fs/ext4/crypto.c - kernel/bruno - Git at Google

 /*
  * linux/fs/ext4/crypto.c
  *
  * Copyright (C) 2015, Google, Inc.
  *
  * This contains encryption functions for ext4
  *
  * Written by Michael Halcrow, 2014.
  *
  * Filename encryption additions
  *	Uday Savagaonkar, 2014
  * Encryption policy handling additions
  *	Ildar Muslukhov, 2014
  *
  * This has not yet undergone a rigorous security audit.
  *
  * The usage of AES-XTS should conform to recommendations in NIST
  * Special Publication 800-38E and IEEE P1619/D16.
  */

 #include <crypto/hash.h>
 #include <crypto/sha.h>
 #include <keys/user-type.h>
 #include <keys/encrypted-type.h>
 #include <linux/crypto.h>
 #include <linux/ecryptfs.h>
 #include <linux/gfp.h>
 #include <linux/kernel.h>
 #include <linux/key.h>
 #include <linux/list.h>
 #include <linux/mempool.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/random.h>
 #include <linux/scatterlist.h>
 #include <linux/spinlock_types.h>

 #include "ext4_extents.h"
 #include "xattr.h"

 /* Encryption added and removed here! (L: */

 static unsigned int num_prealloc_crypto_pages = 32;
 static unsigned int num_prealloc_crypto_ctxs = 128;

 module_param(num_prealloc_crypto_pages, uint, 0444);
 MODULE_PARM_DESC(num_prealloc_crypto_pages,
 		 "Number of crypto pages to preallocate");
 module_param(num_prealloc_crypto_ctxs, uint, 0444);
 MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
 		 "Number of crypto contexts to preallocate");

 static mempool_t *ext4_bounce_page_pool;

 static LIST_HEAD(ext4_free_crypto_ctxs);
 static DEFINE_SPINLOCK(ext4_crypto_ctx_lock);

 static struct kmem_cache *ext4_crypto_ctx_cachep;
 struct kmem_cache *ext4_crypt_info_cachep;

 /**
  * ext4_release_crypto_ctx() - Releases an encryption context
  * @ctx: The encryption context to release.
  *
  * If the encryption context was allocated from the pre-allocated pool, returns
  * it to that pool. Else, frees it.
  *
  * If there's a bounce page in the context, this frees that.
  */
 void ext4_release_crypto_ctx(struct ext4_crypto_ctx *ctx)
 {
 	unsigned long flags;

 	if (ctx->flags & EXT4_WRITE_PATH_FL && ctx->w.bounce_page)
 		mempool_free(ctx->w.bounce_page, ext4_bounce_page_pool);
 	ctx->w.bounce_page = NULL;
 	ctx->w.control_page = NULL;
 	if (ctx->flags & EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL) {
 		kmem_cache_free(ext4_crypto_ctx_cachep, ctx);
 	} else {
 		spin_lock_irqsave(&ext4_crypto_ctx_lock, flags);
 		list_add(&ctx->free_list, &ext4_free_crypto_ctxs);
 		spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags);
 	}
 }

 /**
  * ext4_get_crypto_ctx() - Gets an encryption context
  * @inode:       The inode for which we are doing the crypto
  *
  * Allocates and initializes an encryption context.
  *
  * Return: An allocated and initialized encryption context on success; error
  * value or NULL otherwise.
  */
 struct ext4_crypto_ctx *ext4_get_crypto_ctx(struct inode *inode)
 {
 	struct ext4_crypto_ctx *ctx = NULL;
 	int res = 0;
 	unsigned long flags;
 	struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;

 	if (ci == NULL)
 		return ERR_PTR(-ENOKEY);

 	/*
 	 * We first try getting the ctx from a free list because in
 	 * the common case the ctx will have an allocated and
 	 * initialized crypto tfm, so it's probably a worthwhile
 	 * optimization. For the bounce page, we first try getting it
 	 * from the kernel allocator because that's just about as fast
 	 * as getting it from a list and because a cache of free pages
 	 * should generally be a "last resort" option for a filesystem
 	 * to be able to do its job.
 	 */
 	spin_lock_irqsave(&ext4_crypto_ctx_lock, flags);
 	ctx = list_first_entry_or_null(&ext4_free_crypto_ctxs,
 				       struct ext4_crypto_ctx, free_list);
 	if (ctx)
 		list_del(&ctx->free_list);
 	spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags);
 	if (!ctx) {
 		ctx = kmem_cache_zalloc(ext4_crypto_ctx_cachep, GFP_NOFS);
 		if (!ctx) {
 			res = -ENOMEM;
 			goto out;
 		}
 		ctx->flags |= EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL;
 	} else {
 		ctx->flags &= ~EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL;
 	}
 	ctx->flags &= ~EXT4_WRITE_PATH_FL;

 out:
 	if (res) {
 		if (!IS_ERR_OR_NULL(ctx))
 			ext4_release_crypto_ctx(ctx);
 		ctx = ERR_PTR(res);
 	}
 	return ctx;
 }

 struct workqueue_struct *ext4_read_workqueue;
 static DEFINE_MUTEX(crypto_init);

 /**
  * ext4_exit_crypto() - Shutdown the ext4 encryption system
  */
 void ext4_exit_crypto(void)
 {
 	struct ext4_crypto_ctx *pos, *n;

 	list_for_each_entry_safe(pos, n, &ext4_free_crypto_ctxs, free_list)
 		kmem_cache_free(ext4_crypto_ctx_cachep, pos);
 	INIT_LIST_HEAD(&ext4_free_crypto_ctxs);
 	if (ext4_bounce_page_pool)
 		mempool_destroy(ext4_bounce_page_pool);
 	ext4_bounce_page_pool = NULL;
 	if (ext4_read_workqueue)
 		destroy_workqueue(ext4_read_workqueue);
 	ext4_read_workqueue = NULL;
 	if (ext4_crypto_ctx_cachep)
 		kmem_cache_destroy(ext4_crypto_ctx_cachep);
 	ext4_crypto_ctx_cachep = NULL;
 	if (ext4_crypt_info_cachep)
 		kmem_cache_destroy(ext4_crypt_info_cachep);
 	ext4_crypt_info_cachep = NULL;
 }

 /**
  * ext4_init_crypto() - Set up for ext4 encryption.
  *
  * We only call this when we start accessing encrypted files, since it
  * results in memory getting allocated that wouldn't otherwise be used.
  *
  * Return: Zero on success, non-zero otherwise.
  */
 int ext4_init_crypto(void)
 {
 	int i, res = -ENOMEM;

 	mutex_lock(&crypto_init);
 	if (ext4_read_workqueue)
 		goto already_initialized;
 	ext4_read_workqueue = alloc_workqueue("ext4_crypto", WQ_HIGHPRI, 0);
 	if (!ext4_read_workqueue)
 		goto fail;

 	ext4_crypto_ctx_cachep = KMEM_CACHE(ext4_crypto_ctx,
 					    SLAB_RECLAIM_ACCOUNT);
 	if (!ext4_crypto_ctx_cachep)
 		goto fail;

 	ext4_crypt_info_cachep = KMEM_CACHE(ext4_crypt_info,
 					    SLAB_RECLAIM_ACCOUNT);
 	if (!ext4_crypt_info_cachep)
 		goto fail;

 	for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
 		struct ext4_crypto_ctx *ctx;

 		ctx = kmem_cache_zalloc(ext4_crypto_ctx_cachep, GFP_NOFS);
 		if (!ctx) {
 			res = -ENOMEM;
 			goto fail;
 		}
 		list_add(&ctx->free_list, &ext4_free_crypto_ctxs);
 	}

 	ext4_bounce_page_pool =
 		mempool_create_page_pool(num_prealloc_crypto_pages, 0);
 	if (!ext4_bounce_page_pool) {
 		res = -ENOMEM;
 		goto fail;
 	}
 already_initialized:
 	mutex_unlock(&crypto_init);
 	return 0;
 fail:
 	ext4_exit_crypto();
 	mutex_unlock(&crypto_init);
 	return res;
 }

 void ext4_restore_control_page(struct page *data_page)
 {
 	struct ext4_crypto_ctx *ctx =
 		(struct ext4_crypto_ctx *)page_private(data_page);

 	set_page_private(data_page, (unsigned long)NULL);
 	ClearPagePrivate(data_page);
 	unlock_page(data_page);
 	ext4_release_crypto_ctx(ctx);
 }

 /**
  * ext4_crypt_complete() - The completion callback for page encryption
  * @req: The asynchronous encryption request context
  * @res: The result of the encryption operation
  */
 static void ext4_crypt_complete(struct crypto_async_request *req, int res)
 {
 	struct ext4_completion_result *ecr = req->data;

 	if (res == -EINPROGRESS)
 		return;
 	ecr->res = res;
 	complete(&ecr->completion);
 }

 typedef enum {
 	EXT4_DECRYPT = 0,
 	EXT4_ENCRYPT,
 } ext4_direction_t;

 static int ext4_page_crypto(struct inode *inode,
 			    ext4_direction_t rw,
 			    pgoff_t index,
 			    struct page *src_page,
 			    struct page *dest_page)

 {
 	u8 xts_tweak[EXT4_XTS_TWEAK_SIZE];
 	struct ablkcipher_request *req = NULL;
 	DECLARE_EXT4_COMPLETION_RESULT(ecr);
 	struct scatterlist dst, src;
 	struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
 	struct crypto_ablkcipher *tfm = ci->ci_ctfm;
 	int res = 0;

 	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
 	if (!req) {
 		printk_ratelimited(KERN_ERR
 				   "%s: crypto_request_alloc() failed\n",
 				   __func__);
 		return -ENOMEM;
 	}
 	ablkcipher_request_set_callback(
 		req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 		ext4_crypt_complete, &ecr);

 	BUILD_BUG_ON(EXT4_XTS_TWEAK_SIZE < sizeof(index));
 	memcpy(xts_tweak, &index, sizeof(index));
 	memset(&xts_tweak[sizeof(index)], 0,
 	       EXT4_XTS_TWEAK_SIZE - sizeof(index));

 	sg_init_table(&dst, 1);
 	sg_set_page(&dst, dest_page, PAGE_CACHE_SIZE, 0);
 	sg_init_table(&src, 1);
 	sg_set_page(&src, src_page, PAGE_CACHE_SIZE, 0);
 	ablkcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE,
 				     xts_tweak);
 	if (rw == EXT4_DECRYPT)
 		res = crypto_ablkcipher_decrypt(req);
 	else
 		res = crypto_ablkcipher_encrypt(req);
 	if (res == -EINPROGRESS || res == -EBUSY) {
 		wait_for_completion(&ecr.completion);
 		res = ecr.res;
 	}
 	ablkcipher_request_free(req);
 	if (res) {
 		printk_ratelimited(
 			KERN_ERR
 			"%s: crypto_ablkcipher_encrypt() returned %d\n",
 			__func__, res);
 		return res;
 	}
 	return 0;
 }

 static struct page *alloc_bounce_page(struct ext4_crypto_ctx *ctx)
 {
 	ctx->w.bounce_page = mempool_alloc(ext4_bounce_page_pool, GFP_NOWAIT);
 	if (ctx->w.bounce_page == NULL)
 		return ERR_PTR(-ENOMEM);
 	ctx->flags |= EXT4_WRITE_PATH_FL;
 	return ctx->w.bounce_page;
 }

 /**
  * ext4_encrypt() - Encrypts a page
  * @inode:          The inode for which the encryption should take place
  * @plaintext_page: The page to encrypt. Must be locked.
  *
  * Allocates a ciphertext page and encrypts plaintext_page into it using the ctx
  * encryption context.
  *
  * Called on the page write path.  The caller must call
  * ext4_restore_control_page() on the returned ciphertext page to
  * release the bounce buffer and the encryption context.
  *
  * Return: An allocated page with the encrypted content on success. Else, an
  * error value or NULL.
  */
 struct page *ext4_encrypt(struct inode *inode,
 			  struct page *plaintext_page)
 {
 	struct ext4_crypto_ctx *ctx;
 	struct page *ciphertext_page = NULL;
 	int err;

 	BUG_ON(!PageLocked(plaintext_page));

 	ctx = ext4_get_crypto_ctx(inode);
 	if (IS_ERR(ctx))
 		return (struct page *) ctx;

 	/* The encryption operation will require a bounce page. */
 	ciphertext_page = alloc_bounce_page(ctx);
 	if (IS_ERR(ciphertext_page))
 		goto errout;
 	ctx->w.control_page = plaintext_page;
 	err = ext4_page_crypto(inode, EXT4_ENCRYPT, plaintext_page->index,
 			       plaintext_page, ciphertext_page);
 	if (err) {
 		ciphertext_page = ERR_PTR(err);
 	errout:
 		ext4_release_crypto_ctx(ctx);
 		return ciphertext_page;
 	}
 	SetPagePrivate(ciphertext_page);
 	set_page_private(ciphertext_page, (unsigned long)ctx);
 	lock_page(ciphertext_page);
 	return ciphertext_page;
 }

 /**
  * ext4_decrypt() - Decrypts a page in-place
  * @ctx:  The encryption context.
  * @page: The page to decrypt. Must be locked.
  *
  * Decrypts page in-place using the ctx encryption context.
  *
  * Called from the read completion callback.
  *
  * Return: Zero on success, non-zero otherwise.
  */
 int ext4_decrypt(struct page *page)
 {
 	BUG_ON(!PageLocked(page));

 	return ext4_page_crypto(page->mapping->host,
 				EXT4_DECRYPT, page->index, page, page);
 }

 int ext4_encrypted_zeroout(struct inode *inode, struct ext4_extent *ex)
 {
 	struct ext4_crypto_ctx	*ctx;
 	struct page		*ciphertext_page = NULL;
 	struct bio		*bio;
 	ext4_lblk_t		lblk = le32_to_cpu(ex->ee_block);
 	ext4_fsblk_t		pblk = ext4_ext_pblock(ex);
 	unsigned int		len = ext4_ext_get_actual_len(ex);
 	int			ret, err = 0;

 #if 0
 	ext4_msg(inode->i_sb, KERN_CRIT,
 		 "ext4_encrypted_zeroout ino %lu lblk %u len %u",
 		 (unsigned long) inode->i_ino, lblk, len);
 #endif

 	BUG_ON(inode->i_sb->s_blocksize != PAGE_CACHE_SIZE);

 	ctx = ext4_get_crypto_ctx(inode);
 	if (IS_ERR(ctx))
 		return PTR_ERR(ctx);

 	ciphertext_page = alloc_bounce_page(ctx);
 	if (IS_ERR(ciphertext_page)) {
 		err = PTR_ERR(ciphertext_page);
 		goto errout;
 	}

 	while (len--) {
 		err = ext4_page_crypto(inode, EXT4_ENCRYPT, lblk,
 				       ZERO_PAGE(0), ciphertext_page);
 		if (err)
 			goto errout;

 		bio = bio_alloc(GFP_KERNEL, 1);
 		if (!bio) {
 			err = -ENOMEM;
 			goto errout;
 		}
 		bio->bi_bdev = inode->i_sb->s_bdev;
 		bio->bi_iter.bi_sector =
 			pblk << (inode->i_sb->s_blocksize_bits - 9);
 		ret = bio_add_page(bio, ciphertext_page,
 				   inode->i_sb->s_blocksize, 0);
 		if (ret != inode->i_sb->s_blocksize) {
 			/* should never happen! */
 			ext4_msg(inode->i_sb, KERN_ERR,
 				 "bio_add_page failed: %d", ret);
 			WARN_ON(1);
 			bio_put(bio);
 			err = -EIO;
 			goto errout;
 		}
 		err = submit_bio_wait(WRITE, bio);
 		if ((err == 0) && bio->bi_error)
 			err = -EIO;
 		bio_put(bio);
 		if (err)
 			goto errout;
 		lblk++; pblk++;
 	}
 	err = 0;
 errout:
 	ext4_release_crypto_ctx(ctx);
 	return err;
 }

 bool ext4_valid_contents_enc_mode(uint32_t mode)
 {
 	return (mode == EXT4_ENCRYPTION_MODE_AES_256_XTS);
 }

 /**
  * ext4_validate_encryption_key_size() - Validate the encryption key size
  * @mode: The key mode.
  * @size: The key size to validate.
  *
  * Return: The validated key size for @mode. Zero if invalid.
  */
 uint32_t ext4_validate_encryption_key_size(uint32_t mode, uint32_t size)
 {
 	if (size == ext4_encryption_key_size(mode))
 		return size;
 	return 0;
 }
	/*
	* linux/fs/ext4/crypto.c
	*
	* Copyright (C) 2015, Google, Inc.
	*
	* This contains encryption functions for ext4
	*
	* Written by Michael Halcrow, 2014.
	*
	* Filename encryption additions
	* Uday Savagaonkar, 2014
	* Encryption policy handling additions
	* Ildar Muslukhov, 2014
	*
	* This has not yet undergone a rigorous security audit.
	*
	* The usage of AES-XTS should conform to recommendations in NIST
	* Special Publication 800-38E and IEEE P1619/D16.
	*/

	#include <crypto/hash.h>
	#include <crypto/sha.h>
	#include <keys/user-type.h>
	#include <keys/encrypted-type.h>
	#include <linux/crypto.h>
	#include <linux/ecryptfs.h>
	#include <linux/gfp.h>
	#include <linux/kernel.h>
	#include <linux/key.h>
	#include <linux/list.h>
	#include <linux/mempool.h>
	#include <linux/module.h>
	#include <linux/mutex.h>
	#include <linux/random.h>
	#include <linux/scatterlist.h>
	#include <linux/spinlock_types.h>

	#include "ext4_extents.h"
	#include "xattr.h"

	/* Encryption added and removed here! (L: */

	static unsigned int num_prealloc_crypto_pages = 32;
	static unsigned int num_prealloc_crypto_ctxs = 128;

	module_param(num_prealloc_crypto_pages, uint, 0444);
	MODULE_PARM_DESC(num_prealloc_crypto_pages,
	"Number of crypto pages to preallocate");
	module_param(num_prealloc_crypto_ctxs, uint, 0444);
	MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
	"Number of crypto contexts to preallocate");

	static mempool_t *ext4_bounce_page_pool;

	static LIST_HEAD(ext4_free_crypto_ctxs);
	static DEFINE_SPINLOCK(ext4_crypto_ctx_lock);

	static struct kmem_cache *ext4_crypto_ctx_cachep;
	struct kmem_cache *ext4_crypt_info_cachep;

	/**
	* ext4_release_crypto_ctx() - Releases an encryption context
	* @ctx: The encryption context to release.
	*
	* If the encryption context was allocated from the pre-allocated pool, returns
	* it to that pool. Else, frees it.
	*
	* If there's a bounce page in the context, this frees that.
	*/
	void ext4_release_crypto_ctx(struct ext4_crypto_ctx *ctx)
	{
	unsigned long flags;

	if (ctx->flags & EXT4_WRITE_PATH_FL && ctx->w.bounce_page)
	mempool_free(ctx->w.bounce_page, ext4_bounce_page_pool);
	ctx->w.bounce_page = NULL;
	ctx->w.control_page = NULL;
	if (ctx->flags & EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL) {
	kmem_cache_free(ext4_crypto_ctx_cachep, ctx);
	} else {
	spin_lock_irqsave(&ext4_crypto_ctx_lock, flags);
	list_add(&ctx->free_list, &ext4_free_crypto_ctxs);
	spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags);
	}
	}

	/**
	* ext4_get_crypto_ctx() - Gets an encryption context
	* @inode: The inode for which we are doing the crypto
	*
	* Allocates and initializes an encryption context.
	*
	* Return: An allocated and initialized encryption context on success; error
	* value or NULL otherwise.
	*/
	struct ext4_crypto_ctx ext4_get_crypto_ctx(struct inode inode)
	{
	struct ext4_crypto_ctx *ctx = NULL;
	int res = 0;
	unsigned long flags;
	struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;

	if (ci == NULL)
	return ERR_PTR(-ENOKEY);

	/*
	* We first try getting the ctx from a free list because in
	* the common case the ctx will have an allocated and
	* initialized crypto tfm, so it's probably a worthwhile
	* optimization. For the bounce page, we first try getting it
	* from the kernel allocator because that's just about as fast
	* as getting it from a list and because a cache of free pages
	* should generally be a "last resort" option for a filesystem
	* to be able to do its job.
	*/
	spin_lock_irqsave(&ext4_crypto_ctx_lock, flags);
	ctx = list_first_entry_or_null(&ext4_free_crypto_ctxs,
	struct ext4_crypto_ctx, free_list);
	if (ctx)
	list_del(&ctx->free_list);
	spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags);
	if (!ctx) {
	ctx = kmem_cache_zalloc(ext4_crypto_ctx_cachep, GFP_NOFS);
	if (!ctx) {
	res = -ENOMEM;
	goto out;
	}
	ctx->flags \|= EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL;
	} else {
	ctx->flags &= ~EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL;
	}
	ctx->flags &= ~EXT4_WRITE_PATH_FL;

	out:
	if (res) {
	if (!IS_ERR_OR_NULL(ctx))
	ext4_release_crypto_ctx(ctx);
	ctx = ERR_PTR(res);
	}
	return ctx;
	}

	struct workqueue_struct *ext4_read_workqueue;
	static DEFINE_MUTEX(crypto_init);

	/**
	* ext4_exit_crypto() - Shutdown the ext4 encryption system
	*/
	void ext4_exit_crypto(void)
	{
	struct ext4_crypto_ctx pos, n;

	list_for_each_entry_safe(pos, n, &ext4_free_crypto_ctxs, free_list)
	kmem_cache_free(ext4_crypto_ctx_cachep, pos);
	INIT_LIST_HEAD(&ext4_free_crypto_ctxs);
	if (ext4_bounce_page_pool)
	mempool_destroy(ext4_bounce_page_pool);
	ext4_bounce_page_pool = NULL;
	if (ext4_read_workqueue)
	destroy_workqueue(ext4_read_workqueue);
	ext4_read_workqueue = NULL;
	if (ext4_crypto_ctx_cachep)
	kmem_cache_destroy(ext4_crypto_ctx_cachep);
	ext4_crypto_ctx_cachep = NULL;
	if (ext4_crypt_info_cachep)
	kmem_cache_destroy(ext4_crypt_info_cachep);
	ext4_crypt_info_cachep = NULL;
	}

	/**
	* ext4_init_crypto() - Set up for ext4 encryption.
	*
	* We only call this when we start accessing encrypted files, since it
	* results in memory getting allocated that wouldn't otherwise be used.
	*
	* Return: Zero on success, non-zero otherwise.
	*/
	int ext4_init_crypto(void)
	{
	int i, res = -ENOMEM;

	mutex_lock(&crypto_init);
	if (ext4_read_workqueue)
	goto already_initialized;
	ext4_read_workqueue = alloc_workqueue("ext4_crypto", WQ_HIGHPRI, 0);
	if (!ext4_read_workqueue)
	goto fail;

	ext4_crypto_ctx_cachep = KMEM_CACHE(ext4_crypto_ctx,
	SLAB_RECLAIM_ACCOUNT);
	if (!ext4_crypto_ctx_cachep)
	goto fail;

	ext4_crypt_info_cachep = KMEM_CACHE(ext4_crypt_info,
	SLAB_RECLAIM_ACCOUNT);
	if (!ext4_crypt_info_cachep)
	goto fail;

	for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
	struct ext4_crypto_ctx *ctx;

	ctx = kmem_cache_zalloc(ext4_crypto_ctx_cachep, GFP_NOFS);
	if (!ctx) {
	res = -ENOMEM;
	goto fail;
	}
	list_add(&ctx->free_list, &ext4_free_crypto_ctxs);
	}

	ext4_bounce_page_pool =
	mempool_create_page_pool(num_prealloc_crypto_pages, 0);
	if (!ext4_bounce_page_pool) {
	res = -ENOMEM;
	goto fail;
	}
	already_initialized:
	mutex_unlock(&crypto_init);
	return 0;
	fail:
	ext4_exit_crypto();
	mutex_unlock(&crypto_init);
	return res;
	}

	void ext4_restore_control_page(struct page *data_page)
	{
	struct ext4_crypto_ctx *ctx =
	(struct ext4_crypto_ctx *)page_private(data_page);

	set_page_private(data_page, (unsigned long)NULL);
	ClearPagePrivate(data_page);
	unlock_page(data_page);
	ext4_release_crypto_ctx(ctx);
	}

	/**
	* ext4_crypt_complete() - The completion callback for page encryption
	* @req: The asynchronous encryption request context
	* @res: The result of the encryption operation
	*/
	static void ext4_crypt_complete(struct crypto_async_request *req, int res)
	{
	struct ext4_completion_result *ecr = req->data;

	if (res == -EINPROGRESS)
	return;
	ecr->res = res;
	complete(&ecr->completion);
	}

	typedef enum {
	EXT4_DECRYPT = 0,
	EXT4_ENCRYPT,
	} ext4_direction_t;

	static int ext4_page_crypto(struct inode *inode,
	ext4_direction_t rw,
	pgoff_t index,
	struct page *src_page,
	struct page *dest_page)

	{
	u8 xts_tweak[EXT4_XTS_TWEAK_SIZE];
	struct ablkcipher_request *req = NULL;
	DECLARE_EXT4_COMPLETION_RESULT(ecr);
	struct scatterlist dst, src;
	struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
	struct crypto_ablkcipher *tfm = ci->ci_ctfm;
	int res = 0;

	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
	if (!req) {
	printk_ratelimited(KERN_ERR
	"%s: crypto_request_alloc() failed\n",
	__func__);
	return -ENOMEM;
	}
	ablkcipher_request_set_callback(
	req, CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	ext4_crypt_complete, &ecr);

	BUILD_BUG_ON(EXT4_XTS_TWEAK_SIZE < sizeof(index));
	memcpy(xts_tweak, &index, sizeof(index));
	memset(&xts_tweak[sizeof(index)], 0,
	EXT4_XTS_TWEAK_SIZE - sizeof(index));

	sg_init_table(&dst, 1);
	sg_set_page(&dst, dest_page, PAGE_CACHE_SIZE, 0);
	sg_init_table(&src, 1);
	sg_set_page(&src, src_page, PAGE_CACHE_SIZE, 0);
	ablkcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE,
	xts_tweak);
	if (rw == EXT4_DECRYPT)
	res = crypto_ablkcipher_decrypt(req);
	else
	res = crypto_ablkcipher_encrypt(req);
	if (res == -EINPROGRESS \|\| res == -EBUSY) {
	wait_for_completion(&ecr.completion);
	res = ecr.res;
	}
	ablkcipher_request_free(req);
	if (res) {
	printk_ratelimited(
	KERN_ERR
	"%s: crypto_ablkcipher_encrypt() returned %d\n",
	__func__, res);
	return res;
	}
	return 0;
	}

	static struct page alloc_bounce_page(struct ext4_crypto_ctx ctx)
	{
	ctx->w.bounce_page = mempool_alloc(ext4_bounce_page_pool, GFP_NOWAIT);
	if (ctx->w.bounce_page == NULL)
	return ERR_PTR(-ENOMEM);
	ctx->flags \|= EXT4_WRITE_PATH_FL;
	return ctx->w.bounce_page;
	}

	/**
	* ext4_encrypt() - Encrypts a page
	* @inode: The inode for which the encryption should take place
	* @plaintext_page: The page to encrypt. Must be locked.
	*
	* Allocates a ciphertext page and encrypts plaintext_page into it using the ctx
	* encryption context.
	*
	* Called on the page write path. The caller must call
	* ext4_restore_control_page() on the returned ciphertext page to
	* release the bounce buffer and the encryption context.
	*
	* Return: An allocated page with the encrypted content on success. Else, an
	* error value or NULL.
	*/
	struct page ext4_encrypt(struct inode inode,
	struct page *plaintext_page)
	{
	struct ext4_crypto_ctx *ctx;
	struct page *ciphertext_page = NULL;
	int err;

	BUG_ON(!PageLocked(plaintext_page));

	ctx = ext4_get_crypto_ctx(inode);
	if (IS_ERR(ctx))
	return (struct page *) ctx;

	/* The encryption operation will require a bounce page. */
	ciphertext_page = alloc_bounce_page(ctx);
	if (IS_ERR(ciphertext_page))
	goto errout;
	ctx->w.control_page = plaintext_page;
	err = ext4_page_crypto(inode, EXT4_ENCRYPT, plaintext_page->index,
	plaintext_page, ciphertext_page);
	if (err) {
	ciphertext_page = ERR_PTR(err);
	errout:
	ext4_release_crypto_ctx(ctx);
	return ciphertext_page;
	}
	SetPagePrivate(ciphertext_page);
	set_page_private(ciphertext_page, (unsigned long)ctx);
	lock_page(ciphertext_page);
	return ciphertext_page;
	}

	/**
	* ext4_decrypt() - Decrypts a page in-place
	* @ctx: The encryption context.
	* @page: The page to decrypt. Must be locked.
	*
	* Decrypts page in-place using the ctx encryption context.
	*
	* Called from the read completion callback.
	*
	* Return: Zero on success, non-zero otherwise.
	*/
	int ext4_decrypt(struct page *page)
	{
	BUG_ON(!PageLocked(page));

	return ext4_page_crypto(page->mapping->host,
	EXT4_DECRYPT, page->index, page, page);
	}

	int ext4_encrypted_zeroout(struct inode inode, struct ext4_extent ex)
	{
	struct ext4_crypto_ctx *ctx;
	struct page *ciphertext_page = NULL;
	struct bio *bio;
	ext4_lblk_t lblk = le32_to_cpu(ex->ee_block);
	ext4_fsblk_t pblk = ext4_ext_pblock(ex);
	unsigned int len = ext4_ext_get_actual_len(ex);
	int ret, err = 0;

	#if 0
	ext4_msg(inode->i_sb, KERN_CRIT,
	"ext4_encrypted_zeroout ino %lu lblk %u len %u",
	(unsigned long) inode->i_ino, lblk, len);
	#endif

	BUG_ON(inode->i_sb->s_blocksize != PAGE_CACHE_SIZE);

	ctx = ext4_get_crypto_ctx(inode);
	if (IS_ERR(ctx))
	return PTR_ERR(ctx);

	ciphertext_page = alloc_bounce_page(ctx);
	if (IS_ERR(ciphertext_page)) {
	err = PTR_ERR(ciphertext_page);
	goto errout;
	}

	while (len--) {
	err = ext4_page_crypto(inode, EXT4_ENCRYPT, lblk,
	ZERO_PAGE(0), ciphertext_page);
	if (err)
	goto errout;

	bio = bio_alloc(GFP_KERNEL, 1);
	if (!bio) {
	err = -ENOMEM;
	goto errout;
	}
	bio->bi_bdev = inode->i_sb->s_bdev;
	bio->bi_iter.bi_sector =
	pblk << (inode->i_sb->s_blocksize_bits - 9);
	ret = bio_add_page(bio, ciphertext_page,
	inode->i_sb->s_blocksize, 0);
	if (ret != inode->i_sb->s_blocksize) {
	/* should never happen! */
	ext4_msg(inode->i_sb, KERN_ERR,
	"bio_add_page failed: %d", ret);
	WARN_ON(1);
	bio_put(bio);
	err = -EIO;
	goto errout;
	}
	err = submit_bio_wait(WRITE, bio);
	if ((err == 0) && bio->bi_error)
	err = -EIO;
	bio_put(bio);
	if (err)
	goto errout;
	lblk++; pblk++;
	}
	err = 0;
	errout:
	ext4_release_crypto_ctx(ctx);
	return err;
	}

	bool ext4_valid_contents_enc_mode(uint32_t mode)
	{
	return (mode == EXT4_ENCRYPTION_MODE_AES_256_XTS);
	}

	/**
	* ext4_validate_encryption_key_size() - Validate the encryption key size
	* @mode: The key mode.
	* @size: The key size to validate.
	*
	* Return: The validated key size for @mode. Zero if invalid.
	*/
	uint32_t ext4_validate_encryption_key_size(uint32_t mode, uint32_t size)
	{
	if (size == ext4_encryption_key_size(mode))
	return size;
	return 0;
	}