summaryrefslogtreecommitdiffstats
path: root/block/blk-crypto-fallback.c
blob: 7c854584b52b506fece323d6275948a10f9a7849 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright 2019 Google LLC
 */

/*
 * Refer to Documentation/block/inline-encryption.rst for detailed explanation.
 */

#define pr_fmt(fmt) "blk-crypto-fallback: " fmt

#include <crypto/skcipher.h>
#include <linux/blk-crypto.h>
#include <linux/blk-crypto-profile.h>
#include <linux/blkdev.h>
#include <linux/crypto.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/scatterlist.h>

#include "blk-cgroup.h"
#include "blk-crypto-internal.h"

static unsigned int num_prealloc_bounce_pg = 32;
module_param(num_prealloc_bounce_pg, uint, 0);
MODULE_PARM_DESC(num_prealloc_bounce_pg,
		 "Number of preallocated bounce pages for the blk-crypto crypto API fallback");

static unsigned int blk_crypto_num_keyslots = 100;
module_param_named(num_keyslots, blk_crypto_num_keyslots, uint, 0);
MODULE_PARM_DESC(num_keyslots,
		 "Number of keyslots for the blk-crypto crypto API fallback");

static unsigned int num_prealloc_fallback_crypt_ctxs = 128;
module_param(num_prealloc_fallback_crypt_ctxs, uint, 0);
MODULE_PARM_DESC(num_prealloc_crypt_fallback_ctxs,
		 "Number of preallocated bio fallback crypto contexts for blk-crypto to use during crypto API fallback");

struct bio_fallback_crypt_ctx {
	struct bio_crypt_ctx crypt_ctx;
	/*
	 * Copy of the bvec_iter when this bio was submitted.
	 * We only want to en/decrypt the part of the bio as described by the
	 * bvec_iter upon submission because bio might be split before being
	 * resubmitted
	 */
	struct bvec_iter crypt_iter;
	union {
		struct {
			struct work_struct work;
			struct bio *bio;
		};
		struct {
			void *bi_private_orig;
			bio_end_io_t *bi_end_io_orig;
		};
	};
};

static struct kmem_cache *bio_fallback_crypt_ctx_cache;
static mempool_t *bio_fallback_crypt_ctx_pool;

/*
 * Allocating a crypto tfm during I/O can deadlock, so we have to preallocate
 * all of a mode's tfms when that mode starts being used. Since each mode may
 * need all the keyslots at some point, each mode needs its own tfm for each
 * keyslot; thus, a keyslot may contain tfms for multiple modes.  However, to
 * match the behavior of real inline encryption hardware (which only supports a
 * single encryption context per keyslot), we only allow one tfm per keyslot to
 * be used at a time - the rest of the unused tfms have their keys cleared.
 */
static DEFINE_MUTEX(tfms_init_lock);
static bool tfms_inited[BLK_ENCRYPTION_MODE_MAX];

static struct blk_crypto_fallback_keyslot {
	enum blk_crypto_mode_num crypto_mode;
	struct crypto_skcipher *tfms[BLK_ENCRYPTION_MODE_MAX];
} *blk_crypto_keyslots;

static struct blk_crypto_profile blk_crypto_fallback_profile;
static struct workqueue_struct *blk_crypto_wq;
static mempool_t *blk_crypto_bounce_page_pool;
static struct bio_set crypto_bio_split;

/*
 * This is the key we set when evicting a keyslot. This *should* be the all 0's
 * key, but AES-XTS rejects that key, so we use some random bytes instead.
 */
static u8 blank_key[BLK_CRYPTO_MAX_KEY_SIZE];

static void blk_crypto_fallback_evict_keyslot(unsigned int slot)
{
	struct blk_crypto_fallback_keyslot *slotp = &blk_crypto_keyslots[slot];
	enum blk_crypto_mode_num crypto_mode = slotp->crypto_mode;
	int err;

	WARN_ON(slotp->crypto_mode == BLK_ENCRYPTION_MODE_INVALID);

	/* Clear the key in the skcipher */
	err = crypto_skcipher_setkey(slotp->tfms[crypto_mode], blank_key,
				     blk_crypto_modes[crypto_mode].keysize);
	WARN_ON(err);
	slotp->crypto_mode = BLK_ENCRYPTION_MODE_INVALID;
}

static int
blk_crypto_fallback_keyslot_program(struct blk_crypto_profile *profile,
				    const struct blk_crypto_key *key,
				    unsigned int slot)
{
	struct blk_crypto_fallback_keyslot *slotp = &blk_crypto_keyslots[slot];
	const enum blk_crypto_mode_num crypto_mode =
						key->crypto_cfg.crypto_mode;
	int err;

	if (crypto_mode != slotp->crypto_mode &&
	    slotp->crypto_mode != BLK_ENCRYPTION_MODE_INVALID)
		blk_crypto_fallback_evict_keyslot(slot);

	slotp->crypto_mode = crypto_mode;
	err = crypto_skcipher_setkey(slotp->tfms[crypto_mode], key->raw,
				     key->size);
	if (err) {
		blk_crypto_fallback_evict_keyslot(slot);
		return err;
	}
	return 0;
}

static int blk_crypto_fallback_keyslot_evict(struct blk_crypto_profile *profile,
					     const struct blk_crypto_key *key,
					     unsigned int slot)
{
	blk_crypto_fallback_evict_keyslot(slot);
	return 0;
}

static const struct blk_crypto_ll_ops blk_crypto_fallback_ll_ops = {
	.keyslot_program        = blk_crypto_fallback_keyslot_program,
	.keyslot_evict          = blk_crypto_fallback_keyslot_evict,
};

static void blk_crypto_fallback_encrypt_endio(struct bio *enc_bio)
{
	struct bio *src_bio = enc_bio->bi_private;
	int i;

	for (i = 0; i < enc_bio->bi_vcnt; i++)
		mempool_free(enc_bio->bi_io_vec[i].bv_page,
			     blk_crypto_bounce_page_pool);

	src_bio->bi_status = enc_bio->bi_status;

	bio_put(enc_bio);
	bio_endio(src_bio);
}

static struct bio *blk_crypto_fallback_clone_bio(struct bio *bio_src)
{
	struct bvec_iter iter;
	struct bio_vec bv;
	struct bio *bio;

	bio = bio_kmalloc(GFP_NOIO, bio_segments(bio_src));
	if (!bio)
		return NULL;
	bio->bi_bdev		= bio_src->bi_bdev;
	if (bio_flagged(bio_src, BIO_REMAPPED))
		bio_set_flag(bio, BIO_REMAPPED);
	bio->bi_opf		= bio_src->bi_opf;
	bio->bi_ioprio		= bio_src->bi_ioprio;
	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;

	bio_for_each_segment(bv, bio_src, iter)
		bio->bi_io_vec[bio->bi_vcnt++] = bv;

	bio_clone_blkg_association(bio, bio_src);
	blkcg_bio_issue_init(bio);

	return bio;
}

static bool
blk_crypto_fallback_alloc_cipher_req(struct blk_crypto_keyslot *slot,
				     struct skcipher_request **ciph_req_ret,
				     struct crypto_wait *wait)
{
	struct skcipher_request *ciph_req;
	const struct blk_crypto_fallback_keyslot *slotp;
	int keyslot_idx = blk_crypto_keyslot_index(slot);

	slotp = &blk_crypto_keyslots[keyslot_idx];
	ciph_req = skcipher_request_alloc(slotp->tfms[slotp->crypto_mode],
					  GFP_NOIO);
	if (!ciph_req)
		return false;

	skcipher_request_set_callback(ciph_req,
				      CRYPTO_TFM_REQ_MAY_BACKLOG |
				      CRYPTO_TFM_REQ_MAY_SLEEP,
				      crypto_req_done, wait);
	*ciph_req_ret = ciph_req;

	return true;
}

static bool blk_crypto_fallback_split_bio_if_needed(struct bio **bio_ptr)
{
	struct bio *bio = *bio_ptr;
	unsigned int i = 0;
	unsigned int num_sectors = 0;
	struct bio_vec bv;
	struct bvec_iter iter;

	bio_for_each_segment(bv, bio, iter) {
		num_sectors += bv.bv_len >> SECTOR_SHIFT;
		if (++i == BIO_MAX_VECS)
			break;
	}
	if (num_sectors < bio_sectors(bio)) {
		struct bio *split_bio;

		split_bio = bio_split(bio, num_sectors, GFP_NOIO,
				      &crypto_bio_split);
		if (!split_bio) {
			bio->bi_status = BLK_STS_RESOURCE;
			return false;
		}
		bio_chain(split_bio, bio);
		submit_bio_noacct(bio);
		*bio_ptr = split_bio;
	}

	return true;
}

union blk_crypto_iv {
	__le64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
	u8 bytes[BLK_CRYPTO_MAX_IV_SIZE];
};

static void blk_crypto_dun_to_iv(const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
				 union blk_crypto_iv *iv)
{
	int i;

	for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++)
		iv->dun[i] = cpu_to_le64(dun[i]);
}

/*
 * The crypto API fallback's encryption routine.
 * Allocate a bounce bio for encryption, encrypt the input bio using crypto API,
 * and replace *bio_ptr with the bounce bio. May split input bio if it's too
 * large. Returns true on success. Returns false and sets bio->bi_status on
 * error.
 */
static bool blk_crypto_fallback_encrypt_bio(struct bio **bio_ptr)
{
	struct bio *src_bio, *enc_bio;
	struct bio_crypt_ctx *bc;
	struct blk_crypto_keyslot *slot;
	int data_unit_size;
	struct skcipher_request *ciph_req = NULL;
	DECLARE_CRYPTO_WAIT(wait);
	u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
	struct scatterlist src, dst;
	union blk_crypto_iv iv;
	unsigned int i, j;
	bool ret = false;
	blk_status_t blk_st;

	/* Split the bio if it's too big for single page bvec */
	if (!blk_crypto_fallback_split_bio_if_needed(bio_ptr))
		return false;

	src_bio = *bio_ptr;
	bc = src_bio->bi_crypt_context;
	data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;

	/* Allocate bounce bio for encryption */
	enc_bio = blk_crypto_fallback_clone_bio(src_bio);
	if (!enc_bio) {
		src_bio->bi_status = BLK_STS_RESOURCE;
		return false;
	}

	/*
	 * Get a blk-crypto-fallback keyslot that contains a crypto_skcipher for
	 * this bio's algorithm and key.
	 */
	blk_st = blk_crypto_get_keyslot(&blk_crypto_fallback_profile,
					bc->bc_key, &slot);
	if (blk_st != BLK_STS_OK) {
		src_bio->bi_status = blk_st;
		goto out_put_enc_bio;
	}

	/* and then allocate an skcipher_request for it */
	if (!blk_crypto_fallback_alloc_cipher_req(slot, &ciph_req, &wait)) {
		src_bio->bi_status = BLK_STS_RESOURCE;
		goto out_release_keyslot;
	}

	memcpy(curr_dun, bc->bc_dun, sizeof(curr_dun));
	sg_init_table(&src, 1);
	sg_init_table(&dst, 1);

	skcipher_request_set_crypt(ciph_req, &src, &dst, data_unit_size,
				   iv.bytes);

	/* Encrypt each page in the bounce bio */
	for (i = 0; i < enc_bio->bi_vcnt; i++) {
		struct bio_vec *enc_bvec = &enc_bio->bi_io_vec[i];
		struct page *plaintext_page = enc_bvec->bv_page;
		struct page *ciphertext_page =
			mempool_alloc(blk_crypto_bounce_page_pool, GFP_NOIO);

		enc_bvec->bv_page = ciphertext_page;

		if (!ciphertext_page) {
			src_bio->bi_status = BLK_STS_RESOURCE;
			goto out_free_bounce_pages;
		}

		sg_set_page(&src, plaintext_page, data_unit_size,
			    enc_bvec->bv_offset);
		sg_set_page(&dst, ciphertext_page, data_unit_size,
			    enc_bvec->bv_offset);

		/* Encrypt each data unit in this page */
		for (j = 0; j < enc_bvec->bv_len; j += data_unit_size) {
			blk_crypto_dun_to_iv(curr_dun, &iv);
			if (crypto_wait_req(crypto_skcipher_encrypt(ciph_req),
					    &wait)) {
				i++;
				src_bio->bi_status = BLK_STS_IOERR;
				goto out_free_bounce_pages;
			}
			bio_crypt_dun_increment(curr_dun, 1);
			src.offset += data_unit_size;
			dst.offset += data_unit_size;
		}
	}

	enc_bio->bi_private = src_bio;
	enc_bio->bi_end_io = blk_crypto_fallback_encrypt_endio;
	*bio_ptr = enc_bio;
	ret = true;

	enc_bio = NULL;
	goto out_free_ciph_req;

out_free_bounce_pages:
	while (i > 0)
		mempool_free(enc_bio->bi_io_vec[--i].bv_page,
			     blk_crypto_bounce_page_pool);
out_free_ciph_req:
	skcipher_request_free(ciph_req);
out_release_keyslot:
	blk_crypto_put_keyslot(slot);
out_put_enc_bio:
	if (enc_bio)
		bio_put(enc_bio);

	return ret;
}

/*
 * The crypto API fallback's main decryption routine.
 * Decrypts input bio in place, and calls bio_endio on the bio.
 */
static void blk_crypto_fallback_decrypt_bio(struct work_struct *work)
{
	struct bio_fallback_crypt_ctx *f_ctx =
		container_of(work, struct bio_fallback_crypt_ctx, work);
	struct bio *bio = f_ctx->bio;
	struct bio_crypt_ctx *bc = &f_ctx->crypt_ctx;
	struct blk_crypto_keyslot *slot;
	struct skcipher_request *ciph_req = NULL;
	DECLARE_CRYPTO_WAIT(wait);
	u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
	union blk_crypto_iv iv;
	struct scatterlist sg;
	struct bio_vec bv;
	struct bvec_iter iter;
	const int data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
	unsigned int i;
	blk_status_t blk_st;

	/*
	 * Get a blk-crypto-fallback keyslot that contains a crypto_skcipher for
	 * this bio's algorithm and key.
	 */
	blk_st = blk_crypto_get_keyslot(&blk_crypto_fallback_profile,
					bc->bc_key, &slot);
	if (blk_st != BLK_STS_OK) {
		bio->bi_status = blk_st;
		goto out_no_keyslot;
	}

	/* and then allocate an skcipher_request for it */
	if (!blk_crypto_fallback_alloc_cipher_req(slot, &ciph_req, &wait)) {
		bio->bi_status = BLK_STS_RESOURCE;
		goto out;
	}

	memcpy(curr_dun, bc->bc_dun, sizeof(curr_dun));
	sg_init_table(&sg, 1);
	skcipher_request_set_crypt(ciph_req, &sg, &sg, data_unit_size,
				   iv.bytes);

	/* Decrypt each segment in the bio */
	__bio_for_each_segment(bv, bio, iter, f_ctx->crypt_iter) {
		struct page *page = bv.bv_page;

		sg_set_page(&sg, page, data_unit_size, bv.bv_offset);

		/* Decrypt each data unit in the segment */
		for (i = 0; i < bv.bv_len; i += data_unit_size) {
			blk_crypto_dun_to_iv(curr_dun, &iv);
			if (crypto_wait_req(crypto_skcipher_decrypt(ciph_req),
					    &wait)) {
				bio->bi_status = BLK_STS_IOERR;
				goto out;
			}
			bio_crypt_dun_increment(curr_dun, 1);
			sg.offset += data_unit_size;
		}
	}

out:
	skcipher_request_free(ciph_req);
	blk_crypto_put_keyslot(slot);
out_no_keyslot:
	mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);
	bio_endio(bio);
}

/**
 * blk_crypto_fallback_decrypt_endio - queue bio for fallback decryption
 *
 * @bio: the bio to queue
 *
 * Restore bi_private and bi_end_io, and queue the bio for decryption into a
 * workqueue, since this function will be called from an atomic context.
 */
static void blk_crypto_fallback_decrypt_endio(struct bio *bio)
{
	struct bio_fallback_crypt_ctx *f_ctx = bio->bi_private;

	bio->bi_private = f_ctx->bi_private_orig;
	bio->bi_end_io = f_ctx->bi_end_io_orig;

	/* If there was an IO error, don't queue for decrypt. */
	if (bio->bi_status) {
		mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);
		bio_endio(bio);
		return;
	}

	INIT_WORK(&f_ctx->work, blk_crypto_fallback_decrypt_bio);
	f_ctx->bio = bio;
	queue_work(blk_crypto_wq, &f_ctx->work);
}

/**
 * blk_crypto_fallback_bio_prep - Prepare a bio to use fallback en/decryption
 *
 * @bio_ptr: pointer to the bio to prepare
 *
 * If bio is doing a WRITE operation, this splits the bio into two parts if it's
 * too big (see blk_crypto_fallback_split_bio_if_needed()). It then allocates a
 * bounce bio for the first part, encrypts it, and updates bio_ptr to point to
 * the bounce bio.
 *
 * For a READ operation, we mark the bio for decryption by using bi_private and
 * bi_end_io.
 *
 * In either case, this function will make the bio look like a regular bio (i.e.
 * as if no encryption context was ever specified) for the purposes of the rest
 * of the stack except for blk-integrity (blk-integrity and blk-crypto are not
 * currently supported together).
 *
 * Return: true on success. Sets bio->bi_status and returns false on error.
 */
bool blk_crypto_fallback_bio_prep(struct bio **bio_ptr)
{
	struct bio *bio = *bio_ptr;
	struct bio_crypt_ctx *bc = bio->bi_crypt_context;
	struct bio_fallback_crypt_ctx *f_ctx;

	if (WARN_ON_ONCE(!tfms_inited[bc->bc_key->crypto_cfg.crypto_mode])) {
		/* User didn't call blk_crypto_start_using_key() first */
		bio->bi_status = BLK_STS_IOERR;
		return false;
	}

	if (!__blk_crypto_cfg_supported(&blk_crypto_fallback_profile,
					&bc->bc_key->crypto_cfg)) {
		bio->bi_status = BLK_STS_NOTSUPP;
		return false;
	}

	if (bio_data_dir(bio) == WRITE)
		return blk_crypto_fallback_encrypt_bio(bio_ptr);

	/*
	 * bio READ case: Set up a f_ctx in the bio's bi_private and set the
	 * bi_end_io appropriately to trigger decryption when the bio is ended.
	 */
	f_ctx = mempool_alloc(bio_fallback_crypt_ctx_pool, GFP_NOIO);
	f_ctx->crypt_ctx = *bc;
	f_ctx->crypt_iter = bio->bi_iter;
	f_ctx->bi_private_orig = bio->bi_private;
	f_ctx->bi_end_io_orig = bio->bi_end_io;
	bio->bi_private = (void *)f_ctx;
	bio->bi_end_io = blk_crypto_fallback_decrypt_endio;
	bio_crypt_free_ctx(bio);

	return true;
}

int blk_crypto_fallback_evict_key(const struct blk_crypto_key *key)
{
	return __blk_crypto_evict_key(&blk_crypto_fallback_profile, key);
}

static bool blk_crypto_fallback_inited;
static int blk_crypto_fallback_init(void)
{
	int i;
	int err;
	struct blk_crypto_profile *profile = &blk_crypto_fallback_profile;

	if (blk_crypto_fallback_inited)
		return 0;

	prandom_bytes(blank_key, BLK_CRYPTO_MAX_KEY_SIZE);

	err = bioset_init(&crypto_bio_split, 64, 0, 0);
	if (err)
		goto out;

	err = blk_crypto_profile_init(profile, blk_crypto_num_keyslots);
	if (err)
		goto fail_free_bioset;
	err = -ENOMEM;

	profile->ll_ops = blk_crypto_fallback_ll_ops;
	profile->max_dun_bytes_supported = BLK_CRYPTO_MAX_IV_SIZE;

	/* All blk-crypto modes have a crypto API fallback. */
	for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++)
		profile->modes_supported[i] = 0xFFFFFFFF;
	profile->modes_supported[BLK_ENCRYPTION_MODE_INVALID] = 0;

	blk_crypto_wq = alloc_workqueue("blk_crypto_wq",
					WQ_UNBOUND | WQ_HIGHPRI |
					WQ_MEM_RECLAIM, num_online_cpus());
	if (!blk_crypto_wq)
		goto fail_destroy_profile;

	blk_crypto_keyslots = kcalloc(blk_crypto_num_keyslots,
				      sizeof(blk_crypto_keyslots[0]),
				      GFP_KERNEL);
	if (!blk_crypto_keyslots)
		goto fail_free_wq;

	blk_crypto_bounce_page_pool =
		mempool_create_page_pool(num_prealloc_bounce_pg, 0);
	if (!blk_crypto_bounce_page_pool)
		goto fail_free_keyslots;

	bio_fallback_crypt_ctx_cache = KMEM_CACHE(bio_fallback_crypt_ctx, 0);
	if (!bio_fallback_crypt_ctx_cache)
		goto fail_free_bounce_page_pool;

	bio_fallback_crypt_ctx_pool =
		mempool_create_slab_pool(num_prealloc_fallback_crypt_ctxs,
					 bio_fallback_crypt_ctx_cache);
	if (!bio_fallback_crypt_ctx_pool)
		goto fail_free_crypt_ctx_cache;

	blk_crypto_fallback_inited = true;

	return 0;
fail_free_crypt_ctx_cache:
	kmem_cache_destroy(bio_fallback_crypt_ctx_cache);
fail_free_bounce_page_pool:
	mempool_destroy(blk_crypto_bounce_page_pool);
fail_free_keyslots:
	kfree(blk_crypto_keyslots);
fail_free_wq:
	destroy_workqueue(blk_crypto_wq);
fail_destroy_profile:
	blk_crypto_profile_destroy(profile);
fail_free_bioset:
	bioset_exit(&crypto_bio_split);
out:
	return err;
}

/*
 * Prepare blk-crypto-fallback for the specified crypto mode.
 * Returns -ENOPKG if the needed crypto API support is missing.
 */
int blk_crypto_fallback_start_using_mode(enum blk_crypto_mode_num mode_num)
{
	const char *cipher_str = blk_crypto_modes[mode_num].cipher_str;
	struct blk_crypto_fallback_keyslot *slotp;
	unsigned int i;
	int err = 0;

	/*
	 * Fast path
	 * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
	 * for each i are visible before we try to access them.
	 */
	if (likely(smp_load_acquire(&tfms_inited[mode_num])))
		return 0;

	mutex_lock(&tfms_init_lock);
	if (tfms_inited[mode_num])
		goto out;

	err = blk_crypto_fallback_init();
	if (err)
		goto out;

	for (i = 0; i < blk_crypto_num_keyslots; i++) {
		slotp = &blk_crypto_keyslots[i];
		slotp->tfms[mode_num] = crypto_alloc_skcipher(cipher_str, 0, 0);
		if (IS_ERR(slotp->tfms[mode_num])) {
			err = PTR_ERR(slotp->tfms[mode_num]);
			if (err == -ENOENT) {
				pr_warn_once("Missing crypto API support for \"%s\"\n",
					     cipher_str);
				err = -ENOPKG;
			}
			slotp->tfms[mode_num] = NULL;
			goto out_free_tfms;
		}

		crypto_skcipher_set_flags(slotp->tfms[mode_num],
					  CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
	}

	/*
	 * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
	 * for each i are visible before we set tfms_inited[mode_num].
	 */
	smp_store_release(&tfms_inited[mode_num], true);
	goto out;

out_free_tfms:
	for (i = 0; i < blk_crypto_num_keyslots; i++) {
		slotp = &blk_crypto_keyslots[i];
		crypto_free_skcipher(slotp->tfms[mode_num]);
		slotp->tfms[mode_num] = NULL;
	}
out:
	mutex_unlock(&tfms_init_lock);
	return err;
}