Message-ID: <1428584082.30295.7.camel@dhcp-27-107.brq.redhat.com>
Date:	Thu, 09 Apr 2015 14:54:42 +0200
From:	Maurizio Lombardi <mlombard@...hat.com>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	jaegeuk@...nel.org, mhalcrow@...gle.com,
	Ildar Muslukhov <ildarm@...gle.com>
Subject: Re: [PATCH 08/22] ext4 crypto: add ext4 encryption facilities

On Thu, 2015-04-02 at 18:10 -0400, Theodore Ts'o wrote:
> From: Michael Halcrow <mhalcrow@...gle.com>
> 
> On encrypt, we will re-assign the buffer_heads to point to a bounce
> page rather than the control_page (which is the original page to write
> that contains the plaintext). The block I/O occurs against the bounce
> page.  On write completion, we re-assign the buffer_heads to the
> original plaintext page.
> 
> On decrypt, we will attach a read completion callback to the bio
> struct. This read completion will decrypt the read contents in-place
> prior to setting the page up-to-date.
> 
> The current encryption mode, AES-256-XTS, lacks cryptographic
> integrity. AES-256-GCM is in-plan, but we will need to devise a
> mechanism for handling the integrity data.
> 
> Change-Id: I5ed4c913d49971d7f7e9b10bb4e694df86f960d7
> Signed-off-by: Michael Halcrow <mhalcrow@...gle.com>
> Signed-off-by: Ildar Muslukhov <ildarm@...gle.com>
> Signed-off-by: Theodore Ts'o <tytso@....edu>
> ---
>  fs/ext4/Makefile        |   2 +-
>  fs/ext4/crypto.c        | 601 ++++++++++++++++++++++++++++++++++++++++++++++++
>  fs/ext4/crypto_policy.c |  21 +-
>  fs/ext4/ext4.h          |  39 ++++
>  fs/ext4/ext4_crypto.h   |  43 ++++
>  fs/ext4/super.c         |  11 +
>  6 files changed, 714 insertions(+), 3 deletions(-)
>  create mode 100644 fs/ext4/crypto.c
> 
> diff --git a/fs/ext4/Makefile b/fs/ext4/Makefile
> index 3886ee4..1b1c561 100644
> --- a/fs/ext4/Makefile
> +++ b/fs/ext4/Makefile
> @@ -12,4 +12,4 @@ ext4-y	:= balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o page-io.o \
>  
>  ext4-$(CONFIG_EXT4_FS_POSIX_ACL)	+= acl.o
>  ext4-$(CONFIG_EXT4_FS_SECURITY)		+= xattr_security.o
> -ext4-$(CONFIG_EXT4_FS_ENCRYPTION)	+= crypto_policy.o
> +ext4-$(CONFIG_EXT4_FS_ENCRYPTION)	+= crypto_policy.o crypto.o
> diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c
> new file mode 100644
> index 0000000..5b62bb1
> --- /dev/null
> +++ b/fs/ext4/crypto.c
> @@ -0,0 +1,601 @@
> +/*
> + * linux/fs/ext4/crypto.c
> + *
> + * 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. The usage of AES-GCM should conform to
> + * the recommendations in NIST Special Publication 800-38D. Further
> + * guidance for block-oriented storage is in IEEE P1619/D16. The key
> + * derivation code implements an HKDF (see RFC 5869).
> + */
> +
> +#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.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);
> +
> +/**
> + * 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->bounce_page) {
> +		if (ctx->flags & EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL)
> +			__free_page(ctx->bounce_page);
> +		else
> +			mempool_free(ctx->bounce_page, ext4_bounce_page_pool);
> +		ctx->bounce_page = NULL;
> +	}
> +	ctx->control_page = NULL;
> +	if (ctx->flags & EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL) {
> +		if (ctx->tfm)
> +			crypto_free_tfm(ctx->tfm);
> +		kfree(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_alloc_and_init_crypto_ctx() - Allocates and inits an encryption context
> + * @mask: The allocation mask.
> + *
> + * Return: An allocated and initialized encryption context on success. An error
> + * value or NULL otherwise.
> + */
> +static struct ext4_crypto_ctx *ext4_alloc_and_init_crypto_ctx(gfp_t mask)
> +{
> +	struct ext4_crypto_ctx *ctx = kzalloc(sizeof(struct ext4_crypto_ctx),
> +					      mask);
> +
> +	if (!ctx)
> +		return ERR_PTR(-ENOMEM);
> +	return ctx;
> +}
> +
> +/**
> + * 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_encryption_key *key = &EXT4_I(inode)->i_encryption_key;
> +
> +	/* 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 = ext4_alloc_and_init_crypto_ctx(GFP_NOFS);
> +		if (IS_ERR(ctx)) {
> +			res = PTR_ERR(ctx);
> +			goto out;
> +		}
> +		ctx->flags |= EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL;
> +	} else {
> +		ctx->flags &= ~EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL;
> +	}
> +
> +	/* Allocate a new Crypto API context if we don't already have one or if
> +	 * it isn't the right mode. */
> +	BUG_ON(key->mode == EXT4_ENCRYPTION_MODE_INVALID);
> +	if (ctx->tfm && (ctx->mode != key->mode)) {
> +		crypto_free_tfm(ctx->tfm);
> +		ctx->tfm = NULL;
> +		ctx->mode = EXT4_ENCRYPTION_MODE_INVALID;
> +	}
> +	if (!ctx->tfm) {
> +		switch (key->mode) {
> +		case EXT4_ENCRYPTION_MODE_AES_256_XTS:
> +			ctx->tfm = crypto_ablkcipher_tfm(
> +				crypto_alloc_ablkcipher("xts(aes)", 0, 0));
> +			break;
> +		case EXT4_ENCRYPTION_MODE_AES_256_GCM:
> +			/* TODO(mhalcrow): AEAD w/ gcm(aes);
> +			 * crypto_aead_setauthsize() */
> +			ctx->tfm = ERR_PTR(-ENOTSUPP);
> +			break;
> +		default:
> +			BUG();
> +		}
> +		if (IS_ERR_OR_NULL(ctx->tfm)) {
> +			res = PTR_ERR(ctx->tfm);
> +			ctx->tfm = NULL;
> +			goto out;
> +		}
> +		ctx->mode = key->mode;
> +	}
> +	BUG_ON(key->size != ext4_encryption_key_size(key->mode));
> +
> +	/* There shouldn't be a bounce page attached to the crypto
> +	 * context at this point. */
> +	BUG_ON(ctx->bounce_page);
> +
> +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) {
> +		if (pos->bounce_page) {
> +			if (pos->flags &
> +			    EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL) {
> +				__free_page(pos->bounce_page);
> +			} else {
> +				mempool_free(pos->bounce_page,
> +					     ext4_bounce_page_pool);
> +			}
> +		}
> +		if (pos->tfm)
> +			crypto_free_tfm(pos->tfm);
> +		kfree(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;
> +}
> +
> +/**
> + * ext4_init_crypto() - Set up for ext4 encryption.
> + *
> + * We call this when we mount a file system which has the encryption
> + * feature enabled, since it results in memory getting allocated that
> + * won't be used unless we are using encryption.
> + *
> + * Return: Zero on success, non-zero otherwise.
> + */
> +int ext4_init_crypto(void)
> +{
> +	int i, res = 0;
> +
> +	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) {
> +		res = -ENOMEM;
> +		goto fail;
> +	}
> +
> +	for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
> +		struct ext4_crypto_ctx *ctx;
> +
> +		ctx = ext4_alloc_and_init_crypto_ctx(GFP_KERNEL);
> +		if (IS_ERR(ctx)) {
> +			res = PTR_ERR(ctx);
> +			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)
> +		goto fail;
> +already_initialized:
> +	mutex_unlock(&crypto_init);
> +	return 0;
> +fail:
> +	ext4_exit_crypto();
> +	mutex_unlock(&crypto_init);
> +	return res;
> +}
> +
> +/**
> + * ext4_xts_tweak_for_page() - Generates an XTS tweak for a page
> + * @xts_tweak: Buffer into which this writes the XTS tweak.
> + * @page:      The page for which this generates a tweak.
> + *
> + * Generates an XTS tweak value for the given page.
> + */
> +static void ext4_xts_tweak_for_page(u8 xts_tweak[EXT4_XTS_TWEAK_SIZE],
> +				    const struct page *page)
> +{
> +	/* Only do this for XTS tweak values. For other modes (CBC,
> +	 * GCM, etc.), you most likely will need to do something
> +	 * different. */
> +	BUILD_BUG_ON(EXT4_XTS_TWEAK_SIZE < sizeof(page->index));
> +	memcpy(xts_tweak, &page->index, sizeof(page->index));
> +	memset(&xts_tweak[sizeof(page->index)], 0,
> +	       EXT4_XTS_TWEAK_SIZE - sizeof(page->index));
> +}
> +
> +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);
> +}
> +
> +struct ext4_crypt_result {
> +	struct completion completion;
> +	int res;
> +};
> +
> +/**
> + * 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_crypt_result *ecr = req->data;
> +
> +	if (res == -EINPROGRESS)
> +		return;
> +	ecr->res = res;
> +	complete(&ecr->completion);
> +}
> +
> +/**
> + * ext4_prep_pages_for_write() - Prepares pages for write
> + * @ciphertext_page: Ciphertext page that will actually be written.
> + * @plaintext_page:  Plaintext page that acts as a control page.
> + * @ctx:             Encryption context for the pages.
> + */
> +static void ext4_prep_pages_for_write(struct page *ciphertext_page,
> +				      struct page *plaintext_page,
> +				      struct ext4_crypto_ctx *ctx)
> +{
> +	SetPageDirty(ciphertext_page);
> +	SetPagePrivate(ciphertext_page);
> +	ctx->control_page = plaintext_page;
> +	set_page_private(ciphertext_page, (unsigned long)ctx);
> +	lock_page(ciphertext_page);
> +}
> +
> +/**
> + * ext4_xts_encrypt() - Encrypts a page using AES-256-XTS
> + * @ctx:            The encryption context.
> + * @plaintext_page: The page to encrypt. Must be locked.
> + *
> + * Allocates a ciphertext page and encrypts plaintext_page into it using the ctx
> + * encryption context. Uses AES-256-XTS.
> + *
> + * Called on the page write path.
> + *
> + * Return: An allocated page with the encrypted content on success. Else, an
> + * error value or NULL.
> + */
> +static struct page *ext4_xts_encrypt(struct ext4_crypto_ctx *ctx,
> +				     struct page *plaintext_page)
> +{
> +	struct page *ciphertext_page = ctx->bounce_page;
> +	u8 xts_tweak[EXT4_XTS_TWEAK_SIZE];
> +	struct ablkcipher_request *req = NULL;
> +	struct ext4_crypt_result ecr;
> +	struct scatterlist dst, src;
> +	struct ext4_inode_info *ei = EXT4_I(plaintext_page->mapping->host);
> +	struct crypto_ablkcipher *atfm = __crypto_ablkcipher_cast(ctx->tfm);
> +	int res = 0;
> +
> +	BUG_ON(!ciphertext_page);
> +	BUG_ON(!ctx->tfm);
> +	BUG_ON(ei->i_encryption_key.mode != EXT4_ENCRYPTION_MODE_AES_256_XTS);
> +	crypto_ablkcipher_clear_flags(atfm, ~0);
> +	crypto_tfm_set_flags(ctx->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
> +
> +	/* Since in AES-256-XTS mode we only perform one cryptographic operation
> +	 * on each block and there are no constraints about how many blocks a
> +	 * single key can encrypt, we directly use the inode master key */
> +	res = crypto_ablkcipher_setkey(atfm, ei->i_encryption_key.raw,
> +				       ei->i_encryption_key.size);
> +	req = ablkcipher_request_alloc(atfm, GFP_NOFS);
> +	if (!req) {
> +		printk_ratelimited(KERN_ERR
> +				   "%s: crypto_request_alloc() failed\n",
> +				   __func__);
> +		ciphertext_page = ERR_PTR(-ENOMEM);
> +		goto out;
> +	}
> +	ablkcipher_request_set_callback(
> +		req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
> +		ext4_crypt_complete, &ecr);
> +	ext4_xts_tweak_for_page(xts_tweak, plaintext_page);
> +	sg_init_table(&dst, 1);
> +	sg_set_page(&dst, ciphertext_page, PAGE_CACHE_SIZE, 0);
> +	sg_init_table(&src, 1);
> +	sg_set_page(&src, plaintext_page, PAGE_CACHE_SIZE, 0);
> +	ablkcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE,
> +				     xts_tweak);
> +	res = crypto_ablkcipher_encrypt(req);
> +	if (res == -EINPROGRESS || res == -EBUSY) {
> +		BUG_ON(req->base.data != &ecr);
> +		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);
> +		ciphertext_page = ERR_PTR(res);
> +		goto out;
> +	}
> +out:
> +	return ciphertext_page;
> +}
> +
> +/**
> + * ext4_encrypt() - Encrypts a page
> + * @ctx:            The encryption context.
> + * @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.
> + *
> + * 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;
> +
> +	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. */
> +	ctx->bounce_page = alloc_page(GFP_NOFS);
> +	if (!ctx->bounce_page) {
> +		/* This is a potential bottleneck, but at least we'll have
> +		 * forward progress. */
> +		ctx->bounce_page = mempool_alloc(ext4_bounce_page_pool,
> +						 GFP_NOFS);
> +		if (WARN_ON_ONCE(!ctx->bounce_page)) {
> +			ctx->bounce_page = mempool_alloc(ext4_bounce_page_pool,
> +							 GFP_NOFS | __GFP_WAIT);
> +		}
> +		ctx->flags &= ~EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
> +	} else {
> +		ctx->flags |= EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
> +	}
> +
> +	switch (ctx->mode) {
> +	case EXT4_ENCRYPTION_MODE_AES_256_XTS:
> +		ciphertext_page = ext4_xts_encrypt(ctx, plaintext_page);
> +		break;
> +	case EXT4_ENCRYPTION_MODE_AES_256_GCM:
> +		/* TODO(mhalcrow): We'll need buffers for the
> +		 * generated IV and/or auth tag for this mode and the
> +		 * ones below */
> +		ciphertext_page = ERR_PTR(-ENOTSUPP);
> +		break;
> +	default:
> +		BUG();
> +	}
> +	if (IS_ERR_OR_NULL(ciphertext_page))
> +		ext4_release_crypto_ctx(ctx);
> +	else
> +		ext4_prep_pages_for_write(ciphertext_page, plaintext_page, ctx);
> +	return ciphertext_page;
> +}
> +
> +/**
> + * ext4_xts_decrypt() - Decrypts a page using AES-256-XTS
> + * @ctx:  The encryption context.
> + * @page: The page to decrypt. Must be locked.
> + *
> + * Return: Zero on success, non-zero otherwise.
> + */
> +static int ext4_xts_decrypt(struct ext4_crypto_ctx *ctx, struct page *page)
> +{
> +	u8 xts_tweak[EXT4_XTS_TWEAK_SIZE];
> +	struct ablkcipher_request *req = NULL;
> +	struct ext4_crypt_result ecr;
> +	struct scatterlist sg;
> +	struct ext4_inode_info *ei = EXT4_I(page->mapping->host);
> +	struct crypto_ablkcipher *atfm = __crypto_ablkcipher_cast(ctx->tfm);
> +	int res = 0;
> +
> +	BUG_ON(!ctx->tfm);
> +	BUG_ON(ei->i_encryption_key.mode != EXT4_ENCRYPTION_MODE_AES_256_XTS);
> +	crypto_ablkcipher_clear_flags(atfm, ~0);
> +	crypto_tfm_set_flags(ctx->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
> +
> +	/* Since in AES-256-XTS mode we only perform one cryptographic operation
> +	 * on each block and there are no constraints about how many blocks a
> +	 * single key can encrypt, we directly use the inode master key */
> +	res = crypto_ablkcipher_setkey(atfm, ei->i_encryption_key.raw,
> +				       ei->i_encryption_key.size);

The return value of crypto_ablkcipher_setkey() is not checked for errors.

> +	req = ablkcipher_request_alloc(atfm, GFP_NOFS);
> +	if (!req) {
> +		res = -ENOMEM;
> +		goto out;
> +	}
> +	ablkcipher_request_set_callback(
> +		req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
> +		ext4_crypt_complete, &ecr);
> +	ext4_xts_tweak_for_page(xts_tweak, page);
> +	sg_init_table(&sg, 1);
> +	sg_set_page(&sg, page, PAGE_CACHE_SIZE, 0);
> +	ablkcipher_request_set_crypt(req, &sg, &sg, PAGE_CACHE_SIZE, xts_tweak);
> +	res = crypto_ablkcipher_decrypt(req);
> +	if (res == -EINPROGRESS || res == -EBUSY) {
> +		BUG_ON(req->base.data != &ecr);
> +		wait_for_completion(&ecr.completion);
> +		res = ecr.res;
> +	}
> +	ablkcipher_request_free(req);
> +out:
> +	if (res)
> +		printk_ratelimited(KERN_ERR "%s: res = %d\n", __func__, res);
> +	return res;
> +}
> +
> +/**
> + * 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 ext4_crypto_ctx *ctx, struct page *page)
> +{
> +	int res = 0;
> +
> +	BUG_ON(!PageLocked(page));
> +
> +	switch (ctx->mode) {
> +	case EXT4_ENCRYPTION_MODE_AES_256_XTS:
> +		res = ext4_xts_decrypt(ctx, page);
> +		break;
> +	case EXT4_ENCRYPTION_MODE_AES_256_GCM:
> +		res = -ENOTSUPP;
> +		break;
> +	default:
> +		BUG();
> +	}
> +	return res;
> +}
> +
> +/*
> + * Convenience function which takes care of allocating and
> + * deallocating the encryption context
> + */
> +int ext4_decrypt_one(struct inode *inode, struct page *page)
> +{
> +	int ret;
> +
> +	struct ext4_crypto_ctx *ctx = ext4_get_crypto_ctx(inode);
> +	if (!ctx)
> +		return -ENOMEM;
> +	ret = ext4_decrypt(ctx, page);
> +	ext4_release_crypto_ctx(ctx);
> +	return ret;
> +}
> +
> +/**
> + * ext4_validate_encryption_mode() - Validates the encryption key mode
> + * @mode: The key mode to validate.
> + *
> + * Return: The validated key mode. EXT4_ENCRYPTION_MODE_INVALID if invalid.
> + */
> +uint32_t ext4_validate_encryption_mode(uint32_t mode)
> +{
> +	switch (mode) {
> +	case EXT4_ENCRYPTION_MODE_AES_256_XTS:
> +		return mode;
> +	case EXT4_ENCRYPTION_MODE_AES_256_CBC:
> +		return mode;
> +	default:
> +		break;
> +	}
> +	return EXT4_ENCRYPTION_MODE_INVALID;
> +}
> +
> +/**
> + * 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;
> +}
> diff --git a/fs/ext4/crypto_policy.c b/fs/ext4/crypto_policy.c
> index 5cb4e74..3ff4c75 100644
> --- a/fs/ext4/crypto_policy.c
> +++ b/fs/ext4/crypto_policy.c
> @@ -71,14 +71,31 @@ static int ext4_create_encryption_context_from_policy(
>  	ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V0;
>  	memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
>  	       EXT4_KEY_DESCRIPTOR_SIZE);
> -	ctx.contents_encryption_mode = policy->contents_encryption_mode;
> -	ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
> +	ctx.contents_encryption_mode = ext4_validate_encryption_mode(
> +		policy->contents_encryption_mode);
> +	if (ctx.contents_encryption_mode == EXT4_ENCRYPTION_MODE_INVALID) {
> +		printk(KERN_WARNING
> +		       "%s: Invalid contents encryption mode %d\n", __func__,
> +			policy->contents_encryption_mode);
> +		res = -EINVAL;
> +		goto out;
> +	}
> +	ctx.filenames_encryption_mode = ext4_validate_encryption_mode(
> +		policy->filenames_encryption_mode);
> +	if (ctx.filenames_encryption_mode == EXT4_ENCRYPTION_MODE_INVALID) {
> +		printk(KERN_WARNING
> +		       "%s: Invalid filenames encryption mode %d\n", __func__,
> +			policy->filenames_encryption_mode);
> +		res = -EINVAL;
> +		goto out;
> +	}
>  	BUILD_BUG_ON(sizeof(ctx.nonce) != EXT4_KEY_DERIVATION_NONCE_SIZE);
>  	get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
>  
>  	res = ext4_xattr_set(inode, EXT4_XATTR_INDEX_ENCRYPTION,
>  			     EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
>  			     sizeof(ctx), 0);
> +out:
>  	if (!res)
>  		ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
>  	return res;
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 2d7fcb6..f7ee6c0 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -948,6 +948,11 @@ struct ext4_inode_info {
>  
>  	/* Precomputed uuid+inum+igen checksum for seeding inode checksums */
>  	__u32 i_csum_seed;
> +
> +#ifdef CONFIG_EXT4_FS_ENCRYPTION
> +	/* Encryption params */
> +	struct ext4_encryption_key i_encryption_key;
> +#endif
>  };
>  
>  /*
> @@ -1349,6 +1354,12 @@ struct ext4_sb_info {
>  	struct ratelimit_state s_err_ratelimit_state;
>  	struct ratelimit_state s_warning_ratelimit_state;
>  	struct ratelimit_state s_msg_ratelimit_state;
> +
> +#ifdef CONFIG_EXT4_FS_ENCRYPTION
> +	/* Encryption */
> +	uint32_t s_file_encryption_mode;
> +	uint32_t s_dir_encryption_mode;
> +#endif
>  };
>  
>  static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)
> @@ -1998,6 +2009,34 @@ extern unsigned ext4_free_clusters_after_init(struct super_block *sb,
>  					      struct ext4_group_desc *gdp);
>  ext4_fsblk_t ext4_inode_to_goal_block(struct inode *);
>  
> +/* crypto.c */
> +uint32_t ext4_validate_encryption_mode(uint32_t mode);
> +uint32_t ext4_validate_encryption_key_size(uint32_t mode, uint32_t size);
> +extern struct workqueue_struct *ext4_read_workqueue;
> +struct ext4_crypto_ctx *ext4_get_crypto_ctx(struct inode *inode);
> +void ext4_release_crypto_ctx(struct ext4_crypto_ctx *ctx);
> +void ext4_restore_control_page(struct page *data_page);
> +struct page *ext4_encrypt(struct inode *inode,
> +			  struct page *plaintext_page);
> +int ext4_decrypt(struct ext4_crypto_ctx *ctx, struct page *page);
> +int ext4_decrypt_one(struct inode *inode, struct page *page);
> +
> +#ifdef CONFIG_EXT4_FS_ENCRYPTION
> +int ext4_init_crypto(void);
> +void ext4_exit_crypto(void);
> +static inline int ext4_sb_has_crypto(struct super_block *sb)
> +{
> +	return EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_ENCRYPT);
> +}
> +#else
> +static inline int ext4_init_crypto(void) { return 0; }
> +static inline void ext4_exit_crypto(void) { }
> +static inline int ext4_sb_has_crypto(struct super_block *sb)
> +{
> +	return 0;
> +}
> +#endif
> +
>  /* dir.c */
>  extern int __ext4_check_dir_entry(const char *, unsigned int, struct inode *,
>  				  struct file *,
> diff --git a/fs/ext4/ext4_crypto.h b/fs/ext4/ext4_crypto.h
> index 984ff38..fb73935 100644
> --- a/fs/ext4/ext4_crypto.h
> +++ b/fs/ext4/ext4_crypto.h
> @@ -51,4 +51,47 @@ void ext4_to_hex(char *dst, char *src, size_t src_size);
>  int ext4_process_policy(const struct ext4_encryption_policy *policy,
>  			struct inode *inode);
>  
> +/* Encryption parameters */
> +#define EXT4_AES_256_XTS_KEY_SIZE 64
> +#define EXT4_XTS_TWEAK_SIZE 16
> +#define EXT4_AES_128_ECB_KEY_SIZE 16
> +#define EXT4_AES_256_GCM_KEY_SIZE 32
> +#define EXT4_AES_256_CBC_KEY_SIZE 32
> +#define EXT4_MAX_KEY_SIZE 64
> +
> +struct ext4_encryption_key {
> +	uint32_t mode;
> +	char raw[EXT4_MAX_KEY_SIZE];
> +	uint32_t size;
> +};
> +
> +#define EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL             0x00000001
> +#define EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL     0x00000002
> +
> +struct ext4_crypto_ctx {
> +	struct crypto_tfm *tfm;         /* Crypto API context */
> +	struct page *bounce_page;       /* Ciphertext page on write path */
> +	struct page *control_page;      /* Original page on write path */
> +	struct bio *bio;                /* The bio for this context */
> +	struct work_struct work;        /* Work queue for read complete path */
> +	struct list_head free_list;     /* Free list */
> +	int flags;                      /* Flags */
> +	int mode;                       /* Encryption mode for tfm */
> +};
> +
> +static inline int ext4_encryption_key_size(int mode)
> +{
> +	switch (mode) {
> +	case EXT4_ENCRYPTION_MODE_AES_256_XTS:
> +		return EXT4_AES_256_XTS_KEY_SIZE;
> +	case EXT4_ENCRYPTION_MODE_AES_256_GCM:
> +		return EXT4_AES_256_GCM_KEY_SIZE;
> +	case EXT4_ENCRYPTION_MODE_AES_256_CBC:
> +		return EXT4_AES_256_CBC_KEY_SIZE;
> +	default:
> +		BUG();
> +	}
> +	return 0;
> +}
> +
>  #endif	/* _EXT4_CRYPTO_H */
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 74c5f53..3dcafe9 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -893,6 +893,9 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)
>  	atomic_set(&ei->i_ioend_count, 0);
>  	atomic_set(&ei->i_unwritten, 0);
>  	INIT_WORK(&ei->i_rsv_conversion_work, ext4_end_io_rsv_work);
> +#ifdef CONFIG_EXT4_FS_ENCRYPTION
> +	ei->i_encryption_key.mode = EXT4_ENCRYPTION_MODE_INVALID;
> +#endif
>  
>  	return &ei->vfs_inode;
>  }
> @@ -3439,6 +3442,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  	if (sb->s_bdev->bd_part)
>  		sbi->s_sectors_written_start =
>  			part_stat_read(sb->s_bdev->bd_part, sectors[1]);
> +#ifdef CONFIG_EXT4_FS_ENCRYPTION
> +	/* Modes of operations for file and directory encryption. */
> +	sbi->s_file_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
> +	sbi->s_dir_encryption_mode = EXT4_ENCRYPTION_MODE_INVALID;
> +#endif
>  
>  	/* Cleanup superblock name */
>  	for (cp = sb->s_id; (cp = strchr(cp, '/'));)
> @@ -4052,6 +4060,9 @@ no_journal:
>  		goto failed_mount4;
>  	}
>  
> +	if (ext4_sb_has_crypto(sb))
> +		ext4_init_crypto();
> +
>  	/*
>  	 * The jbd2_journal_load will have done any necessary log recovery,
>  	 * so we can safely mount the rest of the filesystem now.



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