block/blk-crypto-fallback.c - linux/kernel/git/tj/cgroup - 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-crypto.h>
 #include <linux/blk-crypto-profile.h>
 #include <linux/blkdev.h>
 #include <linux/crypto.h>
 #include <linux/mempool.h>
 #include <linux/module.h>
 #include <linux/random.h>
 #include <linux/scatterlist.h>

 #include "blk-cgroup.h"
 #include "blk-crypto-internal.h"

 static unsigned int num_prealloc_bounce_pg = BIO_MAX_VECS;
 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_fallback_keyslot {
 	enum blk_crypto_mode_num crypto_mode;
 	struct crypto_sync_skcipher *tfms[BLK_ENCRYPTION_MODE_MAX];
 } *blk_crypto_keyslots;

 static struct blk_crypto_profile *blk_crypto_fallback_profile;
 static struct workqueue_struct *blk_crypto_wq;
 static mempool_t *blk_crypto_bounce_page_pool;
 static struct bio_set enc_bio_set;

 /*
  * 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_RAW_KEY_SIZE];

 static void blk_crypto_fallback_evict_keyslot(unsigned int slot)
 {
 	struct blk_crypto_fallback_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_sync_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_fallback_keyslot_program(struct blk_crypto_profile *profile,
 				    const struct blk_crypto_key *key,
 				    unsigned int slot)
 {
 	struct blk_crypto_fallback_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_fallback_evict_keyslot(slot);

 	slotp->crypto_mode = crypto_mode;
 	err = crypto_sync_skcipher_setkey(slotp->tfms[crypto_mode], key->bytes,
 				     key->size);
 	if (err) {
 		blk_crypto_fallback_evict_keyslot(slot);
 		return err;
 	}
 	return 0;
 }

 static int blk_crypto_fallback_keyslot_evict(struct blk_crypto_profile *profile,
 					     const struct blk_crypto_key *key,
 					     unsigned int slot)
 {
 	blk_crypto_fallback_evict_keyslot(slot);
 	return 0;
 }

 static const struct blk_crypto_ll_ops blk_crypto_fallback_ll_ops = {
 	.keyslot_program        = blk_crypto_fallback_keyslot_program,
 	.keyslot_evict          = blk_crypto_fallback_keyslot_evict,
 };

 static void blk_crypto_fallback_encrypt_endio(struct bio *enc_bio)
 {
 	struct bio *src_bio = enc_bio->bi_private;
 	struct page **pages = (struct page **)enc_bio->bi_io_vec;
 	struct bio_vec *bv;
 	unsigned int i;

 	/*
 	 * Use the same trick as the alloc side to avoid the need for an extra
 	 * pages array.
 	 */
 	bio_for_each_bvec_all(bv, enc_bio, i)
 		pages[i] = bv->bv_page;

 	i = mempool_free_bulk(blk_crypto_bounce_page_pool, (void **)pages,
 			enc_bio->bi_vcnt);
 	if (i < enc_bio->bi_vcnt)
 		release_pages(pages + i, enc_bio->bi_vcnt - i);

 	if (enc_bio->bi_status)
 		cmpxchg(&src_bio->bi_status, 0, enc_bio->bi_status);

 	bio_put(enc_bio);
 	bio_endio(src_bio);
 }

 #define PAGE_PTRS_PER_BVEC     (sizeof(struct bio_vec) / sizeof(struct page *))

 static struct bio *blk_crypto_alloc_enc_bio(struct bio *bio_src,
 		unsigned int nr_segs, struct page ***pages_ret)
 {
 	unsigned int memflags = memalloc_noio_save();
 	unsigned int nr_allocated;
 	struct page **pages;
 	struct bio *bio;

 	bio = bio_alloc_bioset(bio_src->bi_bdev, nr_segs, bio_src->bi_opf,
 			GFP_NOIO, &enc_bio_set);
 	if (bio_flagged(bio_src, BIO_REMAPPED))
 		bio_set_flag(bio, BIO_REMAPPED);
 	bio->bi_private		= bio_src;
 	bio->bi_end_io		= blk_crypto_fallback_encrypt_endio;
 	bio->bi_ioprio		= bio_src->bi_ioprio;
 	bio->bi_write_hint	= bio_src->bi_write_hint;
 	bio->bi_write_stream	= bio_src->bi_write_stream;
 	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
 	bio_clone_blkg_association(bio, bio_src);

 	/*
 	 * Move page array up in the allocated memory for the bio vecs as far as
 	 * possible so that we can start filling biovecs from the beginning
 	 * without overwriting the temporary page array.
 	 */
 	static_assert(PAGE_PTRS_PER_BVEC > 1);
 	pages = (struct page **)bio->bi_io_vec;
 	pages += nr_segs * (PAGE_PTRS_PER_BVEC - 1);

 	/*
 	 * Try a bulk allocation first.  This could leave random pages in the
 	 * array unallocated, but we'll fix that up later in mempool_alloc_bulk.
 	 *
 	 * Note: alloc_pages_bulk needs the array to be zeroed, as it assumes
 	 * any non-zero slot already contains a valid allocation.
 	 */
 	memset(pages, 0, sizeof(struct page *) * nr_segs);
 	nr_allocated = alloc_pages_bulk(GFP_KERNEL, nr_segs, pages);
 	if (nr_allocated < nr_segs)
 		mempool_alloc_bulk(blk_crypto_bounce_page_pool, (void **)pages,
 				nr_segs, nr_allocated);
 	memalloc_noio_restore(memflags);
 	*pages_ret = pages;
 	return bio;
 }

 static struct crypto_sync_skcipher *
 blk_crypto_fallback_tfm(struct blk_crypto_keyslot *slot)
 {
 	const struct blk_crypto_fallback_keyslot *slotp =
 		&blk_crypto_keyslots[blk_crypto_keyslot_index(slot)];

 	return slotp->tfms[slotp->crypto_mode];
 }

 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]);
 }

 static void __blk_crypto_fallback_encrypt_bio(struct bio *src_bio,
 		struct crypto_sync_skcipher *tfm)
 {
 	struct bio_crypt_ctx *bc = src_bio->bi_crypt_context;
 	int data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
 	SYNC_SKCIPHER_REQUEST_ON_STACK(ciph_req, tfm);
 	u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
 	struct scatterlist src, dst;
 	union blk_crypto_iv iv;
 	unsigned int nr_enc_pages, enc_idx;
 	struct page **enc_pages;
 	struct bio *enc_bio;
 	unsigned int i;

 	skcipher_request_set_callback(ciph_req,
 			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 			NULL, NULL);

 	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 source bio.  Because the source bio could
 	 * have bio_vecs that span more than a single page, but the encrypted
 	 * bios are limited to a single page per bio_vec, this can generate
 	 * more than a single encrypted bio per source bio.
 	 */
 new_bio:
 	nr_enc_pages = min(bio_segments(src_bio), BIO_MAX_VECS);
 	enc_bio = blk_crypto_alloc_enc_bio(src_bio, nr_enc_pages, &enc_pages);
 	enc_idx = 0;
 	for (;;) {
 		struct bio_vec src_bv =
 			bio_iter_iovec(src_bio, src_bio->bi_iter);
 		struct page *enc_page = enc_pages[enc_idx];

 		if (!IS_ALIGNED(src_bv.bv_len | src_bv.bv_offset,
 				data_unit_size)) {
 			enc_bio->bi_status = BLK_STS_INVAL;
 			goto out_free_enc_bio;
 		}

 		__bio_add_page(enc_bio, enc_page, src_bv.bv_len,
 				src_bv.bv_offset);

 		sg_set_page(&src, src_bv.bv_page, data_unit_size,
 			    src_bv.bv_offset);
 		sg_set_page(&dst, enc_page, data_unit_size, src_bv.bv_offset);

 		/*
 		 * Increment the index now that the encrypted page is added to
 		 * the bio.  This is important for the error unwind path.
 		 */
 		enc_idx++;

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

 		bio_advance_iter_single(src_bio, &src_bio->bi_iter,
 				src_bv.bv_len);
 		if (!src_bio->bi_iter.bi_size)
 			break;

 		if (enc_idx == nr_enc_pages) {
 			/*
 			 * For each additional encrypted bio submitted,
 			 * increment the source bio's remaining count.  Each
 			 * encrypted bio's completion handler calls bio_endio on
 			 * the source bio, so this keeps the source bio from
 			 * completing until the last encrypted bio does.
 			 */
 			bio_inc_remaining(src_bio);
 			submit_bio(enc_bio);
 			goto new_bio;
 		}
 	}

 	submit_bio(enc_bio);
 	return;

 out_free_enc_bio:
 	/*
 	 * Add the remaining pages to the bio so that the normal completion path
 	 * in blk_crypto_fallback_encrypt_endio frees them.  The exact data
 	 * layout does not matter for that, so don't bother iterating the source
 	 * bio.
 	 */
 	for (; enc_idx < nr_enc_pages; enc_idx++)
 		__bio_add_page(enc_bio, enc_pages[enc_idx], PAGE_SIZE, 0);
 	bio_endio(enc_bio);
 }

 /*
  * The crypto API fallback's encryption routine.
  *
  * Allocate one or more bios for encryption, encrypt the input bio using the
  * crypto API, and submit the encrypted bios.  Sets bio->bi_status and
  * completes the source bio on error
  */
 static void blk_crypto_fallback_encrypt_bio(struct bio *src_bio)
 {
 	struct bio_crypt_ctx *bc = src_bio->bi_crypt_context;
 	struct blk_crypto_keyslot *slot;
 	blk_status_t status;

 	status = blk_crypto_get_keyslot(blk_crypto_fallback_profile,
 					bc->bc_key, &slot);
 	if (status != BLK_STS_OK) {
 		src_bio->bi_status = status;
 		bio_endio(src_bio);
 		return;
 	}
 	__blk_crypto_fallback_encrypt_bio(src_bio,
 			blk_crypto_fallback_tfm(slot));
 	blk_crypto_put_keyslot(slot);
 }

 static blk_status_t __blk_crypto_fallback_decrypt_bio(struct bio *bio,
 		struct bio_crypt_ctx *bc, struct bvec_iter iter,
 		struct crypto_sync_skcipher *tfm)
 {
 	SYNC_SKCIPHER_REQUEST_ON_STACK(ciph_req, tfm);
 	u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
 	union blk_crypto_iv iv;
 	struct scatterlist sg;
 	struct bio_vec bv;
 	const int data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
 	unsigned int i;

 	skcipher_request_set_callback(ciph_req,
 			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 			NULL, NULL);

 	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, iter) {
 		struct page *page = bv.bv_page;

 		if (!IS_ALIGNED(bv.bv_len | bv.bv_offset, data_unit_size))
 			return BLK_STS_INVAL;

 		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_skcipher_decrypt(ciph_req))
 				return BLK_STS_IOERR;
 			bio_crypt_dun_increment(curr_dun, 1);
 			sg.offset += data_unit_size;
 		}
 	}

 	return BLK_STS_OK;
 }

 /*
  * 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_crypto_keyslot *slot;
 	blk_status_t status;

 	status = blk_crypto_get_keyslot(blk_crypto_fallback_profile,
 					bc->bc_key, &slot);
 	if (status == BLK_STS_OK) {
 		status = __blk_crypto_fallback_decrypt_bio(bio, bc,
 				f_ctx->crypt_iter,
 				blk_crypto_fallback_tfm(slot));
 		blk_crypto_put_keyslot(slot);
 	}
 	mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);

 	bio->bi_status = status;
 	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: bio to prepare
  *
  * If bio is doing a WRITE operation, allocate one or more bios to contain the
  * encrypted payload and submit them.
  *
  * For a READ operation, mark the bio for decryption by using bi_private and
  * bi_end_io.
  *
  * In either case, this function will make the submitted bio(s) look like
  * regular bios (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 if @bio should be submitted to the driver by the caller, else
  * false.  Sets bio->bi_status, calls bio_endio and returns false on error.
  */
 bool blk_crypto_fallback_bio_prep(struct bio *bio)
 {
 	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_io_error(bio);
 		return false;
 	}

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

 	if (bio_data_dir(bio) == WRITE) {
 		blk_crypto_fallback_encrypt_bio(bio);
 		return false;
 	}

 	/*
 	 * 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_crypto_evict_key(blk_crypto_fallback_profile, 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;

 	get_random_bytes(blank_key, sizeof(blank_key));

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

 	/* Dynamic allocation is needed because of lockdep_register_key(). */
 	blk_crypto_fallback_profile =
 		kzalloc(sizeof(*blk_crypto_fallback_profile), GFP_KERNEL);
 	if (!blk_crypto_fallback_profile) {
 		err = -ENOMEM;
 		goto fail_free_bioset;
 	}

 	err = blk_crypto_profile_init(blk_crypto_fallback_profile,
 				      blk_crypto_num_keyslots);
 	if (err)
 		goto fail_free_profile;
 	err = -ENOMEM;

 	blk_crypto_fallback_profile->ll_ops = blk_crypto_fallback_ll_ops;
 	blk_crypto_fallback_profile->max_dun_bytes_supported = BLK_CRYPTO_MAX_IV_SIZE;
 	blk_crypto_fallback_profile->key_types_supported = BLK_CRYPTO_KEY_TYPE_RAW;

 	/* All blk-crypto modes have a crypto API fallback. */
 	for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++)
 		blk_crypto_fallback_profile->modes_supported[i] = 0xFFFFFFFF;
 	blk_crypto_fallback_profile->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_destroy_profile;

 	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_destroy_profile:
 	blk_crypto_profile_destroy(blk_crypto_fallback_profile);
 fail_free_profile:
 	kfree(blk_crypto_fallback_profile);
 fail_free_bioset:
 	bioset_exit(&enc_bio_set);
 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_fallback_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_sync_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_sync_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_sync_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-crypto.h>
	#include <linux/blk-crypto-profile.h>
	#include <linux/blkdev.h>
	#include <linux/crypto.h>
	#include <linux/mempool.h>
	#include <linux/module.h>
	#include <linux/random.h>
	#include <linux/scatterlist.h>

	#include "blk-cgroup.h"
	#include "blk-crypto-internal.h"

	static unsigned int num_prealloc_bounce_pg = BIO_MAX_VECS;
	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_fallback_keyslot {
	enum blk_crypto_mode_num crypto_mode;
	struct crypto_sync_skcipher *tfms[BLK_ENCRYPTION_MODE_MAX];
	} *blk_crypto_keyslots;

	static struct blk_crypto_profile *blk_crypto_fallback_profile;
	static struct workqueue_struct *blk_crypto_wq;
	static mempool_t *blk_crypto_bounce_page_pool;
	static struct bio_set enc_bio_set;

	/*
	* 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_RAW_KEY_SIZE];

	static void blk_crypto_fallback_evict_keyslot(unsigned int slot)
	{
	struct blk_crypto_fallback_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_sync_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_fallback_keyslot_program(struct blk_crypto_profile *profile,
	const struct blk_crypto_key *key,
	unsigned int slot)
	{
	struct blk_crypto_fallback_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_fallback_evict_keyslot(slot);

	slotp->crypto_mode = crypto_mode;
	err = crypto_sync_skcipher_setkey(slotp->tfms[crypto_mode], key->bytes,
	key->size);
	if (err) {
	blk_crypto_fallback_evict_keyslot(slot);
	return err;
	}
	return 0;
	}

	static int blk_crypto_fallback_keyslot_evict(struct blk_crypto_profile *profile,
	const struct blk_crypto_key *key,
	unsigned int slot)
	{
	blk_crypto_fallback_evict_keyslot(slot);
	return 0;
	}

	static const struct blk_crypto_ll_ops blk_crypto_fallback_ll_ops = {
	.keyslot_program = blk_crypto_fallback_keyslot_program,
	.keyslot_evict = blk_crypto_fallback_keyslot_evict,
	};

	static void blk_crypto_fallback_encrypt_endio(struct bio *enc_bio)
	{
	struct bio *src_bio = enc_bio->bi_private;
	struct page pages = (struct page )enc_bio->bi_io_vec;
	struct bio_vec *bv;
	unsigned int i;

	/*
	* Use the same trick as the alloc side to avoid the need for an extra
	* pages array.
	*/
	bio_for_each_bvec_all(bv, enc_bio, i)
	pages[i] = bv->bv_page;

	i = mempool_free_bulk(blk_crypto_bounce_page_pool, (void **)pages,
	enc_bio->bi_vcnt);
	if (i < enc_bio->bi_vcnt)
	release_pages(pages + i, enc_bio->bi_vcnt - i);

	if (enc_bio->bi_status)
	cmpxchg(&src_bio->bi_status, 0, enc_bio->bi_status);

	bio_put(enc_bio);
	bio_endio(src_bio);
	}

	#define PAGE_PTRS_PER_BVEC (sizeof(struct bio_vec) / sizeof(struct page *))

	static struct bio blk_crypto_alloc_enc_bio(struct bio bio_src,
	unsigned int nr_segs, struct page ***pages_ret)
	{
	unsigned int memflags = memalloc_noio_save();
	unsigned int nr_allocated;
	struct page **pages;
	struct bio *bio;

	bio = bio_alloc_bioset(bio_src->bi_bdev, nr_segs, bio_src->bi_opf,
	GFP_NOIO, &enc_bio_set);
	if (bio_flagged(bio_src, BIO_REMAPPED))
	bio_set_flag(bio, BIO_REMAPPED);
	bio->bi_private = bio_src;
	bio->bi_end_io = blk_crypto_fallback_encrypt_endio;
	bio->bi_ioprio = bio_src->bi_ioprio;
	bio->bi_write_hint = bio_src->bi_write_hint;
	bio->bi_write_stream = bio_src->bi_write_stream;
	bio->bi_iter.bi_sector = bio_src->bi_iter.bi_sector;
	bio_clone_blkg_association(bio, bio_src);

	/*
	* Move page array up in the allocated memory for the bio vecs as far as
	* possible so that we can start filling biovecs from the beginning
	* without overwriting the temporary page array.
	*/
	static_assert(PAGE_PTRS_PER_BVEC > 1);
	pages = (struct page **)bio->bi_io_vec;
	pages += nr_segs * (PAGE_PTRS_PER_BVEC - 1);

	/*
	* Try a bulk allocation first. This could leave random pages in the
	* array unallocated, but we'll fix that up later in mempool_alloc_bulk.
	*
	* Note: alloc_pages_bulk needs the array to be zeroed, as it assumes
	* any non-zero slot already contains a valid allocation.
	*/
	memset(pages, 0, sizeof(struct page ) nr_segs);
	nr_allocated = alloc_pages_bulk(GFP_KERNEL, nr_segs, pages);
	if (nr_allocated < nr_segs)
	mempool_alloc_bulk(blk_crypto_bounce_page_pool, (void **)pages,
	nr_segs, nr_allocated);
	memalloc_noio_restore(memflags);
	*pages_ret = pages;
	return bio;
	}

	static struct crypto_sync_skcipher *
	blk_crypto_fallback_tfm(struct blk_crypto_keyslot *slot)
	{
	const struct blk_crypto_fallback_keyslot *slotp =
	&blk_crypto_keyslots[blk_crypto_keyslot_index(slot)];

	return slotp->tfms[slotp->crypto_mode];
	}

	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]);
	}

	static void __blk_crypto_fallback_encrypt_bio(struct bio *src_bio,
	struct crypto_sync_skcipher *tfm)
	{
	struct bio_crypt_ctx *bc = src_bio->bi_crypt_context;
	int data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
	SYNC_SKCIPHER_REQUEST_ON_STACK(ciph_req, tfm);
	u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
	struct scatterlist src, dst;
	union blk_crypto_iv iv;
	unsigned int nr_enc_pages, enc_idx;
	struct page **enc_pages;
	struct bio *enc_bio;
	unsigned int i;

	skcipher_request_set_callback(ciph_req,
	CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	NULL, NULL);

	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 source bio. Because the source bio could
	* have bio_vecs that span more than a single page, but the encrypted
	* bios are limited to a single page per bio_vec, this can generate
	* more than a single encrypted bio per source bio.
	*/
	new_bio:
	nr_enc_pages = min(bio_segments(src_bio), BIO_MAX_VECS);
	enc_bio = blk_crypto_alloc_enc_bio(src_bio, nr_enc_pages, &enc_pages);
	enc_idx = 0;
	for (;;) {
	struct bio_vec src_bv =
	bio_iter_iovec(src_bio, src_bio->bi_iter);
	struct page *enc_page = enc_pages[enc_idx];

	if (!IS_ALIGNED(src_bv.bv_len \| src_bv.bv_offset,
	data_unit_size)) {
	enc_bio->bi_status = BLK_STS_INVAL;
	goto out_free_enc_bio;
	}

	__bio_add_page(enc_bio, enc_page, src_bv.bv_len,
	src_bv.bv_offset);

	sg_set_page(&src, src_bv.bv_page, data_unit_size,
	src_bv.bv_offset);
	sg_set_page(&dst, enc_page, data_unit_size, src_bv.bv_offset);

	/*
	* Increment the index now that the encrypted page is added to
	* the bio. This is important for the error unwind path.
	*/
	enc_idx++;

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

	bio_advance_iter_single(src_bio, &src_bio->bi_iter,
	src_bv.bv_len);
	if (!src_bio->bi_iter.bi_size)
	break;

	if (enc_idx == nr_enc_pages) {
	/*
	* For each additional encrypted bio submitted,
	* increment the source bio's remaining count. Each
	* encrypted bio's completion handler calls bio_endio on
	* the source bio, so this keeps the source bio from
	* completing until the last encrypted bio does.
	*/
	bio_inc_remaining(src_bio);
	submit_bio(enc_bio);
	goto new_bio;
	}
	}

	submit_bio(enc_bio);
	return;

	out_free_enc_bio:
	/*
	* Add the remaining pages to the bio so that the normal completion path
	* in blk_crypto_fallback_encrypt_endio frees them. The exact data
	* layout does not matter for that, so don't bother iterating the source
	* bio.
	*/
	for (; enc_idx < nr_enc_pages; enc_idx++)
	__bio_add_page(enc_bio, enc_pages[enc_idx], PAGE_SIZE, 0);
	bio_endio(enc_bio);
	}

	/*
	* The crypto API fallback's encryption routine.
	*
	* Allocate one or more bios for encryption, encrypt the input bio using the
	* crypto API, and submit the encrypted bios. Sets bio->bi_status and
	* completes the source bio on error
	*/
	static void blk_crypto_fallback_encrypt_bio(struct bio *src_bio)
	{
	struct bio_crypt_ctx *bc = src_bio->bi_crypt_context;
	struct blk_crypto_keyslot *slot;
	blk_status_t status;

	status = blk_crypto_get_keyslot(blk_crypto_fallback_profile,
	bc->bc_key, &slot);
	if (status != BLK_STS_OK) {
	src_bio->bi_status = status;
	bio_endio(src_bio);
	return;
	}
	__blk_crypto_fallback_encrypt_bio(src_bio,
	blk_crypto_fallback_tfm(slot));
	blk_crypto_put_keyslot(slot);
	}

	static blk_status_t __blk_crypto_fallback_decrypt_bio(struct bio *bio,
	struct bio_crypt_ctx *bc, struct bvec_iter iter,
	struct crypto_sync_skcipher *tfm)
	{
	SYNC_SKCIPHER_REQUEST_ON_STACK(ciph_req, tfm);
	u64 curr_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
	union blk_crypto_iv iv;
	struct scatterlist sg;
	struct bio_vec bv;
	const int data_unit_size = bc->bc_key->crypto_cfg.data_unit_size;
	unsigned int i;

	skcipher_request_set_callback(ciph_req,
	CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	NULL, NULL);

	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, iter) {
	struct page *page = bv.bv_page;

	if (!IS_ALIGNED(bv.bv_len \| bv.bv_offset, data_unit_size))
	return BLK_STS_INVAL;

	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_skcipher_decrypt(ciph_req))
	return BLK_STS_IOERR;
	bio_crypt_dun_increment(curr_dun, 1);
	sg.offset += data_unit_size;
	}
	}

	return BLK_STS_OK;
	}

	/*
	* 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_crypto_keyslot *slot;
	blk_status_t status;

	status = blk_crypto_get_keyslot(blk_crypto_fallback_profile,
	bc->bc_key, &slot);
	if (status == BLK_STS_OK) {
	status = __blk_crypto_fallback_decrypt_bio(bio, bc,
	f_ctx->crypt_iter,
	blk_crypto_fallback_tfm(slot));
	blk_crypto_put_keyslot(slot);
	}
	mempool_free(f_ctx, bio_fallback_crypt_ctx_pool);

	bio->bi_status = status;
	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: bio to prepare
	*
	* If bio is doing a WRITE operation, allocate one or more bios to contain the
	* encrypted payload and submit them.
	*
	* For a READ operation, mark the bio for decryption by using bi_private and
	* bi_end_io.
	*
	* In either case, this function will make the submitted bio(s) look like
	* regular bios (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 if @bio should be submitted to the driver by the caller, else
	* false. Sets bio->bi_status, calls bio_endio and returns false on error.
	*/
	bool blk_crypto_fallback_bio_prep(struct bio *bio)
	{
	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_io_error(bio);
	return false;
	}

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

	if (bio_data_dir(bio) == WRITE) {
	blk_crypto_fallback_encrypt_bio(bio);
	return false;
	}

	/*
	* 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_crypto_evict_key(blk_crypto_fallback_profile, 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;

	get_random_bytes(blank_key, sizeof(blank_key));

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

	/* Dynamic allocation is needed because of lockdep_register_key(). */
	blk_crypto_fallback_profile =
	kzalloc(sizeof(*blk_crypto_fallback_profile), GFP_KERNEL);
	if (!blk_crypto_fallback_profile) {
	err = -ENOMEM;
	goto fail_free_bioset;
	}

	err = blk_crypto_profile_init(blk_crypto_fallback_profile,
	blk_crypto_num_keyslots);
	if (err)
	goto fail_free_profile;
	err = -ENOMEM;

	blk_crypto_fallback_profile->ll_ops = blk_crypto_fallback_ll_ops;
	blk_crypto_fallback_profile->max_dun_bytes_supported = BLK_CRYPTO_MAX_IV_SIZE;
	blk_crypto_fallback_profile->key_types_supported = BLK_CRYPTO_KEY_TYPE_RAW;

	/* All blk-crypto modes have a crypto API fallback. */
	for (i = 0; i < BLK_ENCRYPTION_MODE_MAX; i++)
	blk_crypto_fallback_profile->modes_supported[i] = 0xFFFFFFFF;
	blk_crypto_fallback_profile->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_destroy_profile;

	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_destroy_profile:
	blk_crypto_profile_destroy(blk_crypto_fallback_profile);
	fail_free_profile:
	kfree(blk_crypto_fallback_profile);
	fail_free_bioset:
	bioset_exit(&enc_bio_set);
	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_fallback_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_sync_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_sync_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_sync_skcipher(slotp->tfms[mode_num]);
	slotp->tfms[mode_num] = NULL;
	}
	out:
	mutex_unlock(&tfms_init_lock);
	return err;
	}