// 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 = 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_fallback_keyslot {
        enum blk_crypto_mode_num crypto_mode;
        struct crypto_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 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_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_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_skcipher_setkey(slotp->tfms[crypto_mode], key->raw,
                                     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;
        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_uninit(enc_bio);
        kfree(enc_bio);
        bio_endio(src_bio);
}

static struct bio *blk_crypto_fallback_clone_bio(struct bio *bio_src)
{
        unsigned int nr_segs = bio_segments(bio_src);
        struct bvec_iter iter;
        struct bio_vec bv;
        struct bio *bio;

        bio = bio_kmalloc(nr_segs, GFP_NOIO);
        if (!bio)
                return NULL;
        bio_init(bio, bio_src->bi_bdev, bio->bi_inline_vecs, nr_segs,
                 bio_src->bi_opf);
        if (bio_flagged(bio_src, BIO_REMAPPED))
                bio_set_flag(bio, BIO_REMAPPED);
        bio->bi_ioprio          = bio_src->bi_ioprio;
        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);

        return bio;
}

static bool
blk_crypto_fallback_alloc_cipher_req(struct blk_crypto_keyslot *slot,
                                     struct skcipher_request **ciph_req_ret,
                                     struct crypto_wait *wait)
{
        struct skcipher_request *ciph_req;
        const struct blk_crypto_fallback_keyslot *slotp;
        int keyslot_idx = blk_crypto_keyslot_index(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_fallback_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_crypto_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_fallback_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_fallback_clone_bio(src_bio);
        if (!enc_bio) {
                src_bio->bi_status = BLK_STS_RESOURCE;
                return false;
        }

        /*
         * Get a blk-crypto-fallback keyslot that contains a crypto_skcipher for
         * this bio's algorithm and key.
         */
        blk_st = blk_crypto_get_keyslot(blk_crypto_fallback_profile,
                                        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_fallback_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_crypto_put_keyslot(slot);
out_put_enc_bio:
        if (enc_bio)
                bio_uninit(enc_bio);
        kfree(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_crypto_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;

        /*
         * Get a blk-crypto-fallback keyslot that contains a crypto_skcipher for
         * this bio's algorithm and key.
         */
        blk_st = blk_crypto_get_keyslot(blk_crypto_fallback_profile,
                                        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_fallback_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_crypto_put_keyslot(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_fallback_split_bio_if_needed()). It then allocates a
 * bounce bio for the first part, encrypts it, and updates 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_crypto_cfg_supported(blk_crypto_fallback_profile,
                                        &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_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, BLK_CRYPTO_MAX_KEY_SIZE);

        err = bioset_init(&crypto_bio_split, 64, 0, 0);
        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;

        /* 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(&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_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_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;
}