1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright 2019 Google LLC
7 * Refer to Documentation/block/inline-encryption.rst for detailed explanation.
10 #define pr_fmt(fmt) "blk-crypto-fallback: " fmt
12 #include <crypto/skcipher.h>
13 #include <linux/blk-cgroup.h>
14 #include <linux/blk-crypto.h>
15 #include <linux/blkdev.h>
16 #include <linux/crypto.h>
17 #include <linux/keyslot-manager.h>
18 #include <linux/mempool.h>
19 #include <linux/module.h>
20 #include <linux/random.h>
22 #include "blk-crypto-internal.h"
24 static unsigned int num_prealloc_bounce_pg = 32;
25 module_param(num_prealloc_bounce_pg, uint, 0);
26 MODULE_PARM_DESC(num_prealloc_bounce_pg,
27 "Number of preallocated bounce pages for the blk-crypto crypto API fallback");
29 static unsigned int blk_crypto_num_keyslots = 100;
30 module_param_named(num_keyslots, blk_crypto_num_keyslots, uint, 0);
31 MODULE_PARM_DESC(num_keyslots,
32 "Number of keyslots for the blk-crypto crypto API fallback");
34 static unsigned int num_prealloc_fallback_crypt_ctxs = 128;
35 module_param(num_prealloc_fallback_crypt_ctxs, uint, 0);
36 MODULE_PARM_DESC(num_prealloc_crypt_fallback_ctxs,
37 "Number of preallocated bio fallback crypto contexts for blk-crypto to use during crypto API fallback");
39 struct bio_fallback_crypt_ctx {
40 struct bio_crypt_ctx crypt_ctx;
42 * Copy of the bvec_iter when this bio was submitted.
43 * We only want to en/decrypt the part of the bio as described by the
44 * bvec_iter upon submission because bio might be split before being
47 struct bvec_iter crypt_iter;
50 struct work_struct work;
54 void *bi_private_orig;
55 bio_end_io_t *bi_end_io_orig;
60 static struct kmem_cache *bio_fallback_crypt_ctx_cache;
61 static mempool_t *bio_fallback_crypt_ctx_pool;
64 * Allocating a crypto tfm during I/O can deadlock, so we have to preallocate
65 * all of a mode's tfms when that mode starts being used. Since each mode may
66 * need all the keyslots at some point, each mode needs its own tfm for each
67 * keyslot; thus, a keyslot may contain tfms for multiple modes. However, to
68 * match the behavior of real inline encryption hardware (which only supports a
69 * single encryption context per keyslot), we only allow one tfm per keyslot to
70 * be used at a time - the rest of the unused tfms have their keys cleared.
72 static DEFINE_MUTEX(tfms_init_lock);
73 static bool tfms_inited[BLK_ENCRYPTION_MODE_MAX];
75 static struct blk_crypto_keyslot {
76 enum blk_crypto_mode_num crypto_mode;
77 struct crypto_skcipher *tfms[BLK_ENCRYPTION_MODE_MAX];
78 } *blk_crypto_keyslots;
80 static struct blk_keyslot_manager blk_crypto_ksm;
81 static struct workqueue_struct *blk_crypto_wq;
82 static mempool_t *blk_crypto_bounce_page_pool;
85 * This is the key we set when evicting a keyslot. This *should* be the all 0's
86 * key, but AES-XTS rejects that key, so we use some random bytes instead.
88 static u8 blank_key[BLK_CRYPTO_MAX_KEY_SIZE];
90 static void blk_crypto_evict_keyslot(unsigned int slot)
92 struct blk_crypto_keyslot *slotp = &blk_crypto_keyslots[slot];
93 enum blk_crypto_mode_num crypto_mode = slotp->crypto_mode;
96 WARN_ON(slotp->crypto_mode == BLK_ENCRYPTION_MODE_INVALID);
98 /* Clear the key in the skcipher */
99 err = crypto_skcipher_setkey(slotp->tfms[crypto_mode], blank_key,
100 blk_crypto_modes[crypto_mode].keysize);
102 slotp->crypto_mode = BLK_ENCRYPTION_MODE_INVALID;
105 static int blk_crypto_keyslot_program(struct blk_keyslot_manager *ksm,
106 const struct blk_crypto_key *key,
109 struct blk_crypto_keyslot *slotp = &blk_crypto_keyslots[slot];
110 const enum blk_crypto_mode_num crypto_mode =
111 key->crypto_cfg.crypto_mode;
114 if (crypto_mode != slotp->crypto_mode &&
115 slotp->crypto_mode != BLK_ENCRYPTION_MODE_INVALID)
116 blk_crypto_evict_keyslot(slot);
118 slotp->crypto_mode = crypto_mode;
119 err = crypto_skcipher_setkey(slotp->tfms[crypto_mode], key->raw,
122 blk_crypto_evict_keyslot(slot);
128 static int blk_crypto_keyslot_evict(struct blk_keyslot_manager *ksm,
129 const struct blk_crypto_key *key,
132 blk_crypto_evict_keyslot(slot);
137 * The crypto API fallback KSM ops - only used for a bio when it specifies a
138 * blk_crypto_key that was not supported by the device's inline encryption
141 static const struct blk_ksm_ll_ops blk_crypto_ksm_ll_ops = {
142 .keyslot_program = blk_crypto_keyslot_program,
143 .keyslot_evict = blk_crypto_keyslot_evict,
146 static void blk_crypto_fallback_encrypt_endio(struct bio *enc_bio)
148 struct bio *src_bio = enc_bio->bi_private;
151 for (i = 0; i < enc_bio->bi_vcnt; i++)
152 mempool_free(enc_bio->bi_io_vec[i].bv_page,
153 blk_crypto_bounce_page_pool);
155 src_bio->bi_status = enc_bio->bi_status;
161 static struct bio *blk_crypto_clone_bio(struct bio *bio_src)
163 struct bvec_iter iter;
167 bio = bio_kmalloc(GFP_NOIO, bio_segments(bio_src));
170 bio->bi_bdev = bio_src->bi_bdev;
171 if (bio_flagged(bio_src, BIO_REMAPPED))
172 bio_set_flag(bio, BIO_REMAPPED);
173 bio->bi_opf = bio_src->bi_opf;
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;
179 bio_for_each_segment(bv, bio_src, iter)
180 bio->bi_io_vec[bio->bi_vcnt++] = bv;
182 bio_clone_blkg_association(bio, bio_src);
183 blkcg_bio_issue_init(bio);
188 static bool blk_crypto_alloc_cipher_req(struct blk_ksm_keyslot *slot,
189 struct skcipher_request **ciph_req_ret,
190 struct crypto_wait *wait)
192 struct skcipher_request *ciph_req;
193 const struct blk_crypto_keyslot *slotp;
194 int keyslot_idx = blk_ksm_get_slot_idx(slot);
196 slotp = &blk_crypto_keyslots[keyslot_idx];
197 ciph_req = skcipher_request_alloc(slotp->tfms[slotp->crypto_mode],
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;
211 static bool blk_crypto_split_bio_if_needed(struct bio **bio_ptr)
213 struct bio *bio = *bio_ptr;
215 unsigned int num_sectors = 0;
217 struct bvec_iter iter;
219 bio_for_each_segment(bv, bio, iter) {
220 num_sectors += bv.bv_len >> SECTOR_SHIFT;
221 if (++i == BIO_MAX_PAGES)
224 if (num_sectors < bio_sectors(bio)) {
225 struct bio *split_bio;
227 split_bio = bio_split(bio, num_sectors, GFP_NOIO, NULL);
229 bio->bi_status = BLK_STS_RESOURCE;
232 bio_chain(split_bio, bio);
233 submit_bio_noacct(bio);
234 *bio_ptr = split_bio;
240 union blk_crypto_iv {
241 __le64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
242 u8 bytes[BLK_CRYPTO_MAX_IV_SIZE];
245 static void blk_crypto_dun_to_iv(const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
246 union blk_crypto_iv *iv)
250 for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++)
251 iv->dun[i] = cpu_to_le64(dun[i]);
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
261 static bool blk_crypto_fallback_encrypt_bio(struct bio **bio_ptr)
263 struct bio *src_bio, *enc_bio;
264 struct bio_crypt_ctx *bc;
265 struct blk_ksm_keyslot *slot;
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;
276 /* Split the bio if it's too big for single page bvec */
277 if (!blk_crypto_split_bio_if_needed(bio_ptr))
281 bc = src_bio->bi_crypt_context;
282 data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
284 /* Allocate bounce bio for encryption */
285 enc_bio = blk_crypto_clone_bio(src_bio);
287 src_bio->bi_status = BLK_STS_RESOURCE;
292 * Use the crypto API fallback keyslot manager to get a crypto_skcipher
293 * for the algorithm and key specified for this bio.
295 blk_st = blk_ksm_get_slot_for_key(&blk_crypto_ksm, bc->bc_key, &slot);
296 if (blk_st != BLK_STS_OK) {
297 src_bio->bi_status = blk_st;
298 goto out_put_enc_bio;
301 /* and then allocate an skcipher_request for it */
302 if (!blk_crypto_alloc_cipher_req(slot, &ciph_req, &wait)) {
303 src_bio->bi_status = BLK_STS_RESOURCE;
304 goto out_release_keyslot;
307 memcpy(curr_dun, bc->bc_dun, sizeof(curr_dun));
308 sg_init_table(&src, 1);
309 sg_init_table(&dst, 1);
311 skcipher_request_set_crypt(ciph_req, &src, &dst, data_unit_size,
314 /* Encrypt each page in the bounce bio */
315 for (i = 0; i < enc_bio->bi_vcnt; i++) {
316 struct bio_vec *enc_bvec = &enc_bio->bi_io_vec[i];
317 struct page *plaintext_page = enc_bvec->bv_page;
318 struct page *ciphertext_page =
319 mempool_alloc(blk_crypto_bounce_page_pool, GFP_NOIO);
321 enc_bvec->bv_page = ciphertext_page;
323 if (!ciphertext_page) {
324 src_bio->bi_status = BLK_STS_RESOURCE;
325 goto out_free_bounce_pages;
328 sg_set_page(&src, plaintext_page, data_unit_size,
329 enc_bvec->bv_offset);
330 sg_set_page(&dst, ciphertext_page, data_unit_size,
331 enc_bvec->bv_offset);
333 /* Encrypt each data unit in this page */
334 for (j = 0; j < enc_bvec->bv_len; j += data_unit_size) {
335 blk_crypto_dun_to_iv(curr_dun, &iv);
336 if (crypto_wait_req(crypto_skcipher_encrypt(ciph_req),
339 src_bio->bi_status = BLK_STS_IOERR;
340 goto out_free_bounce_pages;
342 bio_crypt_dun_increment(curr_dun, 1);
343 src.offset += data_unit_size;
344 dst.offset += data_unit_size;
348 enc_bio->bi_private = src_bio;
349 enc_bio->bi_end_io = blk_crypto_fallback_encrypt_endio;
354 goto out_free_ciph_req;
356 out_free_bounce_pages:
358 mempool_free(enc_bio->bi_io_vec[--i].bv_page,
359 blk_crypto_bounce_page_pool);
361 skcipher_request_free(ciph_req);
363 blk_ksm_put_slot(slot);
372 * The crypto API fallback's main decryption routine.
373 * Decrypts input bio in place, and calls bio_endio on the bio.
375 static void blk_crypto_fallback_decrypt_bio(struct work_struct *work)
377 struct bio_fallback_crypt_ctx *f_ctx =
378 container_of(work, struct bio_fallback_crypt_ctx, work);
379 struct bio *bio = f_ctx->bio;
380 struct bio_crypt_ctx *bc = &f_ctx->crypt_ctx;
381 struct blk_ksm_keyslot *slot;
382 struct skcipher_request *ciph_req = NULL;
383 DECLARE_CRYPTO_WAIT(wait);
384 u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
385 union blk_crypto_iv iv;
386 struct scatterlist sg;
388 struct bvec_iter iter;
389 const int data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
394 * Use the crypto API fallback keyslot manager to get a crypto_skcipher
395 * for the algorithm and key specified for this bio.
397 blk_st = blk_ksm_get_slot_for_key(&blk_crypto_ksm, bc->bc_key, &slot);
398 if (blk_st != BLK_STS_OK) {
399 bio->bi_status = blk_st;
403 /* and then allocate an skcipher_request for it */
404 if (!blk_crypto_alloc_cipher_req(slot, &ciph_req, &wait)) {
405 bio->bi_status = BLK_STS_RESOURCE;
409 memcpy(curr_dun, bc->bc_dun, sizeof(curr_dun));
410 sg_init_table(&sg, 1);
411 skcipher_request_set_crypt(ciph_req, &sg, &sg, data_unit_size,
414 /* Decrypt each segment in the bio */
415 __bio_for_each_segment(bv, bio, iter, f_ctx->crypt_iter) {
416 struct page *page = bv.bv_page;
418 sg_set_page(&sg, page, data_unit_size, bv.bv_offset);
420 /* Decrypt each data unit in the segment */
421 for (i = 0; i < bv.bv_len; i += data_unit_size) {
422 blk_crypto_dun_to_iv(curr_dun, &iv);
423 if (crypto_wait_req(crypto_skcipher_decrypt(ciph_req),
425 bio->bi_status = BLK_STS_IOERR;
428 bio_crypt_dun_increment(curr_dun, 1);
429 sg.offset += data_unit_size;
434 skcipher_request_free(ciph_req);
435 blk_ksm_put_slot(slot);
437 mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);
442 * blk_crypto_fallback_decrypt_endio - queue bio for fallback decryption
444 * @bio: the bio to queue
446 * Restore bi_private and bi_end_io, and queue the bio for decryption into a
447 * workqueue, since this function will be called from an atomic context.
449 static void blk_crypto_fallback_decrypt_endio(struct bio *bio)
451 struct bio_fallback_crypt_ctx *f_ctx = bio->bi_private;
453 bio->bi_private = f_ctx->bi_private_orig;
454 bio->bi_end_io = f_ctx->bi_end_io_orig;
456 /* If there was an IO error, don't queue for decrypt. */
457 if (bio->bi_status) {
458 mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);
463 INIT_WORK(&f_ctx->work, blk_crypto_fallback_decrypt_bio);
465 queue_work(blk_crypto_wq, &f_ctx->work);
469 * blk_crypto_fallback_bio_prep - Prepare a bio to use fallback en/decryption
471 * @bio_ptr: pointer to the bio to prepare
473 * If bio is doing a WRITE operation, this splits the bio into two parts if it's
474 * too big (see blk_crypto_split_bio_if_needed). It then allocates a bounce bio
475 * for the first part, encrypts it, and update bio_ptr to point to the bounce
478 * For a READ operation, we mark the bio for decryption by using bi_private and
481 * In either case, this function will make the bio look like a regular bio (i.e.
482 * as if no encryption context was ever specified) for the purposes of the rest
483 * of the stack except for blk-integrity (blk-integrity and blk-crypto are not
484 * currently supported together).
486 * Return: true on success. Sets bio->bi_status and returns false on error.
488 bool blk_crypto_fallback_bio_prep(struct bio **bio_ptr)
490 struct bio *bio = *bio_ptr;
491 struct bio_crypt_ctx *bc = bio->bi_crypt_context;
492 struct bio_fallback_crypt_ctx *f_ctx;
494 if (WARN_ON_ONCE(!tfms_inited[bc->bc_key->crypto_cfg.crypto_mode])) {
495 /* User didn't call blk_crypto_start_using_key() first */
496 bio->bi_status = BLK_STS_IOERR;
500 if (!blk_ksm_crypto_cfg_supported(&blk_crypto_ksm,
501 &bc->bc_key->crypto_cfg)) {
502 bio->bi_status = BLK_STS_NOTSUPP;
506 if (bio_data_dir(bio) == WRITE)
507 return blk_crypto_fallback_encrypt_bio(bio_ptr);
510 * bio READ case: Set up a f_ctx in the bio's bi_private and set the
511 * bi_end_io appropriately to trigger decryption when the bio is ended.
513 f_ctx = mempool_alloc(bio_fallback_crypt_ctx_pool, GFP_NOIO);
514 f_ctx->crypt_ctx = *bc;
515 f_ctx->crypt_iter = bio->bi_iter;
516 f_ctx->bi_private_orig = bio->bi_private;
517 f_ctx->bi_end_io_orig = bio->bi_end_io;
518 bio->bi_private = (void *)f_ctx;
519 bio->bi_end_io = blk_crypto_fallback_decrypt_endio;
520 bio_crypt_free_ctx(bio);
525 int blk_crypto_fallback_evict_key(const struct blk_crypto_key *key)
527 return blk_ksm_evict_key(&blk_crypto_ksm, key);
530 static bool blk_crypto_fallback_inited;
531 static int blk_crypto_fallback_init(void)
536 if (blk_crypto_fallback_inited)
539 prandom_bytes(blank_key, BLK_CRYPTO_MAX_KEY_SIZE);
541 err = blk_ksm_init(&blk_crypto_ksm, blk_crypto_num_keyslots);
546 blk_crypto_ksm.ksm_ll_ops = blk_crypto_ksm_ll_ops;
547 blk_crypto_ksm.max_dun_bytes_supported = BLK_CRYPTO_MAX_IV_SIZE;
549 /* All blk-crypto modes have a crypto API fallback. */
550 for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++)
551 blk_crypto_ksm.crypto_modes_supported[i] = 0xFFFFFFFF;
552 blk_crypto_ksm.crypto_modes_supported[BLK_ENCRYPTION_MODE_INVALID] = 0;
554 blk_crypto_wq = alloc_workqueue("blk_crypto_wq",
555 WQ_UNBOUND | WQ_HIGHPRI |
556 WQ_MEM_RECLAIM, num_online_cpus());
560 blk_crypto_keyslots = kcalloc(blk_crypto_num_keyslots,
561 sizeof(blk_crypto_keyslots[0]),
563 if (!blk_crypto_keyslots)
566 blk_crypto_bounce_page_pool =
567 mempool_create_page_pool(num_prealloc_bounce_pg, 0);
568 if (!blk_crypto_bounce_page_pool)
569 goto fail_free_keyslots;
571 bio_fallback_crypt_ctx_cache = KMEM_CACHE(bio_fallback_crypt_ctx, 0);
572 if (!bio_fallback_crypt_ctx_cache)
573 goto fail_free_bounce_page_pool;
575 bio_fallback_crypt_ctx_pool =
576 mempool_create_slab_pool(num_prealloc_fallback_crypt_ctxs,
577 bio_fallback_crypt_ctx_cache);
578 if (!bio_fallback_crypt_ctx_pool)
579 goto fail_free_crypt_ctx_cache;
581 blk_crypto_fallback_inited = true;
584 fail_free_crypt_ctx_cache:
585 kmem_cache_destroy(bio_fallback_crypt_ctx_cache);
586 fail_free_bounce_page_pool:
587 mempool_destroy(blk_crypto_bounce_page_pool);
589 kfree(blk_crypto_keyslots);
591 destroy_workqueue(blk_crypto_wq);
593 blk_ksm_destroy(&blk_crypto_ksm);
599 * Prepare blk-crypto-fallback for the specified crypto mode.
600 * Returns -ENOPKG if the needed crypto API support is missing.
602 int blk_crypto_fallback_start_using_mode(enum blk_crypto_mode_num mode_num)
604 const char *cipher_str = blk_crypto_modes[mode_num].cipher_str;
605 struct blk_crypto_keyslot *slotp;
611 * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
612 * for each i are visible before we try to access them.
614 if (likely(smp_load_acquire(&tfms_inited[mode_num])))
617 mutex_lock(&tfms_init_lock);
618 if (tfms_inited[mode_num])
621 err = blk_crypto_fallback_init();
625 for (i = 0; i < blk_crypto_num_keyslots; i++) {
626 slotp = &blk_crypto_keyslots[i];
627 slotp->tfms[mode_num] = crypto_alloc_skcipher(cipher_str, 0, 0);
628 if (IS_ERR(slotp->tfms[mode_num])) {
629 err = PTR_ERR(slotp->tfms[mode_num]);
630 if (err == -ENOENT) {
631 pr_warn_once("Missing crypto API support for \"%s\"\n",
635 slotp->tfms[mode_num] = NULL;
639 crypto_skcipher_set_flags(slotp->tfms[mode_num],
640 CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
644 * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
645 * for each i are visible before we set tfms_inited[mode_num].
647 smp_store_release(&tfms_inited[mode_num], true);
651 for (i = 0; i < blk_crypto_num_keyslots; i++) {
652 slotp = &blk_crypto_keyslots[i];
653 crypto_free_skcipher(slotp->tfms[mode_num]);
654 slotp->tfms[mode_num] = NULL;
657 mutex_unlock(&tfms_init_lock);