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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_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->raw,
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(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_iter.bi_sector = bio_src->bi_iter.bi_sector;
176 bio->bi_iter.bi_size = bio_src->bi_iter.bi_size;
177
178 bio_for_each_segment(bv, bio_src, iter)
179 bio->bi_io_vec[bio->bi_vcnt++] = bv;
180
181 bio_clone_blkg_association(bio, bio_src);
182
183 return bio;
184}
185
186static bool
187blk_crypto_fallback_alloc_cipher_req(struct blk_crypto_keyslot *slot,
188 struct skcipher_request **ciph_req_ret,
189 struct crypto_wait *wait)
190{
191 struct skcipher_request *ciph_req;
192 const struct blk_crypto_fallback_keyslot *slotp;
193 int keyslot_idx = blk_crypto_keyslot_index(slot);
194
195 slotp = &blk_crypto_keyslots[keyslot_idx];
196 ciph_req = skcipher_request_alloc(slotp->tfms[slotp->crypto_mode],
197 GFP_NOIO);
198 if (!ciph_req)
199 return false;
200
201 skcipher_request_set_callback(ciph_req,
202 CRYPTO_TFM_REQ_MAY_BACKLOG |
203 CRYPTO_TFM_REQ_MAY_SLEEP,
204 crypto_req_done, wait);
205 *ciph_req_ret = ciph_req;
206
207 return true;
208}
209
210static bool blk_crypto_fallback_split_bio_if_needed(struct bio **bio_ptr)
211{
212 struct bio *bio = *bio_ptr;
213 unsigned int i = 0;
214 unsigned int num_sectors = 0;
215 struct bio_vec bv;
216 struct bvec_iter iter;
217
218 bio_for_each_segment(bv, bio, iter) {
219 num_sectors += bv.bv_len >> SECTOR_SHIFT;
220 if (++i == BIO_MAX_VECS)
221 break;
222 }
223 if (num_sectors < bio_sectors(bio)) {
224 struct bio *split_bio;
225
226 split_bio = bio_split(bio, num_sectors, GFP_NOIO,
227 &crypto_bio_split);
228 if (!split_bio) {
229 bio->bi_status = BLK_STS_RESOURCE;
230 return false;
231 }
232 bio_chain(split_bio, bio);
233 submit_bio_noacct(bio);
234 *bio_ptr = split_bio;
235 }
236
237 return true;
238}
239
240union blk_crypto_iv {
241 __le64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
242 u8 bytes[BLK_CRYPTO_MAX_IV_SIZE];
243};
244
245static void blk_crypto_dun_to_iv(const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
246 union blk_crypto_iv *iv)
247{
248 int i;
249
250 for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++)
251 iv->dun[i] = cpu_to_le64(dun[i]);
252}
253
254/*
255 * The crypto API fallback's encryption routine.
256 * Allocate a bounce bio for encryption, encrypt the input bio using crypto API,
257 * and replace *bio_ptr with the bounce bio. May split input bio if it's too
258 * large. Returns true on success. Returns false and sets bio->bi_status on
259 * error.
260 */
261static bool blk_crypto_fallback_encrypt_bio(struct bio **bio_ptr)
262{
263 struct bio *src_bio, *enc_bio;
264 struct bio_crypt_ctx *bc;
265 struct blk_crypto_keyslot *slot;
266 int data_unit_size;
267 struct skcipher_request *ciph_req = NULL;
268 DECLARE_CRYPTO_WAIT(wait);
269 u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
270 struct scatterlist src, dst;
271 union blk_crypto_iv iv;
272 unsigned int i, j;
273 bool ret = false;
274 blk_status_t blk_st;
275
276 /* Split the bio if it's too big for single page bvec */
277 if (!blk_crypto_fallback_split_bio_if_needed(bio_ptr))
278 return false;
279
280 src_bio = *bio_ptr;
281 bc = src_bio->bi_crypt_context;
282 data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
283
284 /* Allocate bounce bio for encryption */
285 enc_bio = blk_crypto_fallback_clone_bio(src_bio);
286 if (!enc_bio) {
287 src_bio->bi_status = BLK_STS_RESOURCE;
288 return false;
289 }
290
291 /*
292 * Get a blk-crypto-fallback keyslot that contains a crypto_skcipher for
293 * this bio's algorithm and key.
294 */
295 blk_st = blk_crypto_get_keyslot(&blk_crypto_fallback_profile,
296 bc->bc_key, &slot);
297 if (blk_st != BLK_STS_OK) {
298 src_bio->bi_status = blk_st;
299 goto out_put_enc_bio;
300 }
301
302 /* and then allocate an skcipher_request for it */
303 if (!blk_crypto_fallback_alloc_cipher_req(slot, &ciph_req, &wait)) {
304 src_bio->bi_status = BLK_STS_RESOURCE;
305 goto out_release_keyslot;
306 }
307
308 memcpy(curr_dun, bc->bc_dun, sizeof(curr_dun));
309 sg_init_table(&src, 1);
310 sg_init_table(&dst, 1);
311
312 skcipher_request_set_crypt(ciph_req, &src, &dst, data_unit_size,
313 iv.bytes);
314
315 /* Encrypt each page in the bounce bio */
316 for (i = 0; i < enc_bio->bi_vcnt; i++) {
317 struct bio_vec *enc_bvec = &enc_bio->bi_io_vec[i];
318 struct page *plaintext_page = enc_bvec->bv_page;
319 struct page *ciphertext_page =
320 mempool_alloc(blk_crypto_bounce_page_pool, GFP_NOIO);
321
322 enc_bvec->bv_page = ciphertext_page;
323
324 if (!ciphertext_page) {
325 src_bio->bi_status = BLK_STS_RESOURCE;
326 goto out_free_bounce_pages;
327 }
328
329 sg_set_page(&src, plaintext_page, data_unit_size,
330 enc_bvec->bv_offset);
331 sg_set_page(&dst, ciphertext_page, data_unit_size,
332 enc_bvec->bv_offset);
333
334 /* Encrypt each data unit in this page */
335 for (j = 0; j < enc_bvec->bv_len; j += data_unit_size) {
336 blk_crypto_dun_to_iv(curr_dun, &iv);
337 if (crypto_wait_req(crypto_skcipher_encrypt(ciph_req),
338 &wait)) {
339 i++;
340 src_bio->bi_status = BLK_STS_IOERR;
341 goto out_free_bounce_pages;
342 }
343 bio_crypt_dun_increment(curr_dun, 1);
344 src.offset += data_unit_size;
345 dst.offset += data_unit_size;
346 }
347 }
348
349 enc_bio->bi_private = src_bio;
350 enc_bio->bi_end_io = blk_crypto_fallback_encrypt_endio;
351 *bio_ptr = enc_bio;
352 ret = true;
353
354 enc_bio = NULL;
355 goto out_free_ciph_req;
356
357out_free_bounce_pages:
358 while (i > 0)
359 mempool_free(enc_bio->bi_io_vec[--i].bv_page,
360 blk_crypto_bounce_page_pool);
361out_free_ciph_req:
362 skcipher_request_free(ciph_req);
363out_release_keyslot:
364 blk_crypto_put_keyslot(slot);
365out_put_enc_bio:
366 if (enc_bio)
367 bio_uninit(enc_bio);
368 kfree(enc_bio);
369 return ret;
370}
371
372/*
373 * The crypto API fallback's main decryption routine.
374 * Decrypts input bio in place, and calls bio_endio on the bio.
375 */
376static void blk_crypto_fallback_decrypt_bio(struct work_struct *work)
377{
378 struct bio_fallback_crypt_ctx *f_ctx =
379 container_of(work, struct bio_fallback_crypt_ctx, work);
380 struct bio *bio = f_ctx->bio;
381 struct bio_crypt_ctx *bc = &f_ctx->crypt_ctx;
382 struct blk_crypto_keyslot *slot;
383 struct skcipher_request *ciph_req = NULL;
384 DECLARE_CRYPTO_WAIT(wait);
385 u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
386 union blk_crypto_iv iv;
387 struct scatterlist sg;
388 struct bio_vec bv;
389 struct bvec_iter iter;
390 const int data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
391 unsigned int i;
392 blk_status_t blk_st;
393
394 /*
395 * Get a blk-crypto-fallback keyslot that contains a crypto_skcipher for
396 * this bio's algorithm and key.
397 */
398 blk_st = blk_crypto_get_keyslot(&blk_crypto_fallback_profile,
399 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_fallback_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
435out:
436 skcipher_request_free(ciph_req);
437 blk_crypto_put_keyslot(slot);
438out_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 */
451static 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_fallback_split_bio_if_needed()). It then allocates a
477 * bounce bio for the first part, encrypts it, and updates bio_ptr to point to
478 * the bounce 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 */
490bool 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_crypto_cfg_supported(&blk_crypto_fallback_profile,
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
527int blk_crypto_fallback_evict_key(const struct blk_crypto_key *key)
528{
529 return __blk_crypto_evict_key(&blk_crypto_fallback_profile, key);
530}
531
532static bool blk_crypto_fallback_inited;
533static int blk_crypto_fallback_init(void)
534{
535 int i;
536 int err;
537 struct blk_crypto_profile *profile = &blk_crypto_fallback_profile;
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 err = blk_crypto_profile_init(profile, blk_crypto_num_keyslots);
549 if (err)
550 goto fail_free_bioset;
551 err = -ENOMEM;
552
553 profile->ll_ops = blk_crypto_fallback_ll_ops;
554 profile->max_dun_bytes_supported = BLK_CRYPTO_MAX_IV_SIZE;
555
556 /* All blk-crypto modes have a crypto API fallback. */
557 for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++)
558 profile->modes_supported[i] = 0xFFFFFFFF;
559 profile->modes_supported[BLK_ENCRYPTION_MODE_INVALID] = 0;
560
561 blk_crypto_wq = alloc_workqueue("blk_crypto_wq",
562 WQ_UNBOUND | WQ_HIGHPRI |
563 WQ_MEM_RECLAIM, num_online_cpus());
564 if (!blk_crypto_wq)
565 goto fail_destroy_profile;
566
567 blk_crypto_keyslots = kcalloc(blk_crypto_num_keyslots,
568 sizeof(blk_crypto_keyslots[0]),
569 GFP_KERNEL);
570 if (!blk_crypto_keyslots)
571 goto fail_free_wq;
572
573 blk_crypto_bounce_page_pool =
574 mempool_create_page_pool(num_prealloc_bounce_pg, 0);
575 if (!blk_crypto_bounce_page_pool)
576 goto fail_free_keyslots;
577
578 bio_fallback_crypt_ctx_cache = KMEM_CACHE(bio_fallback_crypt_ctx, 0);
579 if (!bio_fallback_crypt_ctx_cache)
580 goto fail_free_bounce_page_pool;
581
582 bio_fallback_crypt_ctx_pool =
583 mempool_create_slab_pool(num_prealloc_fallback_crypt_ctxs,
584 bio_fallback_crypt_ctx_cache);
585 if (!bio_fallback_crypt_ctx_pool)
586 goto fail_free_crypt_ctx_cache;
587
588 blk_crypto_fallback_inited = true;
589
590 return 0;
591fail_free_crypt_ctx_cache:
592 kmem_cache_destroy(bio_fallback_crypt_ctx_cache);
593fail_free_bounce_page_pool:
594 mempool_destroy(blk_crypto_bounce_page_pool);
595fail_free_keyslots:
596 kfree(blk_crypto_keyslots);
597fail_free_wq:
598 destroy_workqueue(blk_crypto_wq);
599fail_destroy_profile:
600 blk_crypto_profile_destroy(profile);
601fail_free_bioset:
602 bioset_exit(&crypto_bio_split);
603out:
604 return err;
605}
606
607/*
608 * Prepare blk-crypto-fallback for the specified crypto mode.
609 * Returns -ENOPKG if the needed crypto API support is missing.
610 */
611int blk_crypto_fallback_start_using_mode(enum blk_crypto_mode_num mode_num)
612{
613 const char *cipher_str = blk_crypto_modes[mode_num].cipher_str;
614 struct blk_crypto_fallback_keyslot *slotp;
615 unsigned int i;
616 int err = 0;
617
618 /*
619 * Fast path
620 * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
621 * for each i are visible before we try to access them.
622 */
623 if (likely(smp_load_acquire(&tfms_inited[mode_num])))
624 return 0;
625
626 mutex_lock(&tfms_init_lock);
627 if (tfms_inited[mode_num])
628 goto out;
629
630 err = blk_crypto_fallback_init();
631 if (err)
632 goto out;
633
634 for (i = 0; i < blk_crypto_num_keyslots; i++) {
635 slotp = &blk_crypto_keyslots[i];
636 slotp->tfms[mode_num] = crypto_alloc_skcipher(cipher_str, 0, 0);
637 if (IS_ERR(slotp->tfms[mode_num])) {
638 err = PTR_ERR(slotp->tfms[mode_num]);
639 if (err == -ENOENT) {
640 pr_warn_once("Missing crypto API support for \"%s\"\n",
641 cipher_str);
642 err = -ENOPKG;
643 }
644 slotp->tfms[mode_num] = NULL;
645 goto out_free_tfms;
646 }
647
648 crypto_skcipher_set_flags(slotp->tfms[mode_num],
649 CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
650 }
651
652 /*
653 * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
654 * for each i are visible before we set tfms_inited[mode_num].
655 */
656 smp_store_release(&tfms_inited[mode_num], true);
657 goto out;
658
659out_free_tfms:
660 for (i = 0; i < blk_crypto_num_keyslots; i++) {
661 slotp = &blk_crypto_keyslots[i];
662 crypto_free_skcipher(slotp->tfms[mode_num]);
663 slotp->tfms[mode_num] = NULL;
664 }
665out:
666 mutex_unlock(&tfms_init_lock);
667 return err;
668}