fscrypt updates for 6.2

This release adds SM4 encryption support, contributed by Tianjia Zhang.
 SM4 is a Chinese block cipher that is an alternative to AES.
 
 I recommend against using SM4, but (according to Tianjia) some people
 are being required to use it.  Since SM4 has been turning up in many
 other places (crypto API, wireless, TLS, OpenSSL, ARMv8 CPUs, etc.), it
 hasn't been very controversial, and some people have to use it, I don't
 think it would be fair for me to reject this optional feature.
 
 Besides the above, there are a couple cleanups.
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Merge tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt

Pull fscrypt updates from Eric Biggers:
 "This release adds SM4 encryption support, contributed by Tianjia
  Zhang. SM4 is a Chinese block cipher that is an alternative to AES.

  I recommend against using SM4, but (according to Tianjia) some people
  are being required to use it. Since SM4 has been turning up in many
  other places (crypto API, wireless, TLS, OpenSSL, ARMv8 CPUs, etc.),
  it hasn't been very controversial, and some people have to use it, I
  don't think it would be fair for me to reject this optional feature.

  Besides the above, there are a couple cleanups"

* tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt:
  fscrypt: add additional documentation for SM4 support
  fscrypt: remove unused Speck definitions
  fscrypt: Add SM4 XTS/CTS symmetric algorithm support
  blk-crypto: Add support for SM4-XTS blk crypto mode
  fscrypt: add comment for fscrypt_valid_enc_modes_v1()
  fscrypt: pass super_block to fscrypt_put_master_key_activeref()

Documentation/filesystems/fscrypt.rst

@@ -338,6 +338,7 @@ Currently, the following pairs of encryption modes are supported:
 - AES-128-CBC for contents and AES-128-CTS-CBC for filenames
 - Adiantum for both contents and filenames
 - AES-256-XTS for contents and AES-256-HCTR2 for filenames (v2 policies only)
+- SM4-XTS for contents and SM4-CTS-CBC for filenames (v2 policies only)
 
 If unsure, you should use the (AES-256-XTS, AES-256-CTS-CBC) pair.
 
@@ -369,6 +370,12 @@ CONFIG_CRYPTO_HCTR2 must be enabled.  Also, fast implementations of XCTR and
 POLYVAL should be enabled, e.g. CRYPTO_POLYVAL_ARM64_CE and
 CRYPTO_AES_ARM64_CE_BLK for ARM64.
 
+SM4 is a Chinese block cipher that is an alternative to AES.  It has
+not seen as much security review as AES, and it only has a 128-bit key
+size.  It may be useful in cases where its use is mandated.
+Otherwise, it should not be used.  For SM4 support to be available, it
+also needs to be enabled in the kernel crypto API.
+
 New encryption modes can be added relatively easily, without changes
 to individual filesystems.  However, authenticated encryption (AE)
 modes are not currently supported because of the difficulty of dealing

block/blk-crypto.c

@@ -36,6 +36,12 @@ const struct blk_crypto_mode blk_crypto_modes[] = {
 		.keysize = 32,
 		.ivsize = 32,
 	},
+	[BLK_ENCRYPTION_MODE_SM4_XTS] = {
+		.name = "SM4-XTS",
+		.cipher_str = "xts(sm4)",
+		.keysize = 32,
+		.ivsize = 16,
+	},
 };
 
 /*

fs/crypto/fscrypt_private.h

@@ -439,13 +439,7 @@ struct fscrypt_master_key_secret {
 struct fscrypt_master_key {
 
 	/*
-	 * Back-pointer to the super_block of the filesystem to which this
-	 * master key has been added.  Only valid if ->mk_active_refs > 0.
-	 */
-	struct super_block			*mk_sb;
-
-	/*
-	 * Link in ->mk_sb->s_master_keys->key_hashtable.
+	 * Link in ->s_master_keys->key_hashtable.
 	 * Only valid if ->mk_active_refs > 0.
 	 */
 	struct hlist_node			mk_node;
@@ -456,7 +450,7 @@ struct fscrypt_master_key {
 	/*
 	 * Active and structural reference counts.  An active ref guarantees
 	 * that the struct continues to exist, continues to be in the keyring
-	 * ->mk_sb->s_master_keys, and that any embedded subkeys (e.g.
+	 * ->s_master_keys, and that any embedded subkeys (e.g.
 	 * ->mk_direct_keys) that have been prepared continue to exist.
 	 * A structural ref only guarantees that the struct continues to exist.
 	 *
@@ -569,7 +563,8 @@ static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
 
 void fscrypt_put_master_key(struct fscrypt_master_key *mk);
 
-void fscrypt_put_master_key_activeref(struct fscrypt_master_key *mk);
+void fscrypt_put_master_key_activeref(struct super_block *sb,
+				      struct fscrypt_master_key *mk);
 
 struct fscrypt_master_key *
 fscrypt_find_master_key(struct super_block *sb,

fs/crypto/keyring.c

@@ -79,10 +79,9 @@ void fscrypt_put_master_key(struct fscrypt_master_key *mk)
 	call_rcu(&mk->mk_rcu_head, fscrypt_free_master_key);
 }
 
-void fscrypt_put_master_key_activeref(struct fscrypt_master_key *mk)
+void fscrypt_put_master_key_activeref(struct super_block *sb,
+				      struct fscrypt_master_key *mk)
 {
-	struct super_block *sb = mk->mk_sb;
-	struct fscrypt_keyring *keyring = sb->s_master_keys;
 	size_t i;
 
 	if (!refcount_dec_and_test(&mk->mk_active_refs))
@@ -93,9 +92,9 @@ void fscrypt_put_master_key_activeref(struct fscrypt_master_key *mk)
 	 * destroying any subkeys embedded in it.
 	 */
 
-	spin_lock(&keyring->lock);
+	spin_lock(&sb->s_master_keys->lock);
 	hlist_del_rcu(&mk->mk_node);
-	spin_unlock(&keyring->lock);
+	spin_unlock(&sb->s_master_keys->lock);
 
 	/*
 	 * ->mk_active_refs == 0 implies that ->mk_secret is not present and
@@ -243,7 +242,7 @@ void fscrypt_destroy_keyring(struct super_block *sb)
 			WARN_ON(refcount_read(&mk->mk_struct_refs) != 1);
 			WARN_ON(!is_master_key_secret_present(&mk->mk_secret));
 			wipe_master_key_secret(&mk->mk_secret);
-			fscrypt_put_master_key_activeref(mk);
+			fscrypt_put_master_key_activeref(sb, mk);
 		}
 	}
 	kfree_sensitive(keyring);
@@ -424,7 +423,6 @@ static int add_new_master_key(struct super_block *sb,
 	if (!mk)
 		return -ENOMEM;
 
-	mk->mk_sb = sb;
 	init_rwsem(&mk->mk_sem);
 	refcount_set(&mk->mk_struct_refs, 1);
 	mk->mk_spec = *mk_spec;
@@ -1068,7 +1066,7 @@ static int do_remove_key(struct file *filp, void __user *_uarg, bool all_users)
 	err = -ENOKEY;
 	if (is_master_key_secret_present(&mk->mk_secret)) {
 		wipe_master_key_secret(&mk->mk_secret);
-		fscrypt_put_master_key_activeref(mk);
+		fscrypt_put_master_key_activeref(sb, mk);
 		err = 0;
 	}
 	inodes_remain = refcount_read(&mk->mk_active_refs) > 0;

fs/crypto/keysetup.c

@@ -44,6 +44,21 @@ struct fscrypt_mode fscrypt_modes[] = {
 		.security_strength = 16,
 		.ivsize = 16,
 	},
+	[FSCRYPT_MODE_SM4_XTS] = {
+		.friendly_name = "SM4-XTS",
+		.cipher_str = "xts(sm4)",
+		.keysize = 32,
+		.security_strength = 16,
+		.ivsize = 16,
+		.blk_crypto_mode = BLK_ENCRYPTION_MODE_SM4_XTS,
+	},
+	[FSCRYPT_MODE_SM4_CTS] = {
+		.friendly_name = "SM4-CTS-CBC",
+		.cipher_str = "cts(cbc(sm4))",
+		.keysize = 16,
+		.security_strength = 16,
+		.ivsize = 16,
+	},
 	[FSCRYPT_MODE_ADIANTUM] = {
 		.friendly_name = "Adiantum",
 		.cipher_str = "adiantum(xchacha12,aes)",
@@ -509,7 +524,7 @@ static void put_crypt_info(struct fscrypt_info *ci)
 		spin_lock(&mk->mk_decrypted_inodes_lock);
 		list_del(&ci->ci_master_key_link);
 		spin_unlock(&mk->mk_decrypted_inodes_lock);
-		fscrypt_put_master_key_activeref(mk);
+		fscrypt_put_master_key_activeref(ci->ci_inode->i_sb, mk);
 	}
 	memzero_explicit(ci, sizeof(*ci));
 	kmem_cache_free(fscrypt_info_cachep, ci);

fs/crypto/policy.c

@@ -61,6 +61,13 @@ fscrypt_get_dummy_policy(struct super_block *sb)
 	return sb->s_cop->get_dummy_policy(sb);
 }
 
+/*
+ * Return %true if the given combination of encryption modes is supported for v1
+ * (and later) encryption policies.
+ *
+ * Do *not* add anything new here, since v1 encryption policies are deprecated.
+ * New combinations of modes should go in fscrypt_valid_enc_modes_v2() only.
+ */
 static bool fscrypt_valid_enc_modes_v1(u32 contents_mode, u32 filenames_mode)
 {
 	if (contents_mode == FSCRYPT_MODE_AES_256_XTS &&
@@ -83,6 +90,11 @@ static bool fscrypt_valid_enc_modes_v2(u32 contents_mode, u32 filenames_mode)
 	if (contents_mode == FSCRYPT_MODE_AES_256_XTS &&
 	    filenames_mode == FSCRYPT_MODE_AES_256_HCTR2)
 		return true;
+
+	if (contents_mode == FSCRYPT_MODE_SM4_XTS &&
+	    filenames_mode == FSCRYPT_MODE_SM4_CTS)
+		return true;
+
 	return fscrypt_valid_enc_modes_v1(contents_mode, filenames_mode);
 }
 

include/linux/blk-crypto.h

@@ -13,6 +13,7 @@ enum blk_crypto_mode_num {
 	BLK_ENCRYPTION_MODE_AES_256_XTS,
 	BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV,
 	BLK_ENCRYPTION_MODE_ADIANTUM,
+	BLK_ENCRYPTION_MODE_SM4_XTS,
 	BLK_ENCRYPTION_MODE_MAX,
 };
 

include/uapi/linux/fscrypt.h

@@ -26,6 +26,8 @@
 #define FSCRYPT_MODE_AES_256_CTS		4
 #define FSCRYPT_MODE_AES_128_CBC		5
 #define FSCRYPT_MODE_AES_128_CTS		6
+#define FSCRYPT_MODE_SM4_XTS			7
+#define FSCRYPT_MODE_SM4_CTS			8
 #define FSCRYPT_MODE_ADIANTUM			9
 #define FSCRYPT_MODE_AES_256_HCTR2		10
 /* If adding a mode number > 10, update FSCRYPT_MODE_MAX in fscrypt_private.h */
@@ -185,8 +187,6 @@ struct fscrypt_get_key_status_arg {
 #define FS_ENCRYPTION_MODE_AES_256_CTS	FSCRYPT_MODE_AES_256_CTS
 #define FS_ENCRYPTION_MODE_AES_128_CBC	FSCRYPT_MODE_AES_128_CBC
 #define FS_ENCRYPTION_MODE_AES_128_CTS	FSCRYPT_MODE_AES_128_CTS
-#define FS_ENCRYPTION_MODE_SPECK128_256_XTS	7	/* removed */
-#define FS_ENCRYPTION_MODE_SPECK128_256_CTS	8	/* removed */
 #define FS_ENCRYPTION_MODE_ADIANTUM	FSCRYPT_MODE_ADIANTUM
 #define FS_KEY_DESC_PREFIX		FSCRYPT_KEY_DESC_PREFIX
 #define FS_KEY_DESC_PREFIX_SIZE		FSCRYPT_KEY_DESC_PREFIX_SIZE