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-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
 25static unsigned int num_prealloc_bounce_pg = 32;
 26module_param(num_prealloc_bounce_pg, uint, 0);
 27MODULE_PARM_DESC(num_prealloc_bounce_pg,
 28		 "Number of preallocated bounce pages for the blk-crypto crypto API fallback");
 29
 30static unsigned int blk_crypto_num_keyslots = 100;
 31module_param_named(num_keyslots, blk_crypto_num_keyslots, uint, 0);
 32MODULE_PARM_DESC(num_keyslots,
 33		 "Number of keyslots for the blk-crypto crypto API fallback");
 34
 35static unsigned int num_prealloc_fallback_crypt_ctxs = 128;
 36module_param(num_prealloc_fallback_crypt_ctxs, uint, 0);
 37MODULE_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
 40struct 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
 61static struct kmem_cache *bio_fallback_crypt_ctx_cache;
 62static 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 */
 73static DEFINE_MUTEX(tfms_init_lock);
 74static bool tfms_inited[BLK_ENCRYPTION_MODE_MAX];
 75
 76static 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
 81static struct blk_crypto_profile *blk_crypto_fallback_profile;
 82static struct workqueue_struct *blk_crypto_wq;
 83static mempool_t *blk_crypto_bounce_page_pool;
 84static 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 */
 90static u8 blank_key[BLK_CRYPTO_MAX_RAW_KEY_SIZE];
 91
 92static 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
107static int
108blk_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
131static 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
139static 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
144static 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
160static 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
187static bool
188blk_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
211static 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
237union blk_crypto_iv {
238	__le64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
239	u8 bytes[BLK_CRYPTO_MAX_IV_SIZE];
240};
241
242static 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 */
258static 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
354out_free_bounce_pages:
355	while (i > 0)
356		mempool_free(enc_bio->bi_io_vec[--i].bv_page,
357			     blk_crypto_bounce_page_pool);
358out_free_ciph_req:
359	skcipher_request_free(ciph_req);
360out_release_keyslot:
361	blk_crypto_put_keyslot(slot);
362out_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 */
373static 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
432out:
433	skcipher_request_free(ciph_req);
434	blk_crypto_put_keyslot(slot);
435out_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 */
448static 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 */
487bool 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
524int 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
529static bool blk_crypto_fallback_inited;
530static 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;
597fail_free_crypt_ctx_cache:
598	kmem_cache_destroy(bio_fallback_crypt_ctx_cache);
599fail_free_bounce_page_pool:
600	mempool_destroy(blk_crypto_bounce_page_pool);
601fail_free_keyslots:
602	kfree(blk_crypto_keyslots);
603fail_free_wq:
604	destroy_workqueue(blk_crypto_wq);
605fail_destroy_profile:
606	blk_crypto_profile_destroy(blk_crypto_fallback_profile);
607fail_free_profile:
608	kfree(blk_crypto_fallback_profile);
609fail_free_bioset:
610	bioset_exit(&crypto_bio_split);
611out:
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 */
619int 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
667out_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	}
673out:
674	mutex_unlock(&tfms_init_lock);
675	return err;
676}