[mirror_ubuntu-bionic-kernel.git] / fs / ext4 / crypto.c

/*
 * 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) {
		if (ctx->flags & EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL)
			__free_page(ctx->w.bounce_page);
		else
			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;

	BUG_ON(ci == NULL);

	/*
	 * 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 ext4_crypto_ctx *ctx,
			    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) {
		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);
		return res;
	}
	return 0;
}

static struct page *alloc_bounce_page(struct ext4_crypto_ctx *ctx)
{
	struct page *ciphertext_page = alloc_page(GFP_NOFS);

	if (!ciphertext_page) {
		/* This is a potential bottleneck, but at least we'll have
		 * forward progress. */
		ciphertext_page = mempool_alloc(ext4_bounce_page_pool,
						 GFP_NOFS);
		if (ciphertext_page == NULL)
			return ERR_PTR(-ENOMEM);
		ctx->flags &= ~EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
	} else {
		ctx->flags |= EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
	}
	ctx->flags |= EXT4_WRITE_PATH_FL;
	ctx->w.bounce_page = ciphertext_page;
	return ciphertext_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(ctx, 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 ext4_crypto_ctx *ctx, struct page *page)
{
	BUG_ON(!PageLocked(page));

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

/*
 * 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;
}

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 = ex->ee_block;
	ext4_fsblk_t		pblk = ext4_ext_pblock(ex);
	unsigned int		len = ext4_ext_get_actual_len(ex);
	int			err = 0;

	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(ctx, 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;
		err = bio_add_page(bio, ciphertext_page,
				   inode->i_sb->s_blocksize, 0);
		if (err) {
			bio_put(bio);
			goto errout;
		}
		err = submit_bio_wait(WRITE, bio);
		bio_put(bio);
		if (err)
			goto errout;
	}
	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;
}
Commit	Line	Data
b30ab0e0 MH	1	/*
	2	* linux/fs/ext4/crypto.c
	3	*
	4	* Copyright (C) 2015, Google, Inc.
	5	*
	6	* This contains encryption functions for ext4
	7	*
	8	* Written by Michael Halcrow, 2014.
	9	*
	10	* Filename encryption additions
	11	* Uday Savagaonkar, 2014
	12	* Encryption policy handling additions
	13	* Ildar Muslukhov, 2014
	14	*
	15	* This has not yet undergone a rigorous security audit.
	16	*
	17	* The usage of AES-XTS should conform to recommendations in NIST
	18	* Special Publication 800-38E and IEEE P1619/D16.
	19	*/
	20
	21	#include <crypto/hash.h>
	22	#include <crypto/sha.h>
	23	#include <keys/user-type.h>
	24	#include <keys/encrypted-type.h>
	25	#include <linux/crypto.h>
	26	#include <linux/ecryptfs.h>
	27	#include <linux/gfp.h>
	28	#include <linux/kernel.h>
	29	#include <linux/key.h>
	30	#include <linux/list.h>
	31	#include <linux/mempool.h>
	32	#include <linux/module.h>
	33	#include <linux/mutex.h>
	34	#include <linux/random.h>
	35	#include <linux/scatterlist.h>
	36	#include <linux/spinlock_types.h>
	37
	38	#include "ext4_extents.h"
	39	#include "xattr.h"
	40
	41	/* Encryption added and removed here! (L: */
	42
	43	static unsigned int num_prealloc_crypto_pages = 32;
	44	static unsigned int num_prealloc_crypto_ctxs = 128;
	45
	46	module_param(num_prealloc_crypto_pages, uint, 0444);
	47	MODULE_PARM_DESC(num_prealloc_crypto_pages,
	48	"Number of crypto pages to preallocate");
	49	module_param(num_prealloc_crypto_ctxs, uint, 0444);
	50	MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
	51	"Number of crypto contexts to preallocate");
	52
	53	static mempool_t *ext4_bounce_page_pool;
	54
	55	static LIST_HEAD(ext4_free_crypto_ctxs);
	56	static DEFINE_SPINLOCK(ext4_crypto_ctx_lock);
	57
8ee03714 TT	58	static struct kmem_cache *ext4_crypto_ctx_cachep;
	59	struct kmem_cache *ext4_crypt_info_cachep;
	60
b30ab0e0 MH	61	/**
	62	* ext4_release_crypto_ctx() - Releases an encryption context
	63	* @ctx: The encryption context to release.
	64	*
	65	* If the encryption context was allocated from the pre-allocated pool, returns
	66	* it to that pool. Else, frees it.
	67	*
	68	* If there's a bounce page in the context, this frees that.
	69	*/
	70	void ext4_release_crypto_ctx(struct ext4_crypto_ctx *ctx)
	71	{
	72	unsigned long flags;
	73
614def70	74	if (ctx->flags & EXT4_WRITE_PATH_FL && ctx->w.bounce_page) {
b30ab0e0	75	if (ctx->flags & EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL)
614def70	76	__free_page(ctx->w.bounce_page);
b30ab0e0	77	else
614def70	78	mempool_free(ctx->w.bounce_page, ext4_bounce_page_pool);
b30ab0e0	79	}
614def70 TT	80	ctx->w.bounce_page = NULL;
614def70 TT	81	ctx->w.control_page = NULL;
b30ab0e0	82	if (ctx->flags & EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL) {
8ee03714	83	kmem_cache_free(ext4_crypto_ctx_cachep, ctx);
b30ab0e0 MH	84	} else {
	85	spin_lock_irqsave(&ext4_crypto_ctx_lock, flags);
	86	list_add(&ctx->free_list, &ext4_free_crypto_ctxs);
	87	spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags);
	88	}
	89	}
	90
b30ab0e0 MH	91	/**
	92	* ext4_get_crypto_ctx() - Gets an encryption context
	93	* @inode: The inode for which we are doing the crypto
	94	*
	95	* Allocates and initializes an encryption context.
	96	*
	97	* Return: An allocated and initialized encryption context on success; error
	98	* value or NULL otherwise.
	99	*/
	100	struct ext4_crypto_ctx ext4_get_crypto_ctx(struct inode inode)
	101	{
	102	struct ext4_crypto_ctx *ctx = NULL;
	103	int res = 0;
	104	unsigned long flags;
b7236e21	105	struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
b30ab0e0	106
b7236e21	107	BUG_ON(ci == NULL);
b30ab0e0 MH	108
	109	/*
	110	* We first try getting the ctx from a free list because in
	111	* the common case the ctx will have an allocated and
	112	* initialized crypto tfm, so it's probably a worthwhile
	113	* optimization. For the bounce page, we first try getting it
	114	* from the kernel allocator because that's just about as fast
	115	* as getting it from a list and because a cache of free pages
	116	* should generally be a "last resort" option for a filesystem
	117	* to be able to do its job.
	118	*/
	119	spin_lock_irqsave(&ext4_crypto_ctx_lock, flags);
	120	ctx = list_first_entry_or_null(&ext4_free_crypto_ctxs,
	121	struct ext4_crypto_ctx, free_list);
	122	if (ctx)
	123	list_del(&ctx->free_list);
	124	spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags);
	125	if (!ctx) {
8ee03714 TT	126	ctx = kmem_cache_zalloc(ext4_crypto_ctx_cachep, GFP_NOFS);
	127	if (!ctx) {
	128	res = -ENOMEM;
b30ab0e0 MH	129	goto out;
	130	}
	131	ctx->flags \|= EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL;
	132	} else {
	133	ctx->flags &= ~EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL;
	134	}
614def70	135	ctx->flags &= ~EXT4_WRITE_PATH_FL;
b30ab0e0	136
b30ab0e0 MH	137	out:
	138	if (res) {
	139	if (!IS_ERR_OR_NULL(ctx))
	140	ext4_release_crypto_ctx(ctx);
	141	ctx = ERR_PTR(res);
	142	}
	143	return ctx;
	144	}
	145
	146	struct workqueue_struct *ext4_read_workqueue;
	147	static DEFINE_MUTEX(crypto_init);
	148
	149	/**
	150	* ext4_exit_crypto() - Shutdown the ext4 encryption system
	151	*/
	152	void ext4_exit_crypto(void)
	153	{
	154	struct ext4_crypto_ctx pos, n;
	155
c936e1ec	156	list_for_each_entry_safe(pos, n, &ext4_free_crypto_ctxs, free_list)
8ee03714	157	kmem_cache_free(ext4_crypto_ctx_cachep, pos);
b30ab0e0 MH	158	INIT_LIST_HEAD(&ext4_free_crypto_ctxs);
	159	if (ext4_bounce_page_pool)
	160	mempool_destroy(ext4_bounce_page_pool);
	161	ext4_bounce_page_pool = NULL;
	162	if (ext4_read_workqueue)
	163	destroy_workqueue(ext4_read_workqueue);
	164	ext4_read_workqueue = NULL;
8ee03714 TT	165	if (ext4_crypto_ctx_cachep)
	166	kmem_cache_destroy(ext4_crypto_ctx_cachep);
	167	ext4_crypto_ctx_cachep = NULL;
	168	if (ext4_crypt_info_cachep)
	169	kmem_cache_destroy(ext4_crypt_info_cachep);
	170	ext4_crypt_info_cachep = NULL;
b30ab0e0 MH	171	}
	172
	173	/**
	174	* ext4_init_crypto() - Set up for ext4 encryption.
	175	*
	176	* We only call this when we start accessing encrypted files, since it
	177	* results in memory getting allocated that wouldn't otherwise be used.
	178	*
	179	* Return: Zero on success, non-zero otherwise.
	180	*/
	181	int ext4_init_crypto(void)
	182	{
8ee03714	183	int i, res = -ENOMEM;
b30ab0e0 MH	184
	185	mutex_lock(&crypto_init);
	186	if (ext4_read_workqueue)
	187	goto already_initialized;
	188	ext4_read_workqueue = alloc_workqueue("ext4_crypto", WQ_HIGHPRI, 0);
8ee03714 TT	189	if (!ext4_read_workqueue)
	190	goto fail;
	191
	192	ext4_crypto_ctx_cachep = KMEM_CACHE(ext4_crypto_ctx,
	193	SLAB_RECLAIM_ACCOUNT);
	194	if (!ext4_crypto_ctx_cachep)
	195	goto fail;
	196
	197	ext4_crypt_info_cachep = KMEM_CACHE(ext4_crypt_info,
	198	SLAB_RECLAIM_ACCOUNT);
	199	if (!ext4_crypt_info_cachep)
b30ab0e0	200	goto fail;
b30ab0e0 MH	201
	202	for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
	203	struct ext4_crypto_ctx *ctx;
	204
8ee03714 TT	205	ctx = kmem_cache_zalloc(ext4_crypto_ctx_cachep, GFP_NOFS);
	206	if (!ctx) {
	207	res = -ENOMEM;
b30ab0e0 MH	208	goto fail;
	209	}
	210	list_add(&ctx->free_list, &ext4_free_crypto_ctxs);
	211	}
	212
	213	ext4_bounce_page_pool =
	214	mempool_create_page_pool(num_prealloc_crypto_pages, 0);
	215	if (!ext4_bounce_page_pool) {
	216	res = -ENOMEM;
	217	goto fail;
	218	}
	219	already_initialized:
	220	mutex_unlock(&crypto_init);
	221	return 0;
	222	fail:
	223	ext4_exit_crypto();
	224	mutex_unlock(&crypto_init);
	225	return res;
	226	}
	227
	228	void ext4_restore_control_page(struct page *data_page)
	229	{
	230	struct ext4_crypto_ctx *ctx =
	231	(struct ext4_crypto_ctx *)page_private(data_page);
	232
	233	set_page_private(data_page, (unsigned long)NULL);
	234	ClearPagePrivate(data_page);
	235	unlock_page(data_page);
	236	ext4_release_crypto_ctx(ctx);
	237	}
	238
	239	/**
	240	* ext4_crypt_complete() - The completion callback for page encryption
	241	* @req: The asynchronous encryption request context
	242	* @res: The result of the encryption operation
	243	*/
	244	static void ext4_crypt_complete(struct crypto_async_request *req, int res)
	245	{
	246	struct ext4_completion_result *ecr = req->data;
	247
	248	if (res == -EINPROGRESS)
	249	return;
	250	ecr->res = res;
	251	complete(&ecr->completion);
	252	}
	253
	254	typedef enum {
	255	EXT4_DECRYPT = 0,
	256	EXT4_ENCRYPT,
	257	} ext4_direction_t;
	258
	259	static int ext4_page_crypto(struct ext4_crypto_ctx *ctx,
	260	struct inode *inode,
	261	ext4_direction_t rw,
	262	pgoff_t index,
	263	struct page *src_page,
	264	struct page *dest_page)
	265
	266	{
	267	u8 xts_tweak[EXT4_XTS_TWEAK_SIZE];
	268	struct ablkcipher_request *req = NULL;
	269	DECLARE_EXT4_COMPLETION_RESULT(ecr);
	270	struct scatterlist dst, src;
c936e1ec TT	271	struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
c936e1ec TT	272	struct crypto_ablkcipher *tfm = ci->ci_ctfm;
b30ab0e0 MH	273	int res = 0;
b30ab0e0 MH	274
c936e1ec	275	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
b30ab0e0 MH	276	if (!req) {
	277	printk_ratelimited(KERN_ERR
	278	"%s: crypto_request_alloc() failed\n",
	279	__func__);
	280	return -ENOMEM;
	281	}
	282	ablkcipher_request_set_callback(
	283	req, CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	284	ext4_crypt_complete, &ecr);
	285
	286	BUILD_BUG_ON(EXT4_XTS_TWEAK_SIZE < sizeof(index));
	287	memcpy(xts_tweak, &index, sizeof(index));
	288	memset(&xts_tweak[sizeof(index)], 0,
	289	EXT4_XTS_TWEAK_SIZE - sizeof(index));
	290
	291	sg_init_table(&dst, 1);
	292	sg_set_page(&dst, dest_page, PAGE_CACHE_SIZE, 0);
	293	sg_init_table(&src, 1);
	294	sg_set_page(&src, src_page, PAGE_CACHE_SIZE, 0);
	295	ablkcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE,
	296	xts_tweak);
	297	if (rw == EXT4_DECRYPT)
	298	res = crypto_ablkcipher_decrypt(req);
	299	else
	300	res = crypto_ablkcipher_encrypt(req);
	301	if (res == -EINPROGRESS \|\| res == -EBUSY) {
	302	BUG_ON(req->base.data != &ecr);
	303	wait_for_completion(&ecr.completion);
	304	res = ecr.res;
	305	}
	306	ablkcipher_request_free(req);
	307	if (res) {
	308	printk_ratelimited(
	309	KERN_ERR
	310	"%s: crypto_ablkcipher_encrypt() returned %d\n",
	311	__func__, res);
	312	return res;
	313	}
	314	return 0;
	315	}
	316
95ea68b4 TT	317	static struct page alloc_bounce_page(struct ext4_crypto_ctx ctx)
	318	{
	319	struct page *ciphertext_page = alloc_page(GFP_NOFS);
	320
	321	if (!ciphertext_page) {
	322	/* This is a potential bottleneck, but at least we'll have
	323	* forward progress. */
	324	ciphertext_page = mempool_alloc(ext4_bounce_page_pool,
	325	GFP_NOFS);
	326	if (ciphertext_page == NULL)
	327	return ERR_PTR(-ENOMEM);
	328	ctx->flags &= ~EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
	329	} else {
	330	ctx->flags \|= EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
	331	}
	332	ctx->flags \|= EXT4_WRITE_PATH_FL;
	333	ctx->w.bounce_page = ciphertext_page;
	334	return ciphertext_page;
	335	}
	336
b30ab0e0 MH	337	/**
	338	* ext4_encrypt() - Encrypts a page
	339	* @inode: The inode for which the encryption should take place
	340	* @plaintext_page: The page to encrypt. Must be locked.
	341	*
	342	* Allocates a ciphertext page and encrypts plaintext_page into it using the ctx
	343	* encryption context.
	344	*
	345	* Called on the page write path. The caller must call
	346	* ext4_restore_control_page() on the returned ciphertext page to
	347	* release the bounce buffer and the encryption context.
	348	*
	349	* Return: An allocated page with the encrypted content on success. Else, an
	350	* error value or NULL.
	351	*/
	352	struct page ext4_encrypt(struct inode inode,
	353	struct page *plaintext_page)
	354	{
	355	struct ext4_crypto_ctx *ctx;
	356	struct page *ciphertext_page = NULL;
	357	int err;
	358
	359	BUG_ON(!PageLocked(plaintext_page));
	360
	361	ctx = ext4_get_crypto_ctx(inode);
	362	if (IS_ERR(ctx))
	363	return (struct page *) ctx;
	364
	365	/* The encryption operation will require a bounce page. */
95ea68b4 TT	366	ciphertext_page = alloc_bounce_page(ctx);
	367	if (IS_ERR(ciphertext_page))
	368	goto errout;
614def70	369	ctx->w.control_page = plaintext_page;
b30ab0e0 MH	370	err = ext4_page_crypto(ctx, inode, EXT4_ENCRYPT, plaintext_page->index,
	371	plaintext_page, ciphertext_page);
	372	if (err) {
95ea68b4 TT	373	ciphertext_page = ERR_PTR(err);
95ea68b4 TT	374	errout:
b30ab0e0	375	ext4_release_crypto_ctx(ctx);
95ea68b4	376	return ciphertext_page;
b30ab0e0 MH	377	}
	378	SetPagePrivate(ciphertext_page);
	379	set_page_private(ciphertext_page, (unsigned long)ctx);
	380	lock_page(ciphertext_page);
	381	return ciphertext_page;
	382	}
	383
	384	/**
	385	* ext4_decrypt() - Decrypts a page in-place
	386	* @ctx: The encryption context.
	387	* @page: The page to decrypt. Must be locked.
	388	*
	389	* Decrypts page in-place using the ctx encryption context.
	390	*
	391	* Called from the read completion callback.
	392	*
	393	* Return: Zero on success, non-zero otherwise.
	394	*/
	395	int ext4_decrypt(struct ext4_crypto_ctx ctx, struct page page)
	396	{
	397	BUG_ON(!PageLocked(page));
	398
	399	return ext4_page_crypto(ctx, page->mapping->host,
	400	EXT4_DECRYPT, page->index, page, page);
	401	}
	402
	403	/*
	404	* Convenience function which takes care of allocating and
	405	* deallocating the encryption context
	406	*/
	407	int ext4_decrypt_one(struct inode inode, struct page page)
	408	{
	409	int ret;
	410
	411	struct ext4_crypto_ctx *ctx = ext4_get_crypto_ctx(inode);
	412
	413	if (!ctx)
	414	return -ENOMEM;
	415	ret = ext4_decrypt(ctx, page);
	416	ext4_release_crypto_ctx(ctx);
	417	return ret;
	418	}
	419
	420	int ext4_encrypted_zeroout(struct inode inode, struct ext4_extent ex)
	421	{
	422	struct ext4_crypto_ctx *ctx;
	423	struct page *ciphertext_page = NULL;
	424	struct bio *bio;
	425	ext4_lblk_t lblk = ex->ee_block;
	426	ext4_fsblk_t pblk = ext4_ext_pblock(ex);
	427	unsigned int len = ext4_ext_get_actual_len(ex);
	428	int err = 0;
	429
	430	BUG_ON(inode->i_sb->s_blocksize != PAGE_CACHE_SIZE);
	431
	432	ctx = ext4_get_crypto_ctx(inode);
	433	if (IS_ERR(ctx))
	434	return PTR_ERR(ctx);
	435
95ea68b4 TT	436	ciphertext_page = alloc_bounce_page(ctx);
	437	if (IS_ERR(ciphertext_page)) {
	438	err = PTR_ERR(ciphertext_page);
	439	goto errout;
b30ab0e0	440	}
b30ab0e0 MH	441
	442	while (len--) {
	443	err = ext4_page_crypto(ctx, inode, EXT4_ENCRYPT, lblk,
	444	ZERO_PAGE(0), ciphertext_page);
	445	if (err)
	446	goto errout;
	447
	448	bio = bio_alloc(GFP_KERNEL, 1);
	449	if (!bio) {
	450	err = -ENOMEM;
	451	goto errout;
	452	}
	453	bio->bi_bdev = inode->i_sb->s_bdev;
	454	bio->bi_iter.bi_sector = pblk;
	455	err = bio_add_page(bio, ciphertext_page,
	456	inode->i_sb->s_blocksize, 0);
	457	if (err) {
	458	bio_put(bio);
	459	goto errout;
	460	}
	461	err = submit_bio_wait(WRITE, bio);
95ea68b4	462	bio_put(bio);
b30ab0e0 MH	463	if (err)
	464	goto errout;
	465	}
	466	err = 0;
	467	errout:
	468	ext4_release_crypto_ctx(ctx);
	469	return err;
	470	}
	471
	472	bool ext4_valid_contents_enc_mode(uint32_t mode)
	473	{
	474	return (mode == EXT4_ENCRYPTION_MODE_AES_256_XTS);
	475	}
	476
	477	/**
	478	* ext4_validate_encryption_key_size() - Validate the encryption key size
	479	* @mode: The key mode.
	480	* @size: The key size to validate.
	481	*
	482	* Return: The validated key size for @mode. Zero if invalid.
	483	*/
	484	uint32_t ext4_validate_encryption_key_size(uint32_t mode, uint32_t size)
	485	{
	486	if (size == ext4_encryption_key_size(mode))
	487	return size;
	488	return 0;
	489	}