xref: /linux/block/blk-crypto-fallback.c (revision 1e525507)
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_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->raw,
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(bio, bio_src->bi_bdev, bio->bi_inline_vecs, nr_segs,
171 		 bio_src->bi_opf);
172 	if (bio_flagged(bio_src, BIO_REMAPPED))
173 		bio_set_flag(bio, BIO_REMAPPED);
174 	bio->bi_ioprio		= bio_src->bi_ioprio;
175 	bio->bi_write_hint	= bio_src->bi_write_hint;
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 	if (num_sectors < bio_sectors(bio)) {
225 		struct bio *split_bio;
226 
227 		split_bio = bio_split(bio, num_sectors, GFP_NOIO,
228 				      &crypto_bio_split);
229 		if (!split_bio) {
230 			bio->bi_status = BLK_STS_RESOURCE;
231 			return false;
232 		}
233 		bio_chain(split_bio, bio);
234 		submit_bio_noacct(bio);
235 		*bio_ptr = split_bio;
236 	}
237 
238 	return true;
239 }
240 
241 union blk_crypto_iv {
242 	__le64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
243 	u8 bytes[BLK_CRYPTO_MAX_IV_SIZE];
244 };
245 
246 static void blk_crypto_dun_to_iv(const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
247 				 union blk_crypto_iv *iv)
248 {
249 	int i;
250 
251 	for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++)
252 		iv->dun[i] = cpu_to_le64(dun[i]);
253 }
254 
255 /*
256  * The crypto API fallback's encryption routine.
257  * Allocate a bounce bio for encryption, encrypt the input bio using crypto API,
258  * and replace *bio_ptr with the bounce bio. May split input bio if it's too
259  * large. Returns true on success. Returns false and sets bio->bi_status on
260  * error.
261  */
262 static bool blk_crypto_fallback_encrypt_bio(struct bio **bio_ptr)
263 {
264 	struct bio *src_bio, *enc_bio;
265 	struct bio_crypt_ctx *bc;
266 	struct blk_crypto_keyslot *slot;
267 	int data_unit_size;
268 	struct skcipher_request *ciph_req = NULL;
269 	DECLARE_CRYPTO_WAIT(wait);
270 	u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
271 	struct scatterlist src, dst;
272 	union blk_crypto_iv iv;
273 	unsigned int i, j;
274 	bool ret = false;
275 	blk_status_t blk_st;
276 
277 	/* Split the bio if it's too big for single page bvec */
278 	if (!blk_crypto_fallback_split_bio_if_needed(bio_ptr))
279 		return false;
280 
281 	src_bio = *bio_ptr;
282 	bc = src_bio->bi_crypt_context;
283 	data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
284 
285 	/* Allocate bounce bio for encryption */
286 	enc_bio = blk_crypto_fallback_clone_bio(src_bio);
287 	if (!enc_bio) {
288 		src_bio->bi_status = BLK_STS_RESOURCE;
289 		return false;
290 	}
291 
292 	/*
293 	 * Get a blk-crypto-fallback keyslot that contains a crypto_skcipher for
294 	 * this bio's algorithm and key.
295 	 */
296 	blk_st = blk_crypto_get_keyslot(blk_crypto_fallback_profile,
297 					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_fallback_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_crypto_put_keyslot(slot);
366 out_put_enc_bio:
367 	if (enc_bio)
368 		bio_uninit(enc_bio);
369 	kfree(enc_bio);
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_crypto_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 	 * Get a blk-crypto-fallback keyslot that contains a crypto_skcipher for
397 	 * this bio's algorithm and key.
398 	 */
399 	blk_st = blk_crypto_get_keyslot(blk_crypto_fallback_profile,
400 					bc->bc_key, &slot);
401 	if (blk_st != BLK_STS_OK) {
402 		bio->bi_status = blk_st;
403 		goto out_no_keyslot;
404 	}
405 
406 	/* and then allocate an skcipher_request for it */
407 	if (!blk_crypto_fallback_alloc_cipher_req(slot, &ciph_req, &wait)) {
408 		bio->bi_status = BLK_STS_RESOURCE;
409 		goto out;
410 	}
411 
412 	memcpy(curr_dun, bc->bc_dun, sizeof(curr_dun));
413 	sg_init_table(&sg, 1);
414 	skcipher_request_set_crypt(ciph_req, &sg, &sg, data_unit_size,
415 				   iv.bytes);
416 
417 	/* Decrypt each segment in the bio */
418 	__bio_for_each_segment(bv, bio, iter, f_ctx->crypt_iter) {
419 		struct page *page = bv.bv_page;
420 
421 		sg_set_page(&sg, page, data_unit_size, bv.bv_offset);
422 
423 		/* Decrypt each data unit in the segment */
424 		for (i = 0; i < bv.bv_len; i += data_unit_size) {
425 			blk_crypto_dun_to_iv(curr_dun, &iv);
426 			if (crypto_wait_req(crypto_skcipher_decrypt(ciph_req),
427 					    &wait)) {
428 				bio->bi_status = BLK_STS_IOERR;
429 				goto out;
430 			}
431 			bio_crypt_dun_increment(curr_dun, 1);
432 			sg.offset += data_unit_size;
433 		}
434 	}
435 
436 out:
437 	skcipher_request_free(ciph_req);
438 	blk_crypto_put_keyslot(slot);
439 out_no_keyslot:
440 	mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);
441 	bio_endio(bio);
442 }
443 
444 /**
445  * blk_crypto_fallback_decrypt_endio - queue bio for fallback decryption
446  *
447  * @bio: the bio to queue
448  *
449  * Restore bi_private and bi_end_io, and queue the bio for decryption into a
450  * workqueue, since this function will be called from an atomic context.
451  */
452 static void blk_crypto_fallback_decrypt_endio(struct bio *bio)
453 {
454 	struct bio_fallback_crypt_ctx *f_ctx = bio->bi_private;
455 
456 	bio->bi_private = f_ctx->bi_private_orig;
457 	bio->bi_end_io = f_ctx->bi_end_io_orig;
458 
459 	/* If there was an IO error, don't queue for decrypt. */
460 	if (bio->bi_status) {
461 		mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);
462 		bio_endio(bio);
463 		return;
464 	}
465 
466 	INIT_WORK(&f_ctx->work, blk_crypto_fallback_decrypt_bio);
467 	f_ctx->bio = bio;
468 	queue_work(blk_crypto_wq, &f_ctx->work);
469 }
470 
471 /**
472  * blk_crypto_fallback_bio_prep - Prepare a bio to use fallback en/decryption
473  *
474  * @bio_ptr: pointer to the bio to prepare
475  *
476  * If bio is doing a WRITE operation, this splits the bio into two parts if it's
477  * too big (see blk_crypto_fallback_split_bio_if_needed()). It then allocates a
478  * bounce bio for the first part, encrypts it, and updates bio_ptr to point to
479  * the bounce bio.
480  *
481  * For a READ operation, we mark the bio for decryption by using bi_private and
482  * bi_end_io.
483  *
484  * In either case, this function will make the bio look like a regular bio (i.e.
485  * as if no encryption context was ever specified) for the purposes of the rest
486  * of the stack except for blk-integrity (blk-integrity and blk-crypto are not
487  * currently supported together).
488  *
489  * Return: true on success. Sets bio->bi_status and returns false on error.
490  */
491 bool blk_crypto_fallback_bio_prep(struct bio **bio_ptr)
492 {
493 	struct bio *bio = *bio_ptr;
494 	struct bio_crypt_ctx *bc = bio->bi_crypt_context;
495 	struct bio_fallback_crypt_ctx *f_ctx;
496 
497 	if (WARN_ON_ONCE(!tfms_inited[bc->bc_key->crypto_cfg.crypto_mode])) {
498 		/* User didn't call blk_crypto_start_using_key() first */
499 		bio->bi_status = BLK_STS_IOERR;
500 		return false;
501 	}
502 
503 	if (!__blk_crypto_cfg_supported(blk_crypto_fallback_profile,
504 					&bc->bc_key->crypto_cfg)) {
505 		bio->bi_status = BLK_STS_NOTSUPP;
506 		return false;
507 	}
508 
509 	if (bio_data_dir(bio) == WRITE)
510 		return blk_crypto_fallback_encrypt_bio(bio_ptr);
511 
512 	/*
513 	 * bio READ case: Set up a f_ctx in the bio's bi_private and set the
514 	 * bi_end_io appropriately to trigger decryption when the bio is ended.
515 	 */
516 	f_ctx = mempool_alloc(bio_fallback_crypt_ctx_pool, GFP_NOIO);
517 	f_ctx->crypt_ctx = *bc;
518 	f_ctx->crypt_iter = bio->bi_iter;
519 	f_ctx->bi_private_orig = bio->bi_private;
520 	f_ctx->bi_end_io_orig = bio->bi_end_io;
521 	bio->bi_private = (void *)f_ctx;
522 	bio->bi_end_io = blk_crypto_fallback_decrypt_endio;
523 	bio_crypt_free_ctx(bio);
524 
525 	return true;
526 }
527 
528 int blk_crypto_fallback_evict_key(const struct blk_crypto_key *key)
529 {
530 	return __blk_crypto_evict_key(blk_crypto_fallback_profile, key);
531 }
532 
533 static bool blk_crypto_fallback_inited;
534 static int blk_crypto_fallback_init(void)
535 {
536 	int i;
537 	int err;
538 
539 	if (blk_crypto_fallback_inited)
540 		return 0;
541 
542 	get_random_bytes(blank_key, BLK_CRYPTO_MAX_KEY_SIZE);
543 
544 	err = bioset_init(&crypto_bio_split, 64, 0, 0);
545 	if (err)
546 		goto out;
547 
548 	/* Dynamic allocation is needed because of lockdep_register_key(). */
549 	blk_crypto_fallback_profile =
550 		kzalloc(sizeof(*blk_crypto_fallback_profile), GFP_KERNEL);
551 	if (!blk_crypto_fallback_profile) {
552 		err = -ENOMEM;
553 		goto fail_free_bioset;
554 	}
555 
556 	err = blk_crypto_profile_init(blk_crypto_fallback_profile,
557 				      blk_crypto_num_keyslots);
558 	if (err)
559 		goto fail_free_profile;
560 	err = -ENOMEM;
561 
562 	blk_crypto_fallback_profile->ll_ops = blk_crypto_fallback_ll_ops;
563 	blk_crypto_fallback_profile->max_dun_bytes_supported = BLK_CRYPTO_MAX_IV_SIZE;
564 
565 	/* All blk-crypto modes have a crypto API fallback. */
566 	for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++)
567 		blk_crypto_fallback_profile->modes_supported[i] = 0xFFFFFFFF;
568 	blk_crypto_fallback_profile->modes_supported[BLK_ENCRYPTION_MODE_INVALID] = 0;
569 
570 	blk_crypto_wq = alloc_workqueue("blk_crypto_wq",
571 					WQ_UNBOUND | WQ_HIGHPRI |
572 					WQ_MEM_RECLAIM, num_online_cpus());
573 	if (!blk_crypto_wq)
574 		goto fail_destroy_profile;
575 
576 	blk_crypto_keyslots = kcalloc(blk_crypto_num_keyslots,
577 				      sizeof(blk_crypto_keyslots[0]),
578 				      GFP_KERNEL);
579 	if (!blk_crypto_keyslots)
580 		goto fail_free_wq;
581 
582 	blk_crypto_bounce_page_pool =
583 		mempool_create_page_pool(num_prealloc_bounce_pg, 0);
584 	if (!blk_crypto_bounce_page_pool)
585 		goto fail_free_keyslots;
586 
587 	bio_fallback_crypt_ctx_cache = KMEM_CACHE(bio_fallback_crypt_ctx, 0);
588 	if (!bio_fallback_crypt_ctx_cache)
589 		goto fail_free_bounce_page_pool;
590 
591 	bio_fallback_crypt_ctx_pool =
592 		mempool_create_slab_pool(num_prealloc_fallback_crypt_ctxs,
593 					 bio_fallback_crypt_ctx_cache);
594 	if (!bio_fallback_crypt_ctx_pool)
595 		goto fail_free_crypt_ctx_cache;
596 
597 	blk_crypto_fallback_inited = true;
598 
599 	return 0;
600 fail_free_crypt_ctx_cache:
601 	kmem_cache_destroy(bio_fallback_crypt_ctx_cache);
602 fail_free_bounce_page_pool:
603 	mempool_destroy(blk_crypto_bounce_page_pool);
604 fail_free_keyslots:
605 	kfree(blk_crypto_keyslots);
606 fail_free_wq:
607 	destroy_workqueue(blk_crypto_wq);
608 fail_destroy_profile:
609 	blk_crypto_profile_destroy(blk_crypto_fallback_profile);
610 fail_free_profile:
611 	kfree(blk_crypto_fallback_profile);
612 fail_free_bioset:
613 	bioset_exit(&crypto_bio_split);
614 out:
615 	return err;
616 }
617 
618 /*
619  * Prepare blk-crypto-fallback for the specified crypto mode.
620  * Returns -ENOPKG if the needed crypto API support is missing.
621  */
622 int blk_crypto_fallback_start_using_mode(enum blk_crypto_mode_num mode_num)
623 {
624 	const char *cipher_str = blk_crypto_modes[mode_num].cipher_str;
625 	struct blk_crypto_fallback_keyslot *slotp;
626 	unsigned int i;
627 	int err = 0;
628 
629 	/*
630 	 * Fast path
631 	 * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
632 	 * for each i are visible before we try to access them.
633 	 */
634 	if (likely(smp_load_acquire(&tfms_inited[mode_num])))
635 		return 0;
636 
637 	mutex_lock(&tfms_init_lock);
638 	if (tfms_inited[mode_num])
639 		goto out;
640 
641 	err = blk_crypto_fallback_init();
642 	if (err)
643 		goto out;
644 
645 	for (i = 0; i < blk_crypto_num_keyslots; i++) {
646 		slotp = &blk_crypto_keyslots[i];
647 		slotp->tfms[mode_num] = crypto_alloc_skcipher(cipher_str, 0, 0);
648 		if (IS_ERR(slotp->tfms[mode_num])) {
649 			err = PTR_ERR(slotp->tfms[mode_num]);
650 			if (err == -ENOENT) {
651 				pr_warn_once("Missing crypto API support for \"%s\"\n",
652 					     cipher_str);
653 				err = -ENOPKG;
654 			}
655 			slotp->tfms[mode_num] = NULL;
656 			goto out_free_tfms;
657 		}
658 
659 		crypto_skcipher_set_flags(slotp->tfms[mode_num],
660 					  CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
661 	}
662 
663 	/*
664 	 * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
665 	 * for each i are visible before we set tfms_inited[mode_num].
666 	 */
667 	smp_store_release(&tfms_inited[mode_num], true);
668 	goto out;
669 
670 out_free_tfms:
671 	for (i = 0; i < blk_crypto_num_keyslots; i++) {
672 		slotp = &blk_crypto_keyslots[i];
673 		crypto_free_skcipher(slotp->tfms[mode_num]);
674 		slotp->tfms[mode_num] = NULL;
675 	}
676 out:
677 	mutex_unlock(&tfms_init_lock);
678 	return err;
679 }
680