Merge tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt

ea4b71bc · Linus Torvalds <[email protected]> · 2019-11-25 12:19:28 -08:00

Pull fscrypt updates from Eric Biggers:

 - Add the IV_INO_LBLK_64 encryption policy flag which modifies the
   encryption to be optimized for UFS inline encryption hardware.

 - For AES-128-CBC, use the crypto API's implementation of ESSIV (which
   was added in 5.4) rather than doing ESSIV manually.

 - A few other cleanups.

* tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt:
  f2fs: add support for IV_INO_LBLK_64 encryption policies
  ext4: add support for IV_INO_LBLK_64 encryption policies
  fscrypt: add support for IV_INO_LBLK_64 policies
  fscrypt: avoid data race on fscrypt_mode::logged_impl_name
  docs: ioctl-number: document fscrypt ioctl numbers
  fscrypt: zeroize fscrypt_info before freeing
  fscrypt: remove struct fscrypt_ctx
  fscrypt: invoke crypto API for ESSIV handling

Commit: ea4b71bc0bb646f811e4728389485f1d0522f7ea
Parents: ae36607b · 0eee17e3

Merge commit. Changes below are compared with the first parent: ae36607b.

Changes

14 files changed · +208 −328

File	Status	Add	Del	Content
Documentation/filesystems/fscrypt.rst	modified	+44	−24	View file
Documentation/ioctl/ioctl-number.rst	modified	+1	−0	View file
fs/crypto/bio.c	modified	+1	−28	View file
fs/crypto/crypto.c	modified	+17	−107	View file
fs/crypto/fscrypt_private.h	modified	+13	−12	View file
fs/crypto/keyring.c	modified	+4	−2	View file
fs/crypto/keysetup.c	modified	+47	−111	View file
fs/crypto/keysetup_v1.c	modified	+0	−4	View file
fs/crypto/policy.c	modified	+40	−1	View file
fs/ext4/ext4.h	modified	+2	−0	View file
fs/ext4/super.c	modified	+14	−0	View file
fs/f2fs/super.c	modified	+20	−6	View file
include/linux/fscrypt.h	modified	+3	−32	View file
include/uapi/linux/fscrypt.h	modified	+2	−1	View file

Only the first 600 diff lines are shown. Download the complete patch.

Documentation/filesystems/fscrypt.rst

View file

diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
index 8a0700a..471a511 100644
--- a/Documentation/filesystems/fscrypt.rst
+++ b/Documentation/filesystems/fscrypt.rst
@@ -256,13 +256,8 @@ alternative master keys or to support rotating master keys.  Instead,
 the master keys may be wrapped in userspace, e.g. as is done by the
 `fscrypt <https://github.com/google/fscrypt>`_ tool.
 
-Including the inode number in the IVs was considered.  However, it was
-rejected as it would have prevented ext4 filesystems from being
-resized, and by itself still wouldn't have been sufficient to prevent
-the same key from being directly reused for both XTS and CTS-CBC.
-
-DIRECT_KEY and per-mode keys
-----------------------------
+DIRECT_KEY policies
+-------------------
 
 The Adiantum encryption mode (see `Encryption modes and usage`_) is
 suitable for both contents and filenames encryption, and it accepts
@@ -285,6 +280,21 @@ IV.  Moreover:
   key derived using the KDF.  Users may use the same master key for
   other v2 encryption policies.
 
+IV_INO_LBLK_64 policies
+-----------------------
+
+When FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64 is set in the fscrypt policy,
+the encryption keys are derived from the master key, encryption mode
+number, and filesystem UUID.  This normally results in all files
+protected by the same master key sharing a single contents encryption
+key and a single filenames encryption key.  To still encrypt different
+files' data differently, inode numbers are included in the IVs.
+Consequently, shrinking the filesystem may not be allowed.
+
+This format is optimized for use with inline encryption hardware
+compliant with the UFS or eMMC standards, which support only 64 IV
+bits per I/O request and may have only a small number of keyslots.
+
 Key identifiers
 ---------------
 
@@ -308,8 +318,9 @@ If unsure, you should use the (AES-256-XTS, AES-256-CTS-CBC) pair.
 
 AES-128-CBC was added only for low-powered embedded devices with
 crypto accelerators such as CAAM or CESA that do not support XTS.  To
-use AES-128-CBC, CONFIG_CRYPTO_SHA256 (or another SHA-256
-implementation) must be enabled so that ESSIV can be used.
+use AES-128-CBC, CONFIG_CRYPTO_ESSIV and CONFIG_CRYPTO_SHA256 (or
+another SHA-256 implementation) must be enabled so that ESSIV can be
+used.
 
 Adiantum is a (primarily) stream cipher-based mode that is fast even
 on CPUs without dedicated crypto instructions.  It's also a true
@@ -341,10 +352,16 @@ a little endian number, except that:
   is encrypted with AES-256 where the AES-256 key is the SHA-256 hash
   of the file's data encryption key.
 
-- In the "direct key" configuration (FSCRYPT_POLICY_FLAG_DIRECT_KEY
-  set in the fscrypt_policy), the file's nonce is also appended to the
-  IV.  Currently this is only allowed with the Adiantum encryption
-  mode.
+- With `DIRECT_KEY policies`_, the file's nonce is appended to the IV.
+  Currently this is only allowed with the Adiantum encryption mode.
+
+- With `IV_INO_LBLK_64 policies`_, the logical block number is limited
+  to 32 bits and is placed in bits 0-31 of the IV.  The inode number
+  (which is also limited to 32 bits) is placed in bits 32-63.
+
+Note that because file logical block numbers are included in the IVs,
+filesystems must enforce that blocks are never shifted around within
+encrypted files, e.g. via "collapse range" or "insert range".
 
 Filenames encryption
 --------------------
@@ -354,10 +371,10 @@ the requirements to retain support for efficient directory lookups and
 filenames of up to 255 bytes, the same IV is used for every filename
 in a directory.
 
-However, each encrypted directory still uses a unique key; or
-alternatively (for the "direct key" configuration) has the file's
-nonce included in the IVs.  Thus, IV reuse is limited to within a
-single directory.
+However, each encrypted directory still uses a unique key, or
+alternatively has the file's nonce (for `DIRECT_KEY policies`_) or
+inode number (for `IV_INO_LBLK_64 policies`_) included in the IVs.
+Thus, IV reuse is limited to within a single directory.
 
 With CTS-CBC, the IV reuse means that when the plaintext filenames
 share a common prefix at least as long as the cipher block size (16
@@ -431,12 +448,15 @@ This structure must be initialized as follows:
   (1) for ``contents_encryption_mode`` and FSCRYPT_MODE_AES_256_CTS
   (4) for ``filenames_encryption_mode``.
 
-- ``flags`` must contain a value from ``<linux/fscrypt.h>`` which
-  identifies the amount of NUL-padding to use when encrypting
-  filenames.  If unsure, use FSCRYPT_POLICY_FLAGS_PAD_32 (0x3).
-  Additionally, if the encryption modes are both
-  FSCRYPT_MODE_ADIANTUM, this can contain
-  FSCRYPT_POLICY_FLAG_DIRECT_KEY; see `DIRECT_KEY and per-mode keys`_.
+- ``flags`` contains optional flags from ``<linux/fscrypt.h>``:
+
+  - FSCRYPT_POLICY_FLAGS_PAD_*: The amount of NUL padding to use when
+    encrypting filenames.  If unsure, use FSCRYPT_POLICY_FLAGS_PAD_32
+    (0x3).
+  - FSCRYPT_POLICY_FLAG_DIRECT_KEY: See `DIRECT_KEY policies`_.
+  - FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64: See `IV_INO_LBLK_64
+    policies`_.  This is mutually exclusive with DIRECT_KEY and is not
+    supported on v1 policies.
 
 - For v2 encryption policies, ``__reserved`` must be zeroed.
 
@@ -1089,7 +1109,7 @@ policy structs (see `Setting an encryption policy`_), except that the
 context structs also contain a nonce.  The nonce is randomly generated
 by the kernel and is used as KDF input or as a tweak to cause
 different files to be encrypted differently; see `Per-file keys`_ and
-`DIRECT_KEY and per-mode keys`_.
+`DIRECT_KEY policies`_.
 
 Data path changes
 -----------------

Documentation/ioctl/ioctl-number.rst

View file

diff --git a/Documentation/ioctl/ioctl-number.rst b/Documentation/ioctl/ioctl-number.rst
index bef79cd..4ef8643 100644
--- a/Documentation/ioctl/ioctl-number.rst
+++ b/Documentation/ioctl/ioctl-number.rst
@@ -233,6 +233,7 @@ Code  Seq#    Include File                                           Comments
 'f'   00-0F  fs/ext4/ext4.h                                          conflict!
 'f'   00-0F  linux/fs.h                                              conflict!
 'f'   00-0F  fs/ocfs2/ocfs2_fs.h                                     conflict!
+'f'   13-27  linux/fscrypt.h
 'f'   81-8F  linux/fsverity.h
 'g'   00-0F  linux/usb/gadgetfs.h
 'g'   20-2F  linux/usb/g_printer.h

fs/crypto/bio.c

View file

diff --git a/fs/crypto/bio.c b/fs/crypto/bio.c
index 82da251..1f4b8a2 100644
--- a/fs/crypto/bio.c
+++ b/fs/crypto/bio.c
@@ -26,7 +26,7 @@
 #include <linux/namei.h>
 #include "fscrypt_private.h"
 
-static void __fscrypt_decrypt_bio(struct bio *bio, bool done)
+void fscrypt_decrypt_bio(struct bio *bio)
 {
 	struct bio_vec *bv;
 	struct bvec_iter_all iter_all;
@@ -37,37 +37,10 @@ static void __fscrypt_decrypt_bio(struct bio *bio, bool done)
 							   bv->bv_offset);
 		if (ret)
 			SetPageError(page);
-		else if (done)
-			SetPageUptodate(page);
-		if (done)
-			unlock_page(page);
 	}
 }
-
-void fscrypt_decrypt_bio(struct bio *bio)
-{
-	__fscrypt_decrypt_bio(bio, false);
-}
 EXPORT_SYMBOL(fscrypt_decrypt_bio);
 
-static void completion_pages(struct work_struct *work)
-{
-	struct fscrypt_ctx *ctx = container_of(work, struct fscrypt_ctx, work);
-	struct bio *bio = ctx->bio;
-
-	__fscrypt_decrypt_bio(bio, true);
-	fscrypt_release_ctx(ctx);
-	bio_put(bio);
-}
-
-void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx, struct bio *bio)
-{
-	INIT_WORK(&ctx->work, completion_pages);
-	ctx->bio = bio;
-	fscrypt_enqueue_decrypt_work(&ctx->work);
-}
-EXPORT_SYMBOL(fscrypt_enqueue_decrypt_bio);
-
 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
 				sector_t pblk, unsigned int len)
 {

fs/crypto/crypto.c

View file

diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
index 32a7ad0..3719efa 100644
--- a/fs/crypto/crypto.c
+++ b/fs/crypto/crypto.c
@@ -27,29 +27,20 @@
 #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)
@@ -58,62 +49,6 @@ void fscrypt_enqueue_decrypt_work(struct work_struct *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);
@@ -138,14 +73,17 @@ EXPORT_SYMBOL(fscrypt_free_bounce_page);
 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
 			 const struct fscrypt_info *ci)
 {
+	u8 flags = fscrypt_policy_flags(&ci->ci_policy);
+
 	memset(iv, 0, ci->ci_mode->ivsize);
-	iv->lblk_num = cpu_to_le64(lblk_num);
 
-	if (fscrypt_is_direct_key_policy(&ci->ci_policy))
+	if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) {
+		WARN_ON_ONCE((u32)lblk_num != lblk_num);
+		lblk_num |= (u64)ci->ci_inode->i_ino << 32;
+	} else if (flags & FSCRYPT_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);
+	}
+	iv->lblk_num = cpu_to_le64(lblk_num);
 }
 
 /* Encrypt or decrypt a single filesystem block of file contents */
@@ -396,17 +334,6 @@ 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
@@ -414,11 +341,11 @@ static void fscrypt_destroy(void)
  * 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.
+ * Return: 0 on success; -errno on failure
  */
 int fscrypt_initialize(unsigned int cop_flags)
 {
-	int i, res = -ENOMEM;
+	int err = 0;
 
 	/* No need to allocate a bounce page pool if this FS won't use it. */
 	if (cop_flags & FS_CFLG_OWN_PAGES)
@@ -426,29 +353,18 @@ int fscrypt_initialize(unsigned int cop_flags)
 
 	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);
-	}
+		goto out_unlock;
 
+	err = -ENOMEM;
 	fscrypt_bounce_page_pool =
 		mempool_create_page_pool(num_prealloc_crypto_pages, 0);
 	if (!fscrypt_bounce_page_pool)
-		goto fail;
+		goto out_unlock;
 
-already_initialized:
-	mutex_unlock(&fscrypt_init_mutex);
-	return 0;
-fail:
-	fscrypt_destroy();
+	err = 0;
+out_unlock:
 	mutex_unlock(&fscrypt_init_mutex);
-	return res;
+	return err;
 }
 
 void fscrypt_msg(const struct inode *inode, const char *level,
@@ -494,13 +410,9 @@ static int __init fscrypt_init(void)
 	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;
+		goto fail_free_queue;
 
 	err = fscrypt_init_keyring();
 	if (err)
@@ -510,8 +422,6 @@ static int __init fscrypt_init(void)
 
 fail_free_info:
 	kmem_cache_destroy(fscrypt_info_cachep);
-fail_free_ctx:
-	kmem_cache_destroy(fscrypt_ctx_cachep);
 fail_free_queue:
 	destroy_workqueue(fscrypt_read_workqueue);
 fail:

fs/crypto/fscrypt_private.h

View file

diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index e84efc0..130b50e 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -163,11 +163,8 @@ struct fscrypt_info {
 	/* The actual crypto transform used for encryption and decryption */
 	struct crypto_skcipher *ci_ctfm;
 
-	/*
-	 * Cipher for ESSIV IV generation.  Only set for CBC contents
-	 * encryption, otherwise is NULL.
-	 */
-	struct crypto_cipher *ci_essiv_tfm;
+	/* True if the key should be freed when this fscrypt_info is freed */
+	bool ci_owns_key;
 
 	/*
 	 * Encryption mode used for this inode.  It corresponds to either the
@@ -209,8 +206,6 @@ typedef enum {
 	FS_ENCRYPT,
 } fscrypt_direction_t;
 
-#define FS_CTX_REQUIRES_FREE_ENCRYPT_FL		0x00000001
-
 static inline bool fscrypt_valid_enc_modes(u32 contents_mode,
 					   u32 filenames_mode)
 {
@@ -289,7 +284,8 @@ extern int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
  */
 #define HKDF_CONTEXT_KEY_IDENTIFIER	1
 #define HKDF_CONTEXT_PER_FILE_KEY	2
-#define HKDF_CONTEXT_PER_MODE_KEY	3
+#define HKDF_CONTEXT_DIRECT_KEY		3
+#define HKDF_CONTEXT_IV_INO_LBLK_64_KEY	4
 
 extern int fscrypt_hkdf_expand(struct fscrypt_hkdf *hkdf, u8 context,
 			       const u8 *info, unsigned int infolen,
@@ -386,8 +382,14 @@ struct fscrypt_master_key {
 	struct list_head	mk_decrypted_inodes;
 	spinlock_t		mk_decrypted_inodes_lock;
 
-	/* Per-mode tfms for DIRECT_KEY policies, allocated on-demand */
-	struct crypto_skcipher	*mk_mode_keys[__FSCRYPT_MODE_MAX + 1];
+	/* Crypto API transforms for DIRECT_KEY policies, allocated on-demand */
+	struct crypto_skcipher	*mk_direct_tfms[__FSCRYPT_MODE_MAX + 1];
+
+	/*
+	 * Crypto API transforms for filesystem-layer implementation of
+	 * IV_INO_LBLK_64 policies, allocated on-demand.
+	 */
+	struct crypto_skcipher	*mk_iv_ino_lblk_64_tfms[__FSCRYPT_MODE_MAX + 1];
 
 } __randomize_layout;
 
@@ -443,8 +445,7 @@ struct fscrypt_mode {
 	const char *cipher_str;
 	int keysize;
 	int ivsize;
-	bool logged_impl_name;
-	bool needs_essiv;
+	int logged_impl_name;
 };
 
 static inline bool

fs/crypto/keyring.c

View file

diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
index c34fa7c..040df1f 100644
--- a/fs/crypto/keyring.c
+++ b/fs/crypto/keyring.c
@@ -43,8 +43,10 @@ static void free_master_key(struct fscrypt_master_key *mk)
 
 	wipe_master_key_secret(&mk->mk_secret);
 
-	for (i = 0; i < ARRAY_SIZE(mk->mk_mode_keys); i++)
-		crypto_free_skcipher(mk->mk_mode_keys[i]);
+	for (i = 0; i <= __FSCRYPT_MODE_MAX; i++) {
+		crypto_free_skcipher(mk->mk_direct_tfms[i]);
+		crypto_free_skcipher(mk->mk_iv_ino_lblk_64_tfms[i]);
+	}
 
 	key_put(mk->mk_users);
 	kzfree(mk);

fs/crypto/keysetup.c

View file

diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index d71c2d6..f577bb6 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -8,15 +8,11 @@
  * Heavily modified since then.
  */
 
-#include <crypto/aes.h>
-#include <crypto/sha.h>
 #include <crypto/skcipher.h>
 #include <linux/key.h>
 
 #include "fscrypt_private.h"
 
-static struct crypto_shash *essiv_hash_tfm;
-
 static struct fscrypt_mode available_modes[] = {
 	[FSCRYPT_MODE_AES_256_XTS] = {
 		.friendly_name = "AES-256-XTS",
@@ -31,11 +27,10 @@ static struct fscrypt_mode available_modes[] = {
 		.ivsize = 16,
 	},
 	[FSCRYPT_MODE_AES_128_CBC] = {
-		.friendly_name = "AES-128-CBC",
-		.cipher_str = "cbc(aes)",
+		.friendly_name = "AES-128-CBC-ESSIV",
+		.cipher_str = "essiv(cbc(aes),sha256)",
 		.keysize = 16,
 		.ivsize = 16,
-		.needs_essiv = true,
 	},
 	[FSCRYPT_MODE_AES_128_CTS] = {
 		.friendly_name = "AES-128-CTS-CBC",
@@ -86,15 +81,13 @@ struct crypto_skcipher *fscrypt_allocate_skcipher(struct fscrypt_mode *mode,
 			    mode->cipher_str, PTR_ERR(tfm));
 		return tfm;
 	}
-	if (unlikely(!mode->logged_impl_name)) {
+	if (!xchg(&mode->logged_impl_name, 1)) {
 		/*
 		 * fscrypt performance can vary greatly depending on which
 		 * crypto algorithm implementation is used.  Help people debug
 		 * performance problems by logging the ->cra_driver_name the
-		 * first time a mode is used.  Note that multiple threads can
-		 * race here, but it doesn't really matter.
+		 * first time a mode is used.
 		 */
-		mode->logged_impl_name = true;
 		pr_info("fscrypt: %s using implementation \"%s\"\n",
 			mode->friendly_name,
 			crypto_skcipher_alg(tfm)->base.cra_driver_name);
@@ -111,131 +104,64 @@ err_free_tfm:
 	return ERR_PTR(err);
 }
 
-static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt)
-{
-	struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm);
-
-	/* init hash transform on demand */
-	if (unlikely(!tfm)) {
-		struct crypto_shash *prev_tfm;
-
-		tfm = crypto_alloc_shash("sha256", 0, 0);
-		if (IS_ERR(tfm)) {
-			if (PTR_ERR(tfm) == -ENOENT) {
-				fscrypt_warn(NULL,
-					     "Missing crypto API support for SHA-256");
-				return -ENOPKG;
-			}
-			fscrypt_err(NULL,
-				    "Error allocating SHA-256 transform: %ld",
-				    PTR_ERR(tfm));
-			return PTR_ERR(tfm);
-		}
-		prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);
-		if (prev_tfm) {
-			crypto_free_shash(tfm);
-			tfm = prev_tfm;
-		}
-	}
-
-	{
-		SHASH_DESC_ON_STACK(desc, tfm);
-		desc->tfm = tfm;
-
-		return crypto_shash_digest(desc, key, keysize, salt);
-	}
-}
-
-static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key,
-				int keysize)
-{
-	int err;
-	struct crypto_cipher *essiv_tfm;
-	u8 salt[SHA256_DIGEST_SIZE];
-
-	if (WARN_ON(ci->ci_mode->ivsize != AES_BLOCK_SIZE))
-		return -EINVAL;
-
-	essiv_tfm = crypto_alloc_cipher("aes", 0, 0);
-	if (IS_ERR(essiv_tfm))
-		return PTR_ERR(essiv_tfm);
-
-	ci->ci_essiv_tfm = essiv_tfm;
-
-	err = derive_essiv_salt(raw_key, keysize, salt);
-	if (err)
-		goto out;
-
-	/*
-	 * Using SHA256 to derive the salt/key will result in AES-256 being
-	 * used for IV generation. File contents encryption will still use the
-	 * configured keysize (AES-128) nevertheless.
-	 */
-	err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt));
-	if (err)
-		goto out;
-
-out:
-	memzero_explicit(salt, sizeof(salt));
-	return err;