fscrypt updates for 6.9

Fix flakiness in a test by releasing the quota synchronously when a key
 is removed, and other minor cleanups.
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Merge tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/linux

Pull fscrypt updates from Eric Biggers:
 "Fix flakiness in a test by releasing the quota synchronously when a
  key is removed, and other minor cleanups"

* tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/linux:
  fscrypt: shrink the size of struct fscrypt_inode_info slightly
  fscrypt: write CBC-CTS instead of CTS-CBC
  fscrypt: clear keyring before calling key_put()
  fscrypt: explicitly require that inode->i_blkbits be set

Documentation/filesystems/fscrypt.rst

@@ -338,11 +338,14 @@ Supported modes
 
 Currently, the following pairs of encryption modes are supported:
 
-- AES-256-XTS for contents and AES-256-CTS-CBC for filenames
+- AES-256-XTS for contents and AES-256-CBC-CTS for filenames
 - AES-256-XTS for contents and AES-256-HCTR2 for filenames
 - Adiantum for both contents and filenames
-- AES-128-CBC-ESSIV for contents and AES-128-CTS-CBC for filenames
+- AES-128-CBC-ESSIV for contents and AES-128-CBC-CTS for filenames
-- SM4-XTS for contents and SM4-CTS-CBC for filenames
+- SM4-XTS for contents and SM4-CBC-CTS for filenames
+
+Note: in the API, "CBC" means CBC-ESSIV, and "CTS" means CBC-CTS.
+So, for example, FSCRYPT_MODE_AES_256_CTS means AES-256-CBC-CTS.
 
 Authenticated encryption modes are not currently supported because of
 the difficulty of dealing with ciphertext expansion.  Therefore,
@@ -351,11 +354,11 @@ contents encryption uses a block cipher in `XTS mode
 `CBC-ESSIV mode
 <https://en.wikipedia.org/wiki/Disk_encryption_theory#Encrypted_salt-sector_initialization_vector_(ESSIV)>`_,
 or a wide-block cipher.  Filenames encryption uses a
-block cipher in `CTS-CBC mode
+block cipher in `CBC-CTS mode
 <https://en.wikipedia.org/wiki/Ciphertext_stealing>`_ or a wide-block
 cipher.
 
-The (AES-256-XTS, AES-256-CTS-CBC) pair is the recommended default.
+The (AES-256-XTS, AES-256-CBC-CTS) pair is the recommended default.
 It is also the only option that is *guaranteed* to always be supported
 if the kernel supports fscrypt at all; see `Kernel config options`_.
 
@@ -364,7 +367,7 @@ upgrades the filenames encryption to use a wide-block cipher.  (A
 *wide-block cipher*, also called a tweakable super-pseudorandom
 permutation, has the property that changing one bit scrambles the
 entire result.)  As described in `Filenames encryption`_, a wide-block
-cipher is the ideal mode for the problem domain, though CTS-CBC is the
+cipher is the ideal mode for the problem domain, though CBC-CTS is the
 "least bad" choice among the alternatives.  For more information about
 HCTR2, see `the HCTR2 paper <https://eprint.iacr.org/2021/1441.pdf>`_.
 
@@ -375,13 +378,13 @@ the work is done by XChaCha12, which is much faster than AES when AES
 acceleration is unavailable.  For more information about Adiantum, see
 `the Adiantum paper <https://eprint.iacr.org/2018/720.pdf>`_.
 
-The (AES-128-CBC-ESSIV, AES-128-CTS-CBC) pair exists only to support
+The (AES-128-CBC-ESSIV, AES-128-CBC-CTS) pair exists only to support
 systems whose only form of AES acceleration is an off-CPU crypto
 accelerator such as CAAM or CESA that does not support XTS.
 
 The remaining mode pairs are the "national pride ciphers":
 
-- (SM4-XTS, SM4-CTS-CBC)
+- (SM4-XTS, SM4-CBC-CTS)
 
 Generally speaking, these ciphers aren't "bad" per se, but they
 receive limited security review compared to the usual choices such as
@@ -393,7 +396,7 @@ Kernel config options
 
 Enabling fscrypt support (CONFIG_FS_ENCRYPTION) automatically pulls in
 only the basic support from the crypto API needed to use AES-256-XTS
-and AES-256-CTS-CBC encryption.  For optimal performance, it is
+and AES-256-CBC-CTS encryption.  For optimal performance, it is
 strongly recommended to also enable any available platform-specific
 kconfig options that provide acceleration for the algorithm(s) you
 wish to use.  Support for any "non-default" encryption modes typically
@@ -407,7 +410,7 @@ kernel crypto API (see `Inline encryption support`_); in that case,
 the file contents mode doesn't need to supported in the kernel crypto
 API, but the filenames mode still does.
 
-- AES-256-XTS and AES-256-CTS-CBC
+- AES-256-XTS and AES-256-CBC-CTS
     - Recommended:
         - arm64: CONFIG_CRYPTO_AES_ARM64_CE_BLK
         - x86: CONFIG_CRYPTO_AES_NI_INTEL
@@ -433,7 +436,7 @@ API, but the filenames mode still does.
         - x86: CONFIG_CRYPTO_NHPOLY1305_SSE2
         - x86: CONFIG_CRYPTO_NHPOLY1305_AVX2
 
-- AES-128-CBC-ESSIV and AES-128-CTS-CBC:
+- AES-128-CBC-ESSIV and AES-128-CBC-CTS:
     - Mandatory:
         - CONFIG_CRYPTO_ESSIV
         - CONFIG_CRYPTO_SHA256 or another SHA-256 implementation
@@ -521,7 +524,7 @@ 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
+With CBC-CTS, the IV reuse means that when the plaintext filenames share a
 common prefix at least as long as the cipher block size (16 bytes for AES), the
 corresponding encrypted filenames will also share a common prefix.  This is
 undesirable.  Adiantum and HCTR2 do not have this weakness, as they are

fs/crypto/fscrypt_private.h

@@ -222,16 +222,19 @@ struct fscrypt_inode_info {
 	struct fscrypt_prepared_key ci_enc_key;
 
 	/* True if ci_enc_key should be freed when this struct is freed */
-	bool ci_owns_key;
+	u8 ci_owns_key : 1;
 
 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
 	/*
 	 * True if this inode will use inline encryption (blk-crypto) instead of
 	 * the traditional filesystem-layer encryption.
 	 */
-	bool ci_inlinecrypt;
+	u8 ci_inlinecrypt : 1;
 #endif
 
+	/* True if ci_dirhash_key is initialized */
+	u8 ci_dirhash_key_initialized : 1;
+
 	/*
 	 * log2 of the data unit size (granularity of contents encryption) of
 	 * this file.  This is computable from ci_policy and ci_inode but is
@@ -242,6 +245,9 @@ struct fscrypt_inode_info {
 	/* Cached value: log2 of number of data units per FS block */
 	u8 ci_data_units_per_block_bits;
 
+	/* Hashed inode number.  Only set for IV_INO_LBLK_32 */
+	u32 ci_hashed_ino;
+
 	/*
 	 * Encryption mode used for this inode.  It corresponds to either the
 	 * contents or filenames encryption mode, depending on the inode type.
@@ -276,16 +282,12 @@ struct fscrypt_inode_info {
 	 * the plaintext filenames -- currently just casefolded directories.
 	 */
 	siphash_key_t ci_dirhash_key;
-	bool ci_dirhash_key_initialized;
 
 	/* The encryption policy used by this inode */
 	union fscrypt_policy ci_policy;
 
 	/* This inode's nonce, copied from the fscrypt_context */
 	u8 ci_nonce[FSCRYPT_FILE_NONCE_SIZE];
-
-	/* Hashed inode number.  Only set for IV_INO_LBLK_32 */
-	u32 ci_hashed_ino;
 };
 
 typedef enum {

fs/crypto/keyring.c

@@ -74,8 +74,12 @@ void fscrypt_put_master_key(struct fscrypt_master_key *mk)
 	 * that concurrent keyring lookups can no longer find it.
 	 */
 	WARN_ON_ONCE(refcount_read(&mk->mk_active_refs) != 0);
-	key_put(mk->mk_users);
+	if (mk->mk_users) {
-	mk->mk_users = NULL;
+		/* Clear the keyring so the quota gets released right away. */
+		keyring_clear(mk->mk_users);
+		key_put(mk->mk_users);
+		mk->mk_users = NULL;
+	}
 	call_rcu(&mk->mk_rcu_head, fscrypt_free_master_key);
 }
 

fs/crypto/keysetup.c

@@ -23,7 +23,7 @@ struct fscrypt_mode fscrypt_modes[] = {
 		.blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_256_XTS,
 	},
 	[FSCRYPT_MODE_AES_256_CTS] = {
-		.friendly_name = "AES-256-CTS-CBC",
+		.friendly_name = "AES-256-CBC-CTS",
 		.cipher_str = "cts(cbc(aes))",
 		.keysize = 32,
 		.security_strength = 32,
@@ -38,7 +38,7 @@ struct fscrypt_mode fscrypt_modes[] = {
 		.blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV,
 	},
 	[FSCRYPT_MODE_AES_128_CTS] = {
-		.friendly_name = "AES-128-CTS-CBC",
+		.friendly_name = "AES-128-CBC-CTS",
 		.cipher_str = "cts(cbc(aes))",
 		.keysize = 16,
 		.security_strength = 16,
@@ -53,7 +53,7 @@ struct fscrypt_mode fscrypt_modes[] = {
 		.blk_crypto_mode = BLK_ENCRYPTION_MODE_SM4_XTS,
 	},
 	[FSCRYPT_MODE_SM4_CTS] = {
-		.friendly_name = "SM4-CTS-CBC",
+		.friendly_name = "SM4-CBC-CTS",
 		.cipher_str = "cts(cbc(sm4))",
 		.keysize = 16,
 		.security_strength = 16,
@@ -687,7 +687,7 @@ int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported)
 /**
  * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory
  * @dir: a possibly-encrypted directory
- * @inode: the new inode.  ->i_mode must be set already.
+ * @inode: the new inode.  ->i_mode and ->i_blkbits must be set already.
  *	   ->i_ino doesn't need to be set yet.
  * @encrypt_ret: (output) set to %true if the new inode will be encrypted
  *
@@ -717,6 +717,9 @@ int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode,
 	if (IS_ERR(policy))
 		return PTR_ERR(policy);
 
+	if (WARN_ON_ONCE(inode->i_blkbits == 0))
+		return -EINVAL;
+
 	if (WARN_ON_ONCE(inode->i_mode == 0))
 		return -EINVAL;