fs/crypto/crypto.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * This contains encryption functions for per-file encryption.
  *
  * Copyright (C) 2015, Google, Inc.
  * Copyright (C) 2015, Motorola Mobility
  *
  * Written by Michael Halcrow, 2014.
  *
  * Filename encryption additions
  *	Uday Savagaonkar, 2014
  * Encryption policy handling additions
  *	Ildar Muslukhov, 2014
  * Add fscrypt_pullback_bio_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 <linux/pagemap.h>
 #include <linux/mempool.h>
 #include <linux/module.h>
 #include <linux/scatterlist.h>
 #include <linux/ratelimit.h>
 #include <linux/dcache.h>
 #include <linux/namei.h>
 #include <crypto/aes.h>
 #include <crypto/skcipher.h>
 #include "fscrypt_private.h"

 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 *fscrypt_bounce_page_pool = NULL;

 static LIST_HEAD(fscrypt_free_ctxs);
 static DEFINE_SPINLOCK(fscrypt_ctx_lock);

 static struct workqueue_struct *fscrypt_read_workqueue;
 static DEFINE_MUTEX(fscrypt_init_mutex);

 static struct kmem_cache *fscrypt_ctx_cachep;
 struct kmem_cache *fscrypt_info_cachep;

 void fscrypt_enqueue_decrypt_work(struct work_struct *work)
 {
 	queue_work(fscrypt_read_workqueue, work);
 }
 EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);

 /**
  * fscrypt_release_ctx() - Release a decryption context
  * @ctx: The decryption context to release.
  *
  * If the decryption context was allocated from the pre-allocated pool, return
  * it to that pool.  Else, free it.
  */
 void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
 {
 	unsigned long flags;

 	if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
 		kmem_cache_free(fscrypt_ctx_cachep, ctx);
 	} else {
 		spin_lock_irqsave(&fscrypt_ctx_lock, flags);
 		list_add(&ctx->free_list, &fscrypt_free_ctxs);
 		spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
 	}
 }
 EXPORT_SYMBOL(fscrypt_release_ctx);

 /**
  * fscrypt_get_ctx() - Get a decryption context
  * @gfp_flags:   The gfp flag for memory allocation
  *
  * Allocate and initialize a decryption context.
  *
  * Return: A new decryption context on success; an ERR_PTR() otherwise.
  */
 struct fscrypt_ctx *fscrypt_get_ctx(gfp_t gfp_flags)
 {
 	struct fscrypt_ctx *ctx;
 	unsigned long flags;

 	/*
 	 * First try getting a ctx from the free list so that we don't have to
 	 * call into the slab allocator.
 	 */
 	spin_lock_irqsave(&fscrypt_ctx_lock, flags);
 	ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
 					struct fscrypt_ctx, free_list);
 	if (ctx)
 		list_del(&ctx->free_list);
 	spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
 	if (!ctx) {
 		ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
 		if (!ctx)
 			return ERR_PTR(-ENOMEM);
 		ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
 	} else {
 		ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
 	}
 	return ctx;
 }
 EXPORT_SYMBOL(fscrypt_get_ctx);

 struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags)
 {
 	return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
 }

 /**
  * fscrypt_free_bounce_page() - free a ciphertext bounce page
  *
  * Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(),
  * or by fscrypt_alloc_bounce_page() directly.
  */
 void fscrypt_free_bounce_page(struct page *bounce_page)
 {
 	if (!bounce_page)
 		return;
 	set_page_private(bounce_page, (unsigned long)NULL);
 	ClearPagePrivate(bounce_page);
 	mempool_free(bounce_page, fscrypt_bounce_page_pool);
 }
 EXPORT_SYMBOL(fscrypt_free_bounce_page);

 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
 			 const struct fscrypt_info *ci)
 {
 	memset(iv, 0, ci->ci_mode->ivsize);
 	iv->lblk_num = cpu_to_le64(lblk_num);

 	if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY)
 		memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE);

 	if (ci->ci_essiv_tfm != NULL)
 		crypto_cipher_encrypt_one(ci->ci_essiv_tfm, iv->raw, iv->raw);
 }

 /* Encrypt or decrypt a single filesystem block of file contents */
 int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
 			u64 lblk_num, struct page *src_page,
 			struct page *dest_page, unsigned int len,
 			unsigned int offs, gfp_t gfp_flags)
 {
 	union fscrypt_iv iv;
 	struct skcipher_request *req = NULL;
 	DECLARE_CRYPTO_WAIT(wait);
 	struct scatterlist dst, src;
 	struct fscrypt_info *ci = inode->i_crypt_info;
 	struct crypto_skcipher *tfm = ci->ci_ctfm;
 	int res = 0;

 	if (WARN_ON_ONCE(len <= 0))
 		return -EINVAL;
 	if (WARN_ON_ONCE(len % FS_CRYPTO_BLOCK_SIZE != 0))
 		return -EINVAL;

 	fscrypt_generate_iv(&iv, lblk_num, ci);

 	req = skcipher_request_alloc(tfm, gfp_flags);
 	if (!req)
 		return -ENOMEM;

 	skcipher_request_set_callback(
 		req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 		crypto_req_done, &wait);

 	sg_init_table(&dst, 1);
 	sg_set_page(&dst, dest_page, len, offs);
 	sg_init_table(&src, 1);
 	sg_set_page(&src, src_page, len, offs);
 	skcipher_request_set_crypt(req, &src, &dst, len, &iv);
 	if (rw == FS_DECRYPT)
 		res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
 	else
 		res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
 	skcipher_request_free(req);
 	if (res) {
 		fscrypt_err(inode->i_sb,
 			    "%scryption failed for inode %lu, block %llu: %d",
 			    (rw == FS_DECRYPT ? "de" : "en"),
 			    inode->i_ino, lblk_num, res);
 		return res;
 	}
 	return 0;
 }

 /**
  * fscrypt_encrypt_pagecache_blocks() - Encrypt filesystem blocks from a pagecache page
  * @page:      The locked pagecache page containing the block(s) to encrypt
  * @len:       Total size of the block(s) to encrypt.  Must be a nonzero
  *		multiple of the filesystem's block size.
  * @offs:      Byte offset within @page of the first block to encrypt.  Must be
  *		a multiple of the filesystem's block size.
  * @gfp_flags: Memory allocation flags
  *
  * A new bounce page is allocated, and the specified block(s) are encrypted into
  * it.  In the bounce page, the ciphertext block(s) will be located at the same
  * offsets at which the plaintext block(s) were located in the source page; any
  * other parts of the bounce page will be left uninitialized.  However, normally
  * blocksize == PAGE_SIZE and the whole page is encrypted at once.
  *
  * This is for use by the filesystem's ->writepages() method.
  *
  * Return: the new encrypted bounce page on success; an ERR_PTR() on failure
  */
 struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
 					      unsigned int len,
 					      unsigned int offs,
 					      gfp_t gfp_flags)

 {
 	const struct inode *inode = page->mapping->host;
 	const unsigned int blockbits = inode->i_blkbits;
 	const unsigned int blocksize = 1 << blockbits;
 	struct page *ciphertext_page;
 	u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
 		       (offs >> blockbits);
 	unsigned int i;
 	int err;

 	if (WARN_ON_ONCE(!PageLocked(page)))
 		return ERR_PTR(-EINVAL);

 	if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize)))
 		return ERR_PTR(-EINVAL);

 	ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags);
 	if (!ciphertext_page)
 		return ERR_PTR(-ENOMEM);

 	for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
 		err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num,
 					  page, ciphertext_page,
 					  blocksize, i, gfp_flags);
 		if (err) {
 			fscrypt_free_bounce_page(ciphertext_page);
 			return ERR_PTR(err);
 		}
 	}
 	SetPagePrivate(ciphertext_page);
 	set_page_private(ciphertext_page, (unsigned long)page);
 	return ciphertext_page;
 }
 EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks);

 /**
  * fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place
  * @inode:     The inode to which this block belongs
  * @page:      The page containing the block to encrypt
  * @len:       Size of block to encrypt.  Doesn't need to be a multiple of the
  *		fs block size, but must be a multiple of FS_CRYPTO_BLOCK_SIZE.
  * @offs:      Byte offset within @page at which the block to encrypt begins
  * @lblk_num:  Filesystem logical block number of the block, i.e. the 0-based
  *		number of the block within the file
  * @gfp_flags: Memory allocation flags
  *
  * Encrypt a possibly-compressed filesystem block that is located in an
  * arbitrary page, not necessarily in the original pagecache page.  The @inode
  * and @lblk_num must be specified, as they can't be determined from @page.
  *
  * Return: 0 on success; -errno on failure
  */
 int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page,
 				  unsigned int len, unsigned int offs,
 				  u64 lblk_num, gfp_t gfp_flags)
 {
 	return fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, page, page,
 				   len, offs, gfp_flags);
 }
 EXPORT_SYMBOL(fscrypt_encrypt_block_inplace);

 /**
  * fscrypt_decrypt_pagecache_blocks() - Decrypt filesystem blocks in a pagecache page
  * @page:      The locked pagecache page containing the block(s) to decrypt
  * @len:       Total size of the block(s) to decrypt.  Must be a nonzero
  *		multiple of the filesystem's block size.
  * @offs:      Byte offset within @page of the first block to decrypt.  Must be
  *		a multiple of the filesystem's block size.
  *
  * The specified block(s) are decrypted in-place within the pagecache page,
  * which must still be locked and not uptodate.  Normally, blocksize ==
  * PAGE_SIZE and the whole page is decrypted at once.
  *
  * This is for use by the filesystem's ->readpages() method.
  *
  * Return: 0 on success; -errno on failure
  */
 int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len,
 				     unsigned int offs)
 {
 	const struct inode *inode = page->mapping->host;
 	const unsigned int blockbits = inode->i_blkbits;
 	const unsigned int blocksize = 1 << blockbits;
 	u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
 		       (offs >> blockbits);
 	unsigned int i;
 	int err;

 	if (WARN_ON_ONCE(!PageLocked(page)))
 		return -EINVAL;

 	if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize)))
 		return -EINVAL;

 	for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
 		err = fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page,
 					  page, blocksize, i, GFP_NOFS);
 		if (err)
 			return err;
 	}
 	return 0;
 }
 EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks);

 /**
  * fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place
  * @inode:     The inode to which this block belongs
  * @page:      The page containing the block to decrypt
  * @len:       Size of block to decrypt.  Doesn't need to be a multiple of the
  *		fs block size, but must be a multiple of FS_CRYPTO_BLOCK_SIZE.
  * @offs:      Byte offset within @page at which the block to decrypt begins
  * @lblk_num:  Filesystem logical block number of the block, i.e. the 0-based
  *		number of the block within the file
  *
  * Decrypt a possibly-compressed filesystem block that is located in an
  * arbitrary page, not necessarily in the original pagecache page.  The @inode
  * and @lblk_num must be specified, as they can't be determined from @page.
  *
  * Return: 0 on success; -errno on failure
  */
 int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page,
 				  unsigned int len, unsigned int offs,
 				  u64 lblk_num)
 {
 	return fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page, page,
 				   len, offs, GFP_NOFS);
 }
 EXPORT_SYMBOL(fscrypt_decrypt_block_inplace);

 /*
  * Validate dentries in encrypted directories to make sure we aren't potentially
  * caching stale dentries after a key has been added.
  */
 static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
 {
 	struct dentry *dir;
 	int err;
 	int valid;

 	/*
 	 * Plaintext names are always valid, since fscrypt doesn't support
 	 * reverting to ciphertext names without evicting the directory's inode
 	 * -- which implies eviction of the dentries in the directory.
 	 */
 	if (!(dentry->d_flags & DCACHE_ENCRYPTED_NAME))
 		return 1;

 	/*
 	 * Ciphertext name; valid if the directory's key is still unavailable.
 	 *
 	 * Although fscrypt forbids rename() on ciphertext names, we still must
 	 * use dget_parent() here rather than use ->d_parent directly.  That's
 	 * because a corrupted fs image may contain directory hard links, which
 	 * the VFS handles by moving the directory's dentry tree in the dcache
 	 * each time ->lookup() finds the directory and it already has a dentry
 	 * elsewhere.  Thus ->d_parent can be changing, and we must safely grab
 	 * a reference to some ->d_parent to prevent it from being freed.
 	 */

 	if (flags & LOOKUP_RCU)
 		return -ECHILD;

 	dir = dget_parent(dentry);
 	err = fscrypt_get_encryption_info(d_inode(dir));
 	valid = !fscrypt_has_encryption_key(d_inode(dir));
 	dput(dir);

 	if (err < 0)
 		return err;

 	return valid;
 }

 const struct dentry_operations fscrypt_d_ops = {
 	.d_revalidate = fscrypt_d_revalidate,
 };

 static void fscrypt_destroy(void)
 {
 	struct fscrypt_ctx *pos, *n;

 	list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
 		kmem_cache_free(fscrypt_ctx_cachep, pos);
 	INIT_LIST_HEAD(&fscrypt_free_ctxs);
 	mempool_destroy(fscrypt_bounce_page_pool);
 	fscrypt_bounce_page_pool = NULL;
 }

 /**
  * fscrypt_initialize() - allocate major buffers for fs encryption.
  * @cop_flags:  fscrypt operations flags
  *
  * 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 fscrypt_initialize(unsigned int cop_flags)
 {
 	int i, res = -ENOMEM;

 	/* No need to allocate a bounce page pool if this FS won't use it. */
 	if (cop_flags & FS_CFLG_OWN_PAGES)
 		return 0;

 	mutex_lock(&fscrypt_init_mutex);
 	if (fscrypt_bounce_page_pool)
 		goto already_initialized;

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

 		ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
 		if (!ctx)
 			goto fail;
 		list_add(&ctx->free_list, &fscrypt_free_ctxs);
 	}

 	fscrypt_bounce_page_pool =
 		mempool_create_page_pool(num_prealloc_crypto_pages, 0);
 	if (!fscrypt_bounce_page_pool)
 		goto fail;

 already_initialized:
 	mutex_unlock(&fscrypt_init_mutex);
 	return 0;
 fail:
 	fscrypt_destroy();
 	mutex_unlock(&fscrypt_init_mutex);
 	return res;
 }

 void fscrypt_msg(struct super_block *sb, const char *level,
 		 const char *fmt, ...)
 {
 	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
 				      DEFAULT_RATELIMIT_BURST);
 	struct va_format vaf;
 	va_list args;

 	if (!__ratelimit(&rs))
 		return;

 	va_start(args, fmt);
 	vaf.fmt = fmt;
 	vaf.va = &args;
 	if (sb)
 		printk("%sfscrypt (%s): %pV\n", level, sb->s_id, &vaf);
 	else
 		printk("%sfscrypt: %pV\n", level, &vaf);
 	va_end(args);
 }

 /**
  * fscrypt_init() - Set up for fs encryption.
  */
 static int __init fscrypt_init(void)
 {
 	/*
 	 * Use an unbound workqueue to allow bios to be decrypted in parallel
 	 * even when they happen to complete on the same CPU.  This sacrifices
 	 * locality, but it's worthwhile since decryption is CPU-intensive.
 	 *
 	 * Also use a high-priority workqueue to prioritize decryption work,
 	 * which blocks reads from completing, over regular application tasks.
 	 */
 	fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
 						 WQ_UNBOUND | WQ_HIGHPRI,
 						 num_online_cpus());
 	if (!fscrypt_read_workqueue)
 		goto fail;

 	fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
 	if (!fscrypt_ctx_cachep)
 		goto fail_free_queue;

 	fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
 	if (!fscrypt_info_cachep)
 		goto fail_free_ctx;

 	return 0;

 fail_free_ctx:
 	kmem_cache_destroy(fscrypt_ctx_cachep);
 fail_free_queue:
 	destroy_workqueue(fscrypt_read_workqueue);
 fail:
 	return -ENOMEM;
 }
 module_init(fscrypt_init)

 /**
  * fscrypt_exit() - Shutdown the fs encryption system
  */
 static void __exit fscrypt_exit(void)
 {
 	fscrypt_destroy();

 	if (fscrypt_read_workqueue)
 		destroy_workqueue(fscrypt_read_workqueue);
 	kmem_cache_destroy(fscrypt_ctx_cachep);
 	kmem_cache_destroy(fscrypt_info_cachep);

 	fscrypt_essiv_cleanup();
 }
 module_exit(fscrypt_exit);

 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* This contains encryption functions for per-file encryption.
	*
	* Copyright (C) 2015, Google, Inc.
	* Copyright (C) 2015, Motorola Mobility
	*
	* Written by Michael Halcrow, 2014.
	*
	* Filename encryption additions
	* Uday Savagaonkar, 2014
	* Encryption policy handling additions
	* Ildar Muslukhov, 2014
	* Add fscrypt_pullback_bio_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 <linux/pagemap.h>
	#include <linux/mempool.h>
	#include <linux/module.h>
	#include <linux/scatterlist.h>
	#include <linux/ratelimit.h>
	#include <linux/dcache.h>
	#include <linux/namei.h>
	#include <crypto/aes.h>
	#include <crypto/skcipher.h>
	#include "fscrypt_private.h"

	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 *fscrypt_bounce_page_pool = NULL;

	static LIST_HEAD(fscrypt_free_ctxs);
	static DEFINE_SPINLOCK(fscrypt_ctx_lock);

	static struct workqueue_struct *fscrypt_read_workqueue;
	static DEFINE_MUTEX(fscrypt_init_mutex);

	static struct kmem_cache *fscrypt_ctx_cachep;
	struct kmem_cache *fscrypt_info_cachep;

	void fscrypt_enqueue_decrypt_work(struct work_struct *work)
	{
	queue_work(fscrypt_read_workqueue, work);
	}
	EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);

	/**
	* fscrypt_release_ctx() - Release a decryption context
	* @ctx: The decryption context to release.
	*
	* If the decryption context was allocated from the pre-allocated pool, return
	* it to that pool. Else, free it.
	*/
	void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
	{
	unsigned long flags;

	if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
	kmem_cache_free(fscrypt_ctx_cachep, ctx);
	} else {
	spin_lock_irqsave(&fscrypt_ctx_lock, flags);
	list_add(&ctx->free_list, &fscrypt_free_ctxs);
	spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
	}
	}
	EXPORT_SYMBOL(fscrypt_release_ctx);

	/**
	* fscrypt_get_ctx() - Get a decryption context
	* @gfp_flags: The gfp flag for memory allocation
	*
	* Allocate and initialize a decryption context.
	*
	* Return: A new decryption context on success; an ERR_PTR() otherwise.
	*/
	struct fscrypt_ctx *fscrypt_get_ctx(gfp_t gfp_flags)
	{
	struct fscrypt_ctx *ctx;
	unsigned long flags;

	/*
	* First try getting a ctx from the free list so that we don't have to
	* call into the slab allocator.
	*/
	spin_lock_irqsave(&fscrypt_ctx_lock, flags);
	ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
	struct fscrypt_ctx, free_list);
	if (ctx)
	list_del(&ctx->free_list);
	spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
	if (!ctx) {
	ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
	if (!ctx)
	return ERR_PTR(-ENOMEM);
	ctx->flags \|= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
	} else {
	ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
	}
	return ctx;
	}
	EXPORT_SYMBOL(fscrypt_get_ctx);

	struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags)
	{
	return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
	}

	/**
	* fscrypt_free_bounce_page() - free a ciphertext bounce page
	*
	* Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(),
	* or by fscrypt_alloc_bounce_page() directly.
	*/
	void fscrypt_free_bounce_page(struct page *bounce_page)
	{
	if (!bounce_page)
	return;
	set_page_private(bounce_page, (unsigned long)NULL);
	ClearPagePrivate(bounce_page);
	mempool_free(bounce_page, fscrypt_bounce_page_pool);
	}
	EXPORT_SYMBOL(fscrypt_free_bounce_page);

	void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
	const struct fscrypt_info *ci)
	{
	memset(iv, 0, ci->ci_mode->ivsize);
	iv->lblk_num = cpu_to_le64(lblk_num);

	if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY)
	memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE);

	if (ci->ci_essiv_tfm != NULL)
	crypto_cipher_encrypt_one(ci->ci_essiv_tfm, iv->raw, iv->raw);
	}

	/* Encrypt or decrypt a single filesystem block of file contents */
	int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
	u64 lblk_num, struct page *src_page,
	struct page *dest_page, unsigned int len,
	unsigned int offs, gfp_t gfp_flags)
	{
	union fscrypt_iv iv;
	struct skcipher_request *req = NULL;
	DECLARE_CRYPTO_WAIT(wait);
	struct scatterlist dst, src;
	struct fscrypt_info *ci = inode->i_crypt_info;
	struct crypto_skcipher *tfm = ci->ci_ctfm;
	int res = 0;

	if (WARN_ON_ONCE(len <= 0))
	return -EINVAL;
	if (WARN_ON_ONCE(len % FS_CRYPTO_BLOCK_SIZE != 0))
	return -EINVAL;

	fscrypt_generate_iv(&iv, lblk_num, ci);

	req = skcipher_request_alloc(tfm, gfp_flags);
	if (!req)
	return -ENOMEM;

	skcipher_request_set_callback(
	req, CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	crypto_req_done, &wait);

	sg_init_table(&dst, 1);
	sg_set_page(&dst, dest_page, len, offs);
	sg_init_table(&src, 1);
	sg_set_page(&src, src_page, len, offs);
	skcipher_request_set_crypt(req, &src, &dst, len, &iv);
	if (rw == FS_DECRYPT)
	res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
	else
	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
	skcipher_request_free(req);
	if (res) {
	fscrypt_err(inode->i_sb,
	"%scryption failed for inode %lu, block %llu: %d",
	(rw == FS_DECRYPT ? "de" : "en"),
	inode->i_ino, lblk_num, res);
	return res;
	}
	return 0;
	}

	/**
	* fscrypt_encrypt_pagecache_blocks() - Encrypt filesystem blocks from a pagecache page
	* @page: The locked pagecache page containing the block(s) to encrypt
	* @len: Total size of the block(s) to encrypt. Must be a nonzero
	* multiple of the filesystem's block size.
	* @offs: Byte offset within @page of the first block to encrypt. Must be
	* a multiple of the filesystem's block size.
	* @gfp_flags: Memory allocation flags
	*
	* A new bounce page is allocated, and the specified block(s) are encrypted into
	* it. In the bounce page, the ciphertext block(s) will be located at the same
	* offsets at which the plaintext block(s) were located in the source page; any
	* other parts of the bounce page will be left uninitialized. However, normally
	* blocksize == PAGE_SIZE and the whole page is encrypted at once.
	*
	* This is for use by the filesystem's ->writepages() method.
	*
	* Return: the new encrypted bounce page on success; an ERR_PTR() on failure
	*/
	struct page fscrypt_encrypt_pagecache_blocks(struct page page,
	unsigned int len,
	unsigned int offs,
	gfp_t gfp_flags)

	{
	const struct inode *inode = page->mapping->host;
	const unsigned int blockbits = inode->i_blkbits;
	const unsigned int blocksize = 1 << blockbits;
	struct page *ciphertext_page;
	u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
	(offs >> blockbits);
	unsigned int i;
	int err;

	if (WARN_ON_ONCE(!PageLocked(page)))
	return ERR_PTR(-EINVAL);

	if (WARN_ON_ONCE(len <= 0 \|\| !IS_ALIGNED(len \| offs, blocksize)))
	return ERR_PTR(-EINVAL);

	ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags);
	if (!ciphertext_page)
	return ERR_PTR(-ENOMEM);

	for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
	err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num,
	page, ciphertext_page,
	blocksize, i, gfp_flags);
	if (err) {
	fscrypt_free_bounce_page(ciphertext_page);
	return ERR_PTR(err);
	}
	}
	SetPagePrivate(ciphertext_page);
	set_page_private(ciphertext_page, (unsigned long)page);
	return ciphertext_page;
	}
	EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks);

	/**
	* fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place
	* @inode: The inode to which this block belongs
	* @page: The page containing the block to encrypt
	* @len: Size of block to encrypt. Doesn't need to be a multiple of the
	* fs block size, but must be a multiple of FS_CRYPTO_BLOCK_SIZE.
	* @offs: Byte offset within @page at which the block to encrypt begins
	* @lblk_num: Filesystem logical block number of the block, i.e. the 0-based
	* number of the block within the file
	* @gfp_flags: Memory allocation flags
	*
	* Encrypt a possibly-compressed filesystem block that is located in an
	* arbitrary page, not necessarily in the original pagecache page. The @inode
	* and @lblk_num must be specified, as they can't be determined from @page.
	*
	* Return: 0 on success; -errno on failure
	*/
	int fscrypt_encrypt_block_inplace(const struct inode inode, struct page page,
	unsigned int len, unsigned int offs,
	u64 lblk_num, gfp_t gfp_flags)
	{
	return fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, page, page,
	len, offs, gfp_flags);
	}
	EXPORT_SYMBOL(fscrypt_encrypt_block_inplace);

	/**
	* fscrypt_decrypt_pagecache_blocks() - Decrypt filesystem blocks in a pagecache page
	* @page: The locked pagecache page containing the block(s) to decrypt
	* @len: Total size of the block(s) to decrypt. Must be a nonzero
	* multiple of the filesystem's block size.
	* @offs: Byte offset within @page of the first block to decrypt. Must be
	* a multiple of the filesystem's block size.
	*
	* The specified block(s) are decrypted in-place within the pagecache page,
	* which must still be locked and not uptodate. Normally, blocksize ==
	* PAGE_SIZE and the whole page is decrypted at once.
	*
	* This is for use by the filesystem's ->readpages() method.
	*
	* Return: 0 on success; -errno on failure
	*/
	int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len,
	unsigned int offs)
	{
	const struct inode *inode = page->mapping->host;
	const unsigned int blockbits = inode->i_blkbits;
	const unsigned int blocksize = 1 << blockbits;
	u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
	(offs >> blockbits);
	unsigned int i;
	int err;

	if (WARN_ON_ONCE(!PageLocked(page)))
	return -EINVAL;

	if (WARN_ON_ONCE(len <= 0 \|\| !IS_ALIGNED(len \| offs, blocksize)))
	return -EINVAL;

	for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
	err = fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page,
	page, blocksize, i, GFP_NOFS);
	if (err)
	return err;
	}
	return 0;
	}
	EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks);

	/**
	* fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place
	* @inode: The inode to which this block belongs
	* @page: The page containing the block to decrypt
	* @len: Size of block to decrypt. Doesn't need to be a multiple of the
	* fs block size, but must be a multiple of FS_CRYPTO_BLOCK_SIZE.
	* @offs: Byte offset within @page at which the block to decrypt begins
	* @lblk_num: Filesystem logical block number of the block, i.e. the 0-based
	* number of the block within the file
	*
	* Decrypt a possibly-compressed filesystem block that is located in an
	* arbitrary page, not necessarily in the original pagecache page. The @inode
	* and @lblk_num must be specified, as they can't be determined from @page.
	*
	* Return: 0 on success; -errno on failure
	*/
	int fscrypt_decrypt_block_inplace(const struct inode inode, struct page page,
	unsigned int len, unsigned int offs,
	u64 lblk_num)
	{
	return fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page, page,
	len, offs, GFP_NOFS);
	}
	EXPORT_SYMBOL(fscrypt_decrypt_block_inplace);

	/*
	* Validate dentries in encrypted directories to make sure we aren't potentially
	* caching stale dentries after a key has been added.
	*/
	static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
	{
	struct dentry *dir;
	int err;
	int valid;

	/*
	* Plaintext names are always valid, since fscrypt doesn't support
	* reverting to ciphertext names without evicting the directory's inode
	* -- which implies eviction of the dentries in the directory.
	*/
	if (!(dentry->d_flags & DCACHE_ENCRYPTED_NAME))
	return 1;

	/*
	* Ciphertext name; valid if the directory's key is still unavailable.
	*
	* Although fscrypt forbids rename() on ciphertext names, we still must
	* use dget_parent() here rather than use ->d_parent directly. That's
	* because a corrupted fs image may contain directory hard links, which
	* the VFS handles by moving the directory's dentry tree in the dcache
	* each time ->lookup() finds the directory and it already has a dentry
	* elsewhere. Thus ->d_parent can be changing, and we must safely grab
	* a reference to some ->d_parent to prevent it from being freed.
	*/

	if (flags & LOOKUP_RCU)
	return -ECHILD;

	dir = dget_parent(dentry);
	err = fscrypt_get_encryption_info(d_inode(dir));
	valid = !fscrypt_has_encryption_key(d_inode(dir));
	dput(dir);

	if (err < 0)
	return err;

	return valid;
	}

	const struct dentry_operations fscrypt_d_ops = {
	.d_revalidate = fscrypt_d_revalidate,
	};

	static void fscrypt_destroy(void)
	{
	struct fscrypt_ctx pos, n;

	list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
	kmem_cache_free(fscrypt_ctx_cachep, pos);
	INIT_LIST_HEAD(&fscrypt_free_ctxs);
	mempool_destroy(fscrypt_bounce_page_pool);
	fscrypt_bounce_page_pool = NULL;
	}

	/**
	* fscrypt_initialize() - allocate major buffers for fs encryption.
	* @cop_flags: fscrypt operations flags
	*
	* 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 fscrypt_initialize(unsigned int cop_flags)
	{
	int i, res = -ENOMEM;

	/* No need to allocate a bounce page pool if this FS won't use it. */
	if (cop_flags & FS_CFLG_OWN_PAGES)
	return 0;

	mutex_lock(&fscrypt_init_mutex);
	if (fscrypt_bounce_page_pool)
	goto already_initialized;

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

	ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
	if (!ctx)
	goto fail;
	list_add(&ctx->free_list, &fscrypt_free_ctxs);
	}

	fscrypt_bounce_page_pool =
	mempool_create_page_pool(num_prealloc_crypto_pages, 0);
	if (!fscrypt_bounce_page_pool)
	goto fail;

	already_initialized:
	mutex_unlock(&fscrypt_init_mutex);
	return 0;
	fail:
	fscrypt_destroy();
	mutex_unlock(&fscrypt_init_mutex);
	return res;
	}

	void fscrypt_msg(struct super_block sb, const char level,
	const char *fmt, ...)
	{
	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
	DEFAULT_RATELIMIT_BURST);
	struct va_format vaf;
	va_list args;

	if (!__ratelimit(&rs))
	return;

	va_start(args, fmt);
	vaf.fmt = fmt;
	vaf.va = &args;
	if (sb)
	printk("%sfscrypt (%s): %pV\n", level, sb->s_id, &vaf);
	else
	printk("%sfscrypt: %pV\n", level, &vaf);
	va_end(args);
	}

	/**
	* fscrypt_init() - Set up for fs encryption.
	*/
	static int __init fscrypt_init(void)
	{
	/*
	* Use an unbound workqueue to allow bios to be decrypted in parallel
	* even when they happen to complete on the same CPU. This sacrifices
	* locality, but it's worthwhile since decryption is CPU-intensive.
	*
	* Also use a high-priority workqueue to prioritize decryption work,
	* which blocks reads from completing, over regular application tasks.
	*/
	fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
	WQ_UNBOUND \| WQ_HIGHPRI,
	num_online_cpus());
	if (!fscrypt_read_workqueue)
	goto fail;

	fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
	if (!fscrypt_ctx_cachep)
	goto fail_free_queue;

	fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
	if (!fscrypt_info_cachep)
	goto fail_free_ctx;

	return 0;

	fail_free_ctx:
	kmem_cache_destroy(fscrypt_ctx_cachep);
	fail_free_queue:
	destroy_workqueue(fscrypt_read_workqueue);
	fail:
	return -ENOMEM;
	}
	module_init(fscrypt_init)

	/**
	* fscrypt_exit() - Shutdown the fs encryption system
	*/
	static void __exit fscrypt_exit(void)
	{
	fscrypt_destroy();

	if (fscrypt_read_workqueue)
	destroy_workqueue(fscrypt_read_workqueue);
	kmem_cache_destroy(fscrypt_ctx_cachep);
	kmem_cache_destroy(fscrypt_info_cachep);

	fscrypt_essiv_cleanup();
	}
	module_exit(fscrypt_exit);

	MODULE_LICENSE("GPL");