[mirror_ubuntu-artful-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);

/**
 * 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_crypt_info *ci = EXT4_I(inode)->i_crypt_info;

	BUG_ON(ci == NULL);
	if (!ext4_read_workqueue)
		ext4_init_crypto();

	/*
	 * 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(ci->ci_mode == EXT4_ENCRYPTION_MODE_INVALID);
	if (ctx->tfm && (ctx->mode != ci->ci_mode)) {
		crypto_free_tfm(ctx->tfm);
		ctx->tfm = NULL;
		ctx->mode = EXT4_ENCRYPTION_MODE_INVALID;
	}
	if (!ctx->tfm) {
		switch (ci->ci_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_mode;
	}
	BUG_ON(ci->ci_size != ext4_encryption_key_size(ci->ci_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 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;

	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) {
		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_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->bounce_page = ciphertext_page;
	ctx->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->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
	58	/**
	59	* ext4_release_crypto_ctx() - Releases an encryption context
	60	* @ctx: The encryption context to release.
	61	*
	62	* If the encryption context was allocated from the pre-allocated pool, returns
	63	* it to that pool. Else, frees it.
	64	*
65	* If there's a bounce page in the context, this frees that.
66	*/
67	void ext4_release_crypto_ctx(struct ext4_crypto_ctx *ctx)
68	{
69	unsigned long flags;
70
71	if (ctx->bounce_page) {
72	if (ctx->flags & EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL)
73	__free_page(ctx->bounce_page);
74	else
75	mempool_free(ctx->bounce_page, ext4_bounce_page_pool);
76	ctx->bounce_page = NULL;
77	}
78	ctx->control_page = NULL;
79	if (ctx->flags & EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL) {
80	if (ctx->tfm)
81	crypto_free_tfm(ctx->tfm);
82	kfree(ctx);
83	} else {
84	spin_lock_irqsave(&ext4_crypto_ctx_lock, flags);
85	list_add(&ctx->free_list, &ext4_free_crypto_ctxs);
86	spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags);
87	}
88	}
89
90	/**
91	* ext4_alloc_and_init_crypto_ctx() - Allocates and inits an encryption context
92	* @mask: The allocation mask.
93	*
94	* Return: An allocated and initialized encryption context on success. An error
95	* value or NULL otherwise.
96	*/
97	static struct ext4_crypto_ctx *ext4_alloc_and_init_crypto_ctx(gfp_t mask)
98	{
99	struct ext4_crypto_ctx *ctx = kzalloc(sizeof(struct ext4_crypto_ctx),
100	mask);
101
102	if (!ctx)
103	return ERR_PTR(-ENOMEM);
104	return ctx;
105	}
106
107	/**
108	* ext4_get_crypto_ctx() - Gets an encryption context
109	* @inode: The inode for which we are doing the crypto
110	*
111	* Allocates and initializes an encryption context.
112	*
113	* Return: An allocated and initialized encryption context on success; error
114	* value or NULL otherwise.
115	*/
116	struct ext4_crypto_ctx ext4_get_crypto_ctx(struct inode inode)
117	{
118	struct ext4_crypto_ctx *ctx = NULL;
119	int res = 0;
120	unsigned long flags;
b7236e21	121	struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
b30ab0e0	122
b7236e21	123	BUG_ON(ci == NULL);
b30ab0e0 MH	124	if (!ext4_read_workqueue)
	125	ext4_init_crypto();
	126
	127	/*
	128	* We first try getting the ctx from a free list because in
	129	* the common case the ctx will have an allocated and
	130	* initialized crypto tfm, so it's probably a worthwhile
	131	* optimization. For the bounce page, we first try getting it
	132	* from the kernel allocator because that's just about as fast
	133	* as getting it from a list and because a cache of free pages
	134	* should generally be a "last resort" option for a filesystem
	135	* to be able to do its job.
	136	*/
	137	spin_lock_irqsave(&ext4_crypto_ctx_lock, flags);
	138	ctx = list_first_entry_or_null(&ext4_free_crypto_ctxs,
	139	struct ext4_crypto_ctx, free_list);
	140	if (ctx)
	141	list_del(&ctx->free_list);
	142	spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags);
	143	if (!ctx) {
	144	ctx = ext4_alloc_and_init_crypto_ctx(GFP_NOFS);
	145	if (IS_ERR(ctx)) {
	146	res = PTR_ERR(ctx);
	147	goto out;
	148	}
	149	ctx->flags \|= EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL;
	150	} else {
	151	ctx->flags &= ~EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL;
	152	}
	153
	154	/* Allocate a new Crypto API context if we don't already have
	155	* one or if it isn't the right mode. */
e2881b1b TT	156	BUG_ON(ci->ci_mode == EXT4_ENCRYPTION_MODE_INVALID);
e2881b1b TT	157	if (ctx->tfm && (ctx->mode != ci->ci_mode)) {
b30ab0e0 MH	158	crypto_free_tfm(ctx->tfm);
	159	ctx->tfm = NULL;
	160	ctx->mode = EXT4_ENCRYPTION_MODE_INVALID;
	161	}
	162	if (!ctx->tfm) {
e2881b1b	163	switch (ci->ci_mode) {
b30ab0e0 MH	164	case EXT4_ENCRYPTION_MODE_AES_256_XTS:
	165	ctx->tfm = crypto_ablkcipher_tfm(
	166	crypto_alloc_ablkcipher("xts(aes)", 0, 0));
	167	break;
	168	case EXT4_ENCRYPTION_MODE_AES_256_GCM:
	169	/* TODO(mhalcrow): AEAD w/ gcm(aes);
	170	* crypto_aead_setauthsize() */
	171	ctx->tfm = ERR_PTR(-ENOTSUPP);
	172	break;
	173	default:
	174	BUG();
	175	}
	176	if (IS_ERR_OR_NULL(ctx->tfm)) {
	177	res = PTR_ERR(ctx->tfm);
	178	ctx->tfm = NULL;
	179	goto out;
	180	}
e2881b1b	181	ctx->mode = ci->ci_mode;
b30ab0e0	182	}
e2881b1b	183	BUG_ON(ci->ci_size != ext4_encryption_key_size(ci->ci_mode));
b30ab0e0 MH	184
	185	/* There shouldn't be a bounce page attached to the crypto
	186	* context at this point. */
	187	BUG_ON(ctx->bounce_page);
	188
	189	out:
	190	if (res) {
	191	if (!IS_ERR_OR_NULL(ctx))
	192	ext4_release_crypto_ctx(ctx);
	193	ctx = ERR_PTR(res);
	194	}
	195	return ctx;
	196	}
	197
	198	struct workqueue_struct *ext4_read_workqueue;
	199	static DEFINE_MUTEX(crypto_init);
	200
	201	/**
	202	* ext4_exit_crypto() - Shutdown the ext4 encryption system
	203	*/
	204	void ext4_exit_crypto(void)
	205	{
	206	struct ext4_crypto_ctx pos, n;
	207
	208	list_for_each_entry_safe(pos, n, &ext4_free_crypto_ctxs, free_list) {
	209	if (pos->bounce_page) {
	210	if (pos->flags &
	211	EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL) {
	212	__free_page(pos->bounce_page);
	213	} else {
	214	mempool_free(pos->bounce_page,
	215	ext4_bounce_page_pool);
	216	}
	217	}
	218	if (pos->tfm)
	219	crypto_free_tfm(pos->tfm);
	220	kfree(pos);
	221	}
	222	INIT_LIST_HEAD(&ext4_free_crypto_ctxs);
	223	if (ext4_bounce_page_pool)
	224	mempool_destroy(ext4_bounce_page_pool);
	225	ext4_bounce_page_pool = NULL;
	226	if (ext4_read_workqueue)
	227	destroy_workqueue(ext4_read_workqueue);
	228	ext4_read_workqueue = NULL;
	229	}
	230
	231	/**
	232	* ext4_init_crypto() - Set up for ext4 encryption.
	233	*
	234	* We only call this when we start accessing encrypted files, since it
	235	* results in memory getting allocated that wouldn't otherwise be used.
	236	*
	237	* Return: Zero on success, non-zero otherwise.
	238	*/
	239	int ext4_init_crypto(void)
	240	{
	241	int i, res;
	242
	243	mutex_lock(&crypto_init);
	244	if (ext4_read_workqueue)
	245	goto already_initialized;
	246	ext4_read_workqueue = alloc_workqueue("ext4_crypto", WQ_HIGHPRI, 0);
	247	if (!ext4_read_workqueue) {
248	res = -ENOMEM;
249	goto fail;
250	}
251
252	for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
253	struct ext4_crypto_ctx *ctx;
254
255	ctx = ext4_alloc_and_init_crypto_ctx(GFP_KERNEL);
256	if (IS_ERR(ctx)) {
257	res = PTR_ERR(ctx);
258	goto fail;
259	}
260	list_add(&ctx->free_list, &ext4_free_crypto_ctxs);
261	}
262
263	ext4_bounce_page_pool =
264	mempool_create_page_pool(num_prealloc_crypto_pages, 0);
265	if (!ext4_bounce_page_pool) {
266	res = -ENOMEM;
267	goto fail;
268	}
269	already_initialized:
270	mutex_unlock(&crypto_init);
271	return 0;
272	fail:
273	ext4_exit_crypto();
274	mutex_unlock(&crypto_init);
275	return res;
276	}
277
278	void ext4_restore_control_page(struct page *data_page)
279	{
280	struct ext4_crypto_ctx *ctx =
281	(struct ext4_crypto_ctx *)page_private(data_page);
282
283	set_page_private(data_page, (unsigned long)NULL);
284	ClearPagePrivate(data_page);
285	unlock_page(data_page);
286	ext4_release_crypto_ctx(ctx);
287	}
288
289	/**
290	* ext4_crypt_complete() - The completion callback for page encryption
291	* @req: The asynchronous encryption request context
292	* @res: The result of the encryption operation
293	*/
294	static void ext4_crypt_complete(struct crypto_async_request *req, int res)
295	{
296	struct ext4_completion_result *ecr = req->data;
297
298	if (res == -EINPROGRESS)
299	return;
300	ecr->res = res;
301	complete(&ecr->completion);
302	}
303
304	typedef enum {
305	EXT4_DECRYPT = 0,
306	EXT4_ENCRYPT,
307	} ext4_direction_t;
308
309	static int ext4_page_crypto(struct ext4_crypto_ctx *ctx,
310	struct inode *inode,
311	ext4_direction_t rw,
312	pgoff_t index,
313	struct page *src_page,
314	struct page *dest_page)
315
316	{
317	u8 xts_tweak[EXT4_XTS_TWEAK_SIZE];
318	struct ablkcipher_request *req = NULL;
319	DECLARE_EXT4_COMPLETION_RESULT(ecr);
320	struct scatterlist dst, src;
321	struct ext4_inode_info *ei = EXT4_I(inode);
322	struct crypto_ablkcipher *atfm = __crypto_ablkcipher_cast(ctx->tfm);
323	int res = 0;
324
325	BUG_ON(!ctx->tfm);
b7236e21	326	BUG_ON(ctx->mode != ei->i_crypt_info->ci_mode);
b30ab0e0 MH	327
	328	if (ctx->mode != EXT4_ENCRYPTION_MODE_AES_256_XTS) {
	329	printk_ratelimited(KERN_ERR
	330	"%s: unsupported crypto algorithm: %d\n",
	331	__func__, ctx->mode);
	332	return -ENOTSUPP;
	333	}
	334
	335	crypto_ablkcipher_clear_flags(atfm, ~0);
	336	crypto_tfm_set_flags(ctx->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
	337
b7236e21 TT	338	res = crypto_ablkcipher_setkey(atfm, ei->i_crypt_info->ci_raw,
b7236e21 TT	339	ei->i_crypt_info->ci_size);
b30ab0e0 MH	340	if (res) {
	341	printk_ratelimited(KERN_ERR
	342	"%s: crypto_ablkcipher_setkey() failed\n",
	343	__func__);
	344	return res;
	345	}
	346	req = ablkcipher_request_alloc(atfm, GFP_NOFS);
	347	if (!req) {
	348	printk_ratelimited(KERN_ERR
	349	"%s: crypto_request_alloc() failed\n",
	350	__func__);
	351	return -ENOMEM;
	352	}
	353	ablkcipher_request_set_callback(
	354	req, CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	355	ext4_crypt_complete, &ecr);
	356
	357	BUILD_BUG_ON(EXT4_XTS_TWEAK_SIZE < sizeof(index));
	358	memcpy(xts_tweak, &index, sizeof(index));
	359	memset(&xts_tweak[sizeof(index)], 0,
	360	EXT4_XTS_TWEAK_SIZE - sizeof(index));
	361
	362	sg_init_table(&dst, 1);
	363	sg_set_page(&dst, dest_page, PAGE_CACHE_SIZE, 0);
	364	sg_init_table(&src, 1);
	365	sg_set_page(&src, src_page, PAGE_CACHE_SIZE, 0);
	366	ablkcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE,
	367	xts_tweak);
	368	if (rw == EXT4_DECRYPT)
	369	res = crypto_ablkcipher_decrypt(req);
	370	else
	371	res = crypto_ablkcipher_encrypt(req);
	372	if (res == -EINPROGRESS \|\| res == -EBUSY) {
	373	BUG_ON(req->base.data != &ecr);
	374	wait_for_completion(&ecr.completion);
	375	res = ecr.res;
	376	}
	377	ablkcipher_request_free(req);
	378	if (res) {
	379	printk_ratelimited(
	380	KERN_ERR
	381	"%s: crypto_ablkcipher_encrypt() returned %d\n",
	382	__func__, res);
	383	return res;
	384	}
	385	return 0;
	386	}
	387
	388	/**
	389	* ext4_encrypt() - Encrypts a page
	390	* @inode: The inode for which the encryption should take place
	391	* @plaintext_page: The page to encrypt. Must be locked.
	392	*
	393	* Allocates a ciphertext page and encrypts plaintext_page into it using the ctx
	394	* encryption context.
	395	*
	396	* Called on the page write path. The caller must call
	397	* ext4_restore_control_page() on the returned ciphertext page to
	398	* release the bounce buffer and the encryption context.
	399	*
	400	* Return: An allocated page with the encrypted content on success. Else, an
	401	* error value or NULL.
	402	*/
	403	struct page ext4_encrypt(struct inode inode,
404	struct page *plaintext_page)
405	{
406	struct ext4_crypto_ctx *ctx;
407	struct page *ciphertext_page = NULL;
408	int err;
409
410	BUG_ON(!PageLocked(plaintext_page));
411
412	ctx = ext4_get_crypto_ctx(inode);
413	if (IS_ERR(ctx))
414	return (struct page *) ctx;
415
416	/* The encryption operation will require a bounce page. */
417	ciphertext_page = alloc_page(GFP_NOFS);
418	if (!ciphertext_page) {
419	/* This is a potential bottleneck, but at least we'll have
420	* forward progress. */
421	ciphertext_page = mempool_alloc(ext4_bounce_page_pool,
422	GFP_NOFS);
423	if (WARN_ON_ONCE(!ciphertext_page)) {
424	ciphertext_page = mempool_alloc(ext4_bounce_page_pool,
425	GFP_NOFS \| __GFP_WAIT);
426	}
427	ctx->flags &= ~EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
428	} else {
429	ctx->flags \|= EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
430	}
431	ctx->bounce_page = ciphertext_page;
432	ctx->control_page = plaintext_page;
433	err = ext4_page_crypto(ctx, inode, EXT4_ENCRYPT, plaintext_page->index,
434	plaintext_page, ciphertext_page);
435	if (err) {
436	ext4_release_crypto_ctx(ctx);
437	return ERR_PTR(err);
438	}
439	SetPagePrivate(ciphertext_page);
440	set_page_private(ciphertext_page, (unsigned long)ctx);
441	lock_page(ciphertext_page);
442	return ciphertext_page;
443	}
444
445	/**
446	* ext4_decrypt() - Decrypts a page in-place
447	* @ctx: The encryption context.
448	* @page: The page to decrypt. Must be locked.
449	*
450	* Decrypts page in-place using the ctx encryption context.
451	*
452	* Called from the read completion callback.
453	*
454	* Return: Zero on success, non-zero otherwise.
455	*/
456	int ext4_decrypt(struct ext4_crypto_ctx ctx, struct page page)
457	{
458	BUG_ON(!PageLocked(page));
459
460	return ext4_page_crypto(ctx, page->mapping->host,
461	EXT4_DECRYPT, page->index, page, page);
462	}
463
464	/*
465	* Convenience function which takes care of allocating and
466	* deallocating the encryption context
467	*/
468	int ext4_decrypt_one(struct inode inode, struct page page)
469	{
470	int ret;
471
472	struct ext4_crypto_ctx *ctx = ext4_get_crypto_ctx(inode);
473
474	if (!ctx)
475	return -ENOMEM;
476	ret = ext4_decrypt(ctx, page);
477	ext4_release_crypto_ctx(ctx);
478	return ret;
479	}
480
481	int ext4_encrypted_zeroout(struct inode inode, struct ext4_extent ex)
482	{
483	struct ext4_crypto_ctx *ctx;
484	struct page *ciphertext_page = NULL;
485	struct bio *bio;
486	ext4_lblk_t lblk = ex->ee_block;
487	ext4_fsblk_t pblk = ext4_ext_pblock(ex);
488	unsigned int len = ext4_ext_get_actual_len(ex);
489	int err = 0;
490
491	BUG_ON(inode->i_sb->s_blocksize != PAGE_CACHE_SIZE);
492
493	ctx = ext4_get_crypto_ctx(inode);
494	if (IS_ERR(ctx))
495	return PTR_ERR(ctx);
496
497	ciphertext_page = alloc_page(GFP_NOFS);
498	if (!ciphertext_page) {
499	/* This is a potential bottleneck, but at least we'll have
500	* forward progress. */
501	ciphertext_page = mempool_alloc(ext4_bounce_page_pool,
502	GFP_NOFS);
503	if (WARN_ON_ONCE(!ciphertext_page)) {
504	ciphertext_page = mempool_alloc(ext4_bounce_page_pool,
505	GFP_NOFS \| __GFP_WAIT);
506	}
507	ctx->flags &= ~EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
508	} else {
509	ctx->flags \|= EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
510	}
511	ctx->bounce_page = ciphertext_page;
512
513	while (len--) {
514	err = ext4_page_crypto(ctx, inode, EXT4_ENCRYPT, lblk,
515	ZERO_PAGE(0), ciphertext_page);
516	if (err)
517	goto errout;
518
519	bio = bio_alloc(GFP_KERNEL, 1);
520	if (!bio) {
521	err = -ENOMEM;
522	goto errout;
523	}
524	bio->bi_bdev = inode->i_sb->s_bdev;
525	bio->bi_iter.bi_sector = pblk;
526	err = bio_add_page(bio, ciphertext_page,
527	inode->i_sb->s_blocksize, 0);
528	if (err) {
529	bio_put(bio);
530	goto errout;
531	}
532	err = submit_bio_wait(WRITE, bio);
533	if (err)
534	goto errout;
535	}
536	err = 0;
537	errout:
538	ext4_release_crypto_ctx(ctx);
539	return err;
540	}
541
542	bool ext4_valid_contents_enc_mode(uint32_t mode)
543	{
544	return (mode == EXT4_ENCRYPTION_MODE_AES_256_XTS);
545	}
546
547	/**
548	* ext4_validate_encryption_key_size() - Validate the encryption key size
549	* @mode: The key mode.
550	* @size: The key size to validate.
551	*
552	* Return: The validated key size for @mode. Zero if invalid.
553	*/
554	uint32_t ext4_validate_encryption_key_size(uint32_t mode, uint32_t size)
555	{
556	if (size == ext4_encryption_key_size(mode))
557	return size;
558	return 0;
559	}