fs/crypto/crypto.c - kernel/msm-4.19 - Gitiles

 /*
  * This contains encryption functions for per-file encryption.
  *
  * Copyright (C) 2015, Google, Inc.
  * Copyright (C) 2015, Motorola Mobility
  *
  * Written by Michael Halcrow, 2014.
  *
  * Filename encryption additions
  *	Uday Savagaonkar, 2014
  * Encryption policy handling additions
  *	Ildar Muslukhov, 2014
  * Add fscrypt_pullback_bio_page()
  *	Jaegeuk Kim, 2015.
  *
  * 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 <linux/pagemap.h>
 #include <linux/mempool.h>
 #include <linux/module.h>
 #include <linux/scatterlist.h>
 #include <linux/ratelimit.h>
 #include <linux/dcache.h>
 #include <linux/namei.h>
 #include "fscrypt_private.h"

 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 *fscrypt_bounce_page_pool = NULL;

 static LIST_HEAD(fscrypt_free_ctxs);
 static DEFINE_SPINLOCK(fscrypt_ctx_lock);

 struct workqueue_struct *fscrypt_read_workqueue;
 static DEFINE_MUTEX(fscrypt_init_mutex);

 static struct kmem_cache *fscrypt_ctx_cachep;
 struct kmem_cache *fscrypt_info_cachep;

 /**
  * fscrypt_release_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 fscrypt_release_ctx(struct fscrypt_ctx *ctx)
 {
 	unsigned long flags;

 	if (ctx->flags & FS_CTX_HAS_BOUNCE_BUFFER_FL && ctx->w.bounce_page) {
 		mempool_free(ctx->w.bounce_page, fscrypt_bounce_page_pool);
 		ctx->w.bounce_page = NULL;
 	}
 	ctx->w.control_page = NULL;
 	if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
 		kmem_cache_free(fscrypt_ctx_cachep, ctx);
 	} else {
 		spin_lock_irqsave(&fscrypt_ctx_lock, flags);
 		list_add(&ctx->free_list, &fscrypt_free_ctxs);
 		spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
 	}
 }
 EXPORT_SYMBOL(fscrypt_release_ctx);

 /**
  * fscrypt_get_ctx() - Gets an encryption context
  * @inode:       The inode for which we are doing the crypto
  * @gfp_flags:   The gfp flag for memory allocation
  *
  * Allocates and initializes an encryption context.
  *
  * Return: An allocated and initialized encryption context on success; error
  * value or NULL otherwise.
  */
 struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *inode, gfp_t gfp_flags)
 {
 	struct fscrypt_ctx *ctx = NULL;
 	struct fscrypt_info *ci = inode->i_crypt_info;
 	unsigned long flags;

 	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(&fscrypt_ctx_lock, flags);
 	ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
 					struct fscrypt_ctx, free_list);
 	if (ctx)
 		list_del(&ctx->free_list);
 	spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
 	if (!ctx) {
 		ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
 		if (!ctx)
 			return ERR_PTR(-ENOMEM);
 		ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
 	} else {
 		ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
 	}
 	ctx->flags &= ~FS_CTX_HAS_BOUNCE_BUFFER_FL;
 	return ctx;
 }
 EXPORT_SYMBOL(fscrypt_get_ctx);

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

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

 int fscrypt_do_page_crypto(const struct inode *inode, fscrypt_direction_t rw,
 			   u64 lblk_num, struct page *src_page,
 			   struct page *dest_page, unsigned int len,
 			   unsigned int offs, gfp_t gfp_flags)
 {
 	struct {
 		__le64 index;
 		u8 padding[FS_XTS_TWEAK_SIZE - sizeof(__le64)];
 	} xts_tweak;
 	struct skcipher_request *req = NULL;
 	DECLARE_FS_COMPLETION_RESULT(ecr);
 	struct scatterlist dst, src;
 	struct fscrypt_info *ci = inode->i_crypt_info;
 	struct crypto_skcipher *tfm = ci->ci_ctfm;
 	int res = 0;

 	BUG_ON(len == 0);

 	req = skcipher_request_alloc(tfm, gfp_flags);
 	if (!req) {
 		printk_ratelimited(KERN_ERR
 				"%s: crypto_request_alloc() failed\n",
 				__func__);
 		return -ENOMEM;
 	}

 	skcipher_request_set_callback(
 		req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 		page_crypt_complete, &ecr);

 	BUILD_BUG_ON(sizeof(xts_tweak) != FS_XTS_TWEAK_SIZE);
 	xts_tweak.index = cpu_to_le64(lblk_num);
 	memset(xts_tweak.padding, 0, sizeof(xts_tweak.padding));

 	sg_init_table(&dst, 1);
 	sg_set_page(&dst, dest_page, len, offs);
 	sg_init_table(&src, 1);
 	sg_set_page(&src, src_page, len, offs);
 	skcipher_request_set_crypt(req, &src, &dst, len, &xts_tweak);
 	if (rw == FS_DECRYPT)
 		res = crypto_skcipher_decrypt(req);
 	else
 		res = crypto_skcipher_encrypt(req);
 	if (res == -EINPROGRESS || res == -EBUSY) {
 		BUG_ON(req->base.data != &ecr);
 		wait_for_completion(&ecr.completion);
 		res = ecr.res;
 	}
 	skcipher_request_free(req);
 	if (res) {
 		printk_ratelimited(KERN_ERR
 			"%s: crypto_skcipher_encrypt() returned %d\n",
 			__func__, res);
 		return res;
 	}
 	return 0;
 }

 struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx,
 				       gfp_t gfp_flags)
 {
 	ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
 	if (ctx->w.bounce_page == NULL)
 		return ERR_PTR(-ENOMEM);
 	ctx->flags |= FS_CTX_HAS_BOUNCE_BUFFER_FL;
 	return ctx->w.bounce_page;
 }

 /**
  * fscypt_encrypt_page() - Encrypts a page
  * @inode:     The inode for which the encryption should take place
  * @page:      The page to encrypt. Must be locked for bounce-page
  *             encryption.
  * @len:       Length of data to encrypt in @page and encrypted
  *             data in returned page.
  * @offs:      Offset of data within @page and returned
  *             page holding encrypted data.
  * @lblk_num:  Logical block number. This must be unique for multiple
  *             calls with same inode, except when overwriting
  *             previously written data.
  * @gfp_flags: The gfp flag for memory allocation
  *
  * Encrypts @page using the ctx encryption context. Performs encryption
  * either in-place or into a newly allocated bounce page.
  * Called on the page write path.
  *
  * Bounce page allocation is the default.
  * In this case, the contents of @page are encrypted and stored in an
  * allocated bounce page. @page has to be locked and the caller must call
  * fscrypt_restore_control_page() on the returned ciphertext page to
  * release the bounce buffer and the encryption context.
  *
  * In-place encryption is used by setting the FS_CFLG_OWN_PAGES flag in
  * fscrypt_operations. Here, the input-page is returned with its content
  * encrypted.
  *
  * Return: A page with the encrypted content on success. Else, an
  * error value or NULL.
  */
 struct page *fscrypt_encrypt_page(const struct inode *inode,
 				struct page *page,
 				unsigned int len,
 				unsigned int offs,
 				u64 lblk_num, gfp_t gfp_flags)

 {
 	struct fscrypt_ctx *ctx;
 	struct page *ciphertext_page = page;
 	int err;

 	BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0);

 	if (inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES) {
 		/* with inplace-encryption we just encrypt the page */
 		err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num, page,
 					     ciphertext_page, len, offs,
 					     gfp_flags);
 		if (err)
 			return ERR_PTR(err);

 		return ciphertext_page;
 	}

 	BUG_ON(!PageLocked(page));

 	ctx = fscrypt_get_ctx(inode, gfp_flags);
 	if (IS_ERR(ctx))
 		return (struct page *)ctx;

 	/* The encryption operation will require a bounce page. */
 	ciphertext_page = fscrypt_alloc_bounce_page(ctx, gfp_flags);
 	if (IS_ERR(ciphertext_page))
 		goto errout;

 	ctx->w.control_page = page;
 	err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num,
 				     page, ciphertext_page, len, offs,
 				     gfp_flags);
 	if (err) {
 		ciphertext_page = ERR_PTR(err);
 		goto errout;
 	}
 	SetPagePrivate(ciphertext_page);
 	set_page_private(ciphertext_page, (unsigned long)ctx);
 	lock_page(ciphertext_page);
 	return ciphertext_page;

 errout:
 	fscrypt_release_ctx(ctx);
 	return ciphertext_page;
 }
 EXPORT_SYMBOL(fscrypt_encrypt_page);

 /**
  * fscrypt_decrypt_page() - Decrypts a page in-place
  * @inode:     The corresponding inode for the page to decrypt.
  * @page:      The page to decrypt. Must be locked in case
  *             it is a writeback page (FS_CFLG_OWN_PAGES unset).
  * @len:       Number of bytes in @page to be decrypted.
  * @offs:      Start of data in @page.
  * @lblk_num:  Logical block number.
  *
  * Decrypts page in-place using the ctx encryption context.
  *
  * Called from the read completion callback.
  *
  * Return: Zero on success, non-zero otherwise.
  */
 int fscrypt_decrypt_page(const struct inode *inode, struct page *page,
 			unsigned int len, unsigned int offs, u64 lblk_num)
 {
 	if (!(inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES))
 		BUG_ON(!PageLocked(page));

 	return fscrypt_do_page_crypto(inode, FS_DECRYPT, lblk_num, page, page,
 				      len, offs, GFP_NOFS);
 }
 EXPORT_SYMBOL(fscrypt_decrypt_page);

 /*
  * Validate dentries for encrypted directories to make sure we aren't
  * potentially caching stale data after a key has been added or
  * removed.
  */
 static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
 {
 	struct dentry *dir;
 	int dir_has_key, cached_with_key;

 	if (flags & LOOKUP_RCU)
 		return -ECHILD;

 	dir = dget_parent(dentry);
 	if (!d_inode(dir)->i_sb->s_cop->is_encrypted(d_inode(dir))) {
 		dput(dir);
 		return 0;
 	}

 	/* this should eventually be an flag in d_flags */
 	spin_lock(&dentry->d_lock);
 	cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY;
 	spin_unlock(&dentry->d_lock);
 	dir_has_key = (d_inode(dir)->i_crypt_info != NULL);
 	dput(dir);

 	/*
 	 * If the dentry was cached without the key, and it is a
 	 * negative dentry, it might be a valid name.  We can't check
 	 * if the key has since been made available due to locking
 	 * reasons, so we fail the validation so ext4_lookup() can do
 	 * this check.
 	 *
 	 * We also fail the validation if the dentry was created with
 	 * the key present, but we no longer have the key, or vice versa.
 	 */
 	if ((!cached_with_key && d_is_negative(dentry)) ||
 			(!cached_with_key && dir_has_key) ||
 			(cached_with_key && !dir_has_key))
 		return 0;
 	return 1;
 }

 const struct dentry_operations fscrypt_d_ops = {
 	.d_revalidate = fscrypt_d_revalidate,
 };
 EXPORT_SYMBOL(fscrypt_d_ops);

 void fscrypt_restore_control_page(struct page *page)
 {
 	struct fscrypt_ctx *ctx;

 	ctx = (struct fscrypt_ctx *)page_private(page);
 	set_page_private(page, (unsigned long)NULL);
 	ClearPagePrivate(page);
 	unlock_page(page);
 	fscrypt_release_ctx(ctx);
 }
 EXPORT_SYMBOL(fscrypt_restore_control_page);

 static void fscrypt_destroy(void)
 {
 	struct fscrypt_ctx *pos, *n;

 	list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
 		kmem_cache_free(fscrypt_ctx_cachep, pos);
 	INIT_LIST_HEAD(&fscrypt_free_ctxs);
 	mempool_destroy(fscrypt_bounce_page_pool);
 	fscrypt_bounce_page_pool = NULL;
 }

 /**
  * fscrypt_initialize() - allocate major buffers for fs encryption.
  * @cop_flags:  fscrypt operations flags
  *
  * 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 fscrypt_initialize(unsigned int cop_flags)
 {
 	int i, res = -ENOMEM;

 	/*
 	 * No need to allocate a bounce page pool if there already is one or
 	 * this FS won't use it.
 	 */
 	if (cop_flags & FS_CFLG_OWN_PAGES || fscrypt_bounce_page_pool)
 		return 0;

 	mutex_lock(&fscrypt_init_mutex);
 	if (fscrypt_bounce_page_pool)
 		goto already_initialized;

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

 		ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
 		if (!ctx)
 			goto fail;
 		list_add(&ctx->free_list, &fscrypt_free_ctxs);
 	}

 	fscrypt_bounce_page_pool =
 		mempool_create_page_pool(num_prealloc_crypto_pages, 0);
 	if (!fscrypt_bounce_page_pool)
 		goto fail;

 already_initialized:
 	mutex_unlock(&fscrypt_init_mutex);
 	return 0;
 fail:
 	fscrypt_destroy();
 	mutex_unlock(&fscrypt_init_mutex);
 	return res;
 }

 /**
  * fscrypt_init() - Set up for fs encryption.
  */
 static int __init fscrypt_init(void)
 {
 	fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
 							WQ_HIGHPRI, 0);
 	if (!fscrypt_read_workqueue)
 		goto fail;

 	fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
 	if (!fscrypt_ctx_cachep)
 		goto fail_free_queue;

 	fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
 	if (!fscrypt_info_cachep)
 		goto fail_free_ctx;

 	return 0;

 fail_free_ctx:
 	kmem_cache_destroy(fscrypt_ctx_cachep);
 fail_free_queue:
 	destroy_workqueue(fscrypt_read_workqueue);
 fail:
 	return -ENOMEM;
 }
 module_init(fscrypt_init)

 /**
  * fscrypt_exit() - Shutdown the fs encryption system
  */
 static void __exit fscrypt_exit(void)
 {
 	fscrypt_destroy();

 	if (fscrypt_read_workqueue)
 		destroy_workqueue(fscrypt_read_workqueue);
 	kmem_cache_destroy(fscrypt_ctx_cachep);
 	kmem_cache_destroy(fscrypt_info_cachep);
 }
 module_exit(fscrypt_exit);

 MODULE_LICENSE("GPL");
	/*
	* This contains encryption functions for per-file encryption.
	*
	* Copyright (C) 2015, Google, Inc.
	* Copyright (C) 2015, Motorola Mobility
	*
	* Written by Michael Halcrow, 2014.
	*
	* Filename encryption additions
	* Uday Savagaonkar, 2014
	* Encryption policy handling additions
	* Ildar Muslukhov, 2014
	* Add fscrypt_pullback_bio_page()
	* Jaegeuk Kim, 2015.
	*
	* 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 <linux/pagemap.h>
	#include <linux/mempool.h>
	#include <linux/module.h>
	#include <linux/scatterlist.h>
	#include <linux/ratelimit.h>
	#include <linux/dcache.h>
	#include <linux/namei.h>
	#include "fscrypt_private.h"

	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 *fscrypt_bounce_page_pool = NULL;

	static LIST_HEAD(fscrypt_free_ctxs);
	static DEFINE_SPINLOCK(fscrypt_ctx_lock);

	struct workqueue_struct *fscrypt_read_workqueue;
	static DEFINE_MUTEX(fscrypt_init_mutex);

	static struct kmem_cache *fscrypt_ctx_cachep;
	struct kmem_cache *fscrypt_info_cachep;

	/**
	* fscrypt_release_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 fscrypt_release_ctx(struct fscrypt_ctx *ctx)
	{
	unsigned long flags;

	if (ctx->flags & FS_CTX_HAS_BOUNCE_BUFFER_FL && ctx->w.bounce_page) {
	mempool_free(ctx->w.bounce_page, fscrypt_bounce_page_pool);
	ctx->w.bounce_page = NULL;
	}
	ctx->w.control_page = NULL;
	if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
	kmem_cache_free(fscrypt_ctx_cachep, ctx);
	} else {
	spin_lock_irqsave(&fscrypt_ctx_lock, flags);
	list_add(&ctx->free_list, &fscrypt_free_ctxs);
	spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
	}
	}
	EXPORT_SYMBOL(fscrypt_release_ctx);

	/**
	* fscrypt_get_ctx() - Gets an encryption context
	* @inode: The inode for which we are doing the crypto
	* @gfp_flags: The gfp flag for memory allocation
	*
	* Allocates and initializes an encryption context.
	*
	* Return: An allocated and initialized encryption context on success; error
	* value or NULL otherwise.
	*/
	struct fscrypt_ctx fscrypt_get_ctx(const struct inode inode, gfp_t gfp_flags)
	{
	struct fscrypt_ctx *ctx = NULL;
	struct fscrypt_info *ci = inode->i_crypt_info;
	unsigned long flags;

	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(&fscrypt_ctx_lock, flags);
	ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
	struct fscrypt_ctx, free_list);
	if (ctx)
	list_del(&ctx->free_list);
	spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
	if (!ctx) {
	ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
	if (!ctx)
	return ERR_PTR(-ENOMEM);
	ctx->flags \|= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
	} else {
	ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
	}
	ctx->flags &= ~FS_CTX_HAS_BOUNCE_BUFFER_FL;
	return ctx;
	}
	EXPORT_SYMBOL(fscrypt_get_ctx);

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

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

	int fscrypt_do_page_crypto(const struct inode *inode, fscrypt_direction_t rw,
	u64 lblk_num, struct page *src_page,
	struct page *dest_page, unsigned int len,
	unsigned int offs, gfp_t gfp_flags)
	{
	struct {
	__le64 index;
	u8 padding[FS_XTS_TWEAK_SIZE - sizeof(__le64)];
	} xts_tweak;
	struct skcipher_request *req = NULL;
	DECLARE_FS_COMPLETION_RESULT(ecr);
	struct scatterlist dst, src;
	struct fscrypt_info *ci = inode->i_crypt_info;
	struct crypto_skcipher *tfm = ci->ci_ctfm;
	int res = 0;

	BUG_ON(len == 0);

	req = skcipher_request_alloc(tfm, gfp_flags);
	if (!req) {
	printk_ratelimited(KERN_ERR
	"%s: crypto_request_alloc() failed\n",
	__func__);
	return -ENOMEM;
	}

	skcipher_request_set_callback(
	req, CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	page_crypt_complete, &ecr);

	BUILD_BUG_ON(sizeof(xts_tweak) != FS_XTS_TWEAK_SIZE);
	xts_tweak.index = cpu_to_le64(lblk_num);
	memset(xts_tweak.padding, 0, sizeof(xts_tweak.padding));

	sg_init_table(&dst, 1);
	sg_set_page(&dst, dest_page, len, offs);
	sg_init_table(&src, 1);
	sg_set_page(&src, src_page, len, offs);
	skcipher_request_set_crypt(req, &src, &dst, len, &xts_tweak);
	if (rw == FS_DECRYPT)
	res = crypto_skcipher_decrypt(req);
	else
	res = crypto_skcipher_encrypt(req);
	if (res == -EINPROGRESS \|\| res == -EBUSY) {
	BUG_ON(req->base.data != &ecr);
	wait_for_completion(&ecr.completion);
	res = ecr.res;
	}
	skcipher_request_free(req);
	if (res) {
	printk_ratelimited(KERN_ERR
	"%s: crypto_skcipher_encrypt() returned %d\n",
	__func__, res);
	return res;
	}
	return 0;
	}

	struct page fscrypt_alloc_bounce_page(struct fscrypt_ctx ctx,
	gfp_t gfp_flags)
	{
	ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
	if (ctx->w.bounce_page == NULL)
	return ERR_PTR(-ENOMEM);
	ctx->flags \|= FS_CTX_HAS_BOUNCE_BUFFER_FL;
	return ctx->w.bounce_page;
	}

	/**
	* fscypt_encrypt_page() - Encrypts a page
	* @inode: The inode for which the encryption should take place
	* @page: The page to encrypt. Must be locked for bounce-page
	* encryption.
	* @len: Length of data to encrypt in @page and encrypted
	* data in returned page.
	* @offs: Offset of data within @page and returned
	* page holding encrypted data.
	* @lblk_num: Logical block number. This must be unique for multiple
	* calls with same inode, except when overwriting
	* previously written data.
	* @gfp_flags: The gfp flag for memory allocation
	*
	* Encrypts @page using the ctx encryption context. Performs encryption
	* either in-place or into a newly allocated bounce page.
	* Called on the page write path.
	*
	* Bounce page allocation is the default.
	* In this case, the contents of @page are encrypted and stored in an
	* allocated bounce page. @page has to be locked and the caller must call
	* fscrypt_restore_control_page() on the returned ciphertext page to
	* release the bounce buffer and the encryption context.
	*
	* In-place encryption is used by setting the FS_CFLG_OWN_PAGES flag in
	* fscrypt_operations. Here, the input-page is returned with its content
	* encrypted.
	*
	* Return: A page with the encrypted content on success. Else, an
	* error value or NULL.
	*/
	struct page fscrypt_encrypt_page(const struct inode inode,
	struct page *page,
	unsigned int len,
	unsigned int offs,
	u64 lblk_num, gfp_t gfp_flags)

	{
	struct fscrypt_ctx *ctx;
	struct page *ciphertext_page = page;
	int err;

	BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0);

	if (inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES) {
	/* with inplace-encryption we just encrypt the page */
	err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num, page,
	ciphertext_page, len, offs,
	gfp_flags);
	if (err)
	return ERR_PTR(err);

	return ciphertext_page;
	}

	BUG_ON(!PageLocked(page));

	ctx = fscrypt_get_ctx(inode, gfp_flags);
	if (IS_ERR(ctx))
	return (struct page *)ctx;

	/* The encryption operation will require a bounce page. */
	ciphertext_page = fscrypt_alloc_bounce_page(ctx, gfp_flags);
	if (IS_ERR(ciphertext_page))
	goto errout;

	ctx->w.control_page = page;
	err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num,
	page, ciphertext_page, len, offs,
	gfp_flags);
	if (err) {
	ciphertext_page = ERR_PTR(err);
	goto errout;
	}
	SetPagePrivate(ciphertext_page);
	set_page_private(ciphertext_page, (unsigned long)ctx);
	lock_page(ciphertext_page);
	return ciphertext_page;

	errout:
	fscrypt_release_ctx(ctx);
	return ciphertext_page;
	}
	EXPORT_SYMBOL(fscrypt_encrypt_page);

	/**
	* fscrypt_decrypt_page() - Decrypts a page in-place
	* @inode: The corresponding inode for the page to decrypt.
	* @page: The page to decrypt. Must be locked in case
	* it is a writeback page (FS_CFLG_OWN_PAGES unset).
	* @len: Number of bytes in @page to be decrypted.
	* @offs: Start of data in @page.
	* @lblk_num: Logical block number.
	*
	* Decrypts page in-place using the ctx encryption context.
	*
	* Called from the read completion callback.
	*
	* Return: Zero on success, non-zero otherwise.
	*/
	int fscrypt_decrypt_page(const struct inode inode, struct page page,
	unsigned int len, unsigned int offs, u64 lblk_num)
	{
	if (!(inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES))
	BUG_ON(!PageLocked(page));

	return fscrypt_do_page_crypto(inode, FS_DECRYPT, lblk_num, page, page,
	len, offs, GFP_NOFS);
	}
	EXPORT_SYMBOL(fscrypt_decrypt_page);

	/*
	* Validate dentries for encrypted directories to make sure we aren't
	* potentially caching stale data after a key has been added or
	* removed.
	*/
	static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
	{
	struct dentry *dir;
	int dir_has_key, cached_with_key;

	if (flags & LOOKUP_RCU)
	return -ECHILD;

	dir = dget_parent(dentry);
	if (!d_inode(dir)->i_sb->s_cop->is_encrypted(d_inode(dir))) {
	dput(dir);
	return 0;
	}

	/* this should eventually be an flag in d_flags */
	spin_lock(&dentry->d_lock);
	cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY;
	spin_unlock(&dentry->d_lock);
	dir_has_key = (d_inode(dir)->i_crypt_info != NULL);
	dput(dir);

	/*
	* If the dentry was cached without the key, and it is a
	* negative dentry, it might be a valid name. We can't check
	* if the key has since been made available due to locking
	* reasons, so we fail the validation so ext4_lookup() can do
	* this check.
	*
	* We also fail the validation if the dentry was created with
	* the key present, but we no longer have the key, or vice versa.
	*/
	if ((!cached_with_key && d_is_negative(dentry)) \|\|
	(!cached_with_key && dir_has_key) \|\|
	(cached_with_key && !dir_has_key))
	return 0;
	return 1;
	}

	const struct dentry_operations fscrypt_d_ops = {
	.d_revalidate = fscrypt_d_revalidate,
	};
	EXPORT_SYMBOL(fscrypt_d_ops);

	void fscrypt_restore_control_page(struct page *page)
	{
	struct fscrypt_ctx *ctx;

	ctx = (struct fscrypt_ctx *)page_private(page);
	set_page_private(page, (unsigned long)NULL);
	ClearPagePrivate(page);
	unlock_page(page);
	fscrypt_release_ctx(ctx);
	}
	EXPORT_SYMBOL(fscrypt_restore_control_page);

	static void fscrypt_destroy(void)
	{
	struct fscrypt_ctx pos, n;

	list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
	kmem_cache_free(fscrypt_ctx_cachep, pos);
	INIT_LIST_HEAD(&fscrypt_free_ctxs);
	mempool_destroy(fscrypt_bounce_page_pool);
	fscrypt_bounce_page_pool = NULL;
	}

	/**
	* fscrypt_initialize() - allocate major buffers for fs encryption.
	* @cop_flags: fscrypt operations flags
	*
	* 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 fscrypt_initialize(unsigned int cop_flags)
	{
	int i, res = -ENOMEM;

	/*
	* No need to allocate a bounce page pool if there already is one or
	* this FS won't use it.
	*/
	if (cop_flags & FS_CFLG_OWN_PAGES \|\| fscrypt_bounce_page_pool)
	return 0;

	mutex_lock(&fscrypt_init_mutex);
	if (fscrypt_bounce_page_pool)
	goto already_initialized;

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

	ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
	if (!ctx)
	goto fail;
	list_add(&ctx->free_list, &fscrypt_free_ctxs);
	}

	fscrypt_bounce_page_pool =
	mempool_create_page_pool(num_prealloc_crypto_pages, 0);
	if (!fscrypt_bounce_page_pool)
	goto fail;

	already_initialized:
	mutex_unlock(&fscrypt_init_mutex);
	return 0;
	fail:
	fscrypt_destroy();
	mutex_unlock(&fscrypt_init_mutex);
	return res;
	}

	/**
	* fscrypt_init() - Set up for fs encryption.
	*/
	static int __init fscrypt_init(void)
	{
	fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
	WQ_HIGHPRI, 0);
	if (!fscrypt_read_workqueue)
	goto fail;

	fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
	if (!fscrypt_ctx_cachep)
	goto fail_free_queue;

	fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
	if (!fscrypt_info_cachep)
	goto fail_free_ctx;

	return 0;

	fail_free_ctx:
	kmem_cache_destroy(fscrypt_ctx_cachep);
	fail_free_queue:
	destroy_workqueue(fscrypt_read_workqueue);
	fail:
	return -ENOMEM;
	}
	module_init(fscrypt_init)

	/**
	* fscrypt_exit() - Shutdown the fs encryption system
	*/
	static void __exit fscrypt_exit(void)
	{
	fscrypt_destroy();

	if (fscrypt_read_workqueue)
	destroy_workqueue(fscrypt_read_workqueue);
	kmem_cache_destroy(fscrypt_ctx_cachep);
	kmem_cache_destroy(fscrypt_info_cachep);
	}
	module_exit(fscrypt_exit);

	MODULE_LICENSE("GPL");