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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 <linux/backing-dev.h>
#include <asm/atomic.h>
#include <linux/scatterlist.h>
#include <asm/page.h>
#include <asm/unaligned.h>

#include "dm.h"

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

/*
 * per bio private data
 */
struct dm_crypt_io {
      struct dm_target *target;
      struct bio *base_bio;
      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;
      struct bio_set *bs;

      struct workqueue_struct *io_queue;
      struct workqueue_struct *crypt_queue;
      /*
       * crypto related data
       */
      struct crypt_iv_operations *iv_gen_ops;
      char *iv_mode;
      union {
            struct crypto_cipher *essiv_tfm;
            int benbi_shift;
      } 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        16
#define MIN_POOL_PAGES 32
#define MIN_BIO_PAGES  8

static struct kmem_cache *_crypt_io_pool;

static void clone_init(struct dm_crypt_io *, struct bio *);

/*
 * Different IV generation algorithms:
 *
 * plain: the initial vector is the 32-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.
 *
 * 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_init_one(&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";
            kfree(salt);
            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 = essiv_tfm;
      return 0;
}

static void crypt_iv_essiv_dtr(struct crypt_config *cc)
{
      crypto_free_cipher(cc->iv_gen_private.essiv_tfm);
      cc->iv_gen_private.essiv_tfm = 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.essiv_tfm, iv, iv);
      return 0;
}

static int crypt_iv_benbi_ctr(struct crypt_config *cc, struct dm_target *ti,
                        const char *opts)
{
      unsigned int bs = crypto_blkcipher_blocksize(cc->tfm);
      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, sector_t sector)
{
      __be64 val;

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

      val = cpu_to_be64(((u64)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, sector_t sector)
{
      memset(iv, 0, cc->iv_size);

      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 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 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] __attribute__ ((aligned(__alignof__(u64))));
      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, sg_out;

            sg_init_table(&sg_in, 1);
            sg_set_page(&sg_in, bv_in->bv_page, 1 << SECTOR_SHIFT, bv_in->bv_offset + ctx->offset_in);

            sg_init_table(&sg_out, 1);
            sg_set_page(&sg_out, bv_out->bv_page, 1 << SECTOR_SHIFT, bv_out->bv_offset + ctx->offset_out);

            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;
}

static void dm_crypt_bio_destructor(struct bio *bio)
{
      struct dm_crypt_io *io = bio->bi_private;
      struct crypt_config *cc = io->target->private;

      bio_free(bio, cc->bs);
}

/*
 * 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 dm_crypt_io *io, unsigned size)
{
      struct crypt_config *cc = io->target->private;
      struct bio *clone;
      unsigned int nr_iovecs = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
      gfp_t gfp_mask = GFP_NOIO | __GFP_HIGHMEM;
      unsigned i, len;
      struct page *page;

      clone = bio_alloc_bioset(GFP_NOIO, nr_iovecs, cc->bs);
      if (!clone)
            return NULL;

      clone_init(io, clone);

      for (i = 0; i < nr_iovecs; i++) {
            page = mempool_alloc(cc->page_pool, gfp_mask);
            if (!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 == (MIN_BIO_PAGES - 1))
                  gfp_mask = (gfp_mask | __GFP_NOWARN) & ~__GFP_WAIT;

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

            if (!bio_add_page(clone, page, len, 0)) {
                  mempool_free(page, cc->page_pool);
                  break;
            }

            size -= len;
      }

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

      return clone;
}

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

      for (i = 0; i < clone->bi_vcnt; 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 crypt_dec_pending(struct dm_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;

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

      mempool_free(io, cc->io_pool);
}

/*
 * 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.
 */
static void kcryptd_do_work(struct work_struct *work);
static void kcryptd_do_crypt(struct work_struct *work);

static void kcryptd_queue_io(struct dm_crypt_io *io)
{
      struct crypt_config *cc = io->target->private;

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

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

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

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

      if (unlikely(!bio_flagged(clone, BIO_UPTODATE) && !error))
            error = -EIO;

      /*
       * free the processed pages
       */
      if (!read_io) {
            crypt_free_buffer_pages(cc, clone);
            goto out;
      }

      if (unlikely(error))
            goto out;

      bio_put(clone);
      kcryptd_queue_crypt(io);
      return;

out:
      bio_put(clone);
      crypt_dec_pending(io, error);
}

static void clone_init(struct dm_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;
      clone->bi_destructor = dm_crypt_bio_destructor;
}

static void process_read(struct dm_crypt_io *io)
{
      struct crypt_config *cc = io->target->private;
      struct bio *base_bio = io->base_bio;
      struct bio *clone;
      sector_t sector = base_bio->bi_sector - io->target->begin;

      atomic_inc(&io->pending);

      /*
       * 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_bioset(GFP_NOIO, bio_segments(base_bio), cc->bs);
      if (unlikely(!clone)) {
            crypt_dec_pending(io, -ENOMEM);
            return;
      }

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

      generic_make_request(clone);
}

static void process_write(struct dm_crypt_io *io)
{
      struct crypt_config *cc = io->target->private;
      struct bio *base_bio = io->base_bio;
      struct bio *clone;
      struct convert_context ctx;
      unsigned remaining = base_bio->bi_size;
      sector_t sector = base_bio->bi_sector - io->target->begin;

      atomic_inc(&io->pending);

      crypt_convert_init(cc, &ctx, NULL, base_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) {
            clone = crypt_alloc_buffer(io, remaining);
            if (unlikely(!clone)) {
                  crypt_dec_pending(io, -ENOMEM);
                  return;
            }

            ctx.bio_out = clone;
            ctx.idx_out = 0;

            if (unlikely(crypt_convert(cc, &ctx) < 0)) {
                  crypt_free_buffer_pages(cc, clone);
                  bio_put(clone);
                  crypt_dec_pending(io, -EIO);
                  return;
            }

            /* crypt_convert should have filled the clone bio */
            BUG_ON(ctx.idx_out < clone->bi_vcnt);

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

            /* Grab another reference to the io struct
             * before we kick off the request */
            if (remaining)
                  atomic_inc(&io->pending);

            generic_make_request(clone);

            /* Do not reference clone after this - it
             * may be gone already. */

            /* out of memory -> run queues */
            if (remaining)
                  congestion_wait(WRITE, HZ/100);
      }
}

static void process_read_endio(struct dm_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);

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

static void kcryptd_do_work(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)
            process_read(io);
}

static void kcryptd_do_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)
            process_read_endio(io);
      else
            process_write(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 bad_cipher;
      }

      /* 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 bad_cipher;
      }

      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 bad_cipher;
      }

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

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

      /*
       * Choose ivmode. Valid modes: "plain", "essiv:<esshash>", "benbi".
       * 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 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 {
            ti->error = "Invalid IV mode";
            goto bad_ivmode;
      }

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

      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 bad_slab_pool;
      }

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

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

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

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

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

      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 bad_ivmode_string;
            }
            strcpy(cc->iv_mode, ivmode);
      } else
            cc->iv_mode = NULL;

      cc->io_queue = create_singlethread_workqueue("kcryptd_io");
      if (!cc->io_queue) {
            ti->error = "Couldn't create kcryptd io queue";
            goto bad_io_queue;
      }

      cc->crypt_queue = create_singlethread_workqueue("kcryptd");
      if (!cc->crypt_queue) {
            ti->error = "Couldn't create kcryptd queue";
            goto bad_crypt_queue;
      }

      ti->private = cc;
      return 0;

bad_crypt_queue:
      destroy_workqueue(cc->io_queue);
bad_io_queue:
      kfree(cc->iv_mode);
bad_ivmode_string:
      dm_put_device(ti, cc->dev);
bad_device:
      bioset_free(cc->bs);
bad_bs:
      mempool_destroy(cc->page_pool);
bad_page_pool:
      mempool_destroy(cc->io_pool);
bad_slab_pool:
      if (cc->iv_gen_ops && cc->iv_gen_ops->dtr)
            cc->iv_gen_ops->dtr(cc);
bad_ivmode:
      crypto_free_blkcipher(tfm);
bad_cipher:
      /* 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;

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

      bioset_free(cc->bs);
      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 dm_crypt_io *io;

      io = mempool_alloc(cc->io_pool, GFP_NOIO);
      io->target = ti;
      io->base_bio = bio;
      io->error = 0;
      atomic_set(&io->pending, 0);

      if (bio_data_dir(io->base_bio) == READ)
            kcryptd_queue_io(io);
      else
            kcryptd_queue_crypt(io);

      return DM_MAPIO_SUBMITTED;
}

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;
      unsigned int sz = 0;

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

      case STATUSTYPE_TABLE:
            if (cc->iv_mode)
                  DMEMIT("%s-%s-%s ", cc->cipher, cc->chainmode,
                         cc->iv_mode);
            else
                  DMEMIT("%s-%s ", cc->cipher, cc->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, 5, 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(dm_crypt_io, 0);
      if (!_crypt_io_pool)
            return -ENOMEM;

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

      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");

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