block/blk-crypto-fallback.c - linux/kernel/git/davem/net - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright 2019 Google LLC
  */

 /*
  * Refer to Documentation/block/inline-encryption.rst for detailed explanation.
  */

 #define pr_fmt(fmt) "blk-crypto-fallback: " fmt

 #include <crypto/skcipher.h>
 #include <linux/blk-cgroup.h>
 #include <linux/blk-crypto.h>
 #include <linux/blkdev.h>
 #include <linux/crypto.h>
 #include <linux/keyslot-manager.h>
 #include <linux/mempool.h>
 #include <linux/module.h>
 #include <linux/random.h>

 #include "blk-crypto-internal.h"

 static unsigned int num_prealloc_bounce_pg = 32;
 module_param(num_prealloc_bounce_pg, uint, 0);
 MODULE_PARM_DESC(num_prealloc_bounce_pg,
 		 "Number of preallocated bounce pages for the blk-crypto crypto API fallback");

 static unsigned int blk_crypto_num_keyslots = 100;
 module_param_named(num_keyslots, blk_crypto_num_keyslots, uint, 0);
 MODULE_PARM_DESC(num_keyslots,
 		 "Number of keyslots for the blk-crypto crypto API fallback");

 static unsigned int num_prealloc_fallback_crypt_ctxs = 128;
 module_param(num_prealloc_fallback_crypt_ctxs, uint, 0);
 MODULE_PARM_DESC(num_prealloc_crypt_fallback_ctxs,
 		 "Number of preallocated bio fallback crypto contexts for blk-crypto to use during crypto API fallback");

 struct bio_fallback_crypt_ctx {
 	struct bio_crypt_ctx crypt_ctx;
 	/*
 	 * Copy of the bvec_iter when this bio was submitted.
 	 * We only want to en/decrypt the part of the bio as described by the
 	 * bvec_iter upon submission because bio might be split before being
 	 * resubmitted
 	 */
 	struct bvec_iter crypt_iter;
 	union {
 		struct {
 			struct work_struct work;
 			struct bio *bio;
 		};
 		struct {
 			void *bi_private_orig;
 			bio_end_io_t *bi_end_io_orig;
 		};
 	};
 };

 static struct kmem_cache *bio_fallback_crypt_ctx_cache;
 static mempool_t *bio_fallback_crypt_ctx_pool;

 /*
  * Allocating a crypto tfm during I/O can deadlock, so we have to preallocate
  * all of a mode's tfms when that mode starts being used. Since each mode may
  * need all the keyslots at some point, each mode needs its own tfm for each
  * keyslot; thus, a keyslot may contain tfms for multiple modes.  However, to
  * match the behavior of real inline encryption hardware (which only supports a
  * single encryption context per keyslot), we only allow one tfm per keyslot to
  * be used at a time - the rest of the unused tfms have their keys cleared.
  */
 static DEFINE_MUTEX(tfms_init_lock);
 static bool tfms_inited[BLK_ENCRYPTION_MODE_MAX];

 static struct blk_crypto_keyslot {
 	enum blk_crypto_mode_num crypto_mode;
 	struct crypto_skcipher *tfms[BLK_ENCRYPTION_MODE_MAX];
 } *blk_crypto_keyslots;

 static struct blk_keyslot_manager blk_crypto_ksm;
 static struct workqueue_struct *blk_crypto_wq;
 static mempool_t *blk_crypto_bounce_page_pool;
 static struct bio_set crypto_bio_split;

 /*
  * This is the key we set when evicting a keyslot. This *should* be the all 0's
  * key, but AES-XTS rejects that key, so we use some random bytes instead.
  */
 static u8 blank_key[BLK_CRYPTO_MAX_KEY_SIZE];

 static void blk_crypto_evict_keyslot(unsigned int slot)
 {
 	struct blk_crypto_keyslot *slotp = &blk_crypto_keyslots[slot];
 	enum blk_crypto_mode_num crypto_mode = slotp->crypto_mode;
 	int err;

 	WARN_ON(slotp->crypto_mode == BLK_ENCRYPTION_MODE_INVALID);

 	/* Clear the key in the skcipher */
 	err = crypto_skcipher_setkey(slotp->tfms[crypto_mode], blank_key,
 				     blk_crypto_modes[crypto_mode].keysize);
 	WARN_ON(err);
 	slotp->crypto_mode = BLK_ENCRYPTION_MODE_INVALID;
 }

 static int blk_crypto_keyslot_program(struct blk_keyslot_manager *ksm,
 				      const struct blk_crypto_key *key,
 				      unsigned int slot)
 {
 	struct blk_crypto_keyslot *slotp = &blk_crypto_keyslots[slot];
 	const enum blk_crypto_mode_num crypto_mode =
 						key->crypto_cfg.crypto_mode;
 	int err;

 	if (crypto_mode != slotp->crypto_mode &&
 	    slotp->crypto_mode != BLK_ENCRYPTION_MODE_INVALID)
 		blk_crypto_evict_keyslot(slot);

 	slotp->crypto_mode = crypto_mode;
 	err = crypto_skcipher_setkey(slotp->tfms[crypto_mode], key->raw,
 				     key->size);
 	if (err) {
 		blk_crypto_evict_keyslot(slot);
 		return err;
 	}
 	return 0;
 }

 static int blk_crypto_keyslot_evict(struct blk_keyslot_manager *ksm,
 				    const struct blk_crypto_key *key,
 				    unsigned int slot)
 {
 	blk_crypto_evict_keyslot(slot);
 	return 0;
 }

 /*
  * The crypto API fallback KSM ops - only used for a bio when it specifies a
  * blk_crypto_key that was not supported by the device's inline encryption
  * hardware.
  */
 static const struct blk_ksm_ll_ops blk_crypto_ksm_ll_ops = {
 	.keyslot_program	= blk_crypto_keyslot_program,
 	.keyslot_evict		= blk_crypto_keyslot_evict,
 };

 static void blk_crypto_fallback_encrypt_endio(struct bio *enc_bio)
 {
 	struct bio *src_bio = enc_bio->bi_private;
 	int i;

 	for (i = 0; i < enc_bio->bi_vcnt; i++)
 		mempool_free(enc_bio->bi_io_vec[i].bv_page,
 			     blk_crypto_bounce_page_pool);

 	src_bio->bi_status = enc_bio->bi_status;

 	bio_put(enc_bio);
 	bio_endio(src_bio);
 }

 static struct bio *blk_crypto_clone_bio(struct bio *bio_src)
 {
 	struct bvec_iter iter;
 	struct bio_vec bv;
 	struct bio *bio;

 	bio = bio_kmalloc(GFP_NOIO, bio_segments(bio_src));
 	if (!bio)
 		return NULL;
 	bio->bi_bdev		= bio_src->bi_bdev;
 	if (bio_flagged(bio_src, BIO_REMAPPED))
 		bio_set_flag(bio, BIO_REMAPPED);
 	bio->bi_opf		= bio_src->bi_opf;
 	bio->bi_ioprio		= bio_src->bi_ioprio;
 	bio->bi_write_hint	= bio_src->bi_write_hint;
 	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
 	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;

 	bio_for_each_segment(bv, bio_src, iter)
 		bio->bi_io_vec[bio->bi_vcnt++] = bv;

 	bio_clone_blkg_association(bio, bio_src);
 	blkcg_bio_issue_init(bio);

 	return bio;
 }

 static bool blk_crypto_alloc_cipher_req(struct blk_ksm_keyslot *slot,
 					struct skcipher_request **ciph_req_ret,
 					struct crypto_wait *wait)
 {
 	struct skcipher_request *ciph_req;
 	const struct blk_crypto_keyslot *slotp;
 	int keyslot_idx = blk_ksm_get_slot_idx(slot);

 	slotp = &blk_crypto_keyslots[keyslot_idx];
 	ciph_req = skcipher_request_alloc(slotp->tfms[slotp->crypto_mode],
 					  GFP_NOIO);
 	if (!ciph_req)
 		return false;

 	skcipher_request_set_callback(ciph_req,
 				      CRYPTO_TFM_REQ_MAY_BACKLOG |
 				      CRYPTO_TFM_REQ_MAY_SLEEP,
 				      crypto_req_done, wait);
 	*ciph_req_ret = ciph_req;

 	return true;
 }

 static bool blk_crypto_split_bio_if_needed(struct bio **bio_ptr)
 {
 	struct bio *bio = *bio_ptr;
 	unsigned int i = 0;
 	unsigned int num_sectors = 0;
 	struct bio_vec bv;
 	struct bvec_iter iter;

 	bio_for_each_segment(bv, bio, iter) {
 		num_sectors += bv.bv_len >> SECTOR_SHIFT;
 		if (++i == BIO_MAX_VECS)
 			break;
 	}
 	if (num_sectors < bio_sectors(bio)) {
 		struct bio *split_bio;

 		split_bio = bio_split(bio, num_sectors, GFP_NOIO,
 				      &crypto_bio_split);
 		if (!split_bio) {
 			bio->bi_status = BLK_STS_RESOURCE;
 			return false;
 		}
 		bio_chain(split_bio, bio);
 		submit_bio_noacct(bio);
 		*bio_ptr = split_bio;
 	}

 	return true;
 }

 union blk_crypto_iv {
 	__le64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
 	u8 bytes[BLK_CRYPTO_MAX_IV_SIZE];
 };

 static void blk_crypto_dun_to_iv(const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
 				 union blk_crypto_iv *iv)
 {
 	int i;

 	for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++)
 		iv->dun[i] = cpu_to_le64(dun[i]);
 }

 /*
  * The crypto API fallback's encryption routine.
  * Allocate a bounce bio for encryption, encrypt the input bio using crypto API,
  * and replace *bio_ptr with the bounce bio. May split input bio if it's too
  * large. Returns true on success. Returns false and sets bio->bi_status on
  * error.
  */
 static bool blk_crypto_fallback_encrypt_bio(struct bio **bio_ptr)
 {
 	struct bio *src_bio, *enc_bio;
 	struct bio_crypt_ctx *bc;
 	struct blk_ksm_keyslot *slot;
 	int data_unit_size;
 	struct skcipher_request *ciph_req = NULL;
 	DECLARE_CRYPTO_WAIT(wait);
 	u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
 	struct scatterlist src, dst;
 	union blk_crypto_iv iv;
 	unsigned int i, j;
 	bool ret = false;
 	blk_status_t blk_st;

 	/* Split the bio if it's too big for single page bvec */
 	if (!blk_crypto_split_bio_if_needed(bio_ptr))
 		return false;

 	src_bio = *bio_ptr;
 	bc = src_bio->bi_crypt_context;
 	data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;

 	/* Allocate bounce bio for encryption */
 	enc_bio = blk_crypto_clone_bio(src_bio);
 	if (!enc_bio) {
 		src_bio->bi_status = BLK_STS_RESOURCE;
 		return false;
 	}

 	/*
 	 * Use the crypto API fallback keyslot manager to get a crypto_skcipher
 	 * for the algorithm and key specified for this bio.
 	 */
 	blk_st = blk_ksm_get_slot_for_key(&blk_crypto_ksm, bc->bc_key, &slot);
 	if (blk_st != BLK_STS_OK) {
 		src_bio->bi_status = blk_st;
 		goto out_put_enc_bio;
 	}

 	/* and then allocate an skcipher_request for it */
 	if (!blk_crypto_alloc_cipher_req(slot, &ciph_req, &wait)) {
 		src_bio->bi_status = BLK_STS_RESOURCE;
 		goto out_release_keyslot;
 	}

 	memcpy(curr_dun, bc->bc_dun, sizeof(curr_dun));
 	sg_init_table(&src, 1);
 	sg_init_table(&dst, 1);

 	skcipher_request_set_crypt(ciph_req, &src, &dst, data_unit_size,
 				   iv.bytes);

 	/* Encrypt each page in the bounce bio */
 	for (i = 0; i < enc_bio->bi_vcnt; i++) {
 		struct bio_vec *enc_bvec = &enc_bio->bi_io_vec[i];
 		struct page *plaintext_page = enc_bvec->bv_page;
 		struct page *ciphertext_page =
 			mempool_alloc(blk_crypto_bounce_page_pool, GFP_NOIO);

 		enc_bvec->bv_page = ciphertext_page;

 		if (!ciphertext_page) {
 			src_bio->bi_status = BLK_STS_RESOURCE;
 			goto out_free_bounce_pages;
 		}

 		sg_set_page(&src, plaintext_page, data_unit_size,
 			    enc_bvec->bv_offset);
 		sg_set_page(&dst, ciphertext_page, data_unit_size,
 			    enc_bvec->bv_offset);

 		/* Encrypt each data unit in this page */
 		for (j = 0; j < enc_bvec->bv_len; j += data_unit_size) {
 			blk_crypto_dun_to_iv(curr_dun, &iv);
 			if (crypto_wait_req(crypto_skcipher_encrypt(ciph_req),
 					    &wait)) {
 				i++;
 				src_bio->bi_status = BLK_STS_IOERR;
 				goto out_free_bounce_pages;
 			}
 			bio_crypt_dun_increment(curr_dun, 1);
 			src.offset += data_unit_size;
 			dst.offset += data_unit_size;
 		}
 	}

 	enc_bio->bi_private = src_bio;
 	enc_bio->bi_end_io = blk_crypto_fallback_encrypt_endio;
 	*bio_ptr = enc_bio;
 	ret = true;

 	enc_bio = NULL;
 	goto out_free_ciph_req;

 out_free_bounce_pages:
 	while (i > 0)
 		mempool_free(enc_bio->bi_io_vec[--i].bv_page,
 			     blk_crypto_bounce_page_pool);
 out_free_ciph_req:
 	skcipher_request_free(ciph_req);
 out_release_keyslot:
 	blk_ksm_put_slot(slot);
 out_put_enc_bio:
 	if (enc_bio)
 		bio_put(enc_bio);

 	return ret;
 }

 /*
  * The crypto API fallback's main decryption routine.
  * Decrypts input bio in place, and calls bio_endio on the bio.
  */
 static void blk_crypto_fallback_decrypt_bio(struct work_struct *work)
 {
 	struct bio_fallback_crypt_ctx *f_ctx =
 		container_of(work, struct bio_fallback_crypt_ctx, work);
 	struct bio *bio = f_ctx->bio;
 	struct bio_crypt_ctx *bc = &f_ctx->crypt_ctx;
 	struct blk_ksm_keyslot *slot;
 	struct skcipher_request *ciph_req = NULL;
 	DECLARE_CRYPTO_WAIT(wait);
 	u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
 	union blk_crypto_iv iv;
 	struct scatterlist sg;
 	struct bio_vec bv;
 	struct bvec_iter iter;
 	const int data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
 	unsigned int i;
 	blk_status_t blk_st;

 	/*
 	 * Use the crypto API fallback keyslot manager to get a crypto_skcipher
 	 * for the algorithm and key specified for this bio.
 	 */
 	blk_st = blk_ksm_get_slot_for_key(&blk_crypto_ksm, bc->bc_key, &slot);
 	if (blk_st != BLK_STS_OK) {
 		bio->bi_status = blk_st;
 		goto out_no_keyslot;
 	}

 	/* and then allocate an skcipher_request for it */
 	if (!blk_crypto_alloc_cipher_req(slot, &ciph_req, &wait)) {
 		bio->bi_status = BLK_STS_RESOURCE;
 		goto out;
 	}

 	memcpy(curr_dun, bc->bc_dun, sizeof(curr_dun));
 	sg_init_table(&sg, 1);
 	skcipher_request_set_crypt(ciph_req, &sg, &sg, data_unit_size,
 				   iv.bytes);

 	/* Decrypt each segment in the bio */
 	__bio_for_each_segment(bv, bio, iter, f_ctx->crypt_iter) {
 		struct page *page = bv.bv_page;

 		sg_set_page(&sg, page, data_unit_size, bv.bv_offset);

 		/* Decrypt each data unit in the segment */
 		for (i = 0; i < bv.bv_len; i += data_unit_size) {
 			blk_crypto_dun_to_iv(curr_dun, &iv);
 			if (crypto_wait_req(crypto_skcipher_decrypt(ciph_req),
 					    &wait)) {
 				bio->bi_status = BLK_STS_IOERR;
 				goto out;
 			}
 			bio_crypt_dun_increment(curr_dun, 1);
 			sg.offset += data_unit_size;
 		}
 	}

 out:
 	skcipher_request_free(ciph_req);
 	blk_ksm_put_slot(slot);
 out_no_keyslot:
 	mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);
 	bio_endio(bio);
 }

 /**
  * blk_crypto_fallback_decrypt_endio - queue bio for fallback decryption
  *
  * @bio: the bio to queue
  *
  * Restore bi_private and bi_end_io, and queue the bio for decryption into a
  * workqueue, since this function will be called from an atomic context.
  */
 static void blk_crypto_fallback_decrypt_endio(struct bio *bio)
 {
 	struct bio_fallback_crypt_ctx *f_ctx = bio->bi_private;

 	bio->bi_private = f_ctx->bi_private_orig;
 	bio->bi_end_io = f_ctx->bi_end_io_orig;

 	/* If there was an IO error, don't queue for decrypt. */
 	if (bio->bi_status) {
 		mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);
 		bio_endio(bio);
 		return;
 	}

 	INIT_WORK(&f_ctx->work, blk_crypto_fallback_decrypt_bio);
 	f_ctx->bio = bio;
 	queue_work(blk_crypto_wq, &f_ctx->work);
 }

 /**
  * blk_crypto_fallback_bio_prep - Prepare a bio to use fallback en/decryption
  *
  * @bio_ptr: pointer to the bio to prepare
  *
  * If bio is doing a WRITE operation, this splits the bio into two parts if it's
  * too big (see blk_crypto_split_bio_if_needed). It then allocates a bounce bio
  * for the first part, encrypts it, and update bio_ptr to point to the bounce
  * bio.
  *
  * For a READ operation, we mark the bio for decryption by using bi_private and
  * bi_end_io.
  *
  * In either case, this function will make the bio look like a regular bio (i.e.
  * as if no encryption context was ever specified) for the purposes of the rest
  * of the stack except for blk-integrity (blk-integrity and blk-crypto are not
  * currently supported together).
  *
  * Return: true on success. Sets bio->bi_status and returns false on error.
  */
 bool blk_crypto_fallback_bio_prep(struct bio **bio_ptr)
 {
 	struct bio *bio = *bio_ptr;
 	struct bio_crypt_ctx *bc = bio->bi_crypt_context;
 	struct bio_fallback_crypt_ctx *f_ctx;

 	if (WARN_ON_ONCE(!tfms_inited[bc->bc_key->crypto_cfg.crypto_mode])) {
 		/* User didn't call blk_crypto_start_using_key() first */
 		bio->bi_status = BLK_STS_IOERR;
 		return false;
 	}

 	if (!blk_ksm_crypto_cfg_supported(&blk_crypto_ksm,
 					  &bc->bc_key->crypto_cfg)) {
 		bio->bi_status = BLK_STS_NOTSUPP;
 		return false;
 	}

 	if (bio_data_dir(bio) == WRITE)
 		return blk_crypto_fallback_encrypt_bio(bio_ptr);

 	/*
 	 * bio READ case: Set up a f_ctx in the bio's bi_private and set the
 	 * bi_end_io appropriately to trigger decryption when the bio is ended.
 	 */
 	f_ctx = mempool_alloc(bio_fallback_crypt_ctx_pool, GFP_NOIO);
 	f_ctx->crypt_ctx = *bc;
 	f_ctx->crypt_iter = bio->bi_iter;
 	f_ctx->bi_private_orig = bio->bi_private;
 	f_ctx->bi_end_io_orig = bio->bi_end_io;
 	bio->bi_private = (void *)f_ctx;
 	bio->bi_end_io = blk_crypto_fallback_decrypt_endio;
 	bio_crypt_free_ctx(bio);

 	return true;
 }

 int blk_crypto_fallback_evict_key(const struct blk_crypto_key *key)
 {
 	return blk_ksm_evict_key(&blk_crypto_ksm, key);
 }

 static bool blk_crypto_fallback_inited;
 static int blk_crypto_fallback_init(void)
 {
 	int i;
 	int err;

 	if (blk_crypto_fallback_inited)
 		return 0;

 	prandom_bytes(blank_key, BLK_CRYPTO_MAX_KEY_SIZE);

 	err = bioset_init(&crypto_bio_split, 64, 0, 0);
 	if (err)
 		goto out;

 	err = blk_ksm_init(&blk_crypto_ksm, blk_crypto_num_keyslots);
 	if (err)
 		goto fail_free_bioset;
 	err = -ENOMEM;

 	blk_crypto_ksm.ksm_ll_ops = blk_crypto_ksm_ll_ops;
 	blk_crypto_ksm.max_dun_bytes_supported = BLK_CRYPTO_MAX_IV_SIZE;

 	/* All blk-crypto modes have a crypto API fallback. */
 	for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++)
 		blk_crypto_ksm.crypto_modes_supported[i] = 0xFFFFFFFF;
 	blk_crypto_ksm.crypto_modes_supported[BLK_ENCRYPTION_MODE_INVALID] = 0;

 	blk_crypto_wq = alloc_workqueue("blk_crypto_wq",
 					WQ_UNBOUND | WQ_HIGHPRI |
 					WQ_MEM_RECLAIM, num_online_cpus());
 	if (!blk_crypto_wq)
 		goto fail_free_ksm;

 	blk_crypto_keyslots = kcalloc(blk_crypto_num_keyslots,
 				      sizeof(blk_crypto_keyslots[0]),
 				      GFP_KERNEL);
 	if (!blk_crypto_keyslots)
 		goto fail_free_wq;

 	blk_crypto_bounce_page_pool =
 		mempool_create_page_pool(num_prealloc_bounce_pg, 0);
 	if (!blk_crypto_bounce_page_pool)
 		goto fail_free_keyslots;

 	bio_fallback_crypt_ctx_cache = KMEM_CACHE(bio_fallback_crypt_ctx, 0);
 	if (!bio_fallback_crypt_ctx_cache)
 		goto fail_free_bounce_page_pool;

 	bio_fallback_crypt_ctx_pool =
 		mempool_create_slab_pool(num_prealloc_fallback_crypt_ctxs,
 					 bio_fallback_crypt_ctx_cache);
 	if (!bio_fallback_crypt_ctx_pool)
 		goto fail_free_crypt_ctx_cache;

 	blk_crypto_fallback_inited = true;

 	return 0;
 fail_free_crypt_ctx_cache:
 	kmem_cache_destroy(bio_fallback_crypt_ctx_cache);
 fail_free_bounce_page_pool:
 	mempool_destroy(blk_crypto_bounce_page_pool);
 fail_free_keyslots:
 	kfree(blk_crypto_keyslots);
 fail_free_wq:
 	destroy_workqueue(blk_crypto_wq);
 fail_free_ksm:
 	blk_ksm_destroy(&blk_crypto_ksm);
 fail_free_bioset:
 	bioset_exit(&crypto_bio_split);
 out:
 	return err;
 }

 /*
  * Prepare blk-crypto-fallback for the specified crypto mode.
  * Returns -ENOPKG if the needed crypto API support is missing.
  */
 int blk_crypto_fallback_start_using_mode(enum blk_crypto_mode_num mode_num)
 {
 	const char *cipher_str = blk_crypto_modes[mode_num].cipher_str;
 	struct blk_crypto_keyslot *slotp;
 	unsigned int i;
 	int err = 0;

 	/*
 	 * Fast path
 	 * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
 	 * for each i are visible before we try to access them.
 	 */
 	if (likely(smp_load_acquire(&tfms_inited[mode_num])))
 		return 0;

 	mutex_lock(&tfms_init_lock);
 	if (tfms_inited[mode_num])
 		goto out;

 	err = blk_crypto_fallback_init();
 	if (err)
 		goto out;

 	for (i = 0; i < blk_crypto_num_keyslots; i++) {
 		slotp = &blk_crypto_keyslots[i];
 		slotp->tfms[mode_num] = crypto_alloc_skcipher(cipher_str, 0, 0);
 		if (IS_ERR(slotp->tfms[mode_num])) {
 			err = PTR_ERR(slotp->tfms[mode_num]);
 			if (err == -ENOENT) {
 				pr_warn_once("Missing crypto API support for \"%s\"\n",
 					     cipher_str);
 				err = -ENOPKG;
 			}
 			slotp->tfms[mode_num] = NULL;
 			goto out_free_tfms;
 		}

 		crypto_skcipher_set_flags(slotp->tfms[mode_num],
 					  CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
 	}

 	/*
 	 * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
 	 * for each i are visible before we set tfms_inited[mode_num].
 	 */
 	smp_store_release(&tfms_inited[mode_num], true);
 	goto out;

 out_free_tfms:
 	for (i = 0; i < blk_crypto_num_keyslots; i++) {
 		slotp = &blk_crypto_keyslots[i];
 		crypto_free_skcipher(slotp->tfms[mode_num]);
 		slotp->tfms[mode_num] = NULL;
 	}
 out:
 	mutex_unlock(&tfms_init_lock);
 	return err;
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright 2019 Google LLC
	*/

	/*
	* Refer to Documentation/block/inline-encryption.rst for detailed explanation.
	*/

	#define pr_fmt(fmt) "blk-crypto-fallback: " fmt

	#include <crypto/skcipher.h>
	#include <linux/blk-cgroup.h>
	#include <linux/blk-crypto.h>
	#include <linux/blkdev.h>
	#include <linux/crypto.h>
	#include <linux/keyslot-manager.h>
	#include <linux/mempool.h>
	#include <linux/module.h>
	#include <linux/random.h>

	#include "blk-crypto-internal.h"

	static unsigned int num_prealloc_bounce_pg = 32;
	module_param(num_prealloc_bounce_pg, uint, 0);
	MODULE_PARM_DESC(num_prealloc_bounce_pg,
	"Number of preallocated bounce pages for the blk-crypto crypto API fallback");

	static unsigned int blk_crypto_num_keyslots = 100;
	module_param_named(num_keyslots, blk_crypto_num_keyslots, uint, 0);
	MODULE_PARM_DESC(num_keyslots,
	"Number of keyslots for the blk-crypto crypto API fallback");

	static unsigned int num_prealloc_fallback_crypt_ctxs = 128;
	module_param(num_prealloc_fallback_crypt_ctxs, uint, 0);
	MODULE_PARM_DESC(num_prealloc_crypt_fallback_ctxs,
	"Number of preallocated bio fallback crypto contexts for blk-crypto to use during crypto API fallback");

	struct bio_fallback_crypt_ctx {
	struct bio_crypt_ctx crypt_ctx;
	/*
	* Copy of the bvec_iter when this bio was submitted.
	* We only want to en/decrypt the part of the bio as described by the
	* bvec_iter upon submission because bio might be split before being
	* resubmitted
	*/
	struct bvec_iter crypt_iter;
	union {
	struct {
	struct work_struct work;
	struct bio *bio;
	};
	struct {
	void *bi_private_orig;
	bio_end_io_t *bi_end_io_orig;
	};
	};
	};

	static struct kmem_cache *bio_fallback_crypt_ctx_cache;
	static mempool_t *bio_fallback_crypt_ctx_pool;

	/*
	* Allocating a crypto tfm during I/O can deadlock, so we have to preallocate
	* all of a mode's tfms when that mode starts being used. Since each mode may
	* need all the keyslots at some point, each mode needs its own tfm for each
	* keyslot; thus, a keyslot may contain tfms for multiple modes. However, to
	* match the behavior of real inline encryption hardware (which only supports a
	* single encryption context per keyslot), we only allow one tfm per keyslot to
	* be used at a time - the rest of the unused tfms have their keys cleared.
	*/
	static DEFINE_MUTEX(tfms_init_lock);
	static bool tfms_inited[BLK_ENCRYPTION_MODE_MAX];

	static struct blk_crypto_keyslot {
	enum blk_crypto_mode_num crypto_mode;
	struct crypto_skcipher *tfms[BLK_ENCRYPTION_MODE_MAX];
	} *blk_crypto_keyslots;

	static struct blk_keyslot_manager blk_crypto_ksm;
	static struct workqueue_struct *blk_crypto_wq;
	static mempool_t *blk_crypto_bounce_page_pool;
	static struct bio_set crypto_bio_split;

	/*
	* This is the key we set when evicting a keyslot. This should be the all 0's
	* key, but AES-XTS rejects that key, so we use some random bytes instead.
	*/
	static u8 blank_key[BLK_CRYPTO_MAX_KEY_SIZE];

	static void blk_crypto_evict_keyslot(unsigned int slot)
	{
	struct blk_crypto_keyslot *slotp = &blk_crypto_keyslots[slot];
	enum blk_crypto_mode_num crypto_mode = slotp->crypto_mode;
	int err;

	WARN_ON(slotp->crypto_mode == BLK_ENCRYPTION_MODE_INVALID);

	/* Clear the key in the skcipher */
	err = crypto_skcipher_setkey(slotp->tfms[crypto_mode], blank_key,
	blk_crypto_modes[crypto_mode].keysize);
	WARN_ON(err);
	slotp->crypto_mode = BLK_ENCRYPTION_MODE_INVALID;
	}

	static int blk_crypto_keyslot_program(struct blk_keyslot_manager *ksm,
	const struct blk_crypto_key *key,
	unsigned int slot)
	{
	struct blk_crypto_keyslot *slotp = &blk_crypto_keyslots[slot];
	const enum blk_crypto_mode_num crypto_mode =
	key->crypto_cfg.crypto_mode;
	int err;

	if (crypto_mode != slotp->crypto_mode &&
	slotp->crypto_mode != BLK_ENCRYPTION_MODE_INVALID)
	blk_crypto_evict_keyslot(slot);

	slotp->crypto_mode = crypto_mode;
	err = crypto_skcipher_setkey(slotp->tfms[crypto_mode], key->raw,
	key->size);
	if (err) {
	blk_crypto_evict_keyslot(slot);
	return err;
	}
	return 0;
	}

	static int blk_crypto_keyslot_evict(struct blk_keyslot_manager *ksm,
	const struct blk_crypto_key *key,
	unsigned int slot)
	{
	blk_crypto_evict_keyslot(slot);
	return 0;
	}

	/*
	* The crypto API fallback KSM ops - only used for a bio when it specifies a
	* blk_crypto_key that was not supported by the device's inline encryption
	* hardware.
	*/
	static const struct blk_ksm_ll_ops blk_crypto_ksm_ll_ops = {
	.keyslot_program = blk_crypto_keyslot_program,
	.keyslot_evict = blk_crypto_keyslot_evict,
	};

	static void blk_crypto_fallback_encrypt_endio(struct bio *enc_bio)
	{
	struct bio *src_bio = enc_bio->bi_private;
	int i;

	for (i = 0; i < enc_bio->bi_vcnt; i++)
	mempool_free(enc_bio->bi_io_vec[i].bv_page,
	blk_crypto_bounce_page_pool);

	src_bio->bi_status = enc_bio->bi_status;

	bio_put(enc_bio);
	bio_endio(src_bio);
	}

	static struct bio blk_crypto_clone_bio(struct bio bio_src)
	{
	struct bvec_iter iter;
	struct bio_vec bv;
	struct bio *bio;

	bio = bio_kmalloc(GFP_NOIO, bio_segments(bio_src));
	if (!bio)
	return NULL;
	bio->bi_bdev = bio_src->bi_bdev;
	if (bio_flagged(bio_src, BIO_REMAPPED))
	bio_set_flag(bio, BIO_REMAPPED);
	bio->bi_opf = bio_src->bi_opf;
	bio->bi_ioprio = bio_src->bi_ioprio;
	bio->bi_write_hint = bio_src->bi_write_hint;
	bio->bi_iter.bi_sector = bio_src->bi_iter.bi_sector;
	bio->bi_iter.bi_size = bio_src->bi_iter.bi_size;

	bio_for_each_segment(bv, bio_src, iter)
	bio->bi_io_vec[bio->bi_vcnt++] = bv;

	bio_clone_blkg_association(bio, bio_src);
	blkcg_bio_issue_init(bio);

	return bio;
	}

	static bool blk_crypto_alloc_cipher_req(struct blk_ksm_keyslot *slot,
	struct skcipher_request **ciph_req_ret,
	struct crypto_wait *wait)
	{
	struct skcipher_request *ciph_req;
	const struct blk_crypto_keyslot *slotp;
	int keyslot_idx = blk_ksm_get_slot_idx(slot);

	slotp = &blk_crypto_keyslots[keyslot_idx];
	ciph_req = skcipher_request_alloc(slotp->tfms[slotp->crypto_mode],
	GFP_NOIO);
	if (!ciph_req)
	return false;

	skcipher_request_set_callback(ciph_req,
	CRYPTO_TFM_REQ_MAY_BACKLOG \|
	CRYPTO_TFM_REQ_MAY_SLEEP,
	crypto_req_done, wait);
	*ciph_req_ret = ciph_req;

	return true;
	}

	static bool blk_crypto_split_bio_if_needed(struct bio **bio_ptr)
	{
	struct bio bio = bio_ptr;
	unsigned int i = 0;
	unsigned int num_sectors = 0;
	struct bio_vec bv;
	struct bvec_iter iter;

	bio_for_each_segment(bv, bio, iter) {
	num_sectors += bv.bv_len >> SECTOR_SHIFT;
	if (++i == BIO_MAX_VECS)
	break;
	}
	if (num_sectors < bio_sectors(bio)) {
	struct bio *split_bio;

	split_bio = bio_split(bio, num_sectors, GFP_NOIO,
	&crypto_bio_split);
	if (!split_bio) {
	bio->bi_status = BLK_STS_RESOURCE;
	return false;
	}
	bio_chain(split_bio, bio);
	submit_bio_noacct(bio);
	*bio_ptr = split_bio;
	}

	return true;
	}

	union blk_crypto_iv {
	__le64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
	u8 bytes[BLK_CRYPTO_MAX_IV_SIZE];
	};

	static void blk_crypto_dun_to_iv(const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
	union blk_crypto_iv *iv)
	{
	int i;

	for (i = 0; i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++)
	iv->dun[i] = cpu_to_le64(dun[i]);
	}

	/*
	* The crypto API fallback's encryption routine.
	* Allocate a bounce bio for encryption, encrypt the input bio using crypto API,
	* and replace *bio_ptr with the bounce bio. May split input bio if it's too
	* large. Returns true on success. Returns false and sets bio->bi_status on
	* error.
	*/
	static bool blk_crypto_fallback_encrypt_bio(struct bio **bio_ptr)
	{
	struct bio src_bio, enc_bio;
	struct bio_crypt_ctx *bc;
	struct blk_ksm_keyslot *slot;
	int data_unit_size;
	struct skcipher_request *ciph_req = NULL;
	DECLARE_CRYPTO_WAIT(wait);
	u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
	struct scatterlist src, dst;
	union blk_crypto_iv iv;
	unsigned int i, j;
	bool ret = false;
	blk_status_t blk_st;

	/* Split the bio if it's too big for single page bvec */
	if (!blk_crypto_split_bio_if_needed(bio_ptr))
	return false;

	src_bio = *bio_ptr;
	bc = src_bio->bi_crypt_context;
	data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;

	/* Allocate bounce bio for encryption */
	enc_bio = blk_crypto_clone_bio(src_bio);
	if (!enc_bio) {
	src_bio->bi_status = BLK_STS_RESOURCE;
	return false;
	}

	/*
	* Use the crypto API fallback keyslot manager to get a crypto_skcipher
	* for the algorithm and key specified for this bio.
	*/
	blk_st = blk_ksm_get_slot_for_key(&blk_crypto_ksm, bc->bc_key, &slot);
	if (blk_st != BLK_STS_OK) {
	src_bio->bi_status = blk_st;
	goto out_put_enc_bio;
	}

	/* and then allocate an skcipher_request for it */
	if (!blk_crypto_alloc_cipher_req(slot, &ciph_req, &wait)) {
	src_bio->bi_status = BLK_STS_RESOURCE;
	goto out_release_keyslot;
	}

	memcpy(curr_dun, bc->bc_dun, sizeof(curr_dun));
	sg_init_table(&src, 1);
	sg_init_table(&dst, 1);

	skcipher_request_set_crypt(ciph_req, &src, &dst, data_unit_size,
	iv.bytes);

	/* Encrypt each page in the bounce bio */
	for (i = 0; i < enc_bio->bi_vcnt; i++) {
	struct bio_vec *enc_bvec = &enc_bio->bi_io_vec[i];
	struct page *plaintext_page = enc_bvec->bv_page;
	struct page *ciphertext_page =
	mempool_alloc(blk_crypto_bounce_page_pool, GFP_NOIO);

	enc_bvec->bv_page = ciphertext_page;

	if (!ciphertext_page) {
	src_bio->bi_status = BLK_STS_RESOURCE;
	goto out_free_bounce_pages;
	}

	sg_set_page(&src, plaintext_page, data_unit_size,
	enc_bvec->bv_offset);
	sg_set_page(&dst, ciphertext_page, data_unit_size,
	enc_bvec->bv_offset);

	/* Encrypt each data unit in this page */
	for (j = 0; j < enc_bvec->bv_len; j += data_unit_size) {
	blk_crypto_dun_to_iv(curr_dun, &iv);
	if (crypto_wait_req(crypto_skcipher_encrypt(ciph_req),
	&wait)) {
	i++;
	src_bio->bi_status = BLK_STS_IOERR;
	goto out_free_bounce_pages;
	}
	bio_crypt_dun_increment(curr_dun, 1);
	src.offset += data_unit_size;
	dst.offset += data_unit_size;
	}
	}

	enc_bio->bi_private = src_bio;
	enc_bio->bi_end_io = blk_crypto_fallback_encrypt_endio;
	*bio_ptr = enc_bio;
	ret = true;

	enc_bio = NULL;
	goto out_free_ciph_req;

	out_free_bounce_pages:
	while (i > 0)
	mempool_free(enc_bio->bi_io_vec[--i].bv_page,
	blk_crypto_bounce_page_pool);
	out_free_ciph_req:
	skcipher_request_free(ciph_req);
	out_release_keyslot:
	blk_ksm_put_slot(slot);
	out_put_enc_bio:
	if (enc_bio)
	bio_put(enc_bio);

	return ret;
	}

	/*
	* The crypto API fallback's main decryption routine.
	* Decrypts input bio in place, and calls bio_endio on the bio.
	*/
	static void blk_crypto_fallback_decrypt_bio(struct work_struct *work)
	{
	struct bio_fallback_crypt_ctx *f_ctx =
	container_of(work, struct bio_fallback_crypt_ctx, work);
	struct bio *bio = f_ctx->bio;
	struct bio_crypt_ctx *bc = &f_ctx->crypt_ctx;
	struct blk_ksm_keyslot *slot;
	struct skcipher_request *ciph_req = NULL;
	DECLARE_CRYPTO_WAIT(wait);
	u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
	union blk_crypto_iv iv;
	struct scatterlist sg;
	struct bio_vec bv;
	struct bvec_iter iter;
	const int data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
	unsigned int i;
	blk_status_t blk_st;

	/*
	* Use the crypto API fallback keyslot manager to get a crypto_skcipher
	* for the algorithm and key specified for this bio.
	*/
	blk_st = blk_ksm_get_slot_for_key(&blk_crypto_ksm, bc->bc_key, &slot);
	if (blk_st != BLK_STS_OK) {
	bio->bi_status = blk_st;
	goto out_no_keyslot;
	}

	/* and then allocate an skcipher_request for it */
	if (!blk_crypto_alloc_cipher_req(slot, &ciph_req, &wait)) {
	bio->bi_status = BLK_STS_RESOURCE;
	goto out;
	}

	memcpy(curr_dun, bc->bc_dun, sizeof(curr_dun));
	sg_init_table(&sg, 1);
	skcipher_request_set_crypt(ciph_req, &sg, &sg, data_unit_size,
	iv.bytes);

	/* Decrypt each segment in the bio */
	__bio_for_each_segment(bv, bio, iter, f_ctx->crypt_iter) {
	struct page *page = bv.bv_page;

	sg_set_page(&sg, page, data_unit_size, bv.bv_offset);

	/* Decrypt each data unit in the segment */
	for (i = 0; i < bv.bv_len; i += data_unit_size) {
	blk_crypto_dun_to_iv(curr_dun, &iv);
	if (crypto_wait_req(crypto_skcipher_decrypt(ciph_req),
	&wait)) {
	bio->bi_status = BLK_STS_IOERR;
	goto out;
	}
	bio_crypt_dun_increment(curr_dun, 1);
	sg.offset += data_unit_size;
	}
	}

	out:
	skcipher_request_free(ciph_req);
	blk_ksm_put_slot(slot);
	out_no_keyslot:
	mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);
	bio_endio(bio);
	}

	/**
	* blk_crypto_fallback_decrypt_endio - queue bio for fallback decryption
	*
	* @bio: the bio to queue
	*
	* Restore bi_private and bi_end_io, and queue the bio for decryption into a
	* workqueue, since this function will be called from an atomic context.
	*/
	static void blk_crypto_fallback_decrypt_endio(struct bio *bio)
	{
	struct bio_fallback_crypt_ctx *f_ctx = bio->bi_private;

	bio->bi_private = f_ctx->bi_private_orig;
	bio->bi_end_io = f_ctx->bi_end_io_orig;

	/* If there was an IO error, don't queue for decrypt. */
	if (bio->bi_status) {
	mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);
	bio_endio(bio);
	return;
	}

	INIT_WORK(&f_ctx->work, blk_crypto_fallback_decrypt_bio);
	f_ctx->bio = bio;
	queue_work(blk_crypto_wq, &f_ctx->work);
	}

	/**
	* blk_crypto_fallback_bio_prep - Prepare a bio to use fallback en/decryption
	*
	* @bio_ptr: pointer to the bio to prepare
	*
	* If bio is doing a WRITE operation, this splits the bio into two parts if it's
	* too big (see blk_crypto_split_bio_if_needed). It then allocates a bounce bio
	* for the first part, encrypts it, and update bio_ptr to point to the bounce
	* bio.
	*
	* For a READ operation, we mark the bio for decryption by using bi_private and
	* bi_end_io.
	*
	* In either case, this function will make the bio look like a regular bio (i.e.
	* as if no encryption context was ever specified) for the purposes of the rest
	* of the stack except for blk-integrity (blk-integrity and blk-crypto are not
	* currently supported together).
	*
	* Return: true on success. Sets bio->bi_status and returns false on error.
	*/
	bool blk_crypto_fallback_bio_prep(struct bio **bio_ptr)
	{
	struct bio bio = bio_ptr;
	struct bio_crypt_ctx *bc = bio->bi_crypt_context;
	struct bio_fallback_crypt_ctx *f_ctx;

	if (WARN_ON_ONCE(!tfms_inited[bc->bc_key->crypto_cfg.crypto_mode])) {
	/* User didn't call blk_crypto_start_using_key() first */
	bio->bi_status = BLK_STS_IOERR;
	return false;
	}

	if (!blk_ksm_crypto_cfg_supported(&blk_crypto_ksm,
	&bc->bc_key->crypto_cfg)) {
	bio->bi_status = BLK_STS_NOTSUPP;
	return false;
	}

	if (bio_data_dir(bio) == WRITE)
	return blk_crypto_fallback_encrypt_bio(bio_ptr);

	/*
	* bio READ case: Set up a f_ctx in the bio's bi_private and set the
	* bi_end_io appropriately to trigger decryption when the bio is ended.
	*/
	f_ctx = mempool_alloc(bio_fallback_crypt_ctx_pool, GFP_NOIO);
	f_ctx->crypt_ctx = *bc;
	f_ctx->crypt_iter = bio->bi_iter;
	f_ctx->bi_private_orig = bio->bi_private;
	f_ctx->bi_end_io_orig = bio->bi_end_io;
	bio->bi_private = (void *)f_ctx;
	bio->bi_end_io = blk_crypto_fallback_decrypt_endio;
	bio_crypt_free_ctx(bio);

	return true;
	}

	int blk_crypto_fallback_evict_key(const struct blk_crypto_key *key)
	{
	return blk_ksm_evict_key(&blk_crypto_ksm, key);
	}

	static bool blk_crypto_fallback_inited;
	static int blk_crypto_fallback_init(void)
	{
	int i;
	int err;

	if (blk_crypto_fallback_inited)
	return 0;

	prandom_bytes(blank_key, BLK_CRYPTO_MAX_KEY_SIZE);

	err = bioset_init(&crypto_bio_split, 64, 0, 0);
	if (err)
	goto out;

	err = blk_ksm_init(&blk_crypto_ksm, blk_crypto_num_keyslots);
	if (err)
	goto fail_free_bioset;
	err = -ENOMEM;

	blk_crypto_ksm.ksm_ll_ops = blk_crypto_ksm_ll_ops;
	blk_crypto_ksm.max_dun_bytes_supported = BLK_CRYPTO_MAX_IV_SIZE;

	/* All blk-crypto modes have a crypto API fallback. */
	for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++)
	blk_crypto_ksm.crypto_modes_supported[i] = 0xFFFFFFFF;
	blk_crypto_ksm.crypto_modes_supported[BLK_ENCRYPTION_MODE_INVALID] = 0;

	blk_crypto_wq = alloc_workqueue("blk_crypto_wq",
	WQ_UNBOUND \| WQ_HIGHPRI \|
	WQ_MEM_RECLAIM, num_online_cpus());
	if (!blk_crypto_wq)
	goto fail_free_ksm;

	blk_crypto_keyslots = kcalloc(blk_crypto_num_keyslots,
	sizeof(blk_crypto_keyslots[0]),
	GFP_KERNEL);
	if (!blk_crypto_keyslots)
	goto fail_free_wq;

	blk_crypto_bounce_page_pool =
	mempool_create_page_pool(num_prealloc_bounce_pg, 0);
	if (!blk_crypto_bounce_page_pool)
	goto fail_free_keyslots;

	bio_fallback_crypt_ctx_cache = KMEM_CACHE(bio_fallback_crypt_ctx, 0);
	if (!bio_fallback_crypt_ctx_cache)
	goto fail_free_bounce_page_pool;

	bio_fallback_crypt_ctx_pool =
	mempool_create_slab_pool(num_prealloc_fallback_crypt_ctxs,
	bio_fallback_crypt_ctx_cache);
	if (!bio_fallback_crypt_ctx_pool)
	goto fail_free_crypt_ctx_cache;

	blk_crypto_fallback_inited = true;

	return 0;
	fail_free_crypt_ctx_cache:
	kmem_cache_destroy(bio_fallback_crypt_ctx_cache);
	fail_free_bounce_page_pool:
	mempool_destroy(blk_crypto_bounce_page_pool);
	fail_free_keyslots:
	kfree(blk_crypto_keyslots);
	fail_free_wq:
	destroy_workqueue(blk_crypto_wq);
	fail_free_ksm:
	blk_ksm_destroy(&blk_crypto_ksm);
	fail_free_bioset:
	bioset_exit(&crypto_bio_split);
	out:
	return err;
	}

	/*
	* Prepare blk-crypto-fallback for the specified crypto mode.
	* Returns -ENOPKG if the needed crypto API support is missing.
	*/
	int blk_crypto_fallback_start_using_mode(enum blk_crypto_mode_num mode_num)
	{
	const char *cipher_str = blk_crypto_modes[mode_num].cipher_str;
	struct blk_crypto_keyslot *slotp;
	unsigned int i;
	int err = 0;

	/*
	* Fast path
	* Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
	* for each i are visible before we try to access them.
	*/
	if (likely(smp_load_acquire(&tfms_inited[mode_num])))
	return 0;

	mutex_lock(&tfms_init_lock);
	if (tfms_inited[mode_num])
	goto out;

	err = blk_crypto_fallback_init();
	if (err)
	goto out;

	for (i = 0; i < blk_crypto_num_keyslots; i++) {
	slotp = &blk_crypto_keyslots[i];
	slotp->tfms[mode_num] = crypto_alloc_skcipher(cipher_str, 0, 0);
	if (IS_ERR(slotp->tfms[mode_num])) {
	err = PTR_ERR(slotp->tfms[mode_num]);
	if (err == -ENOENT) {
	pr_warn_once("Missing crypto API support for \"%s\"\n",
	cipher_str);
	err = -ENOPKG;
	}
	slotp->tfms[mode_num] = NULL;
	goto out_free_tfms;
	}

	crypto_skcipher_set_flags(slotp->tfms[mode_num],
	CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
	}

	/*
	* Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
	* for each i are visible before we set tfms_inited[mode_num].
	*/
	smp_store_release(&tfms_inited[mode_num], true);
	goto out;

	out_free_tfms:
	for (i = 0; i < blk_crypto_num_keyslots; i++) {
	slotp = &blk_crypto_keyslots[i];
	crypto_free_skcipher(slotp->tfms[mode_num]);
	slotp->tfms[mode_num] = NULL;
	}
	out:
	mutex_unlock(&tfms_init_lock);
	return err;
	}