xref: /linux/block/blk-crypto-fallback.c (revision 55a42f78ffd386e01a5404419f8c5ded7db70a21)
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-crypto.h>
14 #include <linux/blk-crypto-profile.h>
15 #include <linux/blkdev.h>
16 #include <linux/crypto.h>
17 #include <linux/mempool.h>
18 #include <linux/module.h>
19 #include <linux/random.h>
20 #include <linux/scatterlist.h>
21 
22 #include "blk-cgroup.h"
23 #include "blk-crypto-internal.h"
24 
25 static unsigned int num_prealloc_bounce_pg = 32;
26 module_param(num_prealloc_bounce_pg, uint, 0);
27 MODULE_PARM_DESC(num_prealloc_bounce_pg,
28 		 "Number of preallocated bounce pages for the blk-crypto crypto API fallback");
29 
30 static unsigned int blk_crypto_num_keyslots = 100;
31 module_param_named(num_keyslots, blk_crypto_num_keyslots, uint, 0);
32 MODULE_PARM_DESC(num_keyslots,
33 		 "Number of keyslots for the blk-crypto crypto API fallback");
34 
35 static unsigned int num_prealloc_fallback_crypt_ctxs = 128;
36 module_param(num_prealloc_fallback_crypt_ctxs, uint, 0);
37 MODULE_PARM_DESC(num_prealloc_crypt_fallback_ctxs,
38 		 "Number of preallocated bio fallback crypto contexts for blk-crypto to use during crypto API fallback");
39 
40 struct bio_fallback_crypt_ctx {
41 	struct bio_crypt_ctx crypt_ctx;
42 	/*
43 	 * Copy of the bvec_iter when this bio was submitted.
44 	 * We only want to en/decrypt the part of the bio as described by the
45 	 * bvec_iter upon submission because bio might be split before being
46 	 * resubmitted
47 	 */
48 	struct bvec_iter crypt_iter;
49 	union {
50 		struct {
51 			struct work_struct work;
52 			struct bio *bio;
53 		};
54 		struct {
55 			void *bi_private_orig;
56 			bio_end_io_t *bi_end_io_orig;
57 		};
58 	};
59 };
60 
61 static struct kmem_cache *bio_fallback_crypt_ctx_cache;
62 static mempool_t *bio_fallback_crypt_ctx_pool;
63 
64 /*
65  * Allocating a crypto tfm during I/O can deadlock, so we have to preallocate
66  * all of a mode's tfms when that mode starts being used. Since each mode may
67  * need all the keyslots at some point, each mode needs its own tfm for each
68  * keyslot; thus, a keyslot may contain tfms for multiple modes.  However, to
69  * match the behavior of real inline encryption hardware (which only supports a
70  * single encryption context per keyslot), we only allow one tfm per keyslot to
71  * be used at a time - the rest of the unused tfms have their keys cleared.
72  */
73 static DEFINE_MUTEX(tfms_init_lock);
74 static bool tfms_inited[BLK_ENCRYPTION_MODE_MAX];
75 
76 static struct blk_crypto_fallback_keyslot {
77 	enum blk_crypto_mode_num crypto_mode;
78 	struct crypto_skcipher *tfms[BLK_ENCRYPTION_MODE_MAX];
79 } *blk_crypto_keyslots;
80 
81 static struct blk_crypto_profile *blk_crypto_fallback_profile;
82 static struct workqueue_struct *blk_crypto_wq;
83 static mempool_t *blk_crypto_bounce_page_pool;
84 static struct bio_set crypto_bio_split;
85 
86 /*
87  * This is the key we set when evicting a keyslot. This *should* be the all 0's
88  * key, but AES-XTS rejects that key, so we use some random bytes instead.
89  */
90 static u8 blank_key[BLK_CRYPTO_MAX_RAW_KEY_SIZE];
91 
92 static void blk_crypto_fallback_evict_keyslot(unsigned int slot)
93 {
94 	struct blk_crypto_fallback_keyslot *slotp = &blk_crypto_keyslots[slot];
95 	enum blk_crypto_mode_num crypto_mode = slotp->crypto_mode;
96 	int err;
97 
98 	WARN_ON(slotp->crypto_mode == BLK_ENCRYPTION_MODE_INVALID);
99 
100 	/* Clear the key in the skcipher */
101 	err = crypto_skcipher_setkey(slotp->tfms[crypto_mode], blank_key,
102 				     blk_crypto_modes[crypto_mode].keysize);
103 	WARN_ON(err);
104 	slotp->crypto_mode = BLK_ENCRYPTION_MODE_INVALID;
105 }
106 
107 static int
108 blk_crypto_fallback_keyslot_program(struct blk_crypto_profile *profile,
109 				    const struct blk_crypto_key *key,
110 				    unsigned int slot)
111 {
112 	struct blk_crypto_fallback_keyslot *slotp = &blk_crypto_keyslots[slot];
113 	const enum blk_crypto_mode_num crypto_mode =
114 						key->crypto_cfg.crypto_mode;
115 	int err;
116 
117 	if (crypto_mode != slotp->crypto_mode &&
118 	    slotp->crypto_mode != BLK_ENCRYPTION_MODE_INVALID)
119 		blk_crypto_fallback_evict_keyslot(slot);
120 
121 	slotp->crypto_mode = crypto_mode;
122 	err = crypto_skcipher_setkey(slotp->tfms[crypto_mode], key->bytes,
123 				     key->size);
124 	if (err) {
125 		blk_crypto_fallback_evict_keyslot(slot);
126 		return err;
127 	}
128 	return 0;
129 }
130 
131 static int blk_crypto_fallback_keyslot_evict(struct blk_crypto_profile *profile,
132 					     const struct blk_crypto_key *key,
133 					     unsigned int slot)
134 {
135 	blk_crypto_fallback_evict_keyslot(slot);
136 	return 0;
137 }
138 
139 static const struct blk_crypto_ll_ops blk_crypto_fallback_ll_ops = {
140 	.keyslot_program        = blk_crypto_fallback_keyslot_program,
141 	.keyslot_evict          = blk_crypto_fallback_keyslot_evict,
142 };
143 
144 static void blk_crypto_fallback_encrypt_endio(struct bio *enc_bio)
145 {
146 	struct bio *src_bio = enc_bio->bi_private;
147 	int i;
148 
149 	for (i = 0; i < enc_bio->bi_vcnt; i++)
150 		mempool_free(enc_bio->bi_io_vec[i].bv_page,
151 			     blk_crypto_bounce_page_pool);
152 
153 	src_bio->bi_status = enc_bio->bi_status;
154 
155 	bio_uninit(enc_bio);
156 	kfree(enc_bio);
157 	bio_endio(src_bio);
158 }
159 
160 static struct bio *blk_crypto_fallback_clone_bio(struct bio *bio_src)
161 {
162 	unsigned int nr_segs = bio_segments(bio_src);
163 	struct bvec_iter iter;
164 	struct bio_vec bv;
165 	struct bio *bio;
166 
167 	bio = bio_kmalloc(nr_segs, GFP_NOIO);
168 	if (!bio)
169 		return NULL;
170 	bio_init_inline(bio, bio_src->bi_bdev, nr_segs, bio_src->bi_opf);
171 	if (bio_flagged(bio_src, BIO_REMAPPED))
172 		bio_set_flag(bio, BIO_REMAPPED);
173 	bio->bi_ioprio		= bio_src->bi_ioprio;
174 	bio->bi_write_hint	= bio_src->bi_write_hint;
175 	bio->bi_write_stream	= bio_src->bi_write_stream;
176 	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
177 	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;
178 
179 	bio_for_each_segment(bv, bio_src, iter)
180 		bio->bi_io_vec[bio->bi_vcnt++] = bv;
181 
182 	bio_clone_blkg_association(bio, bio_src);
183 
184 	return bio;
185 }
186 
187 static bool
188 blk_crypto_fallback_alloc_cipher_req(struct blk_crypto_keyslot *slot,
189 				     struct skcipher_request **ciph_req_ret,
190 				     struct crypto_wait *wait)
191 {
192 	struct skcipher_request *ciph_req;
193 	const struct blk_crypto_fallback_keyslot *slotp;
194 	int keyslot_idx = blk_crypto_keyslot_index(slot);
195 
196 	slotp = &blk_crypto_keyslots[keyslot_idx];
197 	ciph_req = skcipher_request_alloc(slotp->tfms[slotp->crypto_mode],
198 					  GFP_NOIO);
199 	if (!ciph_req)
200 		return false;
201 
202 	skcipher_request_set_callback(ciph_req,
203 				      CRYPTO_TFM_REQ_MAY_BACKLOG |
204 				      CRYPTO_TFM_REQ_MAY_SLEEP,
205 				      crypto_req_done, wait);
206 	*ciph_req_ret = ciph_req;
207 
208 	return true;
209 }
210 
211 static bool blk_crypto_fallback_split_bio_if_needed(struct bio **bio_ptr)
212 {
213 	struct bio *bio = *bio_ptr;
214 	unsigned int i = 0;
215 	unsigned int num_sectors = 0;
216 	struct bio_vec bv;
217 	struct bvec_iter iter;
218 
219 	bio_for_each_segment(bv, bio, iter) {
220 		num_sectors += bv.bv_len >> SECTOR_SHIFT;
221 		if (++i == BIO_MAX_VECS)
222 			break;
223 	}
224 
225 	if (num_sectors < bio_sectors(bio)) {
226 		bio = bio_submit_split_bioset(bio, num_sectors,
227 					      &crypto_bio_split);
228 		if (!bio)
229 			return false;
230 
231 		*bio_ptr = bio;
232 	}
233 
234 	return true;
235 }
236 
237 union blk_crypto_iv {
238 	__le64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
239 	u8 bytes[BLK_CRYPTO_MAX_IV_SIZE];
240 };
241 
242 static void blk_crypto_dun_to_iv(const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
243 				 union blk_crypto_iv *iv)
244 {
245 	int i;
246 
247 	for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++)
248 		iv->dun[i] = cpu_to_le64(dun[i]);
249 }
250 
251 /*
252  * The crypto API fallback's encryption routine.
253  * Allocate a bounce bio for encryption, encrypt the input bio using crypto API,
254  * and replace *bio_ptr with the bounce bio. May split input bio if it's too
255  * large. Returns true on success. Returns false and sets bio->bi_status on
256  * error.
257  */
258 static bool blk_crypto_fallback_encrypt_bio(struct bio **bio_ptr)
259 {
260 	struct bio *src_bio, *enc_bio;
261 	struct bio_crypt_ctx *bc;
262 	struct blk_crypto_keyslot *slot;
263 	int data_unit_size;
264 	struct skcipher_request *ciph_req = NULL;
265 	DECLARE_CRYPTO_WAIT(wait);
266 	u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
267 	struct scatterlist src, dst;
268 	union blk_crypto_iv iv;
269 	unsigned int i, j;
270 	bool ret = false;
271 	blk_status_t blk_st;
272 
273 	/* Split the bio if it's too big for single page bvec */
274 	if (!blk_crypto_fallback_split_bio_if_needed(bio_ptr))
275 		return false;
276 
277 	src_bio = *bio_ptr;
278 	bc = src_bio->bi_crypt_context;
279 	data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
280 
281 	/* Allocate bounce bio for encryption */
282 	enc_bio = blk_crypto_fallback_clone_bio(src_bio);
283 	if (!enc_bio) {
284 		src_bio->bi_status = BLK_STS_RESOURCE;
285 		return false;
286 	}
287 
288 	/*
289 	 * Get a blk-crypto-fallback keyslot that contains a crypto_skcipher for
290 	 * this bio's algorithm and key.
291 	 */
292 	blk_st = blk_crypto_get_keyslot(blk_crypto_fallback_profile,
293 					bc->bc_key, &slot);
294 	if (blk_st != BLK_STS_OK) {
295 		src_bio->bi_status = blk_st;
296 		goto out_put_enc_bio;
297 	}
298 
299 	/* and then allocate an skcipher_request for it */
300 	if (!blk_crypto_fallback_alloc_cipher_req(slot, &ciph_req, &wait)) {
301 		src_bio->bi_status = BLK_STS_RESOURCE;
302 		goto out_release_keyslot;
303 	}
304 
305 	memcpy(curr_dun, bc->bc_dun, sizeof(curr_dun));
306 	sg_init_table(&src, 1);
307 	sg_init_table(&dst, 1);
308 
309 	skcipher_request_set_crypt(ciph_req, &src, &dst, data_unit_size,
310 				   iv.bytes);
311 
312 	/* Encrypt each page in the bounce bio */
313 	for (i = 0; i < enc_bio->bi_vcnt; i++) {
314 		struct bio_vec *enc_bvec = &enc_bio->bi_io_vec[i];
315 		struct page *plaintext_page = enc_bvec->bv_page;
316 		struct page *ciphertext_page =
317 			mempool_alloc(blk_crypto_bounce_page_pool, GFP_NOIO);
318 
319 		enc_bvec->bv_page = ciphertext_page;
320 
321 		if (!ciphertext_page) {
322 			src_bio->bi_status = BLK_STS_RESOURCE;
323 			goto out_free_bounce_pages;
324 		}
325 
326 		sg_set_page(&src, plaintext_page, data_unit_size,
327 			    enc_bvec->bv_offset);
328 		sg_set_page(&dst, ciphertext_page, data_unit_size,
329 			    enc_bvec->bv_offset);
330 
331 		/* Encrypt each data unit in this page */
332 		for (j = 0; j < enc_bvec->bv_len; j += data_unit_size) {
333 			blk_crypto_dun_to_iv(curr_dun, &iv);
334 			if (crypto_wait_req(crypto_skcipher_encrypt(ciph_req),
335 					    &wait)) {
336 				i++;
337 				src_bio->bi_status = BLK_STS_IOERR;
338 				goto out_free_bounce_pages;
339 			}
340 			bio_crypt_dun_increment(curr_dun, 1);
341 			src.offset += data_unit_size;
342 			dst.offset += data_unit_size;
343 		}
344 	}
345 
346 	enc_bio->bi_private = src_bio;
347 	enc_bio->bi_end_io = blk_crypto_fallback_encrypt_endio;
348 	*bio_ptr = enc_bio;
349 	ret = true;
350 
351 	enc_bio = NULL;
352 	goto out_free_ciph_req;
353 
354 out_free_bounce_pages:
355 	while (i > 0)
356 		mempool_free(enc_bio->bi_io_vec[--i].bv_page,
357 			     blk_crypto_bounce_page_pool);
358 out_free_ciph_req:
359 	skcipher_request_free(ciph_req);
360 out_release_keyslot:
361 	blk_crypto_put_keyslot(slot);
362 out_put_enc_bio:
363 	if (enc_bio)
364 		bio_uninit(enc_bio);
365 	kfree(enc_bio);
366 	return ret;
367 }
368 
369 /*
370  * The crypto API fallback's main decryption routine.
371  * Decrypts input bio in place, and calls bio_endio on the bio.
372  */
373 static void blk_crypto_fallback_decrypt_bio(struct work_struct *work)
374 {
375 	struct bio_fallback_crypt_ctx *f_ctx =
376 		container_of(work, struct bio_fallback_crypt_ctx, work);
377 	struct bio *bio = f_ctx->bio;
378 	struct bio_crypt_ctx *bc = &f_ctx->crypt_ctx;
379 	struct blk_crypto_keyslot *slot;
380 	struct skcipher_request *ciph_req = NULL;
381 	DECLARE_CRYPTO_WAIT(wait);
382 	u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
383 	union blk_crypto_iv iv;
384 	struct scatterlist sg;
385 	struct bio_vec bv;
386 	struct bvec_iter iter;
387 	const int data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
388 	unsigned int i;
389 	blk_status_t blk_st;
390 
391 	/*
392 	 * Get a blk-crypto-fallback keyslot that contains a crypto_skcipher for
393 	 * this bio's algorithm and key.
394 	 */
395 	blk_st = blk_crypto_get_keyslot(blk_crypto_fallback_profile,
396 					bc->bc_key, &slot);
397 	if (blk_st != BLK_STS_OK) {
398 		bio->bi_status = blk_st;
399 		goto out_no_keyslot;
400 	}
401 
402 	/* and then allocate an skcipher_request for it */
403 	if (!blk_crypto_fallback_alloc_cipher_req(slot, &ciph_req, &wait)) {
404 		bio->bi_status = BLK_STS_RESOURCE;
405 		goto out;
406 	}
407 
408 	memcpy(curr_dun, bc->bc_dun, sizeof(curr_dun));
409 	sg_init_table(&sg, 1);
410 	skcipher_request_set_crypt(ciph_req, &sg, &sg, data_unit_size,
411 				   iv.bytes);
412 
413 	/* Decrypt each segment in the bio */
414 	__bio_for_each_segment(bv, bio, iter, f_ctx->crypt_iter) {
415 		struct page *page = bv.bv_page;
416 
417 		sg_set_page(&sg, page, data_unit_size, bv.bv_offset);
418 
419 		/* Decrypt each data unit in the segment */
420 		for (i = 0; i < bv.bv_len; i += data_unit_size) {
421 			blk_crypto_dun_to_iv(curr_dun, &iv);
422 			if (crypto_wait_req(crypto_skcipher_decrypt(ciph_req),
423 					    &wait)) {
424 				bio->bi_status = BLK_STS_IOERR;
425 				goto out;
426 			}
427 			bio_crypt_dun_increment(curr_dun, 1);
428 			sg.offset += data_unit_size;
429 		}
430 	}
431 
432 out:
433 	skcipher_request_free(ciph_req);
434 	blk_crypto_put_keyslot(slot);
435 out_no_keyslot:
436 	mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);
437 	bio_endio(bio);
438 }
439 
440 /**
441  * blk_crypto_fallback_decrypt_endio - queue bio for fallback decryption
442  *
443  * @bio: the bio to queue
444  *
445  * Restore bi_private and bi_end_io, and queue the bio for decryption into a
446  * workqueue, since this function will be called from an atomic context.
447  */
448 static void blk_crypto_fallback_decrypt_endio(struct bio *bio)
449 {
450 	struct bio_fallback_crypt_ctx *f_ctx = bio->bi_private;
451 
452 	bio->bi_private = f_ctx->bi_private_orig;
453 	bio->bi_end_io = f_ctx->bi_end_io_orig;
454 
455 	/* If there was an IO error, don't queue for decrypt. */
456 	if (bio->bi_status) {
457 		mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);
458 		bio_endio(bio);
459 		return;
460 	}
461 
462 	INIT_WORK(&f_ctx->work, blk_crypto_fallback_decrypt_bio);
463 	f_ctx->bio = bio;
464 	queue_work(blk_crypto_wq, &f_ctx->work);
465 }
466 
467 /**
468  * blk_crypto_fallback_bio_prep - Prepare a bio to use fallback en/decryption
469  *
470  * @bio_ptr: pointer to the bio to prepare
471  *
472  * If bio is doing a WRITE operation, this splits the bio into two parts if it's
473  * too big (see blk_crypto_fallback_split_bio_if_needed()). It then allocates a
474  * bounce bio for the first part, encrypts it, and updates bio_ptr to point to
475  * the bounce bio.
476  *
477  * For a READ operation, we mark the bio for decryption by using bi_private and
478  * bi_end_io.
479  *
480  * In either case, this function will make the bio look like a regular bio (i.e.
481  * as if no encryption context was ever specified) for the purposes of the rest
482  * of the stack except for blk-integrity (blk-integrity and blk-crypto are not
483  * currently supported together).
484  *
485  * Return: true on success. Sets bio->bi_status and returns false on error.
486  */
487 bool blk_crypto_fallback_bio_prep(struct bio **bio_ptr)
488 {
489 	struct bio *bio = *bio_ptr;
490 	struct bio_crypt_ctx *bc = bio->bi_crypt_context;
491 	struct bio_fallback_crypt_ctx *f_ctx;
492 
493 	if (WARN_ON_ONCE(!tfms_inited[bc->bc_key->crypto_cfg.crypto_mode])) {
494 		/* User didn't call blk_crypto_start_using_key() first */
495 		bio->bi_status = BLK_STS_IOERR;
496 		return false;
497 	}
498 
499 	if (!__blk_crypto_cfg_supported(blk_crypto_fallback_profile,
500 					&bc->bc_key->crypto_cfg)) {
501 		bio->bi_status = BLK_STS_NOTSUPP;
502 		return false;
503 	}
504 
505 	if (bio_data_dir(bio) == WRITE)
506 		return blk_crypto_fallback_encrypt_bio(bio_ptr);
507 
508 	/*
509 	 * bio READ case: Set up a f_ctx in the bio's bi_private and set the
510 	 * bi_end_io appropriately to trigger decryption when the bio is ended.
511 	 */
512 	f_ctx = mempool_alloc(bio_fallback_crypt_ctx_pool, GFP_NOIO);
513 	f_ctx->crypt_ctx = *bc;
514 	f_ctx->crypt_iter = bio->bi_iter;
515 	f_ctx->bi_private_orig = bio->bi_private;
516 	f_ctx->bi_end_io_orig = bio->bi_end_io;
517 	bio->bi_private = (void *)f_ctx;
518 	bio->bi_end_io = blk_crypto_fallback_decrypt_endio;
519 	bio_crypt_free_ctx(bio);
520 
521 	return true;
522 }
523 
524 int blk_crypto_fallback_evict_key(const struct blk_crypto_key *key)
525 {
526 	return __blk_crypto_evict_key(blk_crypto_fallback_profile, key);
527 }
528 
529 static bool blk_crypto_fallback_inited;
530 static int blk_crypto_fallback_init(void)
531 {
532 	int i;
533 	int err;
534 
535 	if (blk_crypto_fallback_inited)
536 		return 0;
537 
538 	get_random_bytes(blank_key, sizeof(blank_key));
539 
540 	err = bioset_init(&crypto_bio_split, 64, 0, 0);
541 	if (err)
542 		goto out;
543 
544 	/* Dynamic allocation is needed because of lockdep_register_key(). */
545 	blk_crypto_fallback_profile =
546 		kzalloc(sizeof(*blk_crypto_fallback_profile), GFP_KERNEL);
547 	if (!blk_crypto_fallback_profile) {
548 		err = -ENOMEM;
549 		goto fail_free_bioset;
550 	}
551 
552 	err = blk_crypto_profile_init(blk_crypto_fallback_profile,
553 				      blk_crypto_num_keyslots);
554 	if (err)
555 		goto fail_free_profile;
556 	err = -ENOMEM;
557 
558 	blk_crypto_fallback_profile->ll_ops = blk_crypto_fallback_ll_ops;
559 	blk_crypto_fallback_profile->max_dun_bytes_supported = BLK_CRYPTO_MAX_IV_SIZE;
560 	blk_crypto_fallback_profile->key_types_supported = BLK_CRYPTO_KEY_TYPE_RAW;
561 
562 	/* All blk-crypto modes have a crypto API fallback. */
563 	for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++)
564 		blk_crypto_fallback_profile->modes_supported[i] = 0xFFFFFFFF;
565 	blk_crypto_fallback_profile->modes_supported[BLK_ENCRYPTION_MODE_INVALID] = 0;
566 
567 	blk_crypto_wq = alloc_workqueue("blk_crypto_wq",
568 					WQ_UNBOUND | WQ_HIGHPRI |
569 					WQ_MEM_RECLAIM, num_online_cpus());
570 	if (!blk_crypto_wq)
571 		goto fail_destroy_profile;
572 
573 	blk_crypto_keyslots = kcalloc(blk_crypto_num_keyslots,
574 				      sizeof(blk_crypto_keyslots[0]),
575 				      GFP_KERNEL);
576 	if (!blk_crypto_keyslots)
577 		goto fail_free_wq;
578 
579 	blk_crypto_bounce_page_pool =
580 		mempool_create_page_pool(num_prealloc_bounce_pg, 0);
581 	if (!blk_crypto_bounce_page_pool)
582 		goto fail_free_keyslots;
583 
584 	bio_fallback_crypt_ctx_cache = KMEM_CACHE(bio_fallback_crypt_ctx, 0);
585 	if (!bio_fallback_crypt_ctx_cache)
586 		goto fail_free_bounce_page_pool;
587 
588 	bio_fallback_crypt_ctx_pool =
589 		mempool_create_slab_pool(num_prealloc_fallback_crypt_ctxs,
590 					 bio_fallback_crypt_ctx_cache);
591 	if (!bio_fallback_crypt_ctx_pool)
592 		goto fail_free_crypt_ctx_cache;
593 
594 	blk_crypto_fallback_inited = true;
595 
596 	return 0;
597 fail_free_crypt_ctx_cache:
598 	kmem_cache_destroy(bio_fallback_crypt_ctx_cache);
599 fail_free_bounce_page_pool:
600 	mempool_destroy(blk_crypto_bounce_page_pool);
601 fail_free_keyslots:
602 	kfree(blk_crypto_keyslots);
603 fail_free_wq:
604 	destroy_workqueue(blk_crypto_wq);
605 fail_destroy_profile:
606 	blk_crypto_profile_destroy(blk_crypto_fallback_profile);
607 fail_free_profile:
608 	kfree(blk_crypto_fallback_profile);
609 fail_free_bioset:
610 	bioset_exit(&crypto_bio_split);
611 out:
612 	return err;
613 }
614 
615 /*
616  * Prepare blk-crypto-fallback for the specified crypto mode.
617  * Returns -ENOPKG if the needed crypto API support is missing.
618  */
619 int blk_crypto_fallback_start_using_mode(enum blk_crypto_mode_num mode_num)
620 {
621 	const char *cipher_str = blk_crypto_modes[mode_num].cipher_str;
622 	struct blk_crypto_fallback_keyslot *slotp;
623 	unsigned int i;
624 	int err = 0;
625 
626 	/*
627 	 * Fast path
628 	 * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
629 	 * for each i are visible before we try to access them.
630 	 */
631 	if (likely(smp_load_acquire(&tfms_inited[mode_num])))
632 		return 0;
633 
634 	mutex_lock(&tfms_init_lock);
635 	if (tfms_inited[mode_num])
636 		goto out;
637 
638 	err = blk_crypto_fallback_init();
639 	if (err)
640 		goto out;
641 
642 	for (i = 0; i < blk_crypto_num_keyslots; i++) {
643 		slotp = &blk_crypto_keyslots[i];
644 		slotp->tfms[mode_num] = crypto_alloc_skcipher(cipher_str, 0, 0);
645 		if (IS_ERR(slotp->tfms[mode_num])) {
646 			err = PTR_ERR(slotp->tfms[mode_num]);
647 			if (err == -ENOENT) {
648 				pr_warn_once("Missing crypto API support for \"%s\"\n",
649 					     cipher_str);
650 				err = -ENOPKG;
651 			}
652 			slotp->tfms[mode_num] = NULL;
653 			goto out_free_tfms;
654 		}
655 
656 		crypto_skcipher_set_flags(slotp->tfms[mode_num],
657 					  CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
658 	}
659 
660 	/*
661 	 * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
662 	 * for each i are visible before we set tfms_inited[mode_num].
663 	 */
664 	smp_store_release(&tfms_inited[mode_num], true);
665 	goto out;
666 
667 out_free_tfms:
668 	for (i = 0; i < blk_crypto_num_keyslots; i++) {
669 		slotp = &blk_crypto_keyslots[i];
670 		crypto_free_skcipher(slotp->tfms[mode_num]);
671 		slotp->tfms[mode_num] = NULL;
672 	}
673 out:
674 	mutex_unlock(&tfms_init_lock);
675 	return err;
676 }
677