size >> v->data_dev_block_bits;
        io->had_mismatch = false;

        bio->bi_end_io = verity_end_io;
        bio->bi_private = io;
        io->iter = bio->bi_iter;

        verity_fec_init_io(io);

        verity_submit_prefetch(v, io, bio->bi_ioprio);

        submit_bio_noacct(bio);

        return DM_MAPIO_SUBMITTED;
}

static void verity_postsuspend(struct dm_target *ti)
{
        struct dm_verity *v = ti->private;
        flush_workqueue(v->verify_wq);
        dm_bufio_client_reset(v->bufio);
}

/*
 * Status: V (valid) or C (corruption found)
 */
static void verity_status(struct dm_target *ti, status_type_t type,
                          unsigned int status_flags, char *result, unsigned int maxlen)
{
        struct dm_verity *v = ti->private;
        unsigned int args = 0;
        unsigned int sz = 0;
        unsigned int x;

        switch (type) {
        case STATUSTYPE_INFO:
                DMEMIT("%c", v->hash_failed ? 'C' : 'V');
                if (verity_fec_is_enabled(v))
                        DMEMIT(" %lld", atomic64_read(&v->fec->corrected));
                else
                        DMEMIT(" -");
                break;
        case STATUSTYPE_TABLE:
                DMEMIT("%u %s %s %u %u %llu %llu %s ",
                        v->version,
                        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]);
                if (v->mode != DM_VERITY_MODE_EIO)
                        args++;
                if (v->error_mode != DM_VERITY_MODE_EIO)
                        args++;
                if (verity_fec_is_enabled(v))
                        args += DM_VERITY_OPTS_FEC;
                if (v->zero_digest)
                        args++;
                if (v->validated_blocks)
                        args++;
                if (v->use_bh_wq)
                        args++;
                if (v->signature_key_desc)
                        args += DM_VERITY_ROOT_HASH_VERIFICATION_OPTS;
                if (!args)
                        return;
                DMEMIT(" %u", args);
                if (v->mode != DM_VERITY_MODE_EIO) {
                        DMEMIT(" ");
                        switch (v->mode) {
                        case DM_VERITY_MODE_LOGGING:
                                DMEMIT(DM_VERITY_OPT_LOGGING);
                                break;
                        case DM_VERITY_MODE_RESTART:
                                DMEMIT(DM_VERITY_OPT_RESTART);
                                break;
                        case DM_VERITY_MODE_PANIC:
                                DMEMIT(DM_VERITY_OPT_PANIC);
                                break;
                        default:
                                BUG();
                        }
                }
                if (v->error_mode != DM_VERITY_MODE_EIO) {
                        DMEMIT(" ");
                        switch (v->error_mode) {
                        case DM_VERITY_MODE_RESTART:
                                DMEMIT(DM_VERITY_OPT_ERROR_RESTART);
                                break;
                        case DM_VERITY_MODE_PANIC:
                                DMEMIT(DM_VERITY_OPT_ERROR_PANIC);
                                break;
                        default:
                                BUG();
                        }
                }
                if (v->zero_digest)
                        DMEMIT(" " DM_VERITY_OPT_IGN_ZEROES);
                if (v->validated_blocks)
                        DMEMIT(" " DM_VERITY_OPT_AT_MOST_ONCE);
                if (v->use_bh_wq)
                        DMEMIT(" " DM_VERITY_OPT_TASKLET_VERIFY);
                sz = verity_fec_status_table(v, sz, result, maxlen);
                if (v->signature_key_desc)
                        DMEMIT(" " DM_VERITY_ROOT_HASH_VERIFICATION_OPT_SIG_KEY
                                " %s", v->signature_key_desc);
                break;

        case STATUSTYPE_IMA:
                DMEMIT_TARGET_NAME_VERSION(ti->type);
                DMEMIT(",hash_failed=%c", v->hash_failed ? 'C' : 'V');
                DMEMIT(",verity_version=%u", v->version);
                DMEMIT(",data_device_name=%s", v->data_dev->name);
                DMEMIT(",hash_device_name=%s", v->hash_dev->name);
                DMEMIT(",verity_algorithm=%s", v->alg_name);

                DMEMIT(",root_digest=");
                for (x = 0; x < v->digest_size; x++)
                        DMEMIT("%02x", v->root_digest[x]);

                DMEMIT(",salt=");
                if (!v->salt_size)
                        DMEMIT("-");
                else
                        for (x = 0; x < v->salt_size; x++)
                                DMEMIT("%02x", v->salt[x]);

                DMEMIT(",ignore_zero_blocks=%c", v->zero_digest ? 'y' : 'n');
                DMEMIT(",check_at_most_once=%c", v->validated_blocks ? 'y' : 'n');
                if (v->signature_key_desc)
                        DMEMIT(",root_hash_sig_key_desc=%s", v->signature_key_desc);

                if (v->mode != DM_VERITY_MODE_EIO) {
                        DMEMIT(",verity_mode=");
                        switch (v->mode) {
                        case DM_VERITY_MODE_LOGGING:
                                DMEMIT(DM_VERITY_OPT_LOGGING);
                                break;
                        case DM_VERITY_MODE_RESTART:
                                DMEMIT(DM_VERITY_OPT_RESTART);
                                break;
                        case DM_VERITY_MODE_PANIC:
                                DMEMIT(DM_VERITY_OPT_PANIC);
                                break;
                        default:
                                DMEMIT("invalid");
                        }
                }
                if (v->error_mode != DM_VERITY_MODE_EIO) {
                        DMEMIT(",verity_error_mode=");
                        switch (v->error_mode) {
                        case DM_VERITY_MODE_RESTART:
                                DMEMIT(DM_VERITY_OPT_ERROR_RESTART);
                                break;
                        case DM_VERITY_MODE_PANIC:
                                DMEMIT(DM_VERITY_OPT_ERROR_PANIC);
                                break;
                        default:
                                DMEMIT("invalid");
                        }
                }
                DMEMIT(";");
                break;
        }
}

static int verity_prepare_ioctl(struct dm_target *ti, struct block_device **bdev,
                                unsigned int cmd, unsigned long arg,
                                bool *forward)
{
        struct dm_verity *v = ti->private;

        *bdev = v->data_dev->bdev;

        if (ti->len != bdev_nr_sectors(v->data_dev->bdev))
                return 1;
        return 0;
}

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, 0, 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;

        limits->io_min = limits->logical_block_size;

        /*
         * Similar to what dm-crypt does, opt dm-verity out of support for
         * direct I/O that is aligned to less than the traditional direct I/O
         * alignment requirement of logical_block_size.  This prevents dm-verity
         * data blocks from crossing pages, eliminating various edge cases.
         */
        limits->dma_alignment = limits->logical_block_size - 1;
}

#ifdef CONFIG_SECURITY

static int verity_init_sig(struct dm_verity *v, const void *sig,
                           size_t sig_size)
{
        v->sig_size = sig_size;

        if (sig) {
                v->root_digest_sig = kmemdup(sig, v->sig_size, GFP_KERNEL);
                if (!v->root_digest_sig)
                        return -ENOMEM;
        }

        return 0;
}

static void verity_free_sig(struct dm_verity *v)
{
        kfree(v->root_digest_sig);
}

#else

static inline int verity_init_sig(struct dm_verity *v, const void *sig,
                                  size_t sig_size)
{
        return 0;
}

static inline void verity_free_sig(struct dm_verity *v)
{
}

#endif /* CONFIG_SECURITY */

static void verity_dtr(struct dm_target *ti)
{
        struct dm_verity *v = ti->private;

        if (v->verify_wq)
                destroy_workqueue(v->verify_wq);

        mempool_exit(&v->recheck_pool);
        if (v->io)
                dm_io_client_destroy(v->io);

        if (v->bufio)
                dm_bufio_client_destroy(v->bufio);

        kvfree(v->validated_blocks);
        kfree(v->salt);
        kfree(v->initial_hashstate.shash);
        kfree(v->root_digest);
        kfree(v->zero_digest);
        verity_free_sig(v);

        crypto_free_shash(v->shash_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);

        verity_fec_dtr(v);

        kfree(v->signature_key_desc);

        if (v->use_bh_wq)
                static_branch_dec(&use_bh_wq_enabled);

        kfree(v);

        dm_audit_log_dtr(DM_MSG_PREFIX, ti, 1);
}

static int verity_alloc_most_once(struct dm_verity *v)
{
        struct dm_target *ti = v->ti;

        if (v->validated_blocks)
                return 0;

        /* the bitset can only handle INT_MAX blocks */
        if (v->data_blocks > INT_MAX) {
                ti->error = "device too large to use check_at_most_once";
                return -E2BIG;
        }

        v->validated_blocks = kvcalloc(BITS_TO_LONGS(v->data_blocks),
                                       sizeof(unsigned long),
                                       GFP_KERNEL);
        if (!v->validated_blocks) {
                ti->error = "failed to allocate bitset for check_at_most_once";
                return -ENOMEM;
        }

        return 0;
}

static int verity_alloc_zero_digest(struct dm_verity *v)
{
        int r = -ENOMEM;
        struct dm_verity_io *io;
        u8 *zero_data;

        if (v->zero_digest)
                return 0;

        v->zero_digest = kmalloc(v->digest_size, GFP_KERNEL);

        if (!v->zero_digest)
                return r;

        io = kmalloc(v->ti->per_io_data_size, GFP_KERNEL);

        if (!io)
                return r; /* verity_dtr will free zero_digest */

        zero_data = kzalloc(1 << v->data_dev_block_bits, GFP_KERNEL);

        if (!zero_data)
                goto out;

        r = verity_hash(v, io, zero_data, 1 << v->data_dev_block_bits,
                        v->zero_digest);

out:
        kfree(io);
        kfree(zero_data);

        return r;
}

static inline bool verity_is_verity_mode(const char *arg_name)
{
        return (!strcasecmp(arg_name, DM_VERITY_OPT_LOGGING) ||
                !strcasecmp(arg_name, DM_VERITY_OPT_RESTART) ||
                !strcasecmp(arg_name, DM_VERITY_OPT_PANIC));
}

static int verity_parse_verity_mode(struct dm_verity *v, const char *arg_name)
{
        if (v->mode)
                return -EINVAL;

        if (!strcasecmp(arg_name, DM_VERITY_OPT_LOGGING))
                v->mode = DM_VERITY_MODE_LOGGING;
        else if (!strcasecmp(arg_name, DM_VERITY_OPT_RESTART))
                v->mode = DM_VERITY_MODE_RESTART;
        else if (!strcasecmp(arg_name, DM_VERITY_OPT_PANIC))
                v->mode = DM_VERITY_MODE_PANIC;

        return 0;
}

static inline bool verity_is_verity_error_mode(const char *arg_name)
{
        return (!strcasecmp(arg_name, DM_VERITY_OPT_ERROR_RESTART) ||
                !strcasecmp(arg_name, DM_VERITY_OPT_ERROR_PANIC));
}

static int verity_parse_verity_error_mode(struct dm_verity *v, const char *arg_name)
{
        if (v->error_mode)
                return -EINVAL;

        if (!strcasecmp(arg_name, DM_VERITY_OPT_ERROR_RESTART))
                v->error_mode = DM_VERITY_MODE_RESTART;
        else if (!strcasecmp(arg_name, DM_VERITY_OPT_ERROR_PANIC))
                v->error_mode = DM_VERITY_MODE_PANIC;

        return 0;
}

static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
                                 struct dm_verity_sig_opts *verify_args,
                                 bool only_modifier_opts)
{
        int r = 0;
        unsigned int argc;
        struct dm_target *ti = v->ti;
        const char *arg_name;

        static const struct dm_arg _args[] = {
                {0, DM_VERITY_OPTS_MAX, "Invalid number of feature args"},
        };

        r = dm_read_arg_group(_args, as, &argc, &ti->error);
        if (r)
                return -EINVAL;

        if (!argc)
                return 0;

        do {
                arg_name = dm_shift_arg(as);
                argc--;

                if (verity_is_verity_mode(arg_name)) {
                        if (only_modifier_opts)
                                continue;
                        r = verity_parse_verity_mode(v, arg_name);
                        if (r) {
                                ti->error = "Conflicting error handling parameters";
                                return r;
                        }
                        continue;

                } else if (verity_is_verity_error_mode(arg_name)) {
                        if (only_modifier_opts)
                                continue;
                        r = verity_parse_verity_error_mode(v, arg_name);
                        if (r) {
                                ti->error = "Conflicting error handling parameters";
                                return r;
                        }
                        continue;

                } else if (!strcasecmp(arg_name, DM_VERITY_OPT_IGN_ZEROES)) {
                        if (only_modifier_opts)
                                continue;
                        r = verity_alloc_zero_digest(v);
                        if (r) {
                                ti->error = "Cannot allocate zero digest";
                                return r;
                        }
                        continue;

                } else if (!strcasecmp(arg_name, DM_VERITY_OPT_AT_MOST_ONCE)) {
                        if (only_modifier_opts)
                                continue;
                        r = verity_alloc_most_once(v);
                        if (r)
                                return r;
                        continue;

                } else if (!strcasecmp(arg_name, DM_VERITY_OPT_TASKLET_VERIFY)) {
                        v->use_bh_wq = true;
                        static_branch_inc(&use_bh_wq_enabled);
                        continue;

                } else if (verity_is_fec_opt_arg(arg_name)) {
                        if (only_modifier_opts)
                                continue;
                        r = verity_fec_parse_opt_args(as, v, &argc, arg_name);
                        if (r)
                                return r;
                        continue;

                } else if (verity_verify_is_sig_opt_arg(arg_name)) {
                        if (only_modifier_opts)
                                continue;
                        r = verity_verify_sig_parse_opt_args(as, v,
                                                             verify_args,
                                                             &argc, arg_name);
                        if (r)
                                return r;
                        continue;

                } else if (only_modifier_opts) {
                        /*
                         * Ignore unrecognized opt, could easily be an extra
                         * argument to an option whose parsing was skipped.
                         * Normal parsing (@only_modifier_opts=false) will
                         * properly parse all options (and their extra args).
                         */
                        continue;
                }

                DMERR("Unrecognized verity feature request: %s", arg_name);
                ti->error = "Unrecognized verity feature request";
                return -EINVAL;
        } while (argc && !r);

        return r;
}

static int verity_setup_hash_alg(struct dm_verity *v, const char *alg_name)
{
        struct dm_target *ti = v->ti;
        struct crypto_shash *shash;

        v->alg_name = kstrdup(alg_name, GFP_KERNEL);
        if (!v->alg_name) {
                ti->error = "Cannot allocate algorithm name";
                return -ENOMEM;
        }

        shash = crypto_alloc_shash(alg_name, 0, 0);
        if (IS_ERR(shash)) {
                ti->error = "Cannot initialize hash function";
                return PTR_ERR(shash);
        }
        v->shash_tfm = shash;
        v->digest_size = crypto_shash_digestsize(shash);
        if ((1 << v->hash_dev_block_bits) < v->digest_size * 2) {
                ti->error = "Digest size too big";
                return -EINVAL;
        }
        if (likely(v->version && strcmp(alg_name, "sha256") == 0)) {
                /*
                 * Fast path: use the library API for reduced overhead and
                 * interleaved hashing support.
                 */
                v->use_sha256_lib = true;
                if (sha256_finup_2x_is_optimized())
                        v->use_sha256_finup_2x = true;
                ti->per_io_data_size =
                        offsetofend(struct dm_verity_io, hash_ctx.sha256);
        } else {
                /* Fallback case: use the generic crypto API. */
                ti->per_io_data_size =
                        offsetofend(struct dm_verity_io, hash_ctx.shash) +
                        crypto_shash_descsize(shash);
        }
        return 0;
}

static int verity_setup_salt_and_hashstate(struct dm_verity *v, const char *arg)
{
        struct dm_target *ti = v->ti;

        if (strcmp(arg, "-") != 0) {
                v->salt_size = strlen(arg) / 2;
                v->salt = kmalloc(v->salt_size, GFP_KERNEL);
                if (!v->salt) {
                        ti->error = "Cannot allocate salt";
                        return -ENOMEM;
                }
                if (strlen(arg) != v->salt_size * 2 ||
                    hex2bin(v->salt, arg, v->salt_size)) {
                        ti->error = "Invalid salt";
                        return -EINVAL;
                }
        }
        if (likely(v->use_sha256_lib)) {
                /* Implies version 1: salt at beginning */
                v->initial_hashstate.sha256 =
                        kmalloc_obj(struct sha256_ctx);
                if (!v->initial_hashstate.sha256) {
                        ti->error = "Cannot allocate initial hash state";
                        return -ENOMEM;
                }
                sha256_init(v->initial_hashstate.sha256);
                sha256_update(v->initial_hashstate.sha256,
                              v->salt, v->salt_size);
        } else if (v->version) { /* Version 1: salt at beginning */
                SHASH_DESC_ON_STACK(desc, v->shash_tfm);
                int r;

                /*
                 * Compute the pre-salted hash state that can be passed to
                 * crypto_shash_import() for each block later.
                 */
                v->initial_hashstate.shash = kmalloc(
                        crypto_shash_statesize(v->shash_tfm), GFP_KERNEL);
                if (!v->initial_hashstate.shash) {
                        ti->error = "Cannot allocate initial hash state";
                        return -ENOMEM;
                }
                desc->tfm = v->shash_tfm;
                r = crypto_shash_init(desc) ?:
                    crypto_shash_update(desc, v->salt, v->salt_size) ?:
                    crypto_shash_export(desc, v->initial_hashstate.shash);
                if (r) {
                        ti->error = "Cannot set up initial hash state";
                        return r;
                }
        }
        return 0;
}

/*
 * Target parameters:
 *      <version>       The current format is version 1.
 *                      Vsn 0 is compatible with original Chromium OS releases.
 *      <data device>
 *      <hash device>
 *      <data block size>
 *      <hash block size>
 *      <the number of data blocks>
 *      <hash start block>
 *      <algorithm>
 *      <digest>
 *      <salt>          Hex string or "-" if no salt.
 */
static int verity_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
        struct dm_verity *v;
        struct dm_verity_sig_opts verify_args = {0};
        struct dm_arg_set as;
        unsigned int num;
        unsigned long long num_ll;
        int r;
        int i;
        sector_t hash_position;
        char dummy;
        char *root_hash_digest_to_validate;

        v = kzalloc_obj(struct dm_verity);
        if (!v) {
                ti->error = "Cannot allocate verity structure";
                return -ENOMEM;
        }
        ti->private = v;
        v->ti = ti;

        r = verity_fec_ctr_alloc(v);
        if (r)
                goto bad;

        if ((dm_table_get_mode(ti->table) & ~BLK_OPEN_READ)) {
                ti->error = "Device must be readonly";
                r = -EINVAL;
                goto bad;
        }

        if (argc < 10) {
                ti->error = "Not enough arguments";
                r = -EINVAL;
                goto bad;
        }

        /* Parse optional parameters that modify primary args */
        if (argc > 10) {
                as.argc = argc - 10;
                as.argv = argv + 10;
                r = verity_parse_opt_args(&as, v, &verify_args, true);
                if (r < 0)
                        goto bad;
        }

        if (sscanf(argv[0], "%u%c", &num, &dummy) != 1 ||
            num > 1) {
                ti->error = "Invalid version";
                r = -EINVAL;
                goto bad;
        }
        v->version = num;

        r = dm_get_device(ti, argv[1], BLK_OPEN_READ, &v->data_dev);
        if (r) {
                ti->error = "Data device lookup failed";
                goto bad;
        }

        r = dm_get_device(ti, argv[2], BLK_OPEN_READ, &v->hash_dev);
        if (r) {
                ti->error = "Hash 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);

        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);

        if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
            (sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
            >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll) {
                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 ||
            (sector_t)(num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT))
            >> (v->hash_dev_block_bits - SECTOR_SHIFT) != num_ll) {
                ti->error = "Invalid hash start";
                r = -EINVAL;
                goto bad;
        }
        v->hash_start = num_ll;

        r = verity_setup_hash_alg(v, argv[7]);
        if (r)
                goto bad;

        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;
        }
        root_hash_digest_to_validate = argv[8];

        r = verity_setup_salt_and_hashstate(v, argv[9]);
        if (r)
                goto bad;

        argv += 10;
        argc -= 10;

        /* Optional parameters */
        if (argc) {
                as.argc = argc;
                as.argv = argv;
                r = verity_parse_opt_args(&as, v, &verify_args, false);
                if (r < 0)
                        goto bad;
        }

        /* Root hash signature is an optional parameter */
        r = verity_verify_root_hash(root_hash_digest_to_validate,
                                    strlen(root_hash_digest_to_validate),
                                    verify_args.sig,
                                    verify_args.sig_size);
        if (r < 0) {
                ti->error = "Root hash verification failed";
                goto bad;
        }

        r = verity_init_sig(v, verify_args.sig, verify_args.sig_size);
        if (r < 0) {
                ti->error = "Cannot allocate root digest signature";
                goto bad;
        }

        v->hash_per_block_bits =
                __fls((1 << v->hash_dev_block_bits) / v->digest_size);

        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 = (v->data_blocks + ((sector_t)1 << ((i + 1) * v->hash_per_block_bits)) - 1)
                                        >> ((i + 1) * v->hash_per_block_bits);
                if (hash_position + s < hash_position) {
                        ti->error = "Hash device offset overflow";
                        r = -E2BIG;
                        goto bad;
                }
                hash_position += s;
        }
        v->hash_blocks = hash_position;

        r = mempool_init_page_pool(&v->recheck_pool, 1, 0);
        if (unlikely(r)) {
                ti->error = "Cannot allocate mempool";
                goto bad;
        }

        v->io = dm_io_client_create();
        if (IS_ERR(v->io)) {
                r = PTR_ERR(v->io);
                v->io = NULL;
                ti->error = "Cannot allocate dm io";
                goto bad;
        }

        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,
                v->use_bh_wq ? DM_BUFIO_CLIENT_NO_SLEEP : 0);
        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;
        }

        /*
         * Using WQ_HIGHPRI improves throughput and completion latency by
         * reducing wait times when reading from a dm-verity device.
         *
         * Also as required for the "try_verify_in_tasklet" feature: WQ_HIGHPRI
         * allows verify_wq to preempt softirq since verification in softirq
         * will fall-back to using it for error handling (or if the bufio cache
         * doesn't have required hashes).
         */
        v->verify_wq = alloc_workqueue("kverityd",
                                       WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_PERCPU,
                                       0);
        if (!v->verify_wq) {
                ti->error = "Cannot allocate workqueue";
                r = -ENOMEM;
                goto bad;
        }

        r = verity_fec_ctr(v);
        if (r)
                goto bad;

        ti->per_io_data_size = roundup(ti->per_io_data_size,
                                       __alignof__(struct dm_verity_io));

        verity_verify_sig_opts_cleanup(&verify_args);

        dm_audit_log_ctr(DM_MSG_PREFIX, ti, 1);

        return 0;

bad:

        verity_verify_sig_opts_cleanup(&verify_args);
        dm_audit_log_ctr(DM_MSG_PREFIX, ti, 0);
        verity_dtr(ti);

        return r;
}

/*
 * Get the verity mode (error behavior) of a verity target.
 *
 * Returns the verity mode of the target, or -EINVAL if 'ti' is not a verity
 * target.
 */
int dm_verity_get_mode(struct dm_target *ti)
{
        struct dm_verity *v = ti->private;

        if (!dm_is_verity_target(ti))
                return -EINVAL;

        return v->mode;
}

/*
 * Get the root digest of a verity target.
 *
 * Returns a copy of the root digest, the caller is responsible for
 * freeing the memory of the digest.
 */
int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, unsigned int *digest_size)
{
        struct dm_verity *v = ti->private;

        if (!dm_is_verity_target(ti))
                return -EINVAL;

        *root_digest = kmemdup(v->root_digest, v->digest_size, GFP_KERNEL);
        if (*root_digest == NULL)
                return -ENOMEM;

        *digest_size = v->digest_size;

        return 0;
}

#ifdef CONFIG_SECURITY

#ifdef CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG

static int verity_security_set_signature(struct block_device *bdev,
                                         struct dm_verity *v)
{
        /*
         * if the dm-verity target is unsigned, v->root_digest_sig will
         * be NULL, and the hook call is still required to let LSMs mark
         * the device as unsigned. This information is crucial for LSMs to
         * block operations such as execution on unsigned files
         */
        return security_bdev_setintegrity(bdev,
                                          LSM_INT_DMVERITY_SIG_VALID,
                                          v->root_digest_sig,
                                          v->sig_size);
}

#else

static inline int verity_security_set_signature(struct block_device *bdev,
                                                struct dm_verity *v)
{
        return 0;
}

#endif /* CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG */

/*
 * Expose verity target's root hash and signature data to LSMs before resume.
 *
 * Returns 0 on success, or -ENOMEM if the system is out of memory.
 */
static int verity_preresume(struct dm_target *ti)
{
        struct block_device *bdev;
        struct dm_verity_digest root_digest;
        struct dm_verity *v;
        int r;

        v = ti->private;
        bdev = dm_disk(dm_table_get_md(ti->table))->part0;
        root_digest.digest = v->root_digest;
        root_digest.digest_len = v->digest_size;
        root_digest.alg = crypto_shash_alg_name(v->shash_tfm);

        r = security_bdev_setintegrity(bdev, LSM_INT_DMVERITY_ROOTHASH, &root_digest,
                                       sizeof(root_digest));
        if (r)
                return r;

        r =  verity_security_set_signature(bdev, v);
        if (r)
                goto bad;

        return 0;

bad:

        security_bdev_setintegrity(bdev, LSM_INT_DMVERITY_ROOTHASH, NULL, 0);

        return r;
}

#endif /* CONFIG_SECURITY */

static struct target_type verity_target = {
        .name           = "verity",
/* Note: the LSMs depend on the singleton and immutable features */
        .features       = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
        .version        = {1, 13, 0},
        .module         = THIS_MODULE,
        .ctr            = verity_ctr,
        .dtr            = verity_dtr,
        .map            = verity_map,
        .postsuspend    = verity_postsuspend,
        .status         = verity_status,
        .prepare_ioctl  = verity_prepare_ioctl,
        .iterate_devices = verity_iterate_devices,
        .io_hints       = verity_io_hints,
#ifdef CONFIG_SECURITY
        .preresume      = verity_preresume,
#endif /* CONFIG_SECURITY */
};

static int __init dm_verity_init(void)
{
        int r;

        r = dm_verity_verify_sig_init();
        if (r)
                return r;

        r = dm_register_target(&verity_target);
        if (r) {
                dm_verity_verify_sig_exit();
                return r;
        }

        return 0;
}
module_init(dm_verity_init);

static void __exit dm_verity_exit(void)
{
        dm_unregister_target(&verity_target);
        dm_verity_verify_sig_exit();
}
module_exit(dm_verity_exit);

/*
 * Check whether a DM target is a verity target.
 */
bool dm_is_verity_target(struct dm_target *ti)
{
        return ti->type == &verity_target;
}

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");