[mirror_ubuntu-focal-kernel.git] / drivers / md / dm-crypt.c

/*
 * Copyright (C) 2003 Christophe Saout <christophe@saout.de>
 * Copyright (C) 2004 Clemens Fruhwirth <clemens@endorphin.org>
 * Copyright (C) 2006 Red Hat, Inc. All rights reserved.
 *
 * This file is released under the GPL.
 */

#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 <asm/atomic.h>
#include <linux/scatterlist.h>
#include <asm/page.h>

#include "dm.h"

#define DM_MSG_PREFIX "crypt"
#define MESG_STR(x) x, sizeof(x)

/*
 * per bio private data
 */
struct crypt_io {
        struct dm_target *target;
        struct bio *base_bio;
        struct bio *first_clone;
        struct work_struct work;
        atomic_t pending;
        int error;
};

/*
 * context holding the current state of a multi-part conversion
 */
struct convert_context {
        struct bio *bio_in;
        struct bio *bio_out;
        unsigned int offset_in;
        unsigned int offset_out;
        unsigned int idx_in;
        unsigned int idx_out;
        sector_t sector;
        int write;
};

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);
        const char *(*status)(struct crypt_config *cc);
        int (*generator)(struct crypt_config *cc, u8 *iv, sector_t sector);
};

/*
 * 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 };
struct crypt_config {
        struct dm_dev *dev;
        sector_t start;

        /*
         * pool for per bio private data and
         * for encryption buffer pages
         */
        mempool_t *io_pool;
        mempool_t *page_pool;

        /*
         * crypto related data
         */
        struct crypt_iv_operations *iv_gen_ops;
        char *iv_mode;
        struct crypto_cipher *iv_gen_private;
        sector_t iv_offset;
        unsigned int iv_size;

        char cipher[CRYPTO_MAX_ALG_NAME];
        char chainmode[CRYPTO_MAX_ALG_NAME];
        struct crypto_blkcipher *tfm;
        unsigned long flags;
        unsigned int key_size;
        u8 key[0];
};

#define MIN_IOS        256
#define MIN_POOL_PAGES 32
#define MIN_BIO_PAGES  8

static kmem_cache_t *_crypt_io_pool;

/*
 * Different IV generation algorithms:
 *
 * plain: the initial vector is the 32-bit little-endian version of the sector
 *        number, padded with zeros if neccessary.
 *
 * 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.
 *
 * 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, sector_t sector)
{
        memset(iv, 0, cc->iv_size);
        *(u32 *)iv = cpu_to_le32(sector & 0xffffffff);

        return 0;
}

static int crypt_iv_essiv_ctr(struct crypt_config *cc, struct dm_target *ti,
                              const char *opts)
{
        struct crypto_cipher *essiv_tfm;
        struct crypto_hash *hash_tfm;
        struct hash_desc desc;
        struct scatterlist sg;
        unsigned int saltsize;
        u8 *salt;
        int err;

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

        /* Hash the cipher key with the given hash algorithm */
        hash_tfm = crypto_alloc_hash(opts, 0, CRYPTO_ALG_ASYNC);
        if (IS_ERR(hash_tfm)) {
                ti->error = "Error initializing ESSIV hash";
                return PTR_ERR(hash_tfm);
        }

        saltsize = crypto_hash_digestsize(hash_tfm);
        salt = kmalloc(saltsize, GFP_KERNEL);
        if (salt == NULL) {
                ti->error = "Error kmallocing salt storage in ESSIV";
                crypto_free_hash(hash_tfm);
                return -ENOMEM;
        }

        sg_set_buf(&sg, cc->key, cc->key_size);
        desc.tfm = hash_tfm;
        desc.flags = CRYPTO_TFM_REQ_MAY_SLEEP;
        err = crypto_hash_digest(&desc, &sg, cc->key_size, salt);
        crypto_free_hash(hash_tfm);

        if (err) {
                ti->error = "Error calculating hash in ESSIV";
                return 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";
                kfree(salt);
                return PTR_ERR(essiv_tfm);
        }
        if (crypto_cipher_blocksize(essiv_tfm) !=
            crypto_blkcipher_ivsize(cc->tfm)) {
                ti->error = "Block size of ESSIV cipher does "
                                "not match IV size of block cipher";
                crypto_free_cipher(essiv_tfm);
                kfree(salt);
                return -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);
                kfree(salt);
                return err;
        }
        kfree(salt);

        cc->iv_gen_private = essiv_tfm;
        return 0;
}

static void crypt_iv_essiv_dtr(struct crypt_config *cc)
{
        crypto_free_cipher(cc->iv_gen_private);
        cc->iv_gen_private = NULL;
}

static int crypt_iv_essiv_gen(struct crypt_config *cc, u8 *iv, sector_t sector)
{
        memset(iv, 0, cc->iv_size);
        *(u64 *)iv = cpu_to_le64(sector);
        crypto_cipher_encrypt_one(cc->iv_gen_private, iv, iv);
        return 0;
}

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

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


static int
crypt_convert_scatterlist(struct crypt_config *cc, struct scatterlist *out,
                          struct scatterlist *in, unsigned int length,
                          int write, sector_t sector)
{
        u8 iv[cc->iv_size];
        struct blkcipher_desc desc = {
                .tfm = cc->tfm,
                .info = iv,
                .flags = CRYPTO_TFM_REQ_MAY_SLEEP,
        };
        int r;

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

                if (write)
                        r = crypto_blkcipher_encrypt_iv(&desc, out, in, length);
                else
                        r = crypto_blkcipher_decrypt_iv(&desc, out, in, length);
        } else {
                if (write)
                        r = crypto_blkcipher_encrypt(&desc, out, in, length);
                else
                        r = crypto_blkcipher_decrypt(&desc, out, in, length);
        }

        return r;
}

static void
crypt_convert_init(struct crypt_config *cc, struct convert_context *ctx,
                   struct bio *bio_out, struct bio *bio_in,
                   sector_t sector, int write)
{
        ctx->bio_in = bio_in;
        ctx->bio_out = bio_out;
        ctx->offset_in = 0;
        ctx->offset_out = 0;
        ctx->idx_in = bio_in ? bio_in->bi_idx : 0;
        ctx->idx_out = bio_out ? bio_out->bi_idx : 0;
        ctx->sector = sector + cc->iv_offset;
        ctx->write = write;
}

/*
 * 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 = 0;

        while(ctx->idx_in < ctx->bio_in->bi_vcnt &&
              ctx->idx_out < ctx->bio_out->bi_vcnt) {
                struct bio_vec *bv_in = bio_iovec_idx(ctx->bio_in, ctx->idx_in);
                struct bio_vec *bv_out = bio_iovec_idx(ctx->bio_out, ctx->idx_out);
                struct scatterlist sg_in = {
                        .page = bv_in->bv_page,
                        .offset = bv_in->bv_offset + ctx->offset_in,
                        .length = 1 << SECTOR_SHIFT
                };
                struct scatterlist sg_out = {
                        .page = bv_out->bv_page,
                        .offset = bv_out->bv_offset + ctx->offset_out,
                        .length = 1 << SECTOR_SHIFT
                };

                ctx->offset_in += sg_in.length;
                if (ctx->offset_in >= bv_in->bv_len) {
                        ctx->offset_in = 0;
                        ctx->idx_in++;
                }

                ctx->offset_out += sg_out.length;
                if (ctx->offset_out >= bv_out->bv_len) {
                        ctx->offset_out = 0;
                        ctx->idx_out++;
                }

                r = crypt_convert_scatterlist(cc, &sg_out, &sg_in, sg_in.length,
                                              ctx->write, ctx->sector);
                if (r < 0)
                        break;

                ctx->sector++;
        }

        return r;
}

/*
 * Generate a new unfragmented bio with the given size
 * This should never violate the device limitations
 * May return a smaller bio when running out of pages
 */
static struct bio *
crypt_alloc_buffer(struct crypt_config *cc, unsigned int size,
                   struct bio *base_bio, unsigned int *bio_vec_idx)
{
        struct bio *clone;
        unsigned int nr_iovecs = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
        gfp_t gfp_mask = GFP_NOIO | __GFP_HIGHMEM;
        unsigned int i;

        /*
         * Use __GFP_NOMEMALLOC to tell the VM to act less aggressively and
         * to fail earlier.  This is not necessary but increases throughput.
         * FIXME: Is this really intelligent?
         */
        if (base_bio)
                clone = bio_clone(base_bio, GFP_NOIO|__GFP_NOMEMALLOC);
        else
                clone = bio_alloc(GFP_NOIO|__GFP_NOMEMALLOC, nr_iovecs);
        if (!clone)
                return NULL;

        /* if the last bio was not complete, continue where that one ended */
        clone->bi_idx = *bio_vec_idx;
        clone->bi_vcnt = *bio_vec_idx;
        clone->bi_size = 0;
        clone->bi_flags &= ~(1 << BIO_SEG_VALID);

        /* clone->bi_idx pages have already been allocated */
        size -= clone->bi_idx * PAGE_SIZE;

        for (i = clone->bi_idx; i < nr_iovecs; i++) {
                struct bio_vec *bv = bio_iovec_idx(clone, i);

                bv->bv_page = mempool_alloc(cc->page_pool, gfp_mask);
                if (!bv->bv_page)
                        break;

                /*
                 * if additional pages cannot be allocated without waiting,
                 * return a partially allocated bio, the caller will then try
                 * to allocate additional bios while submitting this partial bio
                 */
                if ((i - clone->bi_idx) == (MIN_BIO_PAGES - 1))
                        gfp_mask = (gfp_mask | __GFP_NOWARN) & ~__GFP_WAIT;

                bv->bv_offset = 0;
                if (size > PAGE_SIZE)
                        bv->bv_len = PAGE_SIZE;
                else
                        bv->bv_len = size;

                clone->bi_size += bv->bv_len;
                clone->bi_vcnt++;
                size -= bv->bv_len;
        }

        if (!clone->bi_size) {
                bio_put(clone);
                return NULL;
        }

        /*
         * Remember the last bio_vec allocated to be able
         * to correctly continue after the splitting.
         */
        *bio_vec_idx = clone->bi_vcnt;

        return clone;
}

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

        /*
         * This is ugly, but Jens Axboe thinks that using bi_idx in the
         * endio function is too dangerous at the moment, so I calculate the
         * correct position using bi_vcnt and bi_size.
         * The bv_offset and bv_len fields might already be modified but we
         * know that we always allocated whole pages.
         * A fix to the bi_idx issue in the kernel is in the works, so
         * we will hopefully be able to revert to the cleaner solution soon.
         */
        i = clone->bi_vcnt - 1;
        bv = bio_iovec_idx(clone, i);
        end = (i << PAGE_SHIFT) + (bv->bv_offset + bv->bv_len) - clone->bi_size;
        start = end - bytes;

        start >>= PAGE_SHIFT;
        if (!clone->bi_size)
                end = clone->bi_vcnt;
        else
                end >>= PAGE_SHIFT;

        for (i = start; i < end; i++) {
                bv = bio_iovec_idx(clone, i);
                BUG_ON(!bv->bv_page);
                mempool_free(bv->bv_page, cc->page_pool);
                bv->bv_page = NULL;
        }
}

/*
 * One of the bios was finished. Check for completion of
 * the whole request and correctly clean up the buffer.
 */
static void dec_pending(struct crypt_io *io, int error)
{
        struct crypt_config *cc = (struct crypt_config *) io->target->private;

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

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

        if (io->first_clone)
                bio_put(io->first_clone);

        bio_endio(io->base_bio, io->base_bio->bi_size, io->error);

        mempool_free(io, cc->io_pool);
}

/*
 * kcryptd:
 *
 * Needed because it would be very unwise to do decryption in an
 * interrupt context, so bios returning from read requests get
 * queued here.
 */
static struct workqueue_struct *_kcryptd_workqueue;
static void kcryptd_do_work(void *data);

static void kcryptd_queue_io(struct crypt_io *io)
{
        INIT_WORK(&io->work, kcryptd_do_work, io);
        queue_work(_kcryptd_workqueue, &io->work);
}

static int crypt_endio(struct bio *clone, unsigned int done, int error)
{
        struct crypt_io *io = clone->bi_private;
        struct crypt_config *cc = io->target->private;
        unsigned read_io = bio_data_dir(clone) == READ;

        /*
         * free the processed pages, even if
         * it's only a partially completed write
         */
        if (!read_io)
                crypt_free_buffer_pages(cc, clone, done);

        if (unlikely(clone->bi_size))
                return 1;

        /*
         * successful reads are decrypted by the worker thread
         */
        if (!read_io)
                goto out;

        if (unlikely(!bio_flagged(clone, BIO_UPTODATE))) {
                error = -EIO;
                goto out;
        }

        bio_put(clone);
        kcryptd_queue_io(io);
        return 0;

out:
        bio_put(clone);
        dec_pending(io, error);
        return error;
}

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

        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 struct bio *clone_read(struct crypt_io *io,
                              sector_t sector)
{
        struct crypt_config *cc = io->target->private;
        struct bio *base_bio = io->base_bio;
        struct bio *clone;

        /*
         * The block layer might modify the bvec array, so always
         * copy the required bvecs because we need the original
         * one in order to decrypt the whole bio data *afterwards*.
         */
        clone = bio_alloc(GFP_NOIO, bio_segments(base_bio));
        if (unlikely(!clone))
                return NULL;

        clone_init(io, clone);
        clone->bi_idx = 0;
        clone->bi_vcnt = bio_segments(base_bio);
        clone->bi_size = base_bio->bi_size;
        memcpy(clone->bi_io_vec, bio_iovec(base_bio),
               sizeof(struct bio_vec) * clone->bi_vcnt);
        clone->bi_sector = cc->start + sector;

        return clone;
}

static struct bio *clone_write(struct crypt_io *io,
                               sector_t sector,
                               unsigned *bvec_idx,
                               struct convert_context *ctx)
{
        struct crypt_config *cc = io->target->private;
        struct bio *base_bio = io->base_bio;
        struct bio *clone;

        clone = crypt_alloc_buffer(cc, base_bio->bi_size,
                                   io->first_clone, bvec_idx);
        if (!clone)
                return NULL;

        ctx->bio_out = clone;

        if (unlikely(crypt_convert(cc, ctx) < 0)) {
                crypt_free_buffer_pages(cc, clone,
                                        clone->bi_size);
                bio_put(clone);
                return NULL;
        }

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

        return clone;
}

static void process_read_endio(struct crypt_io *io)
{
        struct crypt_config *cc = io->target->private;
        struct convert_context ctx;

        crypt_convert_init(cc, &ctx, io->base_bio, io->base_bio,
                           io->base_bio->bi_sector - io->target->begin, 0);

        dec_pending(io, crypt_convert(cc, &ctx));
}

static void kcryptd_do_work(void *data)
{
        struct crypt_io *io = data;

        process_read_endio(io);
}

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

        buffer[2] = '\0';

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

                key[i] = (u8)simple_strtoul(buffer, &endp, 16);

                if (endp != &buffer[2])
                        return -EINVAL;
        }

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

        return 0;
}

/*
 * Encode key into its hex representation
 */
static void crypt_encode_key(char *hex, u8 *key, unsigned int size)
{
        unsigned int i;

        for (i = 0; i < size; i++) {
                sprintf(hex, "%02x", *key);
                hex += 2;
                key++;
        }
}

static int crypt_set_key(struct crypt_config *cc, char *key)
{
        unsigned key_size = strlen(key) >> 1;

        if (cc->key_size && cc->key_size != key_size)
                return -EINVAL;

        cc->key_size = key_size; /* initial settings */

        if ((!key_size && strcmp(key, "-")) ||
            (key_size && crypt_decode_key(cc->key, key, key_size) < 0))
                return -EINVAL;

        set_bit(DM_CRYPT_KEY_VALID, &cc->flags);

        return 0;
}

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 0;
}

/*
 * 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;
        struct crypto_blkcipher *tfm;
        char *tmp;
        char *cipher;
        char *chainmode;
        char *ivmode;
        char *ivopts;
        unsigned int key_size;
        unsigned long long tmpll;

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

        tmp = argv[0];
        cipher = strsep(&tmp, "-");
        chainmode = strsep(&tmp, "-");
        ivopts = strsep(&tmp, "-");
        ivmode = strsep(&ivopts, ":");

        if (tmp)
                DMWARN("Unexpected additional cipher options");

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

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

        if (crypt_set_key(cc, argv[1])) {
                ti->error = "Error decoding key";
                goto bad1;
        }

        /* Compatiblity mode for old dm-crypt cipher strings */
        if (!chainmode || (strcmp(chainmode, "plain") == 0 && !ivmode)) {
                chainmode = "cbc";
                ivmode = "plain";
        }

        if (strcmp(chainmode, "ecb") && !ivmode) {
                ti->error = "This chaining mode requires an IV mechanism";
                goto bad1;
        }

        if (snprintf(cc->cipher, CRYPTO_MAX_ALG_NAME, "%s(%s)", chainmode, 
                     cipher) >= CRYPTO_MAX_ALG_NAME) {
                ti->error = "Chain mode + cipher name is too long";
                goto bad1;
        }

        tfm = crypto_alloc_blkcipher(cc->cipher, 0, CRYPTO_ALG_ASYNC);
        if (IS_ERR(tfm)) {
                ti->error = "Error allocating crypto tfm";
                goto bad1;
        }

        strcpy(cc->cipher, cipher);
        strcpy(cc->chainmode, chainmode);
        cc->tfm = tfm;

        /*
         * Choose ivmode. Valid modes: "plain", "essiv:<esshash>".
         * 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, "essiv") == 0)
                cc->iv_gen_ops = &crypt_iv_essiv_ops;
        else {
                ti->error = "Invalid IV mode";
                goto bad2;
        }

        if (cc->iv_gen_ops && cc->iv_gen_ops->ctr &&
            cc->iv_gen_ops->ctr(cc, ti, ivopts) < 0)
                goto bad2;

        cc->iv_size = crypto_blkcipher_ivsize(tfm);
        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 (cc->iv_gen_ops) {
                        DMWARN("Selected cipher does not support IVs");
                        if (cc->iv_gen_ops->dtr)
                                cc->iv_gen_ops->dtr(cc);
                        cc->iv_gen_ops = NULL;
                }
        }

        cc->io_pool = mempool_create_slab_pool(MIN_IOS, _crypt_io_pool);
        if (!cc->io_pool) {
                ti->error = "Cannot allocate crypt io mempool";
                goto bad3;
        }

        cc->page_pool = mempool_create_page_pool(MIN_POOL_PAGES, 0);
        if (!cc->page_pool) {
                ti->error = "Cannot allocate page mempool";
                goto bad4;
        }

        if (crypto_blkcipher_setkey(tfm, cc->key, key_size) < 0) {
                ti->error = "Error setting key";
                goto bad5;
        }

        if (sscanf(argv[2], "%llu", &tmpll) != 1) {
                ti->error = "Invalid iv_offset sector";
                goto bad5;
        }
        cc->iv_offset = tmpll;

        if (sscanf(argv[4], "%llu", &tmpll) != 1) {
                ti->error = "Invalid device sector";
                goto bad5;
        }
        cc->start = tmpll;

        if (dm_get_device(ti, argv[3], cc->start, ti->len,
                          dm_table_get_mode(ti->table), &cc->dev)) {
                ti->error = "Device lookup failed";
                goto bad5;
        }

        if (ivmode && cc->iv_gen_ops) {
                if (ivopts)
                        *(ivopts - 1) = ':';
                cc->iv_mode = kmalloc(strlen(ivmode) + 1, GFP_KERNEL);
                if (!cc->iv_mode) {
                        ti->error = "Error kmallocing iv_mode string";
                        goto bad5;
                }
                strcpy(cc->iv_mode, ivmode);
        } else
                cc->iv_mode = NULL;

        ti->private = cc;
        return 0;

bad5:
        mempool_destroy(cc->page_pool);
bad4:
        mempool_destroy(cc->io_pool);
bad3:
        if (cc->iv_gen_ops && cc->iv_gen_ops->dtr)
                cc->iv_gen_ops->dtr(cc);
bad2:
        crypto_free_blkcipher(tfm);
bad1:
        /* Must zero key material before freeing */
        memset(cc, 0, sizeof(*cc) + cc->key_size * sizeof(u8));
        kfree(cc);
        return -EINVAL;
}

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

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

        kfree(cc->iv_mode);
        if (cc->iv_gen_ops && cc->iv_gen_ops->dtr)
                cc->iv_gen_ops->dtr(cc);
        crypto_free_blkcipher(cc->tfm);
        dm_put_device(ti, cc->dev);

        /* Must zero key material before freeing */
        memset(cc, 0, sizeof(*cc) + cc->key_size * sizeof(u8));
        kfree(cc);
}

static int crypt_map(struct dm_target *ti, struct bio *bio,
                     union map_info *map_context)
{
        struct crypt_config *cc = ti->private;
        struct crypt_io *io;
        struct convert_context ctx;
        struct bio *clone;
        unsigned int remaining = bio->bi_size;
        sector_t sector = bio->bi_sector - ti->begin;
        unsigned int bvec_idx = 0;

        io = mempool_alloc(cc->io_pool, GFP_NOIO);
        io->target = ti;
        io->base_bio = bio;
        io->first_clone = NULL;
        io->error = 0;
        atomic_set(&io->pending, 1); /* hold a reference */

        if (bio_data_dir(bio) == WRITE)
                crypt_convert_init(cc, &ctx, NULL, bio, sector, 1);

        /*
         * The allocated buffers can be smaller than the whole bio,
         * so repeat the whole process until all the data can be handled.
         */
        while (remaining) {
                if (bio_data_dir(bio) == WRITE)
                        clone = clone_write(io, sector, &bvec_idx, &ctx);
                else
                        clone = clone_read(io, sector);
                if (!clone)
                        goto cleanup;

                if (!io->first_clone) {
                        /*
                         * hold a reference to the first clone, because it
                         * holds the bio_vec array and that can't be freed
                         * before all other clones are released
                         */
                        bio_get(clone);
                        io->first_clone = clone;
                }
                atomic_inc(&io->pending);

                remaining -= clone->bi_size;
                sector += bio_sectors(clone);

                generic_make_request(clone);

                /* out of memory -> run queues */
                if (remaining)
                        blk_congestion_wait(bio_data_dir(clone), HZ/100);
        }

        /* drop reference, clones could have returned before we reach this */
        dec_pending(io, 0);
        return 0;

cleanup:
        if (io->first_clone) {
                dec_pending(io, -ENOMEM);
                return 0;
        }

        /* if no bio has been dispatched yet, we can directly return the error */
        mempool_free(io, cc->io_pool);
        return -ENOMEM;
}

static int crypt_status(struct dm_target *ti, status_type_t type,
                        char *result, unsigned int maxlen)
{
        struct crypt_config *cc = (struct crypt_config *) ti->private;
        const char *cipher;
        const char *chainmode = NULL;
        unsigned int sz = 0;

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

        case STATUSTYPE_TABLE:
                cipher = crypto_blkcipher_name(cc->tfm);

                chainmode = cc->chainmode;

                if (cc->iv_mode)
                        DMEMIT("%s-%s-%s ", cipher, chainmode, cc->iv_mode);
                else
                        DMEMIT("%s-%s ", cipher, chainmode);

                if (cc->key_size > 0) {
                        if ((maxlen - sz) < ((cc->key_size << 1) + 1))
                                return -ENOMEM;

                        crypt_encode_key(result + sz, cc->key, cc->key_size);
                        sz += cc->key_size << 1;
                } else {
                        if (sz >= maxlen)
                                return -ENOMEM;
                        result[sz++] = '-';
                }

                DMEMIT(" %llu %s %llu", (unsigned long long)cc->iv_offset,
                                cc->dev->name, (unsigned long long)cc->start);
                break;
        }
        return 0;
}

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;

        if (argc < 2)
                goto error;

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

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

static struct target_type crypt_target = {
        .name   = "crypt",
        .version= {1, 2, 0},
        .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,
};

static int __init dm_crypt_init(void)
{
        int r;

        _crypt_io_pool = kmem_cache_create("dm-crypt_io",
                                           sizeof(struct crypt_io),
                                           0, 0, NULL, NULL);
        if (!_crypt_io_pool)
                return -ENOMEM;

        _kcryptd_workqueue = create_workqueue("kcryptd");
        if (!_kcryptd_workqueue) {
                r = -ENOMEM;
                DMERR("couldn't create kcryptd");
                goto bad1;
        }

        r = dm_register_target(&crypt_target);
        if (r < 0) {
                DMERR("register failed %d", r);
                goto bad2;
        }

        return 0;

bad2:
        destroy_workqueue(_kcryptd_workqueue);
bad1:
        kmem_cache_destroy(_crypt_io_pool);
        return r;
}

static void __exit dm_crypt_exit(void)
{
        int r = dm_unregister_target(&crypt_target);

        if (r < 0)
                DMERR("unregister failed %d", r);

        destroy_workqueue(_kcryptd_workqueue);
        kmem_cache_destroy(_crypt_io_pool);
}

module_init(dm_crypt_init);
module_exit(dm_crypt_exit);

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