block/blk-crypto-fallback.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright 2019 Google LLC
   4  */
   5
   6 /*
   7  * Refer to Documentation/block/inline-encryption.rst for detailed explanation.
   8  */
   9
  10 #define pr_fmt(fmt) "blk-crypto-fallback: " fmt
  11
  12 #include <crypto/skcipher.h>
  13 #include <linux/blk-cgroup.h>
  14 #include <linux/blk-crypto.h>
  15 #include <linux/blkdev.h>
  16 #include <linux/crypto.h>
  17 #include <linux/keyslot-manager.h>
  18 #include <linux/mempool.h>
  19 #include <linux/module.h>
  20 #include <linux/random.h>
  21
  22 #include "blk-crypto-internal.h"
  23
  24 static unsigned int num_prealloc_bounce_pg = 32;
  25 module_param(num_prealloc_bounce_pg, uint, 0);
  26 MODULE_PARM_DESC(num_prealloc_bounce_pg,
  27                  "Number of preallocated bounce pages for the blk-crypto crypto API fallback");
  28
  29 static unsigned int blk_crypto_num_keyslots = 100;
  30 module_param_named(num_keyslots, blk_crypto_num_keyslots, uint, 0);
  31 MODULE_PARM_DESC(num_keyslots,
  32                  "Number of keyslots for the blk-crypto crypto API fallback");
  33
  34 static unsigned int num_prealloc_fallback_crypt_ctxs = 128;
  35 module_param(num_prealloc_fallback_crypt_ctxs, uint, 0);
  36 MODULE_PARM_DESC(num_prealloc_crypt_fallback_ctxs,
  37                  "Number of preallocated bio fallback crypto contexts for blk-crypto to use during crypto API fallback");
  38
  39 struct bio_fallback_crypt_ctx {
  40         struct bio_crypt_ctx crypt_ctx;
  41         /*
  42          * Copy of the bvec_iter when this bio was submitted.
  43          * We only want to en/decrypt the part of the bio as described by the
  44          * bvec_iter upon submission because bio might be split before being
  45          * resubmitted
  46          */
  47         struct bvec_iter crypt_iter;
  48         union {
  49                 struct {
  50                         struct work_struct work;
  51                         struct bio *bio;
  52                 };
  53                 struct {
  54                         void *bi_private_orig;
  55                         bio_end_io_t *bi_end_io_orig;
  56                 };
  57         };
  58 };
  59
  60 static struct kmem_cache *bio_fallback_crypt_ctx_cache;
  61 static mempool_t *bio_fallback_crypt_ctx_pool;
  62
  63 /*
  64  * Allocating a crypto tfm during I/O can deadlock, so we have to preallocate
  65  * all of a mode's tfms when that mode starts being used. Since each mode may
  66  * need all the keyslots at some point, each mode needs its own tfm for each
  67  * keyslot; thus, a keyslot may contain tfms for multiple modes.  However, to
  68  * match the behavior of real inline encryption hardware (which only supports a
  69  * single encryption context per keyslot), we only allow one tfm per keyslot to
  70  * be used at a time - the rest of the unused tfms have their keys cleared.
  71  */
  72 static DEFINE_MUTEX(tfms_init_lock);
  73 static bool tfms_inited[BLK_ENCRYPTION_MODE_MAX];
  74
  75 static struct blk_crypto_keyslot {
  76         enum blk_crypto_mode_num crypto_mode;
  77         struct crypto_skcipher *tfms[BLK_ENCRYPTION_MODE_MAX];
  78 } *blk_crypto_keyslots;
  79
  80 static struct blk_keyslot_manager blk_crypto_ksm;
  81 static struct workqueue_struct *blk_crypto_wq;
  82 static mempool_t *blk_crypto_bounce_page_pool;
  83 static struct bio_set crypto_bio_split;
  84
  85 /*
  86  * This is the key we set when evicting a keyslot. This *should* be the all 0's
  87  * key, but AES-XTS rejects that key, so we use some random bytes instead.
  88  */
  89 static u8 blank_key[BLK_CRYPTO_MAX_KEY_SIZE];
  90
  91 static void blk_crypto_evict_keyslot(unsigned int slot)
  92 {
  93         struct blk_crypto_keyslot *slotp = &blk_crypto_keyslots[slot];
  94         enum blk_crypto_mode_num crypto_mode = slotp->crypto_mode;
  95         int err;
  96
  97         WARN_ON(slotp->crypto_mode == BLK_ENCRYPTION_MODE_INVALID);
  98
  99         /* Clear the key in the skcipher */
 100         err = crypto_skcipher_setkey(slotp->tfms[crypto_mode], blank_key,
 101                                      blk_crypto_modes[crypto_mode].keysize);
 102         WARN_ON(err);
 103         slotp->crypto_mode = BLK_ENCRYPTION_MODE_INVALID;
 104 }
 105
 106 static int blk_crypto_keyslot_program(struct blk_keyslot_manager *ksm,
 107                                       const struct blk_crypto_key *key,
 108                                       unsigned int slot)
 109 {
 110         struct blk_crypto_keyslot *slotp = &blk_crypto_keyslots[slot];
 111         const enum blk_crypto_mode_num crypto_mode =
 112                                                 key->crypto_cfg.crypto_mode;
 113         int err;
 114
 115         if (crypto_mode != slotp->crypto_mode &&
 116             slotp->crypto_mode != BLK_ENCRYPTION_MODE_INVALID)
 117                 blk_crypto_evict_keyslot(slot);
 118
 119         slotp->crypto_mode = crypto_mode;
 120         err = crypto_skcipher_setkey(slotp->tfms[crypto_mode], key->raw,
 121                                      key->size);
 122         if (err) {
 123                 blk_crypto_evict_keyslot(slot);
 124                 return err;
 125         }
 126         return 0;
 127 }
 128
 129 static int blk_crypto_keyslot_evict(struct blk_keyslot_manager *ksm,
 130                                     const struct blk_crypto_key *key,
 131                                     unsigned int slot)
 132 {
 133         blk_crypto_evict_keyslot(slot);
 134         return 0;
 135 }
 136
 137 /*
 138  * The crypto API fallback KSM ops - only used for a bio when it specifies a
 139  * blk_crypto_key that was not supported by the device's inline encryption
 140  * hardware.
 141  */
 142 static const struct blk_ksm_ll_ops blk_crypto_ksm_ll_ops = {
 143         .keyslot_program        = blk_crypto_keyslot_program,
 144         .keyslot_evict          = blk_crypto_keyslot_evict,
 145 };
 146
 147 static void blk_crypto_fallback_encrypt_endio(struct bio *enc_bio)
 148 {
 149         struct bio *src_bio = enc_bio->bi_private;
 150         int i;
 151
 152         for (i = 0; i < enc_bio->bi_vcnt; i++)
 153                 mempool_free(enc_bio->bi_io_vec[i].bv_page,
 154                              blk_crypto_bounce_page_pool);
 155
 156         src_bio->bi_status = enc_bio->bi_status;
 157
 158         bio_put(enc_bio);
 159         bio_endio(src_bio);
 160 }
 161
 162 static struct bio *blk_crypto_clone_bio(struct bio *bio_src)
 163 {
 164         struct bvec_iter iter;
 165         struct bio_vec bv;
 166         struct bio *bio;
 167
 168         bio = bio_kmalloc(GFP_NOIO, bio_segments(bio_src));
 169         if (!bio)
 170                 return NULL;
 171         bio->bi_bdev            = bio_src->bi_bdev;
 172         if (bio_flagged(bio_src, BIO_REMAPPED))
 173                 bio_set_flag(bio, BIO_REMAPPED);
 174         bio->bi_opf             = bio_src->bi_opf;
 175         bio->bi_ioprio          = bio_src->bi_ioprio;
 176         bio->bi_write_hint      = bio_src->bi_write_hint;
 177         bio->bi_iter.bi_sector  = bio_src->bi_iter.bi_sector;
 178         bio->bi_iter.bi_size    = bio_src->bi_iter.bi_size;
 179
 180         bio_for_each_segment(bv, bio_src, iter)
 181                 bio->bi_io_vec[bio->bi_vcnt++] = bv;
 182
 183         bio_clone_blkg_association(bio, bio_src);
 184         blkcg_bio_issue_init(bio);
 185
 186         return bio;
 187 }
 188
 189 static bool blk_crypto_alloc_cipher_req(struct blk_ksm_keyslot *slot,
 190                                         struct skcipher_request **ciph_req_ret,
 191                                         struct crypto_wait *wait)
 192 {
 193         struct skcipher_request *ciph_req;
 194         const struct blk_crypto_keyslot *slotp;
 195         int keyslot_idx = blk_ksm_get_slot_idx(slot);
 196
 197         slotp = &blk_crypto_keyslots[keyslot_idx];
 198         ciph_req = skcipher_request_alloc(slotp->tfms[slotp->crypto_mode],
 199                                           GFP_NOIO);
 200         if (!ciph_req)
 201                 return false;
 202
 203         skcipher_request_set_callback(ciph_req,
 204                                       CRYPTO_TFM_REQ_MAY_BACKLOG |
 205                                       CRYPTO_TFM_REQ_MAY_SLEEP,
 206                                       crypto_req_done, wait);
 207         *ciph_req_ret = ciph_req;
 208
 209         return true;
 210 }
 211
 212 static bool blk_crypto_split_bio_if_needed(struct bio **bio_ptr)
 213 {
 214         struct bio *bio = *bio_ptr;
 215         unsigned int i = 0;
 216         unsigned int num_sectors = 0;
 217         struct bio_vec bv;
 218         struct bvec_iter iter;
 219
 220         bio_for_each_segment(bv, bio, iter) {
 221                 num_sectors += bv.bv_len >> SECTOR_SHIFT;
 222                 if (++i == BIO_MAX_VECS)
 223                         break;
 224         }
 225         if (num_sectors < bio_sectors(bio)) {
 226                 struct bio *split_bio;
 227
 228                 split_bio = bio_split(bio, num_sectors, GFP_NOIO,
 229                                       &crypto_bio_split);
 230                 if (!split_bio) {
 231                         bio->bi_status = BLK_STS_RESOURCE;
 232                         return false;
 233                 }
 234                 bio_chain(split_bio, bio);
 235                 submit_bio_noacct(bio);
 236                 *bio_ptr = split_bio;
 237         }
 238
 239         return true;
 240 }
 241
 242 union blk_crypto_iv {
 243         __le64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
 244         u8 bytes[BLK_CRYPTO_MAX_IV_SIZE];
 245 };
 246
 247 static void blk_crypto_dun_to_iv(const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
 248                                  union blk_crypto_iv *iv)
 249 {
 250         int i;
 251
 252         for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++)
 253                 iv->dun[i] = cpu_to_le64(dun[i]);
 254 }
 255
 256 /*
 257  * The crypto API fallback's encryption routine.
 258  * Allocate a bounce bio for encryption, encrypt the input bio using crypto API,
 259  * and replace *bio_ptr with the bounce bio. May split input bio if it's too
 260  * large. Returns true on success. Returns false and sets bio->bi_status on
 261  * error.
 262  */
 263 static bool blk_crypto_fallback_encrypt_bio(struct bio **bio_ptr)
 264 {
 265         struct bio *src_bio, *enc_bio;
 266         struct bio_crypt_ctx *bc;
 267         struct blk_ksm_keyslot *slot;
 268         int data_unit_size;
 269         struct skcipher_request *ciph_req = NULL;
 270         DECLARE_CRYPTO_WAIT(wait);
 271         u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
 272         struct scatterlist src, dst;
 273         union blk_crypto_iv iv;
 274         unsigned int i, j;
 275         bool ret = false;
 276         blk_status_t blk_st;
 277
 278         /* Split the bio if it's too big for single page bvec */
 279         if (!blk_crypto_split_bio_if_needed(bio_ptr))
 280                 return false;
 281
 282         src_bio = *bio_ptr;
 283         bc = src_bio->bi_crypt_context;
 284         data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
 285
 286         /* Allocate bounce bio for encryption */
 287         enc_bio = blk_crypto_clone_bio(src_bio);
 288         if (!enc_bio) {
 289                 src_bio->bi_status = BLK_STS_RESOURCE;
 290                 return false;
 291         }
 292
 293         /*
 294          * Use the crypto API fallback keyslot manager to get a crypto_skcipher
 295          * for the algorithm and key specified for this bio.
 296          */
 297         blk_st = blk_ksm_get_slot_for_key(&blk_crypto_ksm, bc->bc_key, &slot);
 298         if (blk_st != BLK_STS_OK) {
 299                 src_bio->bi_status = blk_st;
 300                 goto out_put_enc_bio;
 301         }
 302
 303         /* and then allocate an skcipher_request for it */
 304         if (!blk_crypto_alloc_cipher_req(slot, &ciph_req, &wait)) {
 305                 src_bio->bi_status = BLK_STS_RESOURCE;
 306                 goto out_release_keyslot;
 307         }
 308
 309         memcpy(curr_dun, bc->bc_dun, sizeof(curr_dun));
 310         sg_init_table(&src, 1);
 311         sg_init_table(&dst, 1);
 312
 313         skcipher_request_set_crypt(ciph_req, &src, &dst, data_unit_size,
 314                                    iv.bytes);
 315
 316         /* Encrypt each page in the bounce bio */
 317         for (i = 0; i < enc_bio->bi_vcnt; i++) {
 318                 struct bio_vec *enc_bvec = &enc_bio->bi_io_vec[i];
 319                 struct page *plaintext_page = enc_bvec->bv_page;
 320                 struct page *ciphertext_page =
 321                         mempool_alloc(blk_crypto_bounce_page_pool, GFP_NOIO);
 322
 323                 enc_bvec->bv_page = ciphertext_page;
 324
 325                 if (!ciphertext_page) {
 326                         src_bio->bi_status = BLK_STS_RESOURCE;
 327                         goto out_free_bounce_pages;
 328                 }
 329
 330                 sg_set_page(&src, plaintext_page, data_unit_size,
 331                             enc_bvec->bv_offset);
 332                 sg_set_page(&dst, ciphertext_page, data_unit_size,
 333                             enc_bvec->bv_offset);
 334
 335                 /* Encrypt each data unit in this page */
 336                 for (j = 0; j < enc_bvec->bv_len; j += data_unit_size) {
 337                         blk_crypto_dun_to_iv(curr_dun, &iv);
 338                         if (crypto_wait_req(crypto_skcipher_encrypt(ciph_req),
 339                                             &wait)) {
 340                                 i++;
 341                                 src_bio->bi_status = BLK_STS_IOERR;
 342                                 goto out_free_bounce_pages;
 343                         }
 344                         bio_crypt_dun_increment(curr_dun, 1);
 345                         src.offset += data_unit_size;
 346                         dst.offset += data_unit_size;
 347                 }
 348         }
 349
 350         enc_bio->bi_private = src_bio;
 351         enc_bio->bi_end_io = blk_crypto_fallback_encrypt_endio;
 352         *bio_ptr = enc_bio;
 353         ret = true;
 354
 355         enc_bio = NULL;
 356         goto out_free_ciph_req;
 357
 358 out_free_bounce_pages:
 359         while (i > 0)
 360                 mempool_free(enc_bio->bi_io_vec[--i].bv_page,
 361                              blk_crypto_bounce_page_pool);
 362 out_free_ciph_req:
 363         skcipher_request_free(ciph_req);
 364 out_release_keyslot:
 365         blk_ksm_put_slot(slot);
 366 out_put_enc_bio:
 367         if (enc_bio)
 368                 bio_put(enc_bio);
 369
 370         return ret;
 371 }
 372
 373 /*
 374  * The crypto API fallback's main decryption routine.
 375  * Decrypts input bio in place, and calls bio_endio on the bio.
 376  */
 377 static void blk_crypto_fallback_decrypt_bio(struct work_struct *work)
 378 {
 379         struct bio_fallback_crypt_ctx *f_ctx =
 380                 container_of(work, struct bio_fallback_crypt_ctx, work);
 381         struct bio *bio = f_ctx->bio;
 382         struct bio_crypt_ctx *bc = &f_ctx->crypt_ctx;
 383         struct blk_ksm_keyslot *slot;
 384         struct skcipher_request *ciph_req = NULL;
 385         DECLARE_CRYPTO_WAIT(wait);
 386         u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
 387         union blk_crypto_iv iv;
 388         struct scatterlist sg;
 389         struct bio_vec bv;
 390         struct bvec_iter iter;
 391         const int data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
 392         unsigned int i;
 393         blk_status_t blk_st;
 394
 395         /*
 396          * Use the crypto API fallback keyslot manager to get a crypto_skcipher
 397          * for the algorithm and key specified for this bio.
 398          */
 399         blk_st = blk_ksm_get_slot_for_key(&blk_crypto_ksm, bc->bc_key, &slot);
 400         if (blk_st != BLK_STS_OK) {
 401                 bio->bi_status = blk_st;
 402                 goto out_no_keyslot;
 403         }
 404
 405         /* and then allocate an skcipher_request for it */
 406         if (!blk_crypto_alloc_cipher_req(slot, &ciph_req, &wait)) {
 407                 bio->bi_status = BLK_STS_RESOURCE;
 408                 goto out;
 409         }
 410
 411         memcpy(curr_dun, bc->bc_dun, sizeof(curr_dun));
 412         sg_init_table(&sg, 1);
 413         skcipher_request_set_crypt(ciph_req, &sg, &sg, data_unit_size,
 414                                    iv.bytes);
 415
 416         /* Decrypt each segment in the bio */
 417         __bio_for_each_segment(bv, bio, iter, f_ctx->crypt_iter) {
 418                 struct page *page = bv.bv_page;
 419
 420                 sg_set_page(&sg, page, data_unit_size, bv.bv_offset);
 421
 422                 /* Decrypt each data unit in the segment */
 423                 for (i = 0; i < bv.bv_len; i += data_unit_size) {
 424                         blk_crypto_dun_to_iv(curr_dun, &iv);
 425                         if (crypto_wait_req(crypto_skcipher_decrypt(ciph_req),
 426                                             &wait)) {
 427                                 bio->bi_status = BLK_STS_IOERR;
 428                                 goto out;
 429                         }
 430                         bio_crypt_dun_increment(curr_dun, 1);
 431                         sg.offset += data_unit_size;
 432                 }
 433         }
 434
 435 out:
 436         skcipher_request_free(ciph_req);
 437         blk_ksm_put_slot(slot);
 438 out_no_keyslot:
 439         mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);
 440         bio_endio(bio);
 441 }
 442
 443 /**
 444  * blk_crypto_fallback_decrypt_endio - queue bio for fallback decryption
 445  *
 446  * @bio: the bio to queue
 447  *
 448  * Restore bi_private and bi_end_io, and queue the bio for decryption into a
 449  * workqueue, since this function will be called from an atomic context.
 450  */
 451 static void blk_crypto_fallback_decrypt_endio(struct bio *bio)
 452 {
 453         struct bio_fallback_crypt_ctx *f_ctx = bio->bi_private;
 454
 455         bio->bi_private = f_ctx->bi_private_orig;
 456         bio->bi_end_io = f_ctx->bi_end_io_orig;
 457
 458         /* If there was an IO error, don't queue for decrypt. */
 459         if (bio->bi_status) {
 460                 mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);
 461                 bio_endio(bio);
 462                 return;
 463         }
 464
 465         INIT_WORK(&f_ctx->work, blk_crypto_fallback_decrypt_bio);
 466         f_ctx->bio = bio;
 467         queue_work(blk_crypto_wq, &f_ctx->work);
 468 }
 469
 470 /**
 471  * blk_crypto_fallback_bio_prep - Prepare a bio to use fallback en/decryption
 472  *
 473  * @bio_ptr: pointer to the bio to prepare
 474  *
 475  * If bio is doing a WRITE operation, this splits the bio into two parts if it's
 476  * too big (see blk_crypto_split_bio_if_needed). It then allocates a bounce bio
 477  * for the first part, encrypts it, and update bio_ptr to point to the bounce
 478  * bio.
 479  *
 480  * For a READ operation, we mark the bio for decryption by using bi_private and
 481  * bi_end_io.
 482  *
 483  * In either case, this function will make the bio look like a regular bio (i.e.
 484  * as if no encryption context was ever specified) for the purposes of the rest
 485  * of the stack except for blk-integrity (blk-integrity and blk-crypto are not
 486  * currently supported together).
 487  *
 488  * Return: true on success. Sets bio->bi_status and returns false on error.
 489  */
 490 bool blk_crypto_fallback_bio_prep(struct bio **bio_ptr)
 491 {
 492         struct bio *bio = *bio_ptr;
 493         struct bio_crypt_ctx *bc = bio->bi_crypt_context;
 494         struct bio_fallback_crypt_ctx *f_ctx;
 495
 496         if (WARN_ON_ONCE(!tfms_inited[bc->bc_key->crypto_cfg.crypto_mode])) {
 497                 /* User didn't call blk_crypto_start_using_key() first */
 498                 bio->bi_status = BLK_STS_IOERR;
 499                 return false;
 500         }
 501
 502         if (!blk_ksm_crypto_cfg_supported(&blk_crypto_ksm,
 503                                           &bc->bc_key->crypto_cfg)) {
 504                 bio->bi_status = BLK_STS_NOTSUPP;
 505                 return false;
 506         }
 507
 508         if (bio_data_dir(bio) == WRITE)
 509                 return blk_crypto_fallback_encrypt_bio(bio_ptr);
 510
 511         /*
 512          * bio READ case: Set up a f_ctx in the bio's bi_private and set the
 513          * bi_end_io appropriately to trigger decryption when the bio is ended.
 514          */
 515         f_ctx = mempool_alloc(bio_fallback_crypt_ctx_pool, GFP_NOIO);
 516         f_ctx->crypt_ctx = *bc;
 517         f_ctx->crypt_iter = bio->bi_iter;
 518         f_ctx->bi_private_orig = bio->bi_private;
 519         f_ctx->bi_end_io_orig = bio->bi_end_io;
 520         bio->bi_private = (void *)f_ctx;
 521         bio->bi_end_io = blk_crypto_fallback_decrypt_endio;
 522         bio_crypt_free_ctx(bio);
 523
 524         return true;
 525 }
 526
 527 int blk_crypto_fallback_evict_key(const struct blk_crypto_key *key)
 528 {
 529         return blk_ksm_evict_key(&blk_crypto_ksm, key);
 530 }
 531
 532 static bool blk_crypto_fallback_inited;
 533 static int blk_crypto_fallback_init(void)
 534 {
 535         int i;
 536         int err;
 537
 538         if (blk_crypto_fallback_inited)
 539                 return 0;
 540
 541         prandom_bytes(blank_key, BLK_CRYPTO_MAX_KEY_SIZE);
 542
 543         err = bioset_init(&crypto_bio_split, 64, 0, 0);
 544         if (err)
 545                 goto out;
 546
 547         err = blk_ksm_init(&blk_crypto_ksm, blk_crypto_num_keyslots);
 548         if (err)
 549                 goto fail_free_bioset;
 550         err = -ENOMEM;
 551
 552         blk_crypto_ksm.ksm_ll_ops = blk_crypto_ksm_ll_ops;
 553         blk_crypto_ksm.max_dun_bytes_supported = BLK_CRYPTO_MAX_IV_SIZE;
 554
 555         /* All blk-crypto modes have a crypto API fallback. */
 556         for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++)
 557                 blk_crypto_ksm.crypto_modes_supported[i] = 0xFFFFFFFF;
 558         blk_crypto_ksm.crypto_modes_supported[BLK_ENCRYPTION_MODE_INVALID] = 0;
 559
 560         blk_crypto_wq = alloc_workqueue("blk_crypto_wq",
 561                                         WQ_UNBOUND | WQ_HIGHPRI |
 562                                         WQ_MEM_RECLAIM, num_online_cpus());
 563         if (!blk_crypto_wq)
 564                 goto fail_free_ksm;
 565
 566         blk_crypto_keyslots = kcalloc(blk_crypto_num_keyslots,
 567                                       sizeof(blk_crypto_keyslots[0]),
 568                                       GFP_KERNEL);
 569         if (!blk_crypto_keyslots)
 570                 goto fail_free_wq;
 571
 572         blk_crypto_bounce_page_pool =
 573                 mempool_create_page_pool(num_prealloc_bounce_pg, 0);
 574         if (!blk_crypto_bounce_page_pool)
 575                 goto fail_free_keyslots;
 576
 577         bio_fallback_crypt_ctx_cache = KMEM_CACHE(bio_fallback_crypt_ctx, 0);
 578         if (!bio_fallback_crypt_ctx_cache)
 579                 goto fail_free_bounce_page_pool;
 580
 581         bio_fallback_crypt_ctx_pool =
 582                 mempool_create_slab_pool(num_prealloc_fallback_crypt_ctxs,
 583                                          bio_fallback_crypt_ctx_cache);
 584         if (!bio_fallback_crypt_ctx_pool)
 585                 goto fail_free_crypt_ctx_cache;
 586
 587         blk_crypto_fallback_inited = true;
 588
 589         return 0;
 590 fail_free_crypt_ctx_cache:
 591         kmem_cache_destroy(bio_fallback_crypt_ctx_cache);
 592 fail_free_bounce_page_pool:
 593         mempool_destroy(blk_crypto_bounce_page_pool);
 594 fail_free_keyslots:
 595         kfree(blk_crypto_keyslots);
 596 fail_free_wq:
 597         destroy_workqueue(blk_crypto_wq);
 598 fail_free_ksm:
 599         blk_ksm_destroy(&blk_crypto_ksm);
 600 fail_free_bioset:
 601         bioset_exit(&crypto_bio_split);
 602 out:
 603         return err;
 604 }
 605
 606 /*
 607  * Prepare blk-crypto-fallback for the specified crypto mode.
 608  * Returns -ENOPKG if the needed crypto API support is missing.
 609  */
 610 int blk_crypto_fallback_start_using_mode(enum blk_crypto_mode_num mode_num)
 611 {
 612         const char *cipher_str = blk_crypto_modes[mode_num].cipher_str;
 613         struct blk_crypto_keyslot *slotp;
 614         unsigned int i;
 615         int err = 0;
 616
 617         /*
 618          * Fast path
 619          * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
 620          * for each i are visible before we try to access them.
 621          */
 622         if (likely(smp_load_acquire(&tfms_inited[mode_num])))
 623                 return 0;
 624
 625         mutex_lock(&tfms_init_lock);
 626         if (tfms_inited[mode_num])
 627                 goto out;
 628
 629         err = blk_crypto_fallback_init();
 630         if (err)
 631                 goto out;
 632
 633         for (i = 0; i < blk_crypto_num_keyslots; i++) {
 634                 slotp = &blk_crypto_keyslots[i];
 635                 slotp->tfms[mode_num] = crypto_alloc_skcipher(cipher_str, 0, 0);
 636                 if (IS_ERR(slotp->tfms[mode_num])) {
 637                         err = PTR_ERR(slotp->tfms[mode_num]);
 638                         if (err == -ENOENT) {
 639                                 pr_warn_once("Missing crypto API support for \"%s\"\n",
 640                                              cipher_str);
 641                                 err = -ENOPKG;
 642                         }
 643                         slotp->tfms[mode_num] = NULL;
 644                         goto out_free_tfms;
 645                 }
 646
 647                 crypto_skcipher_set_flags(slotp->tfms[mode_num],
 648                                           CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
 649         }
 650
 651         /*
 652          * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
 653          * for each i are visible before we set tfms_inited[mode_num].
 654          */
 655         smp_store_release(&tfms_inited[mode_num], true);
 656         goto out;
 657
 658 out_free_tfms:
 659         for (i = 0; i < blk_crypto_num_keyslots; i++) {
 660                 slotp = &blk_crypto_keyslots[i];
 661                 crypto_free_skcipher(slotp->tfms[mode_num]);
 662                 slotp->tfms[mode_num] = NULL;
 663         }
 664 out:
 665         mutex_unlock(&tfms_init_lock);
 666         return err;
 667 }