/*
 * Copyright (C) 2003 Jana Saout <jana@saout.de>
 * Copyright (C) 2004 Clemens Fruhwirth <clemens@endorphin.org>
 * Copyright (C) 2006-2015 Red Hat, Inc. All rights reserved.
 * Copyright (C) 2013 Milan Broz <gmazyland@gmail.com>
 *
 * This file is released under the GPL.
 */

#include <linux/completion.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/mempool.h>
#include <linux/slab.h>
#include <linux/crypto.h>
#include <linux/workqueue.h>
#include <linux/kthread.h>
#include <linux/backing-dev.h>
#include <linux/atomic.h>
#include <linux/scatterlist.h>
#include <linux/rbtree.h>
#include <asm/page.h>
#include <asm/unaligned.h>
#include <crypto/hash.h>
#include <crypto/md5.h>
#include <crypto/algapi.h>
#include <crypto/skcipher.h>

#include <linux/device-mapper.h>

#define DM_MSG_PREFIX "crypt"

/*
 * context holding the current state of a multi-part conversion
 */
struct convert_context {
        struct completion restart;
        struct bio *bio_in;
        struct bio *bio_out;
        struct bvec_iter iter_in;
        struct bvec_iter iter_out;
        sector_t cc_sector;
        atomic_t cc_pending;
        struct skcipher_request *req;
};

/*
 * per bio private data
 */
struct dm_crypt_io {
        struct crypt_config *cc;
        struct bio *base_bio;
        struct work_struct work;

        struct convert_context ctx;

        atomic_t io_pending;
        int error;
        sector_t sector;

        struct rb_node rb_node;
} CRYPTO_MINALIGN_ATTR;

struct dm_crypt_request {
        struct convert_context *ctx;
        struct scatterlist sg_in;
        struct scatterlist sg_out;
        sector_t iv_sector;
};

struct crypt_config;

struct crypt_iv_operations {
        int (*ctr)(struct crypt_config *cc, struct dm_target *ti,
                   const char *opts);
        void (*dtr)(struct crypt_config *cc);
        int (*init)(struct crypt_config *cc);
        int (*wipe)(struct crypt_config *cc);
        int (*generator)(struct crypt_config *cc, u8 *iv,
                         struct dm_crypt_request *dmreq);
        int (*post)(struct crypt_config *cc, u8 *iv,
                    struct dm_crypt_request *dmreq);
};

struct iv_essiv_private {
        struct crypto_ahash *hash_tfm;
        u8 *salt;
};

struct iv_benbi_private {
        int shift;
};

#define LMK_SEED_SIZE 64 /* hash + 0 */
struct iv_lmk_private {
        struct crypto_shash *hash_tfm;
        u8 *seed;
};

#define TCW_WHITENING_SIZE 16
struct iv_tcw_private {
        struct crypto_shash *crc32_tfm;
        u8 *iv_seed;
        u8 *whitening;
};

/*
 * Crypt: maps a linear range of a block device
 * and encrypts / decrypts at the same time.
 */
enum flags { DM_CRYPT_SUSPENDED, DM_CRYPT_KEY_VALID,
             DM_CRYPT_SAME_CPU, DM_CRYPT_NO_OFFLOAD,
             DM_CRYPT_EXIT_THREAD};

/*
 * The fields in here must be read only after initialization.
 */
struct crypt_config {
        struct dm_dev *dev;
        sector_t start;

        /*
         * pool for per bio private data, crypto requests and
         * encryption requeusts/buffer pages
         */
        mempool_t *req_pool;
        mempool_t *page_pool;
        struct bio_set *bs;
        struct mutex bio_alloc_lock;

        struct workqueue_struct *io_queue;
        struct workqueue_struct *crypt_queue;

        struct task_struct *write_thread;
        wait_queue_head_t write_thread_wait;
        struct rb_root write_tree;

        char *cipher;
        char *cipher_string;

        struct crypt_iv_operations *iv_gen_ops;
        union {
                struct iv_essiv_private essiv;
                struct iv_benbi_private benbi;
                struct iv_lmk_private lmk;
                struct iv_tcw_private tcw;
        } iv_gen_private;
        sector_t iv_offset;
        unsigned int iv_size;

        /* ESSIV: struct crypto_cipher *essiv_tfm */
        void *iv_private;
        struct crypto_skcipher **tfms;
        unsigned tfms_count;

        /*
         * Layout of each crypto request:
         *
         *   struct skcipher_request
         *      context
         *      padding
         *   struct dm_crypt_request
         *      padding
         *   IV
         *
         * The padding is added so that dm_crypt_request and the IV are
         * correctly aligned.
         */
        unsigned int dmreq_start;

        unsigned int per_bio_data_size;

        unsigned long flags;
        unsigned int key_size;
        unsigned int key_parts;      /* independent parts in key buffer */
        unsigned int key_extra_size; /* additional keys length */
        u8 key[0];
};

#define MIN_IOS        16

static void clone_init(struct dm_crypt_io *, struct bio *);
static void kcryptd_queue_crypt(struct dm_crypt_io *io);
static u8 *iv_of_dmreq(struct crypt_config *cc, struct dm_crypt_request *dmreq);

/*
 * Use this to access cipher attributes that are the same for each CPU.
 */
static struct crypto_skcipher *any_tfm(struct crypt_config *cc)
{
        return cc->tfms[0];
}

/*
 * Different IV generation algorithms:
 *
 * plain: the initial vector is the 32-bit little-endian version of the sector
 *        number, padded with zeros if necessary.
 *
 * plain64: the initial vector is the 64-bit little-endian version of the sector
 *        number, padded with zeros if necessary.
 *
 * essiv: "encrypted sector|salt initial vector", the sector number is
 *        encrypted with the bulk cipher using a salt as key. The salt
 *        should be derived from the bulk cipher's key via hashing.
 *
 * benbi: the 64-bit "big-endian 'narrow block'-count", starting at 1
 *        (needed for LRW-32-AES and possible other narrow block modes)
 *
 * null: the initial vector is always zero.  Provides compatibility with
 *       obsolete loop_fish2 devices.  Do not use for new devices.
 *
 * lmk:  Compatible implementation of the block chaining mode used
 *       by the Loop-AES block device encryption system
 *       designed by Jari Ruusu. See http://loop-aes.sourceforge.net/
 *       It operates on full 512 byte sectors and uses CBC
 *       with an IV derived from the sector number, the data and
 *       optionally extra IV seed.
 *       This means that after decryption the first block
 *       of sector must be tweaked according to decrypted data.
 *       Loop-AES can use three encryption schemes:
 *         version 1: is plain aes-cbc mode
 *         version 2: uses 64 multikey scheme with lmk IV generator
 *         version 3: the same as version 2 with additional IV seed
 *                   (it uses 65 keys, last key is used as IV seed)
 *
 * tcw:  Compatible implementation of the block chaining mode used
 *       by the TrueCrypt device encryption system (prior to version 4.1).
 *       For more info see: https://gitlab.com/cryptsetup/cryptsetup/wikis/TrueCryptOnDiskFormat
 *       It operates on full 512 byte sectors and uses CBC
 *       with an IV derived from initial key and the sector number.
 *       In addition, whitening value is applied on every sector, whitening
 *       is calculated from initial key, sector number and mixed using CRC32.
 *       Note that this encryption scheme is vulnerable to watermarking attacks
 *       and should be used for old compatible containers access only.
 *
 * plumb: unimplemented, see:
 * http://article.gmane.org/gmane.linux.kernel.device-mapper.dm-crypt/454
 */

static int crypt_iv_plain_gen(struct crypt_config *cc, u8 *iv,
                              struct dm_crypt_request *dmreq)
{
        memset(iv, 0, cc->iv_size);
        *(__le32 *)iv = cpu_to_le32(dmreq->iv_sector & 0xffffffff);

        return 0;
}

static int crypt_iv_plain64_gen(struct crypt_config *cc, u8 *iv,
                                struct dm_crypt_request *dmreq)
{
        memset(iv, 0, cc->iv_size);
        *(__le64 *)iv = cpu_to_le64(dmreq->iv_sector);

        return 0;
}

/* Initialise ESSIV - compute salt but no local memory allocations */
static int crypt_iv_essiv_init(struct crypt_config *cc)
{
        struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
        AHASH_REQUEST_ON_STACK(req, essiv->hash_tfm);
        struct scatterlist sg;
        struct crypto_cipher *essiv_tfm;
        int err;

        sg_init_one(&sg, cc->key, cc->key_size);
        ahash_request_set_tfm(req, essiv->hash_tfm);
        ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
        ahash_request_set_crypt(req, &sg, essiv->salt, cc->key_size);

        err = crypto_ahash_digest(req);
        ahash_request_zero(req);
        if (err)
                return err;

        essiv_tfm = cc->iv_private;

        err = crypto_cipher_setkey(essiv_tfm, essiv->salt,
                            crypto_ahash_digestsize(essiv->hash_tfm));
        if (err)
                return err;

        return 0;
}

/* Wipe salt and reset key derived from volume key */
static int crypt_iv_essiv_wipe(struct crypt_config *cc)
{
        struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;
        unsigned salt_size = crypto_ahash_digestsize(essiv->hash_tfm);
        struct crypto_cipher *essiv_tfm;
        int r, err = 0;

        memset(essiv->salt, 0, salt_size);

        essiv_tfm = cc->iv_private;
        r = crypto_cipher_setkey(essiv_tfm, essiv->salt, salt_size);
        if (r)
                err = r;

        return err;
}

/* Set up per cpu cipher state */
static struct crypto_cipher *setup_essiv_cpu(struct crypt_config *cc,
                                             struct dm_target *ti,
                                             u8 *salt, unsigned saltsize)
{
        struct crypto_cipher *essiv_tfm;
        int err;

        /* Setup the essiv_tfm with the given salt */
        essiv_tfm = crypto_alloc_cipher(cc->cipher, 0, CRYPTO_ALG_ASYNC);
        if (IS_ERR(essiv_tfm)) {
                ti->error = "Error allocating crypto tfm for ESSIV";
                return essiv_tfm;
        }

        if (crypto_cipher_blocksize(essiv_tfm) !=
            crypto_skcipher_ivsize(any_tfm(cc))) {
                ti->error = "Block size of ESSIV cipher does "
                            "not match IV size of block cipher";
                crypto_free_cipher(essiv_tfm);
                return ERR_PTR(-EINVAL);
        }

        err = crypto_cipher_setkey(essiv_tfm, salt, saltsize);
        if (err) {
                ti->error = "Failed to set key for ESSIV cipher";
                crypto_free_cipher(essiv_tfm);
                return ERR_PTR(err);
        }

        return essiv_tfm;
}

static void crypt_iv_essiv_dtr(struct crypt_config *cc)
{
        struct crypto_cipher *essiv_tfm;
        struct iv_essiv_private *essiv = &cc->iv_gen_private.essiv;

        crypto_free_ahash(essiv->hash_tfm);
        essiv->hash_tfm = NULL;

        kzfree(essiv->salt);
        essiv->salt = NULL;

        essiv_tfm = cc->iv_private;

        if (essiv_tfm)
                crypto_free_cipher(essiv_tfm);

        cc->iv_private = NULL;
}

static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
                              const char *opts)
{
        struct crypto_cipher *essiv_tfm = NULL;
        struct crypto_ahash *hash_tfm = NULL;
        u8 *salt = NULL;
        int err;

        if (!opts) {
                ti->error = "Digest algorithm missing for ESSIV mode";
                return -EINVAL;
        }

        /* Allocate hash algorithm */
        hash_tfm = crypto_alloc_ahash(opts, 0, CRYPTO_ALG_ASYNC);
        if (IS_ERR(hash_tfm)) {
                ti->error = "Error initializing ESSIV hash";
                err = PTR_ERR(hash_tfm);
                goto bad;
        }

        salt = kzalloc(crypto_ahash_digestsize(hash_tfm), GFP_KERNEL);
        if (!salt) {
                ti->error = "Error kmallocing salt storage in ESSIV";
                err = -ENOMEM;
                goto bad;
        }

        cc->iv_gen_private.essiv.salt = salt;
        cc->iv_gen_private.essiv.hash_tfm = hash_tfm;

        essiv_tfm = setup_essiv_cpu(cc, ti, salt,
                                crypto_ahash_digestsize(hash_tfm));
        if (IS_ERR(essiv_tfm)) {
                crypt_iv_essiv_dtr(cc);
                return PTR_ERR(essiv_tfm);
        }
        cc->iv_private = essiv_tfm;

        return 0;

bad:
        if (hash_tfm && !IS_ERR(hash_tfm))
                crypto_free_ahash(hash_tfm);
        kfree(salt);
        return err;
}

static int crypt_iv_essiv_gen(struct crypt_config *cc, u8 *iv,
                              struct dm_crypt_request *dmreq)
{
        struct crypto_cipher *essiv_tfm = cc->iv_private;

        memset(iv, 0, cc->iv_size);
        *(__le64 *)iv = cpu_to_le64(dmreq->iv_sector);
        crypto_cipher_encrypt_one(essiv_tfm, iv, iv);

        return 0;
}

static int crypt_iv_benbi_ctr(struct crypt_config *cc, struct dm_target *ti,
                              const char *opts)
{
        unsigned bs = crypto_skcipher_blocksize(any_tfm(cc));
        int log = ilog2(bs);

        /* we need to calculate how far we must shift the sector count
         * to get the cipher block count, we use this shift in _gen */

        if (1 << log != bs) {
                ti->error = "cypher blocksize is not a power of 2";
                return -EINVAL;
        }

        if (log > 9) {
                ti->error = "cypher blocksize is > 512";
                return -EINVAL;
        }

        cc->iv_gen_private.benbi.shift = 9 - log;

        return 0;
}

static void crypt_iv_benbi_dtr(struct crypt_config *cc)
{
}

static int crypt_iv_benbi_gen(struct crypt_config *cc, u8 *iv,
                              struct dm_crypt_request *dmreq)
{
        __be64 val;

        memset(iv, 0, cc->iv_size - sizeof(u64)); /* rest is cleared below */

        val = cpu_to_be64(((u64)dmreq->iv_sector << cc->iv_gen_private.benbi.shift) + 1);
        put_unaligned(val, (__be64 *)(iv + cc->iv_size - sizeof(u64)));

        return 0;
}

static int crypt_iv_null_gen(struct crypt_config *cc, u8 *iv,
                             struct dm_crypt_request *dmreq)
{
        memset(iv, 0, cc->iv_size);

        return 0;
}

static void crypt_iv_lmk_dtr(struct crypt_config *cc)
{
        struct iv_lmk_private *lmk = &cc->iv_gen_private.lmk;

        if (lmk->hash_tfm && !IS_ERR(lmk->hash_tfm))
                crypto_free_shash(lmk->hash_tfm);
        lmk->hash_tfm = NULL;

        kzfree(lmk->seed);
        lmk->seed = NULL;
}

static int crypt_iv_lmk_ctr(struct crypt_config *cc, struct dm_target *ti,
                            const char *opts)
{
        struct iv_lmk_private *lmk = &cc->iv_gen_private.lmk;

        lmk->hash_tfm = crypto_alloc_shash("md5", 0, 0);
        if (IS_ERR(lmk->hash_tfm)) {
                ti->error = "Error initializing LMK hash";
                return PTR_ERR(lmk->hash_tfm);
        }

        /* No seed in LMK version 2 */
        if (cc->key_parts == cc->tfms_count) {
                lmk->seed = NULL;
                return 0;
        }

        lmk->seed = kzalloc(LMK_SEED_SIZE, GFP_KERNEL);
        if (!lmk->seed) {
                crypt_iv_lmk_dtr(cc);
                ti->error = "Error kmallocing seed storage in LMK";
                return -ENOMEM;
        }

        return 0;
}

static int crypt_iv_lmk_init(struct crypt_config *cc)
{
        struct iv_lmk_private *lmk = &cc->iv_gen_private.lmk;
        int subkey_size = cc->key_size / cc->key_parts;

        /* LMK seed is on the position of LMK_KEYS + 1 key */
        if (lmk->seed)
                memcpy(lmk->seed, cc->key + (cc->tfms_count * subkey_size),
                       crypto_shash_digestsize(lmk->hash_tfm));

        return 0;
}

static int crypt_iv_lmk_wipe(struct crypt_config *cc)
{
        struct iv_lmk_private *lmk = &cc->iv_gen_private.lmk;

        if (lmk->seed)
                memset(lmk->seed, 0, LMK_SEED_SIZE);

        return 0;
}

static int crypt_iv_lmk_one(struct crypt_config *cc, u8 *iv,
                            struct dm_crypt_request *dmreq,
                            u8 *data)
{
        struct iv_lmk_private *lmk = &cc->iv_gen_private.lmk;
        SHASH_DESC_ON_STACK(desc, lmk->hash_tfm);
        struct md5_state md5state;
        __le32 buf[4];
        int i, r;

        desc->tfm = lmk->hash_tfm;
        desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;

        r = crypto_shash_init(desc);
        if (r)
                return r;

        if (lmk->seed) {
                r = crypto_shash_update(desc, lmk->seed, LMK_SEED_SIZE);
                if (r)
                        return r;
        }

        /* Sector is always 512B, block size 16, add data of blocks 1-31 */
        r = crypto_shash_update(desc, data + 16, 16 * 31);
        if (r)
                return r;

        /* Sector is cropped to 56 bits here */
        buf[0] = cpu_to_le32(dmreq->iv_sector & 0xFFFFFFFF);
        buf[1] = cpu_to_le32((((u64)dmreq->iv_sector >> 32) & 0x00FFFFFF) | 0x80000000);
        buf[2] = cpu_to_le32(4024);
        buf[3] = 0;
        r = crypto_shash_update(desc, (u8 *)buf, sizeof(buf));
        if (r)
                return r;

        /* No MD5 padding here */
        r = crypto_shash_export(desc, &md5state);
        if (r)
                return r;

        for (i = 0; i < MD5_HASH_WORDS; i++)
                __cpu_to_le32s(&md5state.hash[i]);
        memcpy(iv, &md5state.hash, cc->iv_size);

        return 0;
}

static int crypt_iv_lmk_gen(struct crypt_config *cc, u8 *iv,
                            struct dm_crypt_request *dmreq)
{
        u8 *src;
        int r = 0;

        if (bio_data_dir(dmreq->ctx->bio_in) == WRITE) {
                src = kmap_atomic(sg_page(&dmreq->sg_in));
                r = crypt_iv_lmk_one(cc, iv, dmreq, src + dmreq->sg_in.offset);
                kunmap_atomic(src);
        } else
                memset(iv, 0, cc->iv_size);

        return r;
}

static int crypt_iv_lmk_post(struct crypt_config *cc, u8 *iv,
                             struct dm_crypt_request *dmreq)
{
        u8 *dst;
        int r;

        if (bio_data_dir(dmreq->ctx->bio_in) == WRITE)
                return 0;

        dst = kmap_atomic(sg_page(&dmreq->sg_out));
        r = crypt_iv_lmk_one(cc, iv, dmreq, dst + dmreq->sg_out.offset);

        /* Tweak the first block of plaintext sector */
        if (!r)
                crypto_xor(dst + dmreq->sg_out.offset, iv, cc->iv_size);

        kunmap_atomic(dst);
        return r;
}

static void crypt_iv_tcw_dtr(struct crypt_config *cc)
{
        struct iv_tcw_private *tcw = &cc->iv_gen_private.tcw;

        kzfree(tcw->iv_seed);
        tcw->iv_seed = NULL;
        kzfree(tcw->whitening);
        tcw->whitening = NULL;

        if (tcw->crc32_tfm && !IS_ERR(tcw->crc32_tfm))
                crypto_free_shash(tcw->crc32_tfm);
        tcw->crc32_tfm = NULL;
}

static int crypt_iv_tcw_ctr(struct crypt_config *cc, struct dm_target *ti,
                            const char *opts)
{
        struct iv_tcw_private *tcw = &cc->iv_gen_private.tcw;

        if (cc->key_size <= (cc->iv_size + TCW_WHITENING_SIZE)) {
                ti->error = "Wrong key size for TCW";
                return -EINVAL;
        }

        tcw->crc32_tfm = crypto_alloc_shash("crc32", 0, 0);
        if (IS_ERR(tcw->crc32_tfm)) {
                ti->error = "Error initializing CRC32 in TCW";
                return PTR_ERR(tcw->crc32_tfm);
        }

        tcw->iv_seed = kzalloc(cc->iv_size, GFP_KERNEL);
        tcw->whitening = kzalloc(TCW_WHITENING_SIZE, GFP_KERNEL);
        if (!tcw->iv_seed || !tcw->whitening) {
                crypt_iv_tcw_dtr(cc);
                ti->error = "Error allocating seed storage in TCW";
                return -ENOMEM;
        }

        return 0;
}

static int crypt_iv_tcw_init(struct crypt_config *cc)
{
        struct iv_tcw_private *tcw = &cc->iv_gen_private.tcw;
        int key_offset = cc->key_size - cc->iv_size - TCW_WHITENING_SIZE;

        memcpy(tcw->iv_seed, &cc->key[key_offset], cc->iv_size);
        memcpy(tcw->whitening, &cc->key[key_offset + cc->iv_size],
               TCW_WHITENING_SIZE);

        return 0;
}

static int crypt_iv_tcw_wipe(struct crypt_config *cc)
{
        struct iv_tcw_private *tcw = &cc->iv_gen_private.tcw;

        memset(tcw->iv_seed, 0, cc->iv_size);
        memset(tcw->whitening, 0, TCW_WHITENING_SIZE);

        return 0;
}

static int crypt_iv_tcw_whitening(struct crypt_config *cc,
                                  struct dm_crypt_request *dmreq,
                                  u8 *data)
{
        struct iv_tcw_private *tcw = &cc->iv_gen_private.tcw;
        u64 sector = cpu_to_le64((u64)dmreq->iv_sector);
        u8 buf[TCW_WHITENING_SIZE];
        SHASH_DESC_ON_STACK(desc, tcw->crc32_tfm);
        int i, r;

        /* xor whitening with sector number */
        memcpy(buf, tcw->whitening, TCW_WHITENING_SIZE);
        crypto_xor(buf, (u8 *)&sector, 8);
        crypto_xor(&buf[8], (u8 *)&sector, 8);

        /* calculate crc32 for every 32bit part and xor it */
        desc->tfm = tcw->crc32_tfm;
        desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
        for (i = 0; i < 4; i++) {
                r = crypto_shash_init(desc);
                if (r)
                        goto out;
                r = crypto_shash_update(desc, &buf[i * 4], 4);
                if (r)
                        goto out;
                r = crypto_shash_final(desc, &buf[i * 4]);
                if (r)
                        goto out;
        }
        crypto_xor(&buf[0], &buf[12], 4);
        crypto_xor(&buf[4], &buf[8], 4);

        /* apply whitening (8 bytes) to whole sector */
        for (i = 0; i < ((1 << SECTOR_SHIFT) / 8); i++)
                crypto_xor(data + i * 8, buf, 8);
out:
        memzero_explicit(buf, sizeof(buf));
        return r;
}

static int crypt_iv_tcw_gen(struct crypt_config *cc, u8 *iv,
                            struct dm_crypt_request *dmreq)
{
        struct iv_tcw_private *tcw = &cc->iv_gen_private.tcw;
        u64 sector = cpu_to_le64((u64)dmreq->iv_sector);
        u8 *src;
        int r = 0;

        /* Remove whitening from ciphertext */
        if (bio_data_dir(dmreq->ctx->bio_in) != WRITE) {
                src = kmap_atomic(sg_page(&dmreq->sg_in));
                r = crypt_iv_tcw_whitening(cc, dmreq, src + dmreq->sg_in.offset);
                kunmap_atomic(src);
        }

        /* Calculate IV */
        memcpy(iv, tcw->iv_seed, cc->iv_size);
        crypto_xor(iv, (u8 *)&sector, 8);
        if (cc->iv_size > 8)
                crypto_xor(&iv[8], (u8 *)&sector, cc->iv_size - 8);

        return r;
}

static int crypt_iv_tcw_post(struct crypt_config *cc, u8 *iv,
                             struct dm_crypt_request *dmreq)
{
        u8 *dst;
        int r;

        if (bio_data_dir(dmreq->ctx->bio_in) != WRITE)
                return 0;

        /* Apply whitening on ciphertext */
        dst = kmap_atomic(sg_page(&dmreq->sg_out));
        r = crypt_iv_tcw_whitening(cc, dmreq, dst + dmreq->sg_out.offset);
        kunmap_atomic(dst);

        return r;
}

static struct crypt_iv_operations crypt_iv_plain_ops = {
        .generator = crypt_iv_plain_gen
};

static struct crypt_iv_operations crypt_iv_plain64_ops = {
        .generator = crypt_iv_plain64_gen
};

static struct crypt_iv_operations crypt_iv_essiv_ops = {
        .ctr       = crypt_iv_essiv_ctr,
        .dtr       = crypt_iv_essiv_dtr,
        .init      = crypt_iv_essiv_init,
        .wipe      = crypt_iv_essiv_wipe,
        .generator = crypt_iv_essiv_gen
};

static struct crypt_iv_operations crypt_iv_benbi_ops = {
        .ctr       = crypt_iv_benbi_ctr,
        .dtr       = crypt_iv_benbi_dtr,
        .generator = crypt_iv_benbi_gen
};

static struct crypt_iv_operations crypt_iv_null_ops = {
        .generator = crypt_iv_null_gen
};

static struct crypt_iv_operations crypt_iv_lmk_ops = {
        .ctr       = crypt_iv_lmk_ctr,
        .dtr       = crypt_iv_lmk_dtr,
        .init      = crypt_iv_lmk_init,
        .wipe      = crypt_iv_lmk_wipe,
        .generator = crypt_iv_lmk_gen,
        .post      = crypt_iv_lmk_post
};

static struct crypt_iv_operations crypt_iv_tcw_ops = {
        .ctr       = crypt_iv_tcw_ctr,
        .dtr       = crypt_iv_tcw_dtr,
        .init      = crypt_iv_tcw_init,
        .wipe      = crypt_iv_tcw_wipe,
        .generator = crypt_iv_tcw_gen,
        .post      = crypt_iv_tcw_post
};

static void crypt_convert_init(struct crypt_config *cc,
                               struct convert_context *ctx,
                               struct bio *bio_out, struct bio *bio_in,
                               sector_t sector)
{
        ctx->bio_in = bio_in;
        ctx->bio_out = bio_out;
        if (bio_in)
                ctx->iter_in = bio_in->bi_iter;
        if (bio_out)
                ctx->iter_out = bio_out->bi_iter;
        ctx->cc_sector = sector + cc->iv_offset;
        init_completion(&ctx->restart);
}

static struct dm_crypt_request *dmreq_of_req(struct crypt_config *cc,
                                             struct skcipher_request *req)
{
        return (struct dm_crypt_request *)((char *)req + cc->dmreq_start);
}

static struct skcipher_request *req_of_dmreq(struct crypt_config *cc,
                                               struct dm_crypt_request *dmreq)
{
        return (struct skcipher_request *)((char *)dmreq - cc->dmreq_start);
}

static u8 *iv_of_dmreq(struct crypt_config *cc,
                       struct dm_crypt_request *dmreq)
{
        return (u8 *)ALIGN((unsigned long)(dmreq + 1),
                crypto_skcipher_alignmask(any_tfm(cc)) + 1);
}

static int crypt_convert_block(struct crypt_config *cc,
                               struct convert_context *ctx,
                               struct skcipher_request *req)
{
        struct bio_vec bv_in = bio_iter_iovec(ctx->bio_in, ctx->iter_in);
        struct bio_vec bv_out = bio_iter_iovec(ctx->bio_out, ctx->iter_out);
        struct dm_crypt_request *dmreq;
        u8 *iv;
        int r;

        dmreq = dmreq_of_req(cc, req);
        iv = iv_of_dmreq(cc, dmreq);

        dmreq->iv_sector = ctx->cc_sector;
        dmreq->ctx = ctx;
        sg_init_table(&dmreq->sg_in, 1);
        sg_set_page(&dmreq->sg_in, bv_in.bv_page, 1 << SECTOR_SHIFT,
                    bv_in.bv_offset);

        sg_init_table(&dmreq->sg_out, 1);
        sg_set_page(&dmreq->sg_out, bv_out.bv_page, 1 << SECTOR_SHIFT,
                    bv_out.bv_offset);

        bio_advance_iter(ctx->bio_in, &ctx->iter_in, 1 << SECTOR_SHIFT);
        bio_advance_iter(ctx->bio_out, &ctx->iter_out, 1 << SECTOR_SHIFT);

        if (cc->iv_gen_ops) {
                r = cc->iv_gen_ops->generator(cc, iv, dmreq);
                if (r < 0)
                        return r;
        }

        skcipher_request_set_crypt(req, &dmreq->sg_in, &dmreq->sg_out,
                                   1 << SECTOR_SHIFT, iv);

        if (bio_data_dir(ctx->bio_in) == WRITE)
                r = crypto_skcipher_encrypt(req);
        else
                r = crypto_skcipher_decrypt(req);

        if (!r && cc->iv_gen_ops && cc->iv_gen_ops->post)
                r = cc->iv_gen_ops->post(cc, iv, dmreq);

        return r;
}

static void kcryptd_async_done(struct crypto_async_request *async_req,
                               int error);

static void crypt_alloc_req(struct crypt_config *cc,
                            struct convert_context *ctx)
{
        unsigned key_index = ctx->cc_sector & (cc->tfms_count - 1);

        if (!ctx->req)
                ctx->req = mempool_alloc(cc->req_pool, GFP_NOIO);

        skcipher_request_set_tfm(ctx->req, cc->tfms[key_index]);

        /*
         * Use REQ_MAY_BACKLOG so a cipher driver internally backlogs
         * requests if driver request queue is full.
         */
        skcipher_request_set_callback(ctx->req,
            CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
            kcryptd_async_done, dmreq_of_req(cc, ctx->req));
}

static void crypt_free_req(struct crypt_config *cc,
                           struct skcipher_request *req, struct bio *base_bio)
{
        struct dm_crypt_io *io = dm_per_bio_data(base_bio, cc->per_bio_data_size);

        if ((struct skcipher_request *)(io + 1) != req)
                mempool_free(req, cc->req_pool);
}

/*
 * Encrypt / decrypt data from one bio to another one (can be the same one)
 */
static int crypt_convert(struct crypt_config *cc,
                         struct convert_context *ctx)
{
        int r;

        atomic_set(&ctx->cc_pending, 1);

        while (ctx->iter_in.bi_size && ctx->iter_out.bi_size) {

                crypt_alloc_req(cc, ctx);

                atomic_inc(&ctx->cc_pending);

                r = crypt_convert_block(cc, ctx, ctx->req);

                switch (r) {
                /*
                 * The request was queued by a crypto driver
                 * but the driver request queue is full, let's wait.
                 */
                case -EBUSY:
                        wait_for_completion(&ctx->restart);
                        reinit_completion(&ctx->restart);
                        /* fall through */
                /*
                 * The request is queued and processed asynchronously,
                 * completion function kcryptd_async_done() will be called.
                 */
                case -EINPROGRESS:
                        ctx->req = NULL;
                        ctx->cc_sector++;
                        continue;
                /*
                 * The request was already processed (synchronously).
                 */
                case 0:
                        atomic_dec(&ctx->cc_pending);
                        ctx->cc_sector++;
                        cond_resched();
                        continue;

                /* There was an error while processing the request. */
                default:
                        atomic_dec(&ctx->cc_pending);
                        return r;
                }
        }

        return 0;
}

static void crypt_free_buffer_pages(struct crypt_config *cc, struct bio *clone);

/*
 * Generate a new unfragmented bio with the given size
 * This should never violate the device limitations (but only because
 * max_segment_size is being constrained to PAGE_SIZE).
 *
 * This function may be called concurrently. If we allocate from the mempool
 * concurrently, there is a possibility of deadlock. For example, if we have
 * mempool of 256 pages, two processes, each wanting 256, pages allocate from
 * the mempool concurrently, it may deadlock in a situation where both processes
 * have allocated 128 pages and the mempool is exhausted.
 *
 * In order to avoid this scenario we allocate the pages under a mutex.
 *
 * In order to not degrade performance with excessive locking, we try
 * non-blocking allocations without a mutex first but on failure we fallback
 * to blocking allocations with a mutex.
 */
static struct bio *crypt_alloc_buffer(struct dm_crypt_io *io, unsigned size)
{
        struct crypt_config *cc = io->cc;
        struct bio *clone;
        unsigned int nr_iovecs = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
        gfp_t gfp_mask = GFP_NOWAIT | __GFP_HIGHMEM;
        unsigned i, len, remaining_size;
        struct page *page;
        struct bio_vec *bvec;

retry:

        if (unlikely(gfp_mask & __GFP_DIRECT_RECLAIM))
                mutex_lock(&cc->bio_alloc_lock);

        clone = bio_alloc_bioset(GFP_NOIO, nr_iovecs, cc->bs);
        if (!clone)
                goto return_clone;

        clone_init(io, clone);

        remaining_size = size;

        for (i = 0; i < nr_iovecs; i++) {
                page = mempool_alloc(cc->page_pool, gfp_mask);
                if (!page) {
                        crypt_free_buffer_pages(cc, clone);
                        bio_put(clone);
                        gfp_mask |= __GFP_DIRECT_RECLAIM;
                        goto retry;
                }

                len = (remaining_size > PAGE_SIZE) ? PAGE_SIZE : remaining_size;

                bvec = &clone->bi_io_vec[clone->bi_vcnt++];
                bvec->bv_page = page;
                bvec->bv_len = len;
                bvec->bv_offset = 0;

                clone->bi_iter.bi_size += len;

                remaining_size -= len;
        }

return_clone:
        if (unlikely(gfp_mask & __GFP_DIRECT_RECLAIM))
                mutex_unlock(&cc->bio_alloc_lock);

        return clone;
}

static void crypt_free_buffer_pages(struct crypt_config *cc, struct bio *clone)
{
        unsigned int i;
        struct bio_vec *bv;

        bio_for_each_segment_all(bv, clone, i) {
                BUG_ON(!bv->bv_page);
                mempool_free(bv->bv_page, cc->page_pool);
                bv->bv_page = NULL;
        }
}

static void crypt_io_init(struct dm_crypt_io *io, struct crypt_config *cc,
                          struct bio *bio, sector_t sector)
{
        io->cc = cc;
        io->base_bio = bio;
        io->sector = sector;
        io->error = 0;
        io->ctx.req = NULL;
        atomic_set(&io->io_pending, 0);
}

static void crypt_inc_pending(struct dm_crypt_io *io)
{
        atomic_inc(&io->io_pending);
}

/*
 * One of the bios was finished. Check for completion of
 * the whole request and correctly clean up the buffer.
 */
static void crypt_dec_pending(struct dm_crypt_io *io)
{
        struct crypt_config *cc = io->cc;
        struct bio *base_bio = io->base_bio;
        int error = io->error;

        if (!atomic_dec_and_test(&io->io_pending))
                return;

        if (io->ctx.req)
                crypt_free_req(cc, io->ctx.req, base_bio);

        base_bio->bi_error = error;
        bio_endio(base_bio);
}

/*
 * kcryptd/kcryptd_io:
 *
 * Needed because it would be very unwise to do decryption in an
 * interrupt context.
 *
 * kcryptd performs the actual encryption or decryption.
 *
 * kcryptd_io performs the IO submission.
 *
 * They must be separated as otherwise the final stages could be
 * starved by new requests which can block in the first stages due
 * to memory allocation.
 *
 * The work is done per CPU global for all dm-crypt instances.
 * They should not depend on each other and do not block.
 */
static void crypt_endio(struct bio *clone)
{
        struct dm_crypt_io *io = clone->bi_private;
        struct crypt_config *cc = io->cc;
        unsigned rw = bio_data_dir(clone);
        int error;

        /*
         * free the processed pages
         */
        if (rw == WRITE)
                crypt_free_buffer_pages(cc, clone);

        error = clone->bi_error;
        bio_put(clone);

        if (rw == READ && !error) {
                kcryptd_queue_crypt(io);
                return;
        }

        if (unlikely(error))
                io->error = error;

        crypt_dec_pending(io);
}

static void clone_init(struct dm_crypt_io *io, struct bio *clone)
{
        struct crypt_config *cc = io->cc;

        clone->bi_private = io;
        clone->bi_end_io  = crypt_endio;
        clone->bi_bdev    = cc->dev->bdev;
        clone->bi_rw      = io->base_bio->bi_rw;
}

static int kcryptd_io_read(struct dm_crypt_io *io, gfp_t gfp)
{
        struct crypt_config *cc = io->cc;
        struct bio *clone;

        /*
         * We need the original biovec array in order to decrypt
         * the whole bio data *afterwards* -- thanks to immutable
         * biovecs we don't need to worry about the block layer
         * modifying the biovec array; so leverage bio_clone_fast().
         */
        clone = bio_clone_fast(io->base_bio, gfp, cc->bs);
        if (!clone)
                return 1;

        crypt_inc_pending(io);

        clone_init(io, clone);
        clone->bi_iter.bi_sector = cc->start + io->sector;

        generic_make_request(clone);
        return 0;
}

static void kcryptd_io_read_work(struct work_struct *work)
{
        struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);

        crypt_inc_pending(io);
        if (kcryptd_io_read(io, GFP_NOIO))
                io->error = -ENOMEM;
        crypt_dec_pending(io);
}

static void kcryptd_queue_read(struct dm_crypt_io *io)
{
        struct crypt_config *cc = io->cc;

        INIT_WORK(&io->work, kcryptd_io_read_work);
        queue_work(cc->io_queue, &io->work);
}

static void kcryptd_io_write(struct dm_crypt_io *io)
{
        struct bio *clone = io->ctx.bio_out;

        generic_make_request(clone);
}

#define crypt_io_from_node(node) rb_entry((node), struct dm_crypt_io, rb_node)

static int dmcrypt_write(void *data)
{
        struct crypt_config *cc = data;
        struct dm_crypt_io *io;

        while (1) {
                struct rb_root write_tree;
                struct blk_plug plug;

                DECLARE_WAITQUEUE(wait, current);

                spin_lock_irq(&cc->write_thread_wait.lock);
continue_locked:

                if (!RB_EMPTY_ROOT(&cc->write_tree))
                        goto pop_from_list;

                if (unlikely(test_bit(DM_CRYPT_EXIT_THREAD, &cc->flags))) {
                        spin_unlock_irq(&cc->write_thread_wait.lock);
                        break;
                }

                __set_current_state(TASK_INTERRUPTIBLE);
                __add_wait_queue(&cc->write_thread_wait, &wait);

                spin_unlock_irq(&cc->write_thread_wait.lock);

                schedule();

                spin_lock_irq(&cc->write_thread_wait.lock);
                __remove_wait_queue(&cc->write_thread_wait, &wait);
                goto continue_locked;

pop_from_list:
                write_tree = cc->write_tree;
                cc->write_tree = RB_ROOT;
                spin_unlock_irq(&cc->write_thread_wait.lock);

                BUG_ON(rb_parent(write_tree.rb_node));

                /*
                 * Note: we cannot walk the tree here with rb_next because
                 * the structures may be freed when kcryptd_io_write is called.
                 */
                blk_start_plug(&plug);
                do {
                        io = crypt_io_from_node(rb_first(&write_tree));
                        rb_erase(&io->rb_node, &write_tree);
                        kcryptd_io_write(io);
                } while (!RB_EMPTY_ROOT(&write_tree));
                blk_finish_plug(&plug);
        }
        return 0;
}

static void kcryptd_crypt_write_io_submit(struct dm_crypt_io *io, int async)
{
        struct bio *clone = io->ctx.bio_out;
        struct crypt_config *cc = io->cc;
        unsigned long flags;
        sector_t sector;
        struct rb_node **rbp, *parent;

        if (unlikely(io->error < 0)) {
                crypt_free_buffer_pages(cc, clone);
                bio_put(clone);
                crypt_dec_pending(io);
                return;
        }

        /* crypt_convert should have filled the clone bio */
        BUG_ON(io->ctx.iter_out.bi_size);

        clone->bi_iter.bi_sector = cc->start + io->sector;

        if (likely(!async) && test_bit(DM_CRYPT_NO_OFFLOAD, &cc->flags)) {
                generic_make_request(clone);
                return;
        }

        spin_lock_irqsave(&cc->write_thread_wait.lock, flags);
        rbp = &cc->write_tree.rb_node;
        parent = NULL;
        sector = io->sector;
        while (*rbp) {
                parent = *rbp;
                if (sector < crypt_io_from_node(parent)->sector)
                        rbp = &(*rbp)->rb_left;
                else
                        rbp = &(*rbp)->rb_right;
        }
        rb_link_node(&io->rb_node, parent, rbp);
        rb_insert_color(&io->rb_node, &cc->write_tree);

        wake_up_locked(&cc->write_thread_wait);
        spin_unlock_irqrestore(&cc->write_thread_wait.lock, flags);
}

static void kcryptd_crypt_write_convert(struct dm_crypt_io *io)
{
        struct crypt_config *cc = io->cc;
        struct bio *clone;
        int crypt_finished;
        sector_t sector = io->sector;
        int r;

        /*
         * Prevent io from disappearing until this function completes.
         */
        crypt_inc_pending(io);
        crypt_convert_init(cc, &io->ctx, NULL, io->base_bio, sector);

        clone = crypt_alloc_buffer(io, io->base_bio->bi_iter.bi_size);
        if (unlikely(!clone)) {
                io->error = -EIO;
                goto dec;
        }

        io->ctx.bio_out = clone;
        io->ctx.iter_out = clone->bi_iter;

        sector += bio_sectors(clone);

        crypt_inc_pending(io);
        r = crypt_convert(cc, &io->ctx);
        if (r)
                io->error = -EIO;
        crypt_finished = atomic_dec_and_test(&io->ctx.cc_pending);

        /* Encryption was already finished, submit io now */
        if (crypt_finished) {
                kcryptd_crypt_write_io_submit(io, 0);
                io->sector = sector;
        }

dec:
        crypt_dec_pending(io);
}

static void kcryptd_crypt_read_done(struct dm_crypt_io *io)
{
        crypt_dec_pending(io);
}

static void kcryptd_crypt_read_convert(struct dm_crypt_io *io)
{
        struct crypt_config *cc = io->cc;
        int r = 0;

        crypt_inc_pending(io);

        crypt_convert_init(cc, &io->ctx, io->base_bio, io->base_bio,
                           io->sector);

        r = crypt_convert(cc, &io->ctx);
        if (r < 0)
                io->error = -EIO;

        if (atomic_dec_and_test(&io->ctx.cc_pending))
                kcryptd_crypt_read_done(io);

        crypt_dec_pending(io);
}

static void kcryptd_async_done(struct crypto_async_request *async_req,
                               int error)
{
        struct dm_crypt_request *dmreq = async_req->data;
        struct convert_context *ctx = dmreq->ctx;
        struct dm_crypt_io *io = container_of(ctx, struct dm_crypt_io, ctx);
        struct crypt_config *cc = io->cc;

        /*
         * A request from crypto driver backlog is going to be processed now,
         * finish the completion and continue in crypt_convert().
         * (Callback will be called for the second time for this request.)
         */
        if (error == -EINPROGRESS) {
                complete(&ctx->restart);
                return;
        }

        if (!error && cc->iv_gen_ops && cc->iv_gen_ops->post)
                error = cc->iv_gen_ops->post(cc, iv_of_dmreq(cc, dmreq), dmreq);

        if (error < 0)
                io->error = -EIO;

        crypt_free_req(cc, req_of_dmreq(cc, dmreq), io->base_bio);

        if (!atomic_dec_and_test(&ctx->cc_pending))
                return;

        if (bio_data_dir(io->base_bio) == READ)
                kcryptd_crypt_read_done(io);
        else
                kcryptd_crypt_write_io_submit(io, 1);
}

static void kcryptd_crypt(struct work_struct *work)
{
        struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);

        if (bio_data_dir(io->base_bio) == READ)
                kcryptd_crypt_read_convert(io);
        else
                kcryptd_crypt_write_convert(io);
}

static void kcryptd_queue_crypt(struct dm_crypt_io *io)
{
        struct crypt_config *cc = io->cc;

        INIT_WORK(&io->work, kcryptd_crypt);
        queue_work(cc->crypt_queue, &io->work);
}

/*
 * Decode key from its hex representation
 */
static int crypt_decode_key(u8 *key, char *hex, unsigned int size)
{
        char buffer[3];
        unsigned int i;

        buffer[2] = '\0';

        for (i = 0; i < size; i++) {
                buffer[0] = *hex++;
                buffer[1] = *hex++;

                if (kstrtou8(buffer, 16, &key[i]))
                        return -EINVAL;
        }

        if (*hex != '\0')
                return -EINVAL;

        return 0;
}

static void crypt_free_tfms(struct crypt_config *cc)
{
        unsigned i;

        if (!cc->tfms)
                return;

        for (i = 0; i < cc->tfms_count; i++)
                if (cc->tfms[i] && !IS_ERR(cc->tfms[i])) {
                        crypto_free_skcipher(cc->tfms[i]);
                        cc->tfms[i] = NULL;
                }

        kfree(cc->tfms);
        cc->tfms = NULL;
}

static int crypt_alloc_tfms(struct crypt_config *cc, char *ciphermode)
{
        unsigned i;
        int err;

        cc->tfms = kmalloc(cc->tfms_count * sizeof(struct crypto_skcipher *),
                           GFP_KERNEL);
        if (!cc->tfms)
                return -ENOMEM;

        for (i = 0; i < cc->tfms_count; i++) {
                cc->tfms[i] = crypto_alloc_skcipher(ciphermode, 0, 0);
                if (IS_ERR(cc->tfms[i])) {
                        err = PTR_ERR(cc->tfms[i]);
                        crypt_free_tfms(cc);
                        return err;
                }
        }

        return 0;
}

static int crypt_setkey_allcpus(struct crypt_config *cc)
{
        unsigned subkey_size;
        int err = 0, i, r;

        /* Ignore extra keys (which are used for IV etc) */
        subkey_size = (cc->key_size - cc->key_extra_size) >> ilog2(cc->tfms_count);

        for (i = 0; i < cc->tfms_count; i++) {
                r = crypto_skcipher_setkey(cc->tfms[i],
                                           cc->key + (i * subkey_size),
                                           subkey_size);
                if (r)
                        err = r;
        }

        return err;
}

static int crypt_set_key(struct crypt_config *cc, char *key)
{
        int r = -EINVAL;
        int key_string_len = strlen(key);

        /* The key size may not be changed. */
        if (cc->key_size != (key_string_len >> 1))
                goto out;

        /* Hyphen (which gives a key_size of zero) means there is no key. */
        if (!cc->key_size && strcmp(key, "-"))
                goto out;

        if (cc->key_size && crypt_decode_key(cc->key, key, cc->key_size) < 0)
                goto out;

        set_bit(DM_CRYPT_KEY_VALID, &cc->flags);

        r = crypt_setkey_allcpus(cc);

out:
        /* Hex key string not needed after here, so wipe it. */
        memset(key, '0', key_string_len);

        return r;
}

static int crypt_wipe_key(struct crypt_config *cc)
{
        clear_bit(DM_CRYPT_KEY_VALID, &cc->flags);
        memset(&cc->key, 0, cc->key_size * sizeof(u8));

        return crypt_setkey_allcpus(cc);
}

static void crypt_dtr(struct dm_target *ti)
{
        struct crypt_config *cc = ti->private;

        ti->private = NULL;

        if (!cc)
                return;

        if (cc->write_thread) {
                spin_lock_irq(&cc->write_thread_wait.lock);
                set_bit(DM_CRYPT_EXIT_THREAD, &cc->flags);
                wake_up_locked(&cc->write_thread_wait);
                spin_unlock_irq(&cc->write_thread_wait.lock);
                kthread_stop(cc->write_thread);
        }

        if (cc->io_queue)
                destroy_workqueue(cc->io_queue);
        if (cc->crypt_queue)
                destroy_workqueue(cc->crypt_queue);

        crypt_free_tfms(cc);

        if (cc->bs)
                bioset_free(cc->bs);

        mempool_destroy(cc->page_pool);
        mempool_destroy(cc->req_pool);

        if (cc->iv_gen_ops && cc->iv_gen_ops->dtr)
                cc->iv_gen_ops->dtr(cc);

        if (cc->dev)
                dm_put_device(ti, cc->dev);

        kzfree(cc->cipher);
        kzfree(cc->cipher_string);

        /* Must zero key material before freeing */
        kzfree(cc);
}

static int crypt_ctr_cipher(struct dm_target *ti,
                            char *cipher_in, char *key)
{
        struct crypt_config *cc = ti->private;
        char *tmp, *cipher, *chainmode, *ivmode, *ivopts, *keycount;
        char *cipher_api = NULL;
        int ret = -EINVAL;
        char dummy;

        /* Convert to crypto api definition? */
        if (strchr(cipher_in, '(')) {
                ti->error = "Bad cipher specification";
                return -EINVAL;
        }

        cc->cipher_string = kstrdup(cipher_in, GFP_KERNEL);
        if (!cc->cipher_string)
                goto bad_mem;

        /*
         * Legacy dm-crypt cipher specification
         * cipher[:keycount]-mode-iv:ivopts
         */
        tmp = cipher_in;
        keycount = strsep(&tmp, "-");
        cipher = strsep(&keycount, ":");

        if (!keycount)
                cc->tfms_count = 1;
        else if (sscanf(keycount, "%u%c", &cc->tfms_count, &dummy) != 1 ||
                 !is_power_of_2(cc->tfms_count)) {
                ti->error = "Bad cipher key count specification";
                return -EINVAL;
        }
        cc->key_parts = cc->tfms_count;
        cc->key_extra_size = 0;

        cc->cipher = kstrdup(cipher, GFP_KERNEL);
        if (!cc->cipher)
                goto bad_mem;

        chainmode = strsep(&tmp, "-");
        ivopts = strsep(&tmp, "-");
        ivmode = strsep(&ivopts, ":");

        if (tmp)
                DMWARN("Ignoring unexpected additional cipher options");

        /*
         * For compatibility with the original dm-crypt mapping format, if
         * only the cipher name is supplied, use cbc-plain.
         */
        if (!chainmode || (!strcmp(chainmode, "plain") && !ivmode)) {
                chainmode = "cbc";
                ivmode = "plain";
        }

        if (strcmp(chainmode, "ecb") && !ivmode) {
                ti->error = "IV mechanism required";
                return -EINVAL;
        }

        cipher_api = kmalloc(CRYPTO_MAX_ALG_NAME, GFP_KERNEL);
        if (!cipher_api)
                goto bad_mem;

        ret = snprintf(cipher_api, CRYPTO_MAX_ALG_NAME,
                       "%s(%s)", chainmode, cipher);
        if (ret < 0) {
                kfree(cipher_api);
                goto bad_mem;
        }

        /* Allocate cipher */
        ret = crypt_alloc_tfms(cc, cipher_api);
        if (ret < 0) {
                ti->error = "Error allocating crypto tfm";
                goto bad;
        }

        /* Initialize IV */
        cc->iv_size = crypto_skcipher_ivsize(any_tfm(cc));
        if (cc->iv_size)
                /* at least a 64 bit sector number should fit in our buffer */
                cc->iv_size = max(cc->iv_size,
                                  (unsigned int)(sizeof(u64) / sizeof(u8)));
        else if (ivmode) {
                DMWARN("Selected cipher does not support IVs");
                ivmode = NULL;
        }

        /* Choose ivmode, see comments at iv code. */
        if (ivmode == NULL)
                cc->iv_gen_ops = NULL;
        else if (strcmp(ivmode, "plain") == 0)
                cc->iv_gen_ops = &crypt_iv_plain_ops;
        else if (strcmp(ivmode, "plain64") == 0)
                cc->iv_gen_ops = &crypt_iv_plain64_ops;
        else if (strcmp(ivmode, "essiv") == 0)
                cc->iv_gen_ops = &crypt_iv_essiv_ops;
        else if (strcmp(ivmode, "benbi") == 0)
                cc->iv_gen_ops = &crypt_iv_benbi_ops;
        else if (strcmp(ivmode, "null") == 0)
                cc->iv_gen_ops = &crypt_iv_null_ops;
        else if (strcmp(ivmode, "lmk") == 0) {
                cc->iv_gen_ops = &crypt_iv_lmk_ops;
                /*
                 * Version 2 and 3 is recognised according
                 * to length of provided multi-key string.
                 * If present (version 3), last key is used as IV seed.
                 * All keys (including IV seed) are always the same size.
                 */
                if (cc->key_size % cc->key_parts) {
                        cc->key_parts++;
                        cc->key_extra_size = cc->key_size / cc->key_parts;
                }
        } else if (strcmp(ivmode, "tcw") == 0) {
                cc->iv_gen_ops = &crypt_iv_tcw_ops;
                cc->key_parts += 2; /* IV + whitening */
                cc->key_extra_size = cc->iv_size + TCW_WHITENING_SIZE;
        } else {
                ret = -EINVAL;
                ti->error = "Invalid IV mode";
                goto bad;
        }

        /* Initialize and set key */
        ret = crypt_set_key(cc, key);
        if (ret < 0) {
                ti->error = "Error decoding and setting key";
                goto bad;
        }

        /* Allocate IV */
        if (cc->iv_gen_ops && cc->iv_gen_ops->ctr) {
                ret = cc->iv_gen_ops->ctr(cc, ti, ivopts);
                if (ret < 0) {
                        ti->error = "Error creating IV";
                        goto bad;
                }
        }

        /* Initialize IV (set keys for ESSIV etc) */
        if (cc->iv_gen_ops && cc->iv_gen_ops->init) {
                ret = cc->iv_gen_ops->init(cc);
                if (ret < 0) {
                        ti->error = "Error initialising IV";
                        goto bad;
                }
        }

        ret = 0;
bad:
        kfree(cipher_api);
        return ret;

bad_mem:
        ti->error = "Cannot allocate cipher strings";
        return -ENOMEM;
}

/*
 * Construct an encryption mapping:
 * <cipher> <key> <iv_offset> <dev_path> <start>
 */
static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
        struct crypt_config *cc;
        unsigned int key_size, opt_params;
        unsigned long long tmpll;
        int ret;
        size_t iv_size_padding;
        struct dm_arg_set as;
        const char *opt_string;
        char dummy;

        static struct dm_arg _args[] = {
                {0, 3, "Invalid number of feature args"},
        };

        if (argc < 5) {
                ti->error = "Not enough arguments";
                return -EINVAL;
        }

        key_size = strlen(argv[1]) >> 1;

        cc = kzalloc(sizeof(*cc) + key_size * sizeof(u8), GFP_KERNEL);
        if (!cc) {
                ti->error = "Cannot allocate encryption context";
                return -ENOMEM;
        }
        cc->key_size = key_size;

        ti->private = cc;
        ret = crypt_ctr_cipher(ti, argv[0], argv[1]);
        if (ret < 0)
                goto bad;

        cc->dmreq_start = sizeof(struct skcipher_request);
        cc->dmreq_start += crypto_skcipher_reqsize(any_tfm(cc));
        cc->dmreq_start = ALIGN(cc->dmreq_start, __alignof__(struct dm_crypt_request));

        if (crypto_skcipher_alignmask(any_tfm(cc)) < CRYPTO_MINALIGN) {
                /* Allocate the padding exactly */
                iv_size_padding = -(cc->dmreq_start + sizeof(struct dm_crypt_request))
                                & crypto_skcipher_alignmask(any_tfm(cc));
        } else {
                /*
                 * If the cipher requires greater alignment than kmalloc
                 * alignment, we don't know the exact position of the
                 * initialization vector. We must assume worst case.
                 */
                iv_size_padding = crypto_skcipher_alignmask(any_tfm(cc));
        }

        ret = -ENOMEM;
        cc->req_pool = mempool_create_kmalloc_pool(MIN_IOS, cc->dmreq_start +
                        sizeof(struct dm_crypt_request) + iv_size_padding + cc->iv_size);
        if (!cc->req_pool) {
                ti->error = "Cannot allocate crypt request mempool";
                goto bad;
        }

        cc->per_bio_data_size = ti->per_io_data_size =
                ALIGN(sizeof(struct dm_crypt_io) + cc->dmreq_start +
                      sizeof(struct dm_crypt_request) + iv_size_padding + cc->iv_size,
                      ARCH_KMALLOC_MINALIGN);

        cc->page_pool = mempool_create_page_pool(BIO_MAX_PAGES, 0);
        if (!cc->page_pool) {
                ti->error = "Cannot allocate page mempool";
                goto bad;
        }

        cc->bs = bioset_create(MIN_IOS, 0);
        if (!cc->bs) {
                ti->error = "Cannot allocate crypt bioset";
                goto bad;
        }

        mutex_init(&cc->bio_alloc_lock);

        ret = -EINVAL;
        if (sscanf(argv[2], "%llu%c", &tmpll, &dummy) != 1) {
                ti->error = "Invalid iv_offset sector";
                goto bad;
        }
        cc->iv_offset = tmpll;

        ret = dm_get_device(ti, argv[3], dm_table_get_mode(ti->table), &cc->dev);
        if (ret) {
                ti->error = "Device lookup failed";
                goto bad;
        }

        ret = -EINVAL;
        if (sscanf(argv[4], "%llu%c", &tmpll, &dummy) != 1) {
                ti->error = "Invalid device sector";
                goto bad;
        }
        cc->start = tmpll;

        argv += 5;
        argc -= 5;

        /* Optional parameters */
        if (argc) {
                as.argc = argc;
                as.argv = argv;

                ret = dm_read_arg_group(_args, &as, &opt_params, &ti->error);
                if (ret)
                        goto bad;

                ret = -EINVAL;
                while (opt_params--) {
                        opt_string = dm_shift_arg(&as);
                        if (!opt_string) {
                                ti->error = "Not enough feature arguments";
                                goto bad;
                        }

                        if (!strcasecmp(opt_string, "allow_discards"))
                                ti->num_discard_bios = 1;

                        else if (!strcasecmp(opt_string, "same_cpu_crypt"))
                                set_bit(DM_CRYPT_SAME_CPU, &cc->flags);

                        else if (!strcasecmp(opt_string, "submit_from_crypt_cpus"))
                                set_bit(DM_CRYPT_NO_OFFLOAD, &cc->flags);

                        else {
                                ti->error = "Invalid feature arguments";
                                goto bad;
                        }
                }
        }

        ret = -ENOMEM;
        cc->io_queue = alloc_workqueue("kcryptd_io", WQ_MEM_RECLAIM, 1);
        if (!cc->io_queue) {
                ti->error = "Couldn't create kcryptd io queue";
                goto bad;
        }

        if (test_bit(DM_CRYPT_SAME_CPU, &cc->flags))
                cc->crypt_queue = alloc_workqueue("kcryptd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM, 1);
        else
                cc->crypt_queue = alloc_workqueue("kcryptd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND,
                                                  num_online_cpus());
        if (!cc->crypt_queue) {
                ti->error = "Couldn't create kcryptd queue";
                goto bad;
        }

        init_waitqueue_head(&cc->write_thread_wait);
        cc->write_tree = RB_ROOT;

        cc->write_thread = kthread_create(dmcrypt_write, cc, "dmcrypt_write");
        if (IS_ERR(cc->write_thread)) {
                ret = PTR_ERR(cc->write_thread);
                cc->write_thread = NULL;
                ti->error = "Couldn't spawn write thread";
                goto bad;
        }
        wake_up_process(cc->write_thread);

        ti->num_flush_bios = 1;
        ti->discard_zeroes_data_unsupported = true;

        return 0;

bad:
        crypt_dtr(ti);
        return ret;
}

static int crypt_map(struct dm_target *ti, struct bio *bio)
{
        struct dm_crypt_io *io;
        struct crypt_config *cc = ti->private;

        /*
         * If bio is REQ_FLUSH or REQ_DISCARD, just bypass crypt queues.
         * - for REQ_FLUSH device-mapper core ensures that no IO is in-flight
         * - for REQ_DISCARD caller must use flush if IO ordering matters
         */
        if (unlikely(bio->bi_rw & (REQ_FLUSH | REQ_DISCARD))) {
                bio->bi_bdev = cc->dev->bdev;
                if (bio_sectors(bio))
                        bio->bi_iter.bi_sector = cc->start +
                                dm_target_offset(ti, bio->bi_iter.bi_sector);
                return DM_MAPIO_REMAPPED;
        }

        io = dm_per_bio_data(bio, cc->per_bio_data_size);
        crypt_io_init(io, cc, bio, dm_target_offset(ti, bio->bi_iter.bi_sector));
        io->ctx.req = (struct skcipher_request *)(io + 1);

        if (bio_data_dir(io->base_bio) == READ) {
                if (kcryptd_io_read(io, GFP_NOWAIT))
                        kcryptd_queue_read(io);
        } else
                kcryptd_queue_crypt(io);

        return DM_MAPIO_SUBMITTED;
}

static void crypt_status(struct dm_target *ti, status_type_t type,
                         unsigned status_flags, char *result, unsigned maxlen)
{
        struct crypt_config *cc = ti->private;
        unsigned i, sz = 0;
        int num_feature_args = 0;

        switch (type) {
        case STATUSTYPE_INFO:
                result[0] = '\0';
                break;

        case STATUSTYPE_TABLE:
                DMEMIT("%s ", cc->cipher_string);

                if (cc->key_size > 0)
                        for (i = 0; i < cc->key_size; i++)
                                DMEMIT("%02x", cc->key[i]);
                else
                        DMEMIT("-");

                DMEMIT(" %llu %s %llu", (unsigned long long)cc->iv_offset,
                                cc->dev->name, (unsigned long long)cc->start);

                num_feature_args += !!ti->num_discard_bios;
                num_feature_args += test_bit(DM_CRYPT_SAME_CPU, &cc->flags);
                num_feature_args += test_bit(DM_CRYPT_NO_OFFLOAD, &cc->flags);
                if (num_feature_args) {
                        DMEMIT(" %d", num_feature_args);
                        if (ti->num_discard_bios)
                                DMEMIT(" allow_discards");
                        if (test_bit(DM_CRYPT_SAME_CPU, &cc->flags))
                                DMEMIT(" same_cpu_crypt");
                        if (test_bit(DM_CRYPT_NO_OFFLOAD, &cc->flags))
                                DMEMIT(" submit_from_crypt_cpus");
                }

                break;
        }
}

static void crypt_postsuspend(struct dm_target *ti)
{
        struct crypt_config *cc = ti->private;

        set_bit(DM_CRYPT_SUSPENDED, &cc->flags);
}

static int crypt_preresume(struct dm_target *ti)
{
        struct crypt_config *cc = ti->private;

        if (!test_bit(DM_CRYPT_KEY_VALID, &cc->flags)) {
                DMERR("aborting resume - crypt key is not set.");
                return -EAGAIN;
        }

        return 0;
}

static void crypt_resume(struct dm_target *ti)
{

        struct crypt_config *cc = ti->private;

        clear_bit(DM_CRYPT_SUSPENDED, &cc->flags);
}

/* Message interface
 *      key set <key>
 *      key wipe
 */
static int crypt_message(struct dm_target *ti, unsigned argc, char **argv)
{
        struct crypt_config *cc = ti->private;
        int ret = -EINVAL;

        if (argc < 2)
                goto error;

        if (!strcasecmp(argv[0], "key")) {
                if (!test_bit(DM_CRYPT_SUSPENDED, &cc->flags)) {
                        DMWARN("not suspended during key manipulation.");
                        return -EINVAL;
                }
                if (argc == 3 && !strcasecmp(argv[1], "set")) {
                        ret = crypt_set_key(cc, argv[2]);
                        if (ret)
                                return ret;
                        if (cc->iv_gen_ops && cc->iv_gen_ops->init)
                                ret = cc->iv_gen_ops->init(cc);
                        return ret;
                }
                if (argc == 2 && !strcasecmp(argv[1], "wipe")) {
                        if (cc->iv_gen_ops && cc->iv_gen_ops->wipe) {
                                ret = cc->iv_gen_ops->wipe(cc);
                                if (ret)
                                        return ret;
                        }
                        return crypt_wipe_key(cc);
                }
        }

error:
        DMWARN("unrecognised message received.");
        return -EINVAL;
}

static int crypt_iterate_devices(struct dm_target *ti,
                                 iterate_devices_callout_fn fn, void *data)
{
        struct crypt_config *cc = ti->private;

        return fn(ti, cc->dev, cc->start, ti->len, data);
}

static void crypt_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
        /*
         * Unfortunate constraint that is required to avoid the potential
         * for exceeding underlying device's max_segments limits -- due to
         * crypt_alloc_buffer() possibly allocating pages for the encryption
         * bio that are not as physically contiguous as the original bio.
         */
        limits->max_segment_size = PAGE_SIZE;
}

static struct target_type crypt_target = {
        .name   = "crypt",
        .version = {1, 14, 1},
        .module = THIS_MODULE,
        .ctr    = crypt_ctr,
        .dtr    = crypt_dtr,
        .map    = crypt_map,
        .status = crypt_status,
        .postsuspend = crypt_postsuspend,
        .preresume = crypt_preresume,
        .resume = crypt_resume,
        .message = crypt_message,
        .iterate_devices = crypt_iterate_devices,
        .io_hints = crypt_io_hints,
};

static int __init dm_crypt_init(void)
{
        int r;

        r = dm_register_target(&crypt_target);
        if (r < 0)
                DMERR("register failed %d", r);

        return r;
}

static void __exit dm_crypt_exit(void)
{
        dm_unregister_target(&crypt_target);
}

module_init(dm_crypt_init);
module_exit(dm_crypt_exit);

MODULE_AUTHOR("Jana Saout <jana@saout.de>");
MODULE_DESCRIPTION(DM_NAME " target for transparent encryption / decryption");
MODULE_LICENSE("GPL");