drivers/md/dm-default-key.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2017 Google, Inc.
  */

 #include <linux/blk-crypto.h>
 #include <linux/device-mapper.h>
 #include <linux/module.h>

 #define DM_MSG_PREFIX		"default-key"

 static const struct dm_default_key_cipher {
 	const char *name;
 	enum blk_crypto_mode_num mode_num;
 	int key_size;
 } dm_default_key_ciphers[] = {
 	{
 		.name = "aes-xts-plain64",
 		.mode_num = BLK_ENCRYPTION_MODE_AES_256_XTS,
 		.key_size = 64,
 	}, {
 		.name = "xchacha12,aes-adiantum-plain64",
 		.mode_num = BLK_ENCRYPTION_MODE_ADIANTUM,
 		.key_size = 32,
 	},
 };

 /**
  * struct dm_default_c - private data of a default-key target
  * @dev: the underlying device
  * @start: starting sector of the range of @dev which this target actually maps.
  *	   For this purpose a "sector" is 512 bytes.
  * @cipher_string: the name of the encryption algorithm being used
  * @iv_offset: starting offset for IVs.  IVs are generated as if the target were
  *	       preceded by @iv_offset 512-byte sectors.
  * @sector_size: crypto sector size in bytes (usually 4096)
  * @sector_bits: log2(sector_size)
  * @key: the encryption key to use
  * @max_dun: the maximum DUN that may be used (computed from other params)
  */
 struct default_key_c {
 	struct dm_dev *dev;
 	sector_t start;
 	const char *cipher_string;
 	u64 iv_offset;
 	unsigned int sector_size;
 	unsigned int sector_bits;
 	struct blk_crypto_key key;
 	enum blk_crypto_key_type key_type;
 	u64 max_dun;
 };

 static const struct dm_default_key_cipher *
 lookup_cipher(const char *cipher_string)
 {
 	int i;

 	for (i = 0; i < ARRAY_SIZE(dm_default_key_ciphers); i++) {
 		if (strcmp(cipher_string, dm_default_key_ciphers[i].name) == 0)
 			return &dm_default_key_ciphers[i];
 	}
 	return NULL;
 }

 static void default_key_dtr(struct dm_target *ti)
 {
 	struct default_key_c *dkc = ti->private;

 	if (dkc->dev) {
 		blk_crypto_evict_key(dkc->dev->bdev, &dkc->key);
 		dm_put_device(ti, dkc->dev);
 	}
 	kfree_sensitive(dkc->cipher_string);
 	kfree_sensitive(dkc);
 }

 static int default_key_ctr_optional(struct dm_target *ti,
 				    unsigned int argc, char **argv)
 {
 	struct default_key_c *dkc = ti->private;
 	struct dm_arg_set as;
 	static const struct dm_arg _args[] = {
 		{0, 4, "Invalid number of feature args"},
 	};
 	unsigned int opt_params;
 	const char *opt_string;
 	bool iv_large_sectors = false;
 	char dummy;
 	int err;

 	as.argc = argc;
 	as.argv = argv;

 	err = dm_read_arg_group(_args, &as, &opt_params, &ti->error);
 	if (err)
 		return err;

 	while (opt_params--) {
 		opt_string = dm_shift_arg(&as);
 		if (!opt_string) {
 			ti->error = "Not enough feature arguments";
 			return -EINVAL;
 		}
 		if (!strcmp(opt_string, "allow_discards")) {
 			ti->num_discard_bios = 1;
 		} else if (sscanf(opt_string, "sector_size:%u%c",
 				  &dkc->sector_size, &dummy) == 1) {
 			if (dkc->sector_size < SECTOR_SIZE ||
 			    dkc->sector_size > 4096 ||
 			    !is_power_of_2(dkc->sector_size)) {
 				ti->error = "Invalid sector_size";
 				return -EINVAL;
 			}
 		} else if (!strcmp(opt_string, "iv_large_sectors")) {
 			iv_large_sectors = true;
 		} else if (!strcmp(opt_string, "wrappedkey_v0")) {
 			dkc->key_type = BLK_CRYPTO_KEY_TYPE_HW_WRAPPED;
 		} else {
 			ti->error = "Invalid feature arguments";
 			return -EINVAL;
 		}
 	}

 	/* dm-default-key doesn't implement iv_large_sectors=false. */
 	if (dkc->sector_size != SECTOR_SIZE && !iv_large_sectors) {
 		ti->error = "iv_large_sectors must be specified";
 		return -EINVAL;
 	}

 	return 0;
 }

 /*
  * Construct a default-key mapping:
  * <cipher> <key> <iv_offset> <dev_path> <start>
  *
  * This syntax matches dm-crypt's, but lots of unneeded functionality has been
  * removed.  Also, dm-default-key requires that the "iv_large_sectors" option be
  * given whenever a non-default sector size is used.
  */
 static int default_key_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 {
 	struct default_key_c *dkc;
 	const struct dm_default_key_cipher *cipher;
 	u8 raw_key[BLK_CRYPTO_MAX_ANY_KEY_SIZE];
 	unsigned int raw_key_size;
 	unsigned int dun_bytes;
 	unsigned long long tmpll;
 	char dummy;
 	int err;

 	if (argc < 5) {
 		ti->error = "Not enough arguments";
 		return -EINVAL;
 	}

 	dkc = kzalloc(sizeof(*dkc), GFP_KERNEL);
 	if (!dkc) {
 		ti->error = "Out of memory";
 		return -ENOMEM;
 	}
 	ti->private = dkc;
 	dkc->key_type = BLK_CRYPTO_KEY_TYPE_STANDARD;

 	/* <cipher> */
 	dkc->cipher_string = kstrdup(argv[0], GFP_KERNEL);
 	if (!dkc->cipher_string) {
 		ti->error = "Out of memory";
 		err = -ENOMEM;
 		goto bad;
 	}
 	cipher = lookup_cipher(dkc->cipher_string);
 	if (!cipher) {
 		ti->error = "Unsupported cipher";
 		err = -EINVAL;
 		goto bad;
 	}

 	/* <key> */
 	raw_key_size = strlen(argv[1]);
 	if (raw_key_size > 2 * BLK_CRYPTO_MAX_ANY_KEY_SIZE ||
 	    raw_key_size % 2) {
 		ti->error = "Invalid keysize";
 		err = -EINVAL;
 		goto bad;
 	}
 	raw_key_size /= 2;
 	if (hex2bin(raw_key, argv[1], raw_key_size) != 0) {
 		ti->error = "Malformed key string";
 		err = -EINVAL;
 		goto bad;
 	}

 	/* <iv_offset> */
 	if (sscanf(argv[2], "%llu%c", &dkc->iv_offset, &dummy) != 1) {
 		ti->error = "Invalid iv_offset sector";
 		err = -EINVAL;
 		goto bad;
 	}

 	/* <dev_path> */
 	err = dm_get_device(ti, argv[3], dm_table_get_mode(ti->table),
 			    &dkc->dev);
 	if (err) {
 		ti->error = "Device lookup failed";
 		goto bad;
 	}

 	/* <start> */
 	if (sscanf(argv[4], "%llu%c", &tmpll, &dummy) != 1 ||
 	    tmpll != (sector_t)tmpll) {
 		ti->error = "Invalid start sector";
 		err = -EINVAL;
 		goto bad;
 	}
 	dkc->start = tmpll;

 	/* optional arguments */
 	dkc->sector_size = SECTOR_SIZE;
 	if (argc > 5) {
 		err = default_key_ctr_optional(ti, argc - 5, &argv[5]);
 		if (err)
 			goto bad;
 	}
 	dkc->sector_bits = ilog2(dkc->sector_size);
 	if (ti->len & ((dkc->sector_size >> SECTOR_SHIFT) - 1)) {
 		ti->error = "Device size is not a multiple of sector_size";
 		err = -EINVAL;
 		goto bad;
 	}

 	dkc->max_dun = (dkc->iv_offset + ti->len - 1) >>
 		       (dkc->sector_bits - SECTOR_SHIFT);
 	dun_bytes = DIV_ROUND_UP(fls64(dkc->max_dun), 8);

 	err = blk_crypto_init_key(&dkc->key, raw_key, raw_key_size,
 				  dkc->key_type, cipher->mode_num,
 				  dun_bytes, dkc->sector_size);
 	if (err) {
 		ti->error = "Error initializing blk-crypto key";
 		goto bad;
 	}

 	err = blk_crypto_start_using_key(dkc->dev->bdev, &dkc->key);
 	if (err) {
 		ti->error = "Error starting to use blk-crypto";
 		goto bad;
 	}

 	ti->num_flush_bios = 1;

 	err = 0;
 	goto out;

 bad:
 	default_key_dtr(ti);
 out:
 	memzero_explicit(raw_key, sizeof(raw_key));
 	return err;
 }

 static int default_key_map(struct dm_target *ti, struct bio *bio)
 {
 	const struct default_key_c *dkc = ti->private;
 	sector_t sector_in_target;
 	u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE] = { 0 };

 	bio_set_dev(bio, dkc->dev->bdev);

 	/*
 	 * If the bio is a device-level request which doesn't target a specific
 	 * sector, there's nothing more to do.
 	 */
 	if (bio_sectors(bio) == 0)
 		return DM_MAPIO_REMAPPED;

 	/* Map the bio's sector to the underlying device. (512-byte sectors) */
 	sector_in_target = dm_target_offset(ti, bio->bi_iter.bi_sector);
 	bio->bi_iter.bi_sector = dkc->start + sector_in_target;

 	/*
 	 * If the bio should skip dm-default-key (i.e. if it's for an encrypted
 	 * file's contents), or if it doesn't have any data (e.g. if it's a
 	 * DISCARD request), there's nothing more to do.
 	 */
 	if (bio_should_skip_dm_default_key(bio) || !bio_has_data(bio))
 		return DM_MAPIO_REMAPPED;

 	/*
 	 * Else, dm-default-key needs to set this bio's encryption context.
 	 * It must not already have one.
 	 */
 	if (WARN_ON_ONCE(bio_has_crypt_ctx(bio)))
 		return DM_MAPIO_KILL;

 	/* Calculate the DUN and enforce data-unit (crypto sector) alignment. */
 	dun[0] = dkc->iv_offset + sector_in_target; /* 512-byte sectors */
 	if (dun[0] & ((dkc->sector_size >> SECTOR_SHIFT) - 1))
 		return DM_MAPIO_KILL;
 	dun[0] >>= dkc->sector_bits - SECTOR_SHIFT; /* crypto sectors */

 	/*
 	 * This check isn't necessary as we should have calculated max_dun
 	 * correctly, but be safe.
 	 */
 	if (WARN_ON_ONCE(dun[0] > dkc->max_dun))
 		return DM_MAPIO_KILL;

 	bio_crypt_set_ctx(bio, &dkc->key, dun, GFP_NOIO);

 	return DM_MAPIO_REMAPPED;
 }

 static void default_key_status(struct dm_target *ti, status_type_t type,
 			       unsigned int status_flags, char *result,
 			       unsigned int maxlen)
 {
 	const struct default_key_c *dkc = ti->private;
 	unsigned int sz = 0;
 	int num_feature_args = 0;

 	switch (type) {
 	case STATUSTYPE_INFO:
 	case STATUSTYPE_IMA:
 		result[0] = '\0';
 		break;

 	case STATUSTYPE_TABLE:
 		/* Omit the key for now. */
 		DMEMIT("%s - %llu %s %llu", dkc->cipher_string, dkc->iv_offset,
 		       dkc->dev->name, (unsigned long long)dkc->start);

 		num_feature_args += !!ti->num_discard_bios;
 		if (dkc->sector_size != SECTOR_SIZE)
 			num_feature_args += 2;
 		if (dkc->key_type == BLK_CRYPTO_KEY_TYPE_HW_WRAPPED)
 			num_feature_args += 1;
 		if (num_feature_args != 0) {
 			DMEMIT(" %d", num_feature_args);
 			if (ti->num_discard_bios)
 				DMEMIT(" allow_discards");
 			if (dkc->sector_size != SECTOR_SIZE) {
 				DMEMIT(" sector_size:%u", dkc->sector_size);
 				DMEMIT(" iv_large_sectors");
 			}
 			if (dkc->key_type == BLK_CRYPTO_KEY_TYPE_HW_WRAPPED)
 				DMEMIT(" wrappedkey_v0");
 		}
 		break;
 	}
 }

 static int default_key_prepare_ioctl(struct dm_target *ti,
 				     struct block_device **bdev)
 {
 	const struct default_key_c *dkc = ti->private;
 	const struct dm_dev *dev = dkc->dev;

 	*bdev = dev->bdev;

 	/* Only pass ioctls through if the device sizes match exactly. */
 	if (dkc->start != 0 ||
 	    ti->len != bdev_nr_sectors(dev->bdev))
 		return 1;
 	return 0;
 }

 static int default_key_iterate_devices(struct dm_target *ti,
 				       iterate_devices_callout_fn fn,
 				       void *data)
 {
 	const struct default_key_c *dkc = ti->private;

 	return fn(ti, dkc->dev, dkc->start, ti->len, data);
 }

 static void default_key_io_hints(struct dm_target *ti,
 				 struct queue_limits *limits)
 {
 	const struct default_key_c *dkc = ti->private;
 	const unsigned int sector_size = dkc->sector_size;

 	limits->logical_block_size =
 		max_t(unsigned int, limits->logical_block_size, sector_size);
 	limits->physical_block_size =
 		max_t(unsigned int, limits->physical_block_size, sector_size);
 	limits->io_min = max_t(unsigned int, limits->io_min, sector_size);
 }

 #ifdef CONFIG_BLK_DEV_ZONED
 static int default_key_report_zones(struct dm_target *ti,
 		struct dm_report_zones_args *args, unsigned int nr_zones)
 {
 	struct default_key_c *dkc = ti->private;

 	return dm_report_zones(dkc->dev->bdev, dkc->start,
 			dkc->start + dm_target_offset(ti, args->next_sector),
 			args, nr_zones);
 }
 #else
 #define default_key_report_zones NULL
 #endif

 static struct target_type default_key_target = {
 	.name			= "default-key",
 	.version		= {2, 1, 0},
 	.features		= DM_TARGET_PASSES_CRYPTO | DM_TARGET_ZONED_HM,
 	.report_zones		= default_key_report_zones,
 	.module			= THIS_MODULE,
 	.ctr			= default_key_ctr,
 	.dtr			= default_key_dtr,
 	.map			= default_key_map,
 	.status			= default_key_status,
 	.prepare_ioctl		= default_key_prepare_ioctl,
 	.iterate_devices	= default_key_iterate_devices,
 	.io_hints		= default_key_io_hints,
 };

 static int __init dm_default_key_init(void)
 {
 	return dm_register_target(&default_key_target);
 }

 static void __exit dm_default_key_exit(void)
 {
 	dm_unregister_target(&default_key_target);
 }

 module_init(dm_default_key_init);
 module_exit(dm_default_key_exit);

 MODULE_AUTHOR("Paul Lawrence <paullawrence@google.com>");
 MODULE_AUTHOR("Paul Crowley <paulcrowley@google.com>");
 MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
 MODULE_DESCRIPTION(DM_NAME " target for encrypting filesystem metadata");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright (C) 2017 Google, Inc.
	*/

	#include <linux/blk-crypto.h>
	#include <linux/device-mapper.h>
	#include <linux/module.h>

	#define DM_MSG_PREFIX "default-key"

	static const struct dm_default_key_cipher {
	const char *name;
	enum blk_crypto_mode_num mode_num;
	int key_size;
	} dm_default_key_ciphers[] = {
	{
	.name = "aes-xts-plain64",
	.mode_num = BLK_ENCRYPTION_MODE_AES_256_XTS,
	.key_size = 64,
	}, {
	.name = "xchacha12,aes-adiantum-plain64",
	.mode_num = BLK_ENCRYPTION_MODE_ADIANTUM,
	.key_size = 32,
	},
	};

	/**
	* struct dm_default_c - private data of a default-key target
	* @dev: the underlying device
	* @start: starting sector of the range of @dev which this target actually maps.
	* For this purpose a "sector" is 512 bytes.
	* @cipher_string: the name of the encryption algorithm being used
	* @iv_offset: starting offset for IVs. IVs are generated as if the target were
	* preceded by @iv_offset 512-byte sectors.
	* @sector_size: crypto sector size in bytes (usually 4096)
	* @sector_bits: log2(sector_size)
	* @key: the encryption key to use
	* @max_dun: the maximum DUN that may be used (computed from other params)
	*/
	struct default_key_c {
	struct dm_dev *dev;
	sector_t start;
	const char *cipher_string;
	u64 iv_offset;
	unsigned int sector_size;
	unsigned int sector_bits;
	struct blk_crypto_key key;
	enum blk_crypto_key_type key_type;
	u64 max_dun;
	};

	static const struct dm_default_key_cipher *
	lookup_cipher(const char *cipher_string)
	{
	int i;

	for (i = 0; i < ARRAY_SIZE(dm_default_key_ciphers); i++) {
	if (strcmp(cipher_string, dm_default_key_ciphers[i].name) == 0)
	return &dm_default_key_ciphers[i];
	}
	return NULL;
	}

	static void default_key_dtr(struct dm_target *ti)
	{
	struct default_key_c *dkc = ti->private;

	if (dkc->dev) {
	blk_crypto_evict_key(dkc->dev->bdev, &dkc->key);
	dm_put_device(ti, dkc->dev);
	}
	kfree_sensitive(dkc->cipher_string);
	kfree_sensitive(dkc);
	}

	static int default_key_ctr_optional(struct dm_target *ti,
	unsigned int argc, char **argv)
	{
	struct default_key_c *dkc = ti->private;
	struct dm_arg_set as;
	static const struct dm_arg _args[] = {
	{0, 4, "Invalid number of feature args"},
	};
	unsigned int opt_params;
	const char *opt_string;
	bool iv_large_sectors = false;
	char dummy;
	int err;

	as.argc = argc;
	as.argv = argv;

	err = dm_read_arg_group(_args, &as, &opt_params, &ti->error);
	if (err)
	return err;

	while (opt_params--) {
	opt_string = dm_shift_arg(&as);
	if (!opt_string) {
	ti->error = "Not enough feature arguments";
	return -EINVAL;
	}
	if (!strcmp(opt_string, "allow_discards")) {
	ti->num_discard_bios = 1;
	} else if (sscanf(opt_string, "sector_size:%u%c",
	&dkc->sector_size, &dummy) == 1) {
	if (dkc->sector_size < SECTOR_SIZE \|\|
	dkc->sector_size > 4096 \|\|
	!is_power_of_2(dkc->sector_size)) {
	ti->error = "Invalid sector_size";
	return -EINVAL;
	}
	} else if (!strcmp(opt_string, "iv_large_sectors")) {
	iv_large_sectors = true;
	} else if (!strcmp(opt_string, "wrappedkey_v0")) {
	dkc->key_type = BLK_CRYPTO_KEY_TYPE_HW_WRAPPED;
	} else {
	ti->error = "Invalid feature arguments";
	return -EINVAL;
	}
	}

	/* dm-default-key doesn't implement iv_large_sectors=false. */
	if (dkc->sector_size != SECTOR_SIZE && !iv_large_sectors) {
	ti->error = "iv_large_sectors must be specified";
	return -EINVAL;
	}

	return 0;
	}

	/*
	* Construct a default-key mapping:
	* <cipher> <key> <iv_offset> <dev_path> <start>
	*
	* This syntax matches dm-crypt's, but lots of unneeded functionality has been
	* removed. Also, dm-default-key requires that the "iv_large_sectors" option be
	* given whenever a non-default sector size is used.
	*/
	static int default_key_ctr(struct dm_target ti, unsigned int argc, char *argv)
	{
	struct default_key_c *dkc;
	const struct dm_default_key_cipher *cipher;
	u8 raw_key[BLK_CRYPTO_MAX_ANY_KEY_SIZE];
	unsigned int raw_key_size;
	unsigned int dun_bytes;
	unsigned long long tmpll;
	char dummy;
	int err;

	if (argc < 5) {
	ti->error = "Not enough arguments";
	return -EINVAL;
	}

	dkc = kzalloc(sizeof(*dkc), GFP_KERNEL);
	if (!dkc) {
	ti->error = "Out of memory";
	return -ENOMEM;
	}
	ti->private = dkc;
	dkc->key_type = BLK_CRYPTO_KEY_TYPE_STANDARD;

	/* <cipher> */
	dkc->cipher_string = kstrdup(argv[0], GFP_KERNEL);
	if (!dkc->cipher_string) {
	ti->error = "Out of memory";
	err = -ENOMEM;
	goto bad;
	}
	cipher = lookup_cipher(dkc->cipher_string);
	if (!cipher) {
	ti->error = "Unsupported cipher";
	err = -EINVAL;
	goto bad;
	}

	/* <key> */
	raw_key_size = strlen(argv[1]);
	if (raw_key_size > 2 * BLK_CRYPTO_MAX_ANY_KEY_SIZE \|\|
	raw_key_size % 2) {
	ti->error = "Invalid keysize";
	err = -EINVAL;
	goto bad;
	}
	raw_key_size /= 2;
	if (hex2bin(raw_key, argv[1], raw_key_size) != 0) {
	ti->error = "Malformed key string";
	err = -EINVAL;
	goto bad;
	}

	/* <iv_offset> */
	if (sscanf(argv[2], "%llu%c", &dkc->iv_offset, &dummy) != 1) {
	ti->error = "Invalid iv_offset sector";
	err = -EINVAL;
	goto bad;
	}

	/* <dev_path> */
	err = dm_get_device(ti, argv[3], dm_table_get_mode(ti->table),
	&dkc->dev);
	if (err) {
	ti->error = "Device lookup failed";
	goto bad;
	}

	/* <start> */
	if (sscanf(argv[4], "%llu%c", &tmpll, &dummy) != 1 \|\|
	tmpll != (sector_t)tmpll) {
	ti->error = "Invalid start sector";
	err = -EINVAL;
	goto bad;
	}
	dkc->start = tmpll;

	/* optional arguments */
	dkc->sector_size = SECTOR_SIZE;
	if (argc > 5) {
	err = default_key_ctr_optional(ti, argc - 5, &argv[5]);
	if (err)
	goto bad;
	}
	dkc->sector_bits = ilog2(dkc->sector_size);
	if (ti->len & ((dkc->sector_size >> SECTOR_SHIFT) - 1)) {
	ti->error = "Device size is not a multiple of sector_size";
	err = -EINVAL;
	goto bad;
	}

	dkc->max_dun = (dkc->iv_offset + ti->len - 1) >>
	(dkc->sector_bits - SECTOR_SHIFT);
	dun_bytes = DIV_ROUND_UP(fls64(dkc->max_dun), 8);

	err = blk_crypto_init_key(&dkc->key, raw_key, raw_key_size,
	dkc->key_type, cipher->mode_num,
	dun_bytes, dkc->sector_size);
	if (err) {
	ti->error = "Error initializing blk-crypto key";
	goto bad;
	}

	err = blk_crypto_start_using_key(dkc->dev->bdev, &dkc->key);
	if (err) {
	ti->error = "Error starting to use blk-crypto";
	goto bad;
	}

	ti->num_flush_bios = 1;

	err = 0;
	goto out;

	bad:
	default_key_dtr(ti);
	out:
	memzero_explicit(raw_key, sizeof(raw_key));
	return err;
	}

	static int default_key_map(struct dm_target ti, struct bio bio)
	{
	const struct default_key_c *dkc = ti->private;
	sector_t sector_in_target;
	u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE] = { 0 };

	bio_set_dev(bio, dkc->dev->bdev);

	/*
	* If the bio is a device-level request which doesn't target a specific
	* sector, there's nothing more to do.
	*/
	if (bio_sectors(bio) == 0)
	return DM_MAPIO_REMAPPED;

	/* Map the bio's sector to the underlying device. (512-byte sectors) */
	sector_in_target = dm_target_offset(ti, bio->bi_iter.bi_sector);
	bio->bi_iter.bi_sector = dkc->start + sector_in_target;

	/*
	* If the bio should skip dm-default-key (i.e. if it's for an encrypted
	* file's contents), or if it doesn't have any data (e.g. if it's a
	* DISCARD request), there's nothing more to do.
	*/
	if (bio_should_skip_dm_default_key(bio) \|\| !bio_has_data(bio))
	return DM_MAPIO_REMAPPED;

	/*
	* Else, dm-default-key needs to set this bio's encryption context.
	* It must not already have one.
	*/
	if (WARN_ON_ONCE(bio_has_crypt_ctx(bio)))
	return DM_MAPIO_KILL;

	/* Calculate the DUN and enforce data-unit (crypto sector) alignment. */
	dun[0] = dkc->iv_offset + sector_in_target; /* 512-byte sectors */
	if (dun[0] & ((dkc->sector_size >> SECTOR_SHIFT) - 1))
	return DM_MAPIO_KILL;
	dun[0] >>= dkc->sector_bits - SECTOR_SHIFT; /* crypto sectors */

	/*
	* This check isn't necessary as we should have calculated max_dun
	* correctly, but be safe.
	*/
	if (WARN_ON_ONCE(dun[0] > dkc->max_dun))
	return DM_MAPIO_KILL;

	bio_crypt_set_ctx(bio, &dkc->key, dun, GFP_NOIO);

	return DM_MAPIO_REMAPPED;
	}

	static void default_key_status(struct dm_target *ti, status_type_t type,
	unsigned int status_flags, char *result,
	unsigned int maxlen)
	{
	const struct default_key_c *dkc = ti->private;
	unsigned int sz = 0;
	int num_feature_args = 0;

	switch (type) {
	case STATUSTYPE_INFO:
	case STATUSTYPE_IMA:
	result[0] = '\0';
	break;

	case STATUSTYPE_TABLE:
	/* Omit the key for now. */
	DMEMIT("%s - %llu %s %llu", dkc->cipher_string, dkc->iv_offset,
	dkc->dev->name, (unsigned long long)dkc->start);

	num_feature_args += !!ti->num_discard_bios;
	if (dkc->sector_size != SECTOR_SIZE)
	num_feature_args += 2;
	if (dkc->key_type == BLK_CRYPTO_KEY_TYPE_HW_WRAPPED)
	num_feature_args += 1;
	if (num_feature_args != 0) {
	DMEMIT(" %d", num_feature_args);
	if (ti->num_discard_bios)
	DMEMIT(" allow_discards");
	if (dkc->sector_size != SECTOR_SIZE) {
	DMEMIT(" sector_size:%u", dkc->sector_size);
	DMEMIT(" iv_large_sectors");
	}
	if (dkc->key_type == BLK_CRYPTO_KEY_TYPE_HW_WRAPPED)
	DMEMIT(" wrappedkey_v0");
	}
	break;
	}
	}

	static int default_key_prepare_ioctl(struct dm_target *ti,
	struct block_device **bdev)
	{
	const struct default_key_c *dkc = ti->private;
	const struct dm_dev *dev = dkc->dev;

	*bdev = dev->bdev;

	/* Only pass ioctls through if the device sizes match exactly. */
	if (dkc->start != 0 \|\|
	ti->len != bdev_nr_sectors(dev->bdev))
	return 1;
	return 0;
	}

	static int default_key_iterate_devices(struct dm_target *ti,
	iterate_devices_callout_fn fn,
	void *data)
	{
	const struct default_key_c *dkc = ti->private;

	return fn(ti, dkc->dev, dkc->start, ti->len, data);
	}

	static void default_key_io_hints(struct dm_target *ti,
	struct queue_limits *limits)
	{
	const struct default_key_c *dkc = ti->private;
	const unsigned int sector_size = dkc->sector_size;

	limits->logical_block_size =
	max_t(unsigned int, limits->logical_block_size, sector_size);
	limits->physical_block_size =
	max_t(unsigned int, limits->physical_block_size, sector_size);
	limits->io_min = max_t(unsigned int, limits->io_min, sector_size);
	}

	#ifdef CONFIG_BLK_DEV_ZONED
	static int default_key_report_zones(struct dm_target *ti,
	struct dm_report_zones_args *args, unsigned int nr_zones)
	{
	struct default_key_c *dkc = ti->private;

	return dm_report_zones(dkc->dev->bdev, dkc->start,
	dkc->start + dm_target_offset(ti, args->next_sector),
	args, nr_zones);
	}
	#else
	#define default_key_report_zones NULL
	#endif

	static struct target_type default_key_target = {
	.name = "default-key",
	.version = {2, 1, 0},
	.features = DM_TARGET_PASSES_CRYPTO \| DM_TARGET_ZONED_HM,
	.report_zones = default_key_report_zones,
	.module = THIS_MODULE,
	.ctr = default_key_ctr,
	.dtr = default_key_dtr,
	.map = default_key_map,
	.status = default_key_status,
	.prepare_ioctl = default_key_prepare_ioctl,
	.iterate_devices = default_key_iterate_devices,
	.io_hints = default_key_io_hints,
	};

	static int __init dm_default_key_init(void)
	{
	return dm_register_target(&default_key_target);
	}

	static void __exit dm_default_key_exit(void)
	{
	dm_unregister_target(&default_key_target);
	}

	module_init(dm_default_key_init);
	module_exit(dm_default_key_exit);

	MODULE_AUTHOR("Paul Lawrence <paullawrence@google.com>");
	MODULE_AUTHOR("Paul Crowley <paulcrowley@google.com>");
	MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
	MODULE_DESCRIPTION(DM_NAME " target for encrypting filesystem metadata");
	MODULE_LICENSE("GPL");