[deliverable/linux.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) {
		if (ctx->tfm)
			crypto_free_tfm(ctx->tfm);
		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;

	/* Allocate a new Crypto API context if we don't already have
	 * one or if it isn't the right mode. */
	if (ctx->tfm && (ctx->mode != ci->ci_data_mode)) {
		crypto_free_tfm(ctx->tfm);
		ctx->tfm = NULL;
		ctx->mode = EXT4_ENCRYPTION_MODE_INVALID;
	}
	if (!ctx->tfm) {
		switch (ci->ci_data_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 = ci->ci_data_mode;
	}
	BUG_ON(ci->ci_size != ext4_encryption_key_size(ci->ci_data_mode));

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->tfm)
			crypto_free_tfm(pos->tfm);
		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_inode_info *ei = EXT4_I(inode);
	struct crypto_ablkcipher *atfm = __crypto_ablkcipher_cast(ctx->tfm);
	int res = 0;

	BUG_ON(!ctx->tfm);
	BUG_ON(ctx->mode != ei->i_crypt_info->ci_data_mode);

	if (ctx->mode != EXT4_ENCRYPTION_MODE_AES_256_XTS) {
		printk_ratelimited(KERN_ERR
				   "%s: unsupported crypto algorithm: %d\n",
				   __func__, ctx->mode);
		return -ENOTSUPP;
	}

	crypto_ablkcipher_clear_flags(atfm, ~0);
	crypto_tfm_set_flags(ctx->tfm, CRYPTO_TFM_REQ_WEAK_KEY);

	res = crypto_ablkcipher_setkey(atfm, ei->i_crypt_info->ci_raw,
				       ei->i_crypt_info->ci_size);
	if (res) {
		printk_ratelimited(KERN_ERR
				   "%s: crypto_ablkcipher_setkey() failed\n",
				   __func__);
		return res;
	}
	req = ablkcipher_request_alloc(atfm, 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;
}

/**
 * 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_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 (WARN_ON_ONCE(!ciphertext_page)) {
			ciphertext_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;
	}
	ctx->flags |= EXT4_WRITE_PATH_FL;
	ctx->w.bounce_page = ciphertext_page;
	ctx->w.control_page = plaintext_page;
	err = ext4_page_crypto(ctx, inode, EXT4_ENCRYPT, plaintext_page->index,
			       plaintext_page, ciphertext_page);
	if (err) {
		ext4_release_crypto_ctx(ctx);
		return ERR_PTR(err);
	}
	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_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 (WARN_ON_ONCE(!ciphertext_page)) {
			ciphertext_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;
	}
	ctx->w.bounce_page = ciphertext_page;

	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);
		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 MH	82	if (ctx->flags & EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL) {
	83	if (ctx->tfm)
	84	crypto_free_tfm(ctx->tfm);
8ee03714	85	kmem_cache_free(ext4_crypto_ctx_cachep, ctx);
b30ab0e0 MH	86	} else {
	87	spin_lock_irqsave(&ext4_crypto_ctx_lock, flags);
	88	list_add(&ctx->free_list, &ext4_free_crypto_ctxs);
	89	spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags);
	90	}
	91	}
	92
b30ab0e0 MH	93	/**
	94	* ext4_get_crypto_ctx() - Gets an encryption context
	95	* @inode: The inode for which we are doing the crypto
	96	*
	97	* Allocates and initializes an encryption context.
	98	*
	99	* Return: An allocated and initialized encryption context on success; error
	100	* value or NULL otherwise.
	101	*/
	102	struct ext4_crypto_ctx ext4_get_crypto_ctx(struct inode inode)
	103	{
	104	struct ext4_crypto_ctx *ctx = NULL;
	105	int res = 0;
	106	unsigned long flags;
b7236e21	107	struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
b30ab0e0	108
b7236e21	109	BUG_ON(ci == NULL);
b30ab0e0 MH	110
	111	/*
	112	* We first try getting the ctx from a free list because in
	113	* the common case the ctx will have an allocated and
	114	* initialized crypto tfm, so it's probably a worthwhile
	115	* optimization. For the bounce page, we first try getting it
	116	* from the kernel allocator because that's just about as fast
	117	* as getting it from a list and because a cache of free pages
	118	* should generally be a "last resort" option for a filesystem
	119	* to be able to do its job.
	120	*/
	121	spin_lock_irqsave(&ext4_crypto_ctx_lock, flags);
	122	ctx = list_first_entry_or_null(&ext4_free_crypto_ctxs,
	123	struct ext4_crypto_ctx, free_list);
	124	if (ctx)
	125	list_del(&ctx->free_list);
	126	spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags);
	127	if (!ctx) {
8ee03714 TT	128	ctx = kmem_cache_zalloc(ext4_crypto_ctx_cachep, GFP_NOFS);
	129	if (!ctx) {
	130	res = -ENOMEM;
b30ab0e0 MH	131	goto out;
	132	}
	133	ctx->flags \|= EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL;
	134	} else {
	135	ctx->flags &= ~EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL;
	136	}
614def70	137	ctx->flags &= ~EXT4_WRITE_PATH_FL;
b30ab0e0 MH	138
	139	/* Allocate a new Crypto API context if we don't already have
	140	* one or if it isn't the right mode. */
1aaa6e8b	141	if (ctx->tfm && (ctx->mode != ci->ci_data_mode)) {
b30ab0e0 MH	142	crypto_free_tfm(ctx->tfm);
	143	ctx->tfm = NULL;
	144	ctx->mode = EXT4_ENCRYPTION_MODE_INVALID;
	145	}
	146	if (!ctx->tfm) {
1aaa6e8b	147	switch (ci->ci_data_mode) {
b30ab0e0 MH	148	case EXT4_ENCRYPTION_MODE_AES_256_XTS:
	149	ctx->tfm = crypto_ablkcipher_tfm(
	150	crypto_alloc_ablkcipher("xts(aes)", 0, 0));
	151	break;
	152	case EXT4_ENCRYPTION_MODE_AES_256_GCM:
	153	/* TODO(mhalcrow): AEAD w/ gcm(aes);
	154	* crypto_aead_setauthsize() */
	155	ctx->tfm = ERR_PTR(-ENOTSUPP);
	156	break;
	157	default:
	158	BUG();
	159	}
	160	if (IS_ERR_OR_NULL(ctx->tfm)) {
	161	res = PTR_ERR(ctx->tfm);
	162	ctx->tfm = NULL;
	163	goto out;
	164	}
1aaa6e8b	165	ctx->mode = ci->ci_data_mode;
b30ab0e0	166	}
1aaa6e8b	167	BUG_ON(ci->ci_size != ext4_encryption_key_size(ci->ci_data_mode));
b30ab0e0	168
b30ab0e0 MH	169	out:
	170	if (res) {
	171	if (!IS_ERR_OR_NULL(ctx))
	172	ext4_release_crypto_ctx(ctx);
	173	ctx = ERR_PTR(res);
	174	}
	175	return ctx;
	176	}
	177
	178	struct workqueue_struct *ext4_read_workqueue;
	179	static DEFINE_MUTEX(crypto_init);
	180
	181	/**
	182	* ext4_exit_crypto() - Shutdown the ext4 encryption system
	183	*/
	184	void ext4_exit_crypto(void)
	185	{
	186	struct ext4_crypto_ctx pos, n;
	187
	188	list_for_each_entry_safe(pos, n, &ext4_free_crypto_ctxs, free_list) {
b30ab0e0 MH	189	if (pos->tfm)
b30ab0e0 MH	190	crypto_free_tfm(pos->tfm);
8ee03714	191	kmem_cache_free(ext4_crypto_ctx_cachep, pos);
b30ab0e0 MH	192	}
	193	INIT_LIST_HEAD(&ext4_free_crypto_ctxs);
	194	if (ext4_bounce_page_pool)
	195	mempool_destroy(ext4_bounce_page_pool);
	196	ext4_bounce_page_pool = NULL;
	197	if (ext4_read_workqueue)
	198	destroy_workqueue(ext4_read_workqueue);
	199	ext4_read_workqueue = NULL;
8ee03714 TT	200	if (ext4_crypto_ctx_cachep)
	201	kmem_cache_destroy(ext4_crypto_ctx_cachep);
	202	ext4_crypto_ctx_cachep = NULL;
	203	if (ext4_crypt_info_cachep)
	204	kmem_cache_destroy(ext4_crypt_info_cachep);
	205	ext4_crypt_info_cachep = NULL;
b30ab0e0 MH	206	}
	207
	208	/**
	209	* ext4_init_crypto() - Set up for ext4 encryption.
	210	*
	211	* We only call this when we start accessing encrypted files, since it
	212	* results in memory getting allocated that wouldn't otherwise be used.
	213	*
	214	* Return: Zero on success, non-zero otherwise.
	215	*/
	216	int ext4_init_crypto(void)
	217	{
8ee03714	218	int i, res = -ENOMEM;
b30ab0e0 MH	219
	220	mutex_lock(&crypto_init);
	221	if (ext4_read_workqueue)
	222	goto already_initialized;
	223	ext4_read_workqueue = alloc_workqueue("ext4_crypto", WQ_HIGHPRI, 0);
8ee03714 TT	224	if (!ext4_read_workqueue)
	225	goto fail;
	226
	227	ext4_crypto_ctx_cachep = KMEM_CACHE(ext4_crypto_ctx,
	228	SLAB_RECLAIM_ACCOUNT);
	229	if (!ext4_crypto_ctx_cachep)
	230	goto fail;
	231
	232	ext4_crypt_info_cachep = KMEM_CACHE(ext4_crypt_info,
	233	SLAB_RECLAIM_ACCOUNT);
	234	if (!ext4_crypt_info_cachep)
b30ab0e0	235	goto fail;
b30ab0e0 MH	236
	237	for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
	238	struct ext4_crypto_ctx *ctx;
	239
8ee03714 TT	240	ctx = kmem_cache_zalloc(ext4_crypto_ctx_cachep, GFP_NOFS);
	241	if (!ctx) {
	242	res = -ENOMEM;
b30ab0e0 MH	243	goto fail;
	244	}
	245	list_add(&ctx->free_list, &ext4_free_crypto_ctxs);
	246	}
	247
	248	ext4_bounce_page_pool =
	249	mempool_create_page_pool(num_prealloc_crypto_pages, 0);
	250	if (!ext4_bounce_page_pool) {
	251	res = -ENOMEM;
	252	goto fail;
	253	}
	254	already_initialized:
	255	mutex_unlock(&crypto_init);
	256	return 0;
	257	fail:
	258	ext4_exit_crypto();
	259	mutex_unlock(&crypto_init);
	260	return res;
	261	}
	262
	263	void ext4_restore_control_page(struct page *data_page)
	264	{
	265	struct ext4_crypto_ctx *ctx =
	266	(struct ext4_crypto_ctx *)page_private(data_page);
	267
	268	set_page_private(data_page, (unsigned long)NULL);
	269	ClearPagePrivate(data_page);
	270	unlock_page(data_page);
	271	ext4_release_crypto_ctx(ctx);
	272	}
	273
	274	/**
	275	* ext4_crypt_complete() - The completion callback for page encryption
	276	* @req: The asynchronous encryption request context
	277	* @res: The result of the encryption operation
	278	*/
	279	static void ext4_crypt_complete(struct crypto_async_request *req, int res)
	280	{
	281	struct ext4_completion_result *ecr = req->data;
	282
	283	if (res == -EINPROGRESS)
	284	return;
	285	ecr->res = res;
	286	complete(&ecr->completion);
	287	}
	288
	289	typedef enum {
	290	EXT4_DECRYPT = 0,
	291	EXT4_ENCRYPT,
	292	} ext4_direction_t;
	293
	294	static int ext4_page_crypto(struct ext4_crypto_ctx *ctx,
	295	struct inode *inode,
	296	ext4_direction_t rw,
	297	pgoff_t index,
	298	struct page *src_page,
	299	struct page *dest_page)
	300
	301	{
	302	u8 xts_tweak[EXT4_XTS_TWEAK_SIZE];
	303	struct ablkcipher_request *req = NULL;
	304	DECLARE_EXT4_COMPLETION_RESULT(ecr);
	305	struct scatterlist dst, src;
	306	struct ext4_inode_info *ei = EXT4_I(inode);
307	struct crypto_ablkcipher *atfm = __crypto_ablkcipher_cast(ctx->tfm);
308	int res = 0;
309
310	BUG_ON(!ctx->tfm);
1aaa6e8b	311	BUG_ON(ctx->mode != ei->i_crypt_info->ci_data_mode);
b30ab0e0 MH	312
	313	if (ctx->mode != EXT4_ENCRYPTION_MODE_AES_256_XTS) {
	314	printk_ratelimited(KERN_ERR
	315	"%s: unsupported crypto algorithm: %d\n",
	316	__func__, ctx->mode);
	317	return -ENOTSUPP;
	318	}
	319
	320	crypto_ablkcipher_clear_flags(atfm, ~0);
	321	crypto_tfm_set_flags(ctx->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
	322
b7236e21 TT	323	res = crypto_ablkcipher_setkey(atfm, ei->i_crypt_info->ci_raw,
b7236e21 TT	324	ei->i_crypt_info->ci_size);
b30ab0e0 MH	325	if (res) {
	326	printk_ratelimited(KERN_ERR
	327	"%s: crypto_ablkcipher_setkey() failed\n",
	328	__func__);
	329	return res;
	330	}
	331	req = ablkcipher_request_alloc(atfm, GFP_NOFS);
	332	if (!req) {
	333	printk_ratelimited(KERN_ERR
	334	"%s: crypto_request_alloc() failed\n",
	335	__func__);
	336	return -ENOMEM;
	337	}
	338	ablkcipher_request_set_callback(
	339	req, CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	340	ext4_crypt_complete, &ecr);
	341
	342	BUILD_BUG_ON(EXT4_XTS_TWEAK_SIZE < sizeof(index));
	343	memcpy(xts_tweak, &index, sizeof(index));
	344	memset(&xts_tweak[sizeof(index)], 0,
	345	EXT4_XTS_TWEAK_SIZE - sizeof(index));
	346
	347	sg_init_table(&dst, 1);
	348	sg_set_page(&dst, dest_page, PAGE_CACHE_SIZE, 0);
	349	sg_init_table(&src, 1);
	350	sg_set_page(&src, src_page, PAGE_CACHE_SIZE, 0);
	351	ablkcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE,
	352	xts_tweak);
	353	if (rw == EXT4_DECRYPT)
	354	res = crypto_ablkcipher_decrypt(req);
	355	else
	356	res = crypto_ablkcipher_encrypt(req);
	357	if (res == -EINPROGRESS \|\| res == -EBUSY) {
	358	BUG_ON(req->base.data != &ecr);
	359	wait_for_completion(&ecr.completion);
	360	res = ecr.res;
	361	}
	362	ablkcipher_request_free(req);
	363	if (res) {
	364	printk_ratelimited(
	365	KERN_ERR
	366	"%s: crypto_ablkcipher_encrypt() returned %d\n",
	367	__func__, res);
	368	return res;
	369	}
	370	return 0;
	371	}
	372
	373	/**
	374	* ext4_encrypt() - Encrypts a page
	375	* @inode: The inode for which the encryption should take place
	376	* @plaintext_page: The page to encrypt. Must be locked.
	377	*
	378	* Allocates a ciphertext page and encrypts plaintext_page into it using the ctx
	379	* encryption context.
	380	*
	381	* Called on the page write path. The caller must call
	382	* ext4_restore_control_page() on the returned ciphertext page to
	383	* release the bounce buffer and the encryption context.
	384	*
	385	* Return: An allocated page with the encrypted content on success. Else, an
	386	* error value or NULL.
	387	*/
	388	struct page ext4_encrypt(struct inode inode,
389	struct page *plaintext_page)
390	{
391	struct ext4_crypto_ctx *ctx;
392	struct page *ciphertext_page = NULL;
393	int err;
394
395	BUG_ON(!PageLocked(plaintext_page));
396
397	ctx = ext4_get_crypto_ctx(inode);
398	if (IS_ERR(ctx))
399	return (struct page *) ctx;
400
401	/* The encryption operation will require a bounce page. */
402	ciphertext_page = alloc_page(GFP_NOFS);
403	if (!ciphertext_page) {
404	/* This is a potential bottleneck, but at least we'll have
405	* forward progress. */
406	ciphertext_page = mempool_alloc(ext4_bounce_page_pool,
407	GFP_NOFS);
408	if (WARN_ON_ONCE(!ciphertext_page)) {
409	ciphertext_page = mempool_alloc(ext4_bounce_page_pool,
410	GFP_NOFS \| __GFP_WAIT);
411	}
412	ctx->flags &= ~EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
413	} else {
414	ctx->flags \|= EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
415	}
614def70 TT	416	ctx->flags \|= EXT4_WRITE_PATH_FL;
	417	ctx->w.bounce_page = ciphertext_page;
	418	ctx->w.control_page = plaintext_page;
b30ab0e0 MH	419	err = ext4_page_crypto(ctx, inode, EXT4_ENCRYPT, plaintext_page->index,
	420	plaintext_page, ciphertext_page);
	421	if (err) {
	422	ext4_release_crypto_ctx(ctx);
	423	return ERR_PTR(err);
	424	}
	425	SetPagePrivate(ciphertext_page);
	426	set_page_private(ciphertext_page, (unsigned long)ctx);
	427	lock_page(ciphertext_page);
	428	return ciphertext_page;
	429	}
	430
	431	/**
	432	* ext4_decrypt() - Decrypts a page in-place
	433	* @ctx: The encryption context.
	434	* @page: The page to decrypt. Must be locked.
	435	*
	436	* Decrypts page in-place using the ctx encryption context.
	437	*
	438	* Called from the read completion callback.
	439	*
	440	* Return: Zero on success, non-zero otherwise.
	441	*/
	442	int ext4_decrypt(struct ext4_crypto_ctx ctx, struct page page)
	443	{
	444	BUG_ON(!PageLocked(page));
	445
	446	return ext4_page_crypto(ctx, page->mapping->host,
	447	EXT4_DECRYPT, page->index, page, page);
	448	}
	449
	450	/*
	451	* Convenience function which takes care of allocating and
	452	* deallocating the encryption context
	453	*/
	454	int ext4_decrypt_one(struct inode inode, struct page page)
	455	{
	456	int ret;
	457
	458	struct ext4_crypto_ctx *ctx = ext4_get_crypto_ctx(inode);
	459
	460	if (!ctx)
	461	return -ENOMEM;
	462	ret = ext4_decrypt(ctx, page);
	463	ext4_release_crypto_ctx(ctx);
	464	return ret;
	465	}
	466
	467	int ext4_encrypted_zeroout(struct inode inode, struct ext4_extent ex)
	468	{
	469	struct ext4_crypto_ctx *ctx;
	470	struct page *ciphertext_page = NULL;
	471	struct bio *bio;
	472	ext4_lblk_t lblk = ex->ee_block;
	473	ext4_fsblk_t pblk = ext4_ext_pblock(ex);
	474	unsigned int len = ext4_ext_get_actual_len(ex);
	475	int err = 0;
	476
	477	BUG_ON(inode->i_sb->s_blocksize != PAGE_CACHE_SIZE);
	478
	479	ctx = ext4_get_crypto_ctx(inode);
	480	if (IS_ERR(ctx))
	481	return PTR_ERR(ctx);
	482
483	ciphertext_page = alloc_page(GFP_NOFS);
484	if (!ciphertext_page) {
485	/* This is a potential bottleneck, but at least we'll have
486	* forward progress. */
487	ciphertext_page = mempool_alloc(ext4_bounce_page_pool,
488	GFP_NOFS);
489	if (WARN_ON_ONCE(!ciphertext_page)) {
490	ciphertext_page = mempool_alloc(ext4_bounce_page_pool,
491	GFP_NOFS \| __GFP_WAIT);
492	}
493	ctx->flags &= ~EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
494	} else {
495	ctx->flags \|= EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
496	}
614def70	497	ctx->w.bounce_page = ciphertext_page;
b30ab0e0 MH	498
	499	while (len--) {
	500	err = ext4_page_crypto(ctx, inode, EXT4_ENCRYPT, lblk,
	501	ZERO_PAGE(0), ciphertext_page);
	502	if (err)
	503	goto errout;
	504
	505	bio = bio_alloc(GFP_KERNEL, 1);
	506	if (!bio) {
	507	err = -ENOMEM;
	508	goto errout;
	509	}
	510	bio->bi_bdev = inode->i_sb->s_bdev;
	511	bio->bi_iter.bi_sector = pblk;
	512	err = bio_add_page(bio, ciphertext_page,
	513	inode->i_sb->s_blocksize, 0);
	514	if (err) {
	515	bio_put(bio);
	516	goto errout;
	517	}
	518	err = submit_bio_wait(WRITE, bio);
	519	if (err)
	520	goto errout;
	521	}
	522	err = 0;
	523	errout:
	524	ext4_release_crypto_ctx(ctx);
	525	return err;
	526	}
	527
	528	bool ext4_valid_contents_enc_mode(uint32_t mode)
	529	{
	530	return (mode == EXT4_ENCRYPTION_MODE_AES_256_XTS);
	531	}
	532
	533	/**
	534	* ext4_validate_encryption_key_size() - Validate the encryption key size
	535	* @mode: The key mode.
	536	* @size: The key size to validate.
	537	*
	538	* Return: The validated key size for @mode. Zero if invalid.
	539	*/
	540	uint32_t ext4_validate_encryption_key_size(uint32_t mode, uint32_t size)
	541	{
	542	if (size == ext4_encryption_key_size(mode))
	543	return size;
	544	return 0;
	545	}