[deliverable/linux.git] / fs / f2fs / crypto.c

/*
 * linux/fs/f2fs/crypto.c
 *
 * Copied from linux/fs/ext4/crypto.c
 *
 * Copyright (C) 2015, Google, Inc.
 * Copyright (C) 2015, Motorola Mobility
 *
 * This contains encryption functions for f2fs
 *
 * Written by Michael Halcrow, 2014.
 *
 * Filename encryption additions
 *	Uday Savagaonkar, 2014
 * Encryption policy handling additions
 *	Ildar Muslukhov, 2014
 * Remove ext4_encrypted_zeroout(),
 *   add f2fs_restore_and_release_control_page()
 *	Jaegeuk Kim, 2015.
 *
 * This has not yet undergone a rigorous security audit.
 *
 * The usage of AES-XTS should conform to recommendations in NIST
 * Special Publication 800-38E and IEEE P1619/D16.
 */
#include <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 <linux/f2fs_fs.h>
#include <linux/ratelimit.h>
#include <linux/bio.h>

#include "f2fs.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 *f2fs_bounce_page_pool;

static LIST_HEAD(f2fs_free_crypto_ctxs);
static DEFINE_SPINLOCK(f2fs_crypto_ctx_lock);

struct workqueue_struct *f2fs_read_workqueue;
static DEFINE_MUTEX(crypto_init);

/**
 * f2fs_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 f2fs_release_crypto_ctx(struct f2fs_crypto_ctx *ctx)
{
	unsigned long flags;

	if (ctx->bounce_page) {
		if (ctx->flags & F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL)
			__free_page(ctx->bounce_page);
		else
			mempool_free(ctx->bounce_page, f2fs_bounce_page_pool);
		ctx->bounce_page = NULL;
	}
	ctx->control_page = NULL;
	if (ctx->flags & F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
		if (ctx->tfm)
			crypto_free_tfm(ctx->tfm);
		kfree(ctx);
	} else {
		spin_lock_irqsave(&f2fs_crypto_ctx_lock, flags);
		list_add(&ctx->free_list, &f2fs_free_crypto_ctxs);
		spin_unlock_irqrestore(&f2fs_crypto_ctx_lock, flags);
	}
}

/**
 * f2fs_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 f2fs_crypto_ctx *f2fs_alloc_and_init_crypto_ctx(gfp_t mask)
{
	struct f2fs_crypto_ctx *ctx = kzalloc(sizeof(struct f2fs_crypto_ctx),
						mask);

	if (!ctx)
		return ERR_PTR(-ENOMEM);
	return ctx;
}

/**
 * f2fs_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 f2fs_crypto_ctx *f2fs_get_crypto_ctx(struct inode *inode)
{
	struct f2fs_crypto_ctx *ctx = NULL;
	int res = 0;
	unsigned long flags;
	struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;

	if (ci == NULL)
		return ERR_PTR(-EACCES);

	/*
	 * 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(&f2fs_crypto_ctx_lock, flags);
	ctx = list_first_entry_or_null(&f2fs_free_crypto_ctxs,
					struct f2fs_crypto_ctx, free_list);
	if (ctx)
		list_del(&ctx->free_list);
	spin_unlock_irqrestore(&f2fs_crypto_ctx_lock, flags);
	if (!ctx) {
		ctx = f2fs_alloc_and_init_crypto_ctx(GFP_NOFS);
		if (IS_ERR(ctx)) {
			res = PTR_ERR(ctx);
			goto out;
		}
		ctx->flags |= F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
	} else {
		ctx->flags &= ~F2FS_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 == F2FS_ENCRYPTION_MODE_INVALID);
	if (ctx->tfm && (ctx->mode != ci->ci_mode)) {
		crypto_free_tfm(ctx->tfm);
		ctx->tfm = NULL;
		ctx->mode = F2FS_ENCRYPTION_MODE_INVALID;
	}
	if (!ctx->tfm) {
		switch (ci->ci_mode) {
		case F2FS_ENCRYPTION_MODE_AES_256_XTS:
			ctx->tfm = crypto_ablkcipher_tfm(
				crypto_alloc_ablkcipher("xts(aes)", 0, 0));
			break;
		case F2FS_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 != f2fs_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))
			f2fs_release_crypto_ctx(ctx);
		ctx = ERR_PTR(res);
	}
	return ctx;
}

/*
 * Call f2fs_decrypt on every single page, reusing the encryption
 * context.
 */
static void completion_pages(struct work_struct *work)
{
	struct f2fs_crypto_ctx *ctx =
		container_of(work, struct f2fs_crypto_ctx, work);
	struct bio *bio	= ctx->bio;
	struct bio_vec *bv;
	int i;

	bio_for_each_segment_all(bv, bio, i) {
		struct page *page = bv->bv_page;
		int ret = f2fs_decrypt(ctx, page);

		if (ret) {
			WARN_ON_ONCE(1);
			SetPageError(page);
		} else
			SetPageUptodate(page);
		unlock_page(page);
	}
	f2fs_release_crypto_ctx(ctx);
	bio_put(bio);
}

void f2fs_end_io_crypto_work(struct f2fs_crypto_ctx *ctx, struct bio *bio)
{
	INIT_WORK(&ctx->work, completion_pages);
	ctx->bio = bio;
	queue_work(f2fs_read_workqueue, &ctx->work);
}

/**
 * f2fs_exit_crypto() - Shutdown the f2fs encryption system
 */
void f2fs_exit_crypto(void)
{
	struct f2fs_crypto_ctx *pos, *n;

	list_for_each_entry_safe(pos, n, &f2fs_free_crypto_ctxs, free_list) {
		if (pos->bounce_page) {
			if (pos->flags &
				F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL)
				__free_page(pos->bounce_page);
			else
				mempool_free(pos->bounce_page,
						f2fs_bounce_page_pool);
		}
		if (pos->tfm)
			crypto_free_tfm(pos->tfm);
		kfree(pos);
	}
	INIT_LIST_HEAD(&f2fs_free_crypto_ctxs);
	if (f2fs_bounce_page_pool)
		mempool_destroy(f2fs_bounce_page_pool);
	f2fs_bounce_page_pool = NULL;
	if (f2fs_read_workqueue)
		destroy_workqueue(f2fs_read_workqueue);
	f2fs_read_workqueue = NULL;
}

/**
 * f2fs_init_crypto() - Set up for f2fs 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 f2fs_init_crypto(void)
{
	int i, res;

	mutex_lock(&crypto_init);
	if (f2fs_read_workqueue)
		goto already_initialized;

	f2fs_read_workqueue = alloc_workqueue("f2fs_crypto", WQ_HIGHPRI, 0);
	if (!f2fs_read_workqueue) {
		res = -ENOMEM;
		goto fail;
	}

	for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
		struct f2fs_crypto_ctx *ctx;

		ctx = f2fs_alloc_and_init_crypto_ctx(GFP_KERNEL);
		if (IS_ERR(ctx)) {
			res = PTR_ERR(ctx);
			goto fail;
		}
		list_add(&ctx->free_list, &f2fs_free_crypto_ctxs);
	}

	f2fs_bounce_page_pool =
		mempool_create_page_pool(num_prealloc_crypto_pages, 0);
	if (!f2fs_bounce_page_pool) {
		res = -ENOMEM;
		goto fail;
	}
already_initialized:
	mutex_unlock(&crypto_init);
	return 0;
fail:
	f2fs_exit_crypto();
	mutex_unlock(&crypto_init);
	return res;
}

void f2fs_restore_and_release_control_page(struct page **page)
{
	struct f2fs_crypto_ctx *ctx;
	struct page *bounce_page;

	/* The bounce data pages are unmapped. */
	if ((*page)->mapping)
		return;

	/* The bounce data page is unmapped. */
	bounce_page = *page;
	ctx = (struct f2fs_crypto_ctx *)page_private(bounce_page);

	/* restore control page */
	*page = ctx->control_page;

	f2fs_restore_control_page(bounce_page);
}

void f2fs_restore_control_page(struct page *data_page)
{
	struct f2fs_crypto_ctx *ctx =
		(struct f2fs_crypto_ctx *)page_private(data_page);

	set_page_private(data_page, (unsigned long)NULL);
	ClearPagePrivate(data_page);
	unlock_page(data_page);
	f2fs_release_crypto_ctx(ctx);
}

/**
 * f2fs_crypt_complete() - The completion callback for page encryption
 * @req: The asynchronous encryption request context
 * @res: The result of the encryption operation
 */
static void f2fs_crypt_complete(struct crypto_async_request *req, int res)
{
	struct f2fs_completion_result *ecr = req->data;

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

typedef enum {
	F2FS_DECRYPT = 0,
	F2FS_ENCRYPT,
} f2fs_direction_t;

static int f2fs_page_crypto(struct f2fs_crypto_ctx *ctx,
				struct inode *inode,
				f2fs_direction_t rw,
				pgoff_t index,
				struct page *src_page,
				struct page *dest_page)
{
	u8 xts_tweak[F2FS_XTS_TWEAK_SIZE];
	struct ablkcipher_request *req = NULL;
	DECLARE_F2FS_COMPLETION_RESULT(ecr);
	struct scatterlist dst, src;
	struct f2fs_inode_info *fi = F2FS_I(inode);
	struct crypto_ablkcipher *atfm = __crypto_ablkcipher_cast(ctx->tfm);
	int res = 0;

	BUG_ON(!ctx->tfm);
	BUG_ON(ctx->mode != fi->i_crypt_info->ci_mode);

	if (ctx->mode != F2FS_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, fi->i_crypt_info->ci_raw,
					fi->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,
		f2fs_crypt_complete, &ecr);

	BUILD_BUG_ON(F2FS_XTS_TWEAK_SIZE < sizeof(index));
	memcpy(xts_tweak, &index, sizeof(index));
	memset(&xts_tweak[sizeof(index)], 0,
			F2FS_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 == F2FS_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;
}

/**
 * f2fs_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
 * f2fs_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 *f2fs_encrypt(struct inode *inode,
			  struct page *plaintext_page)
{
	struct f2fs_crypto_ctx *ctx;
	struct page *ciphertext_page = NULL;
	int err;

	BUG_ON(!PageLocked(plaintext_page));

	ctx = f2fs_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(f2fs_bounce_page_pool,
							GFP_NOFS);
		if (WARN_ON_ONCE(!ciphertext_page))
			ciphertext_page = mempool_alloc(f2fs_bounce_page_pool,
						GFP_NOFS | __GFP_WAIT);
		ctx->flags &= ~F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
	} else {
		ctx->flags |= F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
	}
	ctx->bounce_page = ciphertext_page;
	ctx->control_page = plaintext_page;
	err = f2fs_page_crypto(ctx, inode, F2FS_ENCRYPT, plaintext_page->index,
					plaintext_page, ciphertext_page);
	if (err) {
		f2fs_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;
}

/**
 * f2fs_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 f2fs_decrypt(struct f2fs_crypto_ctx *ctx, struct page *page)
{
	BUG_ON(!PageLocked(page));

	return f2fs_page_crypto(ctx, page->mapping->host,
				F2FS_DECRYPT, page->index, page, page);
}

/*
 * Convenience function which takes care of allocating and
 * deallocating the encryption context
 */
int f2fs_decrypt_one(struct inode *inode, struct page *page)
{
	struct f2fs_crypto_ctx *ctx = f2fs_get_crypto_ctx(inode);
	int ret;

	if (!ctx)
		return -ENOMEM;
	ret = f2fs_decrypt(ctx, page);
	f2fs_release_crypto_ctx(ctx);
	return ret;
}

bool f2fs_valid_contents_enc_mode(uint32_t mode)
{
	return (mode == F2FS_ENCRYPTION_MODE_AES_256_XTS);
}

/**
 * f2fs_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 f2fs_validate_encryption_key_size(uint32_t mode, uint32_t size)
{
	if (size == f2fs_encryption_key_size(mode))
		return size;
	return 0;
}
Commit	Line	Data
57e5055b JK	1	/*
	2	* linux/fs/f2fs/crypto.c
	3	*
	4	* Copied from linux/fs/ext4/crypto.c
	5	*
	6	* Copyright (C) 2015, Google, Inc.
	7	* Copyright (C) 2015, Motorola Mobility
	8	*
	9	* This contains encryption functions for f2fs
	10	*
	11	* Written by Michael Halcrow, 2014.
	12	*
	13	* Filename encryption additions
	14	* Uday Savagaonkar, 2014
	15	* Encryption policy handling additions
	16	* Ildar Muslukhov, 2014
	17	* Remove ext4_encrypted_zeroout(),
	18	* add f2fs_restore_and_release_control_page()
	19	* Jaegeuk Kim, 2015.
	20	*
	21	* This has not yet undergone a rigorous security audit.
	22	*
	23	* The usage of AES-XTS should conform to recommendations in NIST
	24	* Special Publication 800-38E and IEEE P1619/D16.
	25	*/
	26	#include <crypto/hash.h>
	27	#include <crypto/sha.h>
	28	#include <keys/user-type.h>
	29	#include <keys/encrypted-type.h>
	30	#include <linux/crypto.h>
	31	#include <linux/ecryptfs.h>
	32	#include <linux/gfp.h>
	33	#include <linux/kernel.h>
	34	#include <linux/key.h>
	35	#include <linux/list.h>
	36	#include <linux/mempool.h>
	37	#include <linux/module.h>
	38	#include <linux/mutex.h>
	39	#include <linux/random.h>
	40	#include <linux/scatterlist.h>
	41	#include <linux/spinlock_types.h>
	42	#include <linux/f2fs_fs.h>
	43	#include <linux/ratelimit.h>
	44	#include <linux/bio.h>
	45
	46	#include "f2fs.h"
	47	#include "xattr.h"
	48
	49	/* Encryption added and removed here! (L: */
	50
	51	static unsigned int num_prealloc_crypto_pages = 32;
	52	static unsigned int num_prealloc_crypto_ctxs = 128;
	53
	54	module_param(num_prealloc_crypto_pages, uint, 0444);
	55	MODULE_PARM_DESC(num_prealloc_crypto_pages,
	56	"Number of crypto pages to preallocate");
	57	module_param(num_prealloc_crypto_ctxs, uint, 0444);
	58	MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
	59	"Number of crypto contexts to preallocate");
	60
	61	static mempool_t *f2fs_bounce_page_pool;
	62
	63	static LIST_HEAD(f2fs_free_crypto_ctxs);
	64	static DEFINE_SPINLOCK(f2fs_crypto_ctx_lock);
65
66	struct workqueue_struct *f2fs_read_workqueue;
67	static DEFINE_MUTEX(crypto_init);
68
69	/**
70	* f2fs_release_crypto_ctx() - Releases an encryption context
71	* @ctx: The encryption context to release.
72	*
73	* If the encryption context was allocated from the pre-allocated pool, returns
74	* it to that pool. Else, frees it.
75	*
76	* If there's a bounce page in the context, this frees that.
77	*/
78	void f2fs_release_crypto_ctx(struct f2fs_crypto_ctx *ctx)
79	{
80	unsigned long flags;
81
82	if (ctx->bounce_page) {
83	if (ctx->flags & F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL)
84	__free_page(ctx->bounce_page);
85	else
86	mempool_free(ctx->bounce_page, f2fs_bounce_page_pool);
87	ctx->bounce_page = NULL;
88	}
89	ctx->control_page = NULL;
90	if (ctx->flags & F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
91	if (ctx->tfm)
92	crypto_free_tfm(ctx->tfm);
93	kfree(ctx);
94	} else {
95	spin_lock_irqsave(&f2fs_crypto_ctx_lock, flags);
96	list_add(&ctx->free_list, &f2fs_free_crypto_ctxs);
97	spin_unlock_irqrestore(&f2fs_crypto_ctx_lock, flags);
98	}
99	}
100
101	/**
102	* f2fs_alloc_and_init_crypto_ctx() - Allocates and inits an encryption context
103	* @mask: The allocation mask.
104	*
105	* Return: An allocated and initialized encryption context on success. An error
106	* value or NULL otherwise.
107	*/
108	static struct f2fs_crypto_ctx *f2fs_alloc_and_init_crypto_ctx(gfp_t mask)
109	{
110	struct f2fs_crypto_ctx *ctx = kzalloc(sizeof(struct f2fs_crypto_ctx),
111	mask);
112
113	if (!ctx)
114	return ERR_PTR(-ENOMEM);
115	return ctx;
116	}
117
118	/**
119	* f2fs_get_crypto_ctx() - Gets an encryption context
120	* @inode: The inode for which we are doing the crypto
121	*
122	* Allocates and initializes an encryption context.
123	*
124	* Return: An allocated and initialized encryption context on success; error
125	* value or NULL otherwise.
126	*/
127	struct f2fs_crypto_ctx f2fs_get_crypto_ctx(struct inode inode)
128	{
129	struct f2fs_crypto_ctx *ctx = NULL;
130	int res = 0;
131	unsigned long flags;
132	struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
133
edf3fb8e JK	134	if (ci == NULL)
	135	return ERR_PTR(-EACCES);
	136
57e5055b JK	137	/*
	138	* We first try getting the ctx from a free list because in
	139	* the common case the ctx will have an allocated and
	140	* initialized crypto tfm, so it's probably a worthwhile
	141	* optimization. For the bounce page, we first try getting it
	142	* from the kernel allocator because that's just about as fast
	143	* as getting it from a list and because a cache of free pages
	144	* should generally be a "last resort" option for a filesystem
	145	* to be able to do its job.
	146	*/
	147	spin_lock_irqsave(&f2fs_crypto_ctx_lock, flags);
	148	ctx = list_first_entry_or_null(&f2fs_free_crypto_ctxs,
	149	struct f2fs_crypto_ctx, free_list);
	150	if (ctx)
	151	list_del(&ctx->free_list);
	152	spin_unlock_irqrestore(&f2fs_crypto_ctx_lock, flags);
	153	if (!ctx) {
	154	ctx = f2fs_alloc_and_init_crypto_ctx(GFP_NOFS);
	155	if (IS_ERR(ctx)) {
	156	res = PTR_ERR(ctx);
	157	goto out;
	158	}
	159	ctx->flags \|= F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
	160	} else {
	161	ctx->flags &= ~F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
	162	}
	163
	164	/*
	165	* Allocate a new Crypto API context if we don't already have
	166	* one or if it isn't the right mode.
	167	*/
	168	BUG_ON(ci->ci_mode == F2FS_ENCRYPTION_MODE_INVALID);
	169	if (ctx->tfm && (ctx->mode != ci->ci_mode)) {
	170	crypto_free_tfm(ctx->tfm);
	171	ctx->tfm = NULL;
	172	ctx->mode = F2FS_ENCRYPTION_MODE_INVALID;
	173	}
	174	if (!ctx->tfm) {
	175	switch (ci->ci_mode) {
	176	case F2FS_ENCRYPTION_MODE_AES_256_XTS:
	177	ctx->tfm = crypto_ablkcipher_tfm(
	178	crypto_alloc_ablkcipher("xts(aes)", 0, 0));
	179	break;
	180	case F2FS_ENCRYPTION_MODE_AES_256_GCM:
	181	/*
	182	* TODO(mhalcrow): AEAD w/ gcm(aes);
	183	* crypto_aead_setauthsize()
	184	*/
	185	ctx->tfm = ERR_PTR(-ENOTSUPP);
	186	break;
	187	default:
	188	BUG();
	189	}
	190	if (IS_ERR_OR_NULL(ctx->tfm)) {
	191	res = PTR_ERR(ctx->tfm);
	192	ctx->tfm = NULL;
	193	goto out;
	194	}
	195	ctx->mode = ci->ci_mode;
	196	}
	197	BUG_ON(ci->ci_size != f2fs_encryption_key_size(ci->ci_mode));
	198
	199	/*
	200	* There shouldn't be a bounce page attached to the crypto
201	* context at this point.
202	*/
203	BUG_ON(ctx->bounce_page);
204
205	out:
206	if (res) {
207	if (!IS_ERR_OR_NULL(ctx))
208	f2fs_release_crypto_ctx(ctx);
209	ctx = ERR_PTR(res);
210	}
211	return ctx;
212	}
213
214	/*
215	* Call f2fs_decrypt on every single page, reusing the encryption
216	* context.
217	*/
218	static void completion_pages(struct work_struct *work)
219	{
220	struct f2fs_crypto_ctx *ctx =
221	container_of(work, struct f2fs_crypto_ctx, work);
222	struct bio *bio = ctx->bio;
223	struct bio_vec *bv;
224	int i;
225
226	bio_for_each_segment_all(bv, bio, i) {
227	struct page *page = bv->bv_page;
228	int ret = f2fs_decrypt(ctx, page);
229
230	if (ret) {
231	WARN_ON_ONCE(1);
232	SetPageError(page);
233	} else
234	SetPageUptodate(page);
235	unlock_page(page);
236	}
237	f2fs_release_crypto_ctx(ctx);
238	bio_put(bio);
239	}
240
241	void f2fs_end_io_crypto_work(struct f2fs_crypto_ctx ctx, struct bio bio)
242	{
243	INIT_WORK(&ctx->work, completion_pages);
244	ctx->bio = bio;
245	queue_work(f2fs_read_workqueue, &ctx->work);
246	}
247
248	/**
249	* f2fs_exit_crypto() - Shutdown the f2fs encryption system
250	*/
251	void f2fs_exit_crypto(void)
252	{
253	struct f2fs_crypto_ctx pos, n;
254
255	list_for_each_entry_safe(pos, n, &f2fs_free_crypto_ctxs, free_list) {
256	if (pos->bounce_page) {
257	if (pos->flags &
258	F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL)
259	__free_page(pos->bounce_page);
260	else
261	mempool_free(pos->bounce_page,
262	f2fs_bounce_page_pool);
263	}
264	if (pos->tfm)
265	crypto_free_tfm(pos->tfm);
266	kfree(pos);
267	}
268	INIT_LIST_HEAD(&f2fs_free_crypto_ctxs);
269	if (f2fs_bounce_page_pool)
270	mempool_destroy(f2fs_bounce_page_pool);
271	f2fs_bounce_page_pool = NULL;
272	if (f2fs_read_workqueue)
273	destroy_workqueue(f2fs_read_workqueue);
274	f2fs_read_workqueue = NULL;
275	}
276
277	/**
278	* f2fs_init_crypto() - Set up for f2fs encryption.
279	*
280	* We only call this when we start accessing encrypted files, since it
281	* results in memory getting allocated that wouldn't otherwise be used.
282	*
283	* Return: Zero on success, non-zero otherwise.
284	*/
285	int f2fs_init_crypto(void)
286	{
287	int i, res;
288
289	mutex_lock(&crypto_init);
290	if (f2fs_read_workqueue)
291	goto already_initialized;
292
293	f2fs_read_workqueue = alloc_workqueue("f2fs_crypto", WQ_HIGHPRI, 0);
294	if (!f2fs_read_workqueue) {
295	res = -ENOMEM;
296	goto fail;
297	}
298
299	for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
300	struct f2fs_crypto_ctx *ctx;
301
302	ctx = f2fs_alloc_and_init_crypto_ctx(GFP_KERNEL);
303	if (IS_ERR(ctx)) {
304	res = PTR_ERR(ctx);
305	goto fail;
306	}
307	list_add(&ctx->free_list, &f2fs_free_crypto_ctxs);
308	}
309
310	f2fs_bounce_page_pool =
311	mempool_create_page_pool(num_prealloc_crypto_pages, 0);
312	if (!f2fs_bounce_page_pool) {
313	res = -ENOMEM;
314	goto fail;
315	}
316	already_initialized:
317	mutex_unlock(&crypto_init);
318	return 0;
319	fail:
320	f2fs_exit_crypto();
321	mutex_unlock(&crypto_init);
322	return res;
323	}
324
325	void f2fs_restore_and_release_control_page(struct page **page)
326	{
327	struct f2fs_crypto_ctx *ctx;
328	struct page *bounce_page;
329
330	/* The bounce data pages are unmapped. */
331	if ((*page)->mapping)
332	return;
333
334	/* The bounce data page is unmapped. */
335	bounce_page = *page;
336	ctx = (struct f2fs_crypto_ctx *)page_private(bounce_page);
337
338	/* restore control page */
339	*page = ctx->control_page;
340
341	f2fs_restore_control_page(bounce_page);
342	}
343
344	void f2fs_restore_control_page(struct page *data_page)
345	{
346	struct f2fs_crypto_ctx *ctx =
347	(struct f2fs_crypto_ctx *)page_private(data_page);
348
349	set_page_private(data_page, (unsigned long)NULL);
350	ClearPagePrivate(data_page);
351	unlock_page(data_page);
352	f2fs_release_crypto_ctx(ctx);
353	}
354
355	/**
356	* f2fs_crypt_complete() - The completion callback for page encryption
357	* @req: The asynchronous encryption request context
358	* @res: The result of the encryption operation
359	*/
360	static void f2fs_crypt_complete(struct crypto_async_request *req, int res)
361	{
362	struct f2fs_completion_result *ecr = req->data;
363
364	if (res == -EINPROGRESS)
365	return;
366	ecr->res = res;
367	complete(&ecr->completion);
368	}
369
370	typedef enum {
371	F2FS_DECRYPT = 0,
372	F2FS_ENCRYPT,
373	} f2fs_direction_t;
374
375	static int f2fs_page_crypto(struct f2fs_crypto_ctx *ctx,
376	struct inode *inode,
377	f2fs_direction_t rw,
378	pgoff_t index,
379	struct page *src_page,
380	struct page *dest_page)
381	{
382	u8 xts_tweak[F2FS_XTS_TWEAK_SIZE];
383	struct ablkcipher_request *req = NULL;
384	DECLARE_F2FS_COMPLETION_RESULT(ecr);
385	struct scatterlist dst, src;
386	struct f2fs_inode_info *fi = F2FS_I(inode);
387	struct crypto_ablkcipher *atfm = __crypto_ablkcipher_cast(ctx->tfm);
388	int res = 0;
389
390	BUG_ON(!ctx->tfm);
391	BUG_ON(ctx->mode != fi->i_crypt_info->ci_mode);
392
393	if (ctx->mode != F2FS_ENCRYPTION_MODE_AES_256_XTS) {
394	printk_ratelimited(KERN_ERR
395	"%s: unsupported crypto algorithm: %d\n",
396	__func__, ctx->mode);
397	return -ENOTSUPP;
398	}
399
400	crypto_ablkcipher_clear_flags(atfm, ~0);
401	crypto_tfm_set_flags(ctx->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
402
403	res = crypto_ablkcipher_setkey(atfm, fi->i_crypt_info->ci_raw,
404	fi->i_crypt_info->ci_size);
405	if (res) {
406	printk_ratelimited(KERN_ERR
407	"%s: crypto_ablkcipher_setkey() failed\n",
408	__func__);
409	return res;
410	}
411	req = ablkcipher_request_alloc(atfm, GFP_NOFS);
412	if (!req) {
413	printk_ratelimited(KERN_ERR
414	"%s: crypto_request_alloc() failed\n",
415	__func__);
416	return -ENOMEM;
417	}
418	ablkcipher_request_set_callback(
419	req, CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
420	f2fs_crypt_complete, &ecr);
421
422	BUILD_BUG_ON(F2FS_XTS_TWEAK_SIZE < sizeof(index));
423	memcpy(xts_tweak, &index, sizeof(index));
424	memset(&xts_tweak[sizeof(index)], 0,
425	F2FS_XTS_TWEAK_SIZE - sizeof(index));
426
427	sg_init_table(&dst, 1);
428	sg_set_page(&dst, dest_page, PAGE_CACHE_SIZE, 0);
429	sg_init_table(&src, 1);
430	sg_set_page(&src, src_page, PAGE_CACHE_SIZE, 0);
431	ablkcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE,
432	xts_tweak);
433	if (rw == F2FS_DECRYPT)
434	res = crypto_ablkcipher_decrypt(req);
435	else
436	res = crypto_ablkcipher_encrypt(req);
437	if (res == -EINPROGRESS \|\| res == -EBUSY) {
438	BUG_ON(req->base.data != &ecr);
439	wait_for_completion(&ecr.completion);
440	res = ecr.res;
441	}
442	ablkcipher_request_free(req);
443	if (res) {
444	printk_ratelimited(KERN_ERR
445	"%s: crypto_ablkcipher_encrypt() returned %d\n",
446	__func__, res);
447	return res;
448	}
449	return 0;
450	}
451
452	/**
453	* f2fs_encrypt() - Encrypts a page
454	* @inode: The inode for which the encryption should take place
455	* @plaintext_page: The page to encrypt. Must be locked.
456	*
457	* Allocates a ciphertext page and encrypts plaintext_page into it using the ctx
458	* encryption context.
459	*
460	* Called on the page write path. The caller must call
461	* f2fs_restore_control_page() on the returned ciphertext page to
462	* release the bounce buffer and the encryption context.
463	*
464	* Return: An allocated page with the encrypted content on success. Else, an
465	* error value or NULL.
466	*/
467	struct page f2fs_encrypt(struct inode inode,
468	struct page *plaintext_page)
469	{
470	struct f2fs_crypto_ctx *ctx;
471	struct page *ciphertext_page = NULL;
472	int err;
473
474	BUG_ON(!PageLocked(plaintext_page));
475
476	ctx = f2fs_get_crypto_ctx(inode);
477	if (IS_ERR(ctx))
478	return (struct page *)ctx;
479
480	/* The encryption operation will require a bounce page. */
481	ciphertext_page = alloc_page(GFP_NOFS);
482	if (!ciphertext_page) {
483	/*
484	* This is a potential bottleneck, but at least we'll have
485	* forward progress.
486	*/
487	ciphertext_page = mempool_alloc(f2fs_bounce_page_pool,
488	GFP_NOFS);
489	if (WARN_ON_ONCE(!ciphertext_page))
490	ciphertext_page = mempool_alloc(f2fs_bounce_page_pool,
491	GFP_NOFS \| __GFP_WAIT);
492	ctx->flags &= ~F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
493	} else {
494	ctx->flags \|= F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
495	}
496	ctx->bounce_page = ciphertext_page;
497	ctx->control_page = plaintext_page;
498	err = f2fs_page_crypto(ctx, inode, F2FS_ENCRYPT, plaintext_page->index,
499	plaintext_page, ciphertext_page);
500	if (err) {
501	f2fs_release_crypto_ctx(ctx);
502	return ERR_PTR(err);
503	}
504	SetPagePrivate(ciphertext_page);
505	set_page_private(ciphertext_page, (unsigned long)ctx);
506	lock_page(ciphertext_page);
507	return ciphertext_page;
508	}
509
510	/**
511	* f2fs_decrypt() - Decrypts a page in-place
512	* @ctx: The encryption context.
513	* @page: The page to decrypt. Must be locked.
514	*
515	* Decrypts page in-place using the ctx encryption context.
516	*
517	* Called from the read completion callback.
518	*
519	* Return: Zero on success, non-zero otherwise.
520	*/
521	int f2fs_decrypt(struct f2fs_crypto_ctx ctx, struct page page)
522	{
523	BUG_ON(!PageLocked(page));
524
525	return f2fs_page_crypto(ctx, page->mapping->host,
526	F2FS_DECRYPT, page->index, page, page);
527	}
528
529	/*
530	* Convenience function which takes care of allocating and
531	* deallocating the encryption context
532	*/
533	int f2fs_decrypt_one(struct inode inode, struct page page)
534	{
535	struct f2fs_crypto_ctx *ctx = f2fs_get_crypto_ctx(inode);
536	int ret;
537
538	if (!ctx)
539	return -ENOMEM;
540	ret = f2fs_decrypt(ctx, page);
541	f2fs_release_crypto_ctx(ctx);
542	return ret;
543	}
544
545	bool f2fs_valid_contents_enc_mode(uint32_t mode)
546	{
547	return (mode == F2FS_ENCRYPTION_MODE_AES_256_XTS);
548	}
549
550	/**
551	* f2fs_validate_encryption_key_size() - Validate the encryption key size
552	* @mode: The key mode.
553	* @size: The key size to validate.
554	*
555	* Return: The validated key size for @mode. Zero if invalid.
556	*/
557	uint32_t f2fs_validate_encryption_key_size(uint32_t mode, uint32_t size)
558	{
559	if (size == f2fs_encryption_key_size(mode))
560	return size;
561	return 0;
562	}