[PATCH v5 0/8] fscrypt: some rearrangements of key setup

[PATCH v5 0/8] fscrypt: some rearrangements of key setup

[Sweet Tea Dorminy]

This is a patchset designed to make key setup slightly clearer to me
ahead of rearranging it to add extent-based encryption. It is basically
a subset of my prior changeset [1] for elegance. The subsequent changes
have minor dependencies on it; I can drop this changeset if it's
preferable, although I do think it makes everything cleaner.

Patchset is built on kdave/misc-next as per base commit and needs a tiny
fixup to apply to fscrypt/for-next. It passes ext4/f2fs tests for me.

[1] https://lore.kernel.org/linux-fscrypt/cover.1681837335.git.sweettea-kernel@dorminy.me/

Changelog:

v5:
- Fixed kernel build robot complaint in patch 3.

v4:
- https://lore.kernel.org/linux-fscrypt/cover.1687988119.git.sweettea-kernel@dorminy.me/T/#t

Sweet Tea Dorminy (8):
  fscrypt: move inline crypt decision to info setup
  fscrypt: split and rename setup_file_encryption_key()
  fscrypt: split setup_per_mode_enc_key()
  fscrypt: move dirhash key setup away from IO key setup
  fscrypt: reduce special-casing of IV_INO_LBLK_32
  fscrypt: move all the shared mode key setup deeper
  fscrypt: make infos have a pointer to prepared keys
  fscrypt: make prepared keys record their type

 fs/crypto/crypto.c          |   2 +-
 fs/crypto/fname.c           |   4 +-
 fs/crypto/fscrypt_private.h |  33 +++-
 fs/crypto/inline_crypt.c    |   4 +-
 fs/crypto/keysetup.c        | 375 +++++++++++++++++++++++-------------
 fs/crypto/keysetup_v1.c     |   9 +-
 6 files changed, 274 insertions(+), 153 deletions(-)


base-commit: e0144e6be2ec62c8d874076a6292a8d83b00ee32
-- 
2.40.1

[PATCH v5 1/8] fscrypt: move inline crypt decision to info setup

[Sweet Tea Dorminy]

setup_file_encryption_key() is doing a lot of things at the moment --
setting the crypt_info's inline encryption bit, finding and locking a
master key, and calling the functions to get the appropriate prepared
key for this info. Since setting the inline encryption bit has nothing
to do with finding the master key, it's easy and hopefully clearer to
select the encryption implementation in fscrypt_setup_encryption_info(),
the main fscrypt_info setup function, instead of in
setup_file_encryption_key() which will long-term only deal in setting
up the prepared key for the info.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
---
 fs/crypto/keysetup.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 361f41ef46c7..b89c32ad19fb 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -443,10 +443,6 @@ static int setup_file_encryption_key(struct fscrypt_info *ci,
 	struct fscrypt_master_key *mk;
 	int err;
 
-	err = fscrypt_select_encryption_impl(ci);
-	if (err)
-		return err;
-
 	err = fscrypt_policy_to_key_spec(&ci->ci_policy, &mk_spec);
 	if (err)
 		return err;
@@ -580,6 +576,10 @@ fscrypt_setup_encryption_info(struct inode *inode,
 	WARN_ON_ONCE(mode->ivsize > FSCRYPT_MAX_IV_SIZE);
 	crypt_info->ci_mode = mode;
 
+	res = fscrypt_select_encryption_impl(crypt_info);
+	if (res)
+		goto out;
+
 	res = setup_file_encryption_key(crypt_info, need_dirhash_key, &mk);
 	if (res)
 		goto out;
-- 
2.40.1

[PATCH v5 2/8] fscrypt: split and rename setup_file_encryption_key()

[Sweet Tea Dorminy]

At present, setup_file_encryption_key() does several things: it finds
and locks the master key, and then calls into the appropriate functions
to setup the prepared key for the fscrypt_info. The code is clearer to
follow if these functions are divided.

Thus, move calling the appropriate file key setup function into a new
fscrypt_setup_file_key() function. After the file key setup functions
are moved, the remaining function can take a const fscrypt_info, and is
renamed find_and_lock_master_key() to precisely describe its action.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
---
 fs/crypto/keysetup.c | 77 ++++++++++++++++++++++++++++++--------------
 1 file changed, 52 insertions(+), 25 deletions(-)

diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index b89c32ad19fb..727d473b6b03 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -386,6 +386,43 @@ static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
 	return 0;
 }
 
+/*
+ * Find or create the appropriate prepared key for an info.
+ */
+static int fscrypt_setup_file_key(struct fscrypt_info *ci,
+				  struct fscrypt_master_key *mk,
+				  bool need_dirhash_key)
+{
+	int err;
+
+	if (!mk) {
+		if (ci->ci_policy.version != FSCRYPT_POLICY_V1)
+			return -ENOKEY;
+
+		/*
+		 * As a legacy fallback for v1 policies, search for the key in
+		 * the current task's subscribed keyrings too.  Don't move this
+		 * to before the search of ->s_master_keys, since users
+		 * shouldn't be able to override filesystem-level keys.
+		 */
+		return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
+	}
+
+	switch (ci->ci_policy.version) {
+	case FSCRYPT_POLICY_V1:
+		err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
+		break;
+	case FSCRYPT_POLICY_V2:
+		err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		err = -EINVAL;
+		break;
+	}
+	return err;
+}
+
 /*
  * Check whether the size of the given master key (@mk) is appropriate for the
  * encryption settings which a particular file will use (@ci).
@@ -426,7 +463,7 @@ static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk,
 }
 
 /*
- * Find the master key, then set up the inode's actual encryption key.
+ * Find and lock the master key.
  *
  * If the master key is found in the filesystem-level keyring, then it is
  * returned in *mk_ret with its semaphore read-locked.  This is needed to ensure
@@ -434,9 +471,8 @@ static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk,
  * multiple tasks may race to create an fscrypt_info for the same inode), and to
  * synchronize the master key being removed with a new inode starting to use it.
  */
-static int setup_file_encryption_key(struct fscrypt_info *ci,
-				     bool need_dirhash_key,
-				     struct fscrypt_master_key **mk_ret)
+static int find_and_lock_master_key(const struct fscrypt_info *ci,
+				    struct fscrypt_master_key **mk_ret)
 {
 	struct super_block *sb = ci->ci_inode->i_sb;
 	struct fscrypt_key_specifier mk_spec;
@@ -466,17 +502,19 @@ static int setup_file_encryption_key(struct fscrypt_info *ci,
 			mk = fscrypt_find_master_key(sb, &mk_spec);
 		}
 	}
+
 	if (unlikely(!mk)) {
 		if (ci->ci_policy.version != FSCRYPT_POLICY_V1)
 			return -ENOKEY;
 
 		/*
-		 * As a legacy fallback for v1 policies, search for the key in
-		 * the current task's subscribed keyrings too.  Don't move this
-		 * to before the search of ->s_master_keys, since users
-		 * shouldn't be able to override filesystem-level keys.
+		 * This might be the case of a v1 policy using a process
+		 * subscribed keyring to get the key, so there may not be
+		 * a relevant master key.
 		 */
-		return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
+
+		*mk_ret = NULL;
+		return 0;
 	}
 	down_read(&mk->mk_sem);
 
@@ -491,21 +529,6 @@ static int setup_file_encryption_key(struct fscrypt_info *ci,
 		goto out_release_key;
 	}
 
-	switch (ci->ci_policy.version) {
-	case FSCRYPT_POLICY_V1:
-		err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
-		break;
-	case FSCRYPT_POLICY_V2:
-		err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key);
-		break;
-	default:
-		WARN_ON_ONCE(1);
-		err = -EINVAL;
-		break;
-	}
-	if (err)
-		goto out_release_key;
-
 	*mk_ret = mk;
 	return 0;
 
@@ -580,7 +603,11 @@ fscrypt_setup_encryption_info(struct inode *inode,
 	if (res)
 		goto out;
 
-	res = setup_file_encryption_key(crypt_info, need_dirhash_key, &mk);
+	res = find_and_lock_master_key(crypt_info, &mk);
+	if (res)
+		goto out;
+
+	res = fscrypt_setup_file_key(crypt_info, mk, need_dirhash_key);
 	if (res)
 		goto out;
 
-- 
2.40.1

[PATCH v5 3/8] fscrypt: split setup_per_mode_enc_key()

[Sweet Tea Dorminy]

At present, setup_per_mode_enc_key() tries to find, within an array of
mode keys in the master key, an already prepared key, and if it doesn't
find a pre-prepared key, sets up a new one. This caching is not super
clear, at least to me, and splitting this function makes it clearer.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
---
 fs/crypto/keysetup.c | 61 +++++++++++++++++++++++++++-----------------
 1 file changed, 37 insertions(+), 24 deletions(-)

diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 727d473b6b03..06deac6f4487 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -184,34 +184,24 @@ int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key)
 	return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci);
 }
 
-static int setup_per_mode_enc_key(struct fscrypt_info *ci,
-				  struct fscrypt_master_key *mk,
-				  struct fscrypt_prepared_key *keys,
-				  u8 hkdf_context, bool include_fs_uuid)
+static int setup_new_mode_prepared_key(struct fscrypt_master_key *mk,
+				       struct fscrypt_prepared_key *prep_key,
+				       const struct fscrypt_info *ci,
+				       u8 hkdf_context, bool include_fs_uuid)
 {
 	const struct inode *inode = ci->ci_inode;
 	const struct super_block *sb = inode->i_sb;
 	struct fscrypt_mode *mode = ci->ci_mode;
 	const u8 mode_num = mode - fscrypt_modes;
-	struct fscrypt_prepared_key *prep_key;
 	u8 mode_key[FSCRYPT_MAX_KEY_SIZE];
 	u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)];
 	unsigned int hkdf_infolen = 0;
-	int err;
-
-	if (WARN_ON_ONCE(mode_num > FSCRYPT_MODE_MAX))
-		return -EINVAL;
-
-	prep_key = &keys[mode_num];
-	if (fscrypt_is_key_prepared(prep_key, ci)) {
-		ci->ci_enc_key = *prep_key;
-		return 0;
-	}
+	int err = 0;
 
 	mutex_lock(&fscrypt_mode_key_setup_mutex);
 
 	if (fscrypt_is_key_prepared(prep_key, ci))
-		goto done_unlock;
+		goto out_unlock;
 
 	BUILD_BUG_ON(sizeof(mode_num) != 1);
 	BUILD_BUG_ON(sizeof(sb->s_uuid) != 16);
@@ -229,16 +219,39 @@ static int setup_per_mode_enc_key(struct fscrypt_info *ci,
 		goto out_unlock;
 	err = fscrypt_prepare_key(prep_key, mode_key, ci);
 	memzero_explicit(mode_key, mode->keysize);
-	if (err)
-		goto out_unlock;
-done_unlock:
-	ci->ci_enc_key = *prep_key;
-	err = 0;
+
 out_unlock:
 	mutex_unlock(&fscrypt_mode_key_setup_mutex);
 	return err;
 }
 
+static int find_mode_prepared_key(struct fscrypt_info *ci,
+				  struct fscrypt_master_key *mk,
+				  struct fscrypt_prepared_key *keys,
+				  u8 hkdf_context, bool include_fs_uuid)
+{
+	struct fscrypt_mode *mode = ci->ci_mode;
+	const u8 mode_num = mode - fscrypt_modes;
+	struct fscrypt_prepared_key *prep_key;
+	int err;
+
+	if (WARN_ON_ONCE(mode_num > FSCRYPT_MODE_MAX))
+		return -EINVAL;
+
+	prep_key = &keys[mode_num];
+	if (fscrypt_is_key_prepared(prep_key, ci)) {
+		ci->ci_enc_key = *prep_key;
+		return 0;
+	}
+	err = setup_new_mode_prepared_key(mk, prep_key, ci, hkdf_context,
+					  include_fs_uuid);
+	if (err)
+		return err;
+
+	ci->ci_enc_key = *prep_key;
+	return 0;
+}
+
 /*
  * Derive a SipHash key from the given fscrypt master key and the given
  * application-specific information string.
@@ -294,7 +307,7 @@ static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_info *ci,
 {
 	int err;
 
-	err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys,
+	err = find_mode_prepared_key(ci, mk, mk->mk_iv_ino_lblk_32_keys,
 				     HKDF_CONTEXT_IV_INO_LBLK_32_KEY, true);
 	if (err)
 		return err;
@@ -344,7 +357,7 @@ static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
 		 * encryption key.  This ensures that the master key is
 		 * consistently used only for HKDF, avoiding key reuse issues.
 		 */
-		err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys,
+		err = find_mode_prepared_key(ci, mk, mk->mk_direct_keys,
 					     HKDF_CONTEXT_DIRECT_KEY, false);
 	} else if (ci->ci_policy.v2.flags &
 		   FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) {
@@ -354,7 +367,7 @@ static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
 		 * the IVs.  This format is optimized for use with inline
 		 * encryption hardware compliant with the UFS standard.
 		 */
-		err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys,
+		err = find_mode_prepared_key(ci, mk, mk->mk_iv_ino_lblk_64_keys,
 					     HKDF_CONTEXT_IV_INO_LBLK_64_KEY,
 					     true);
 	} else if (ci->ci_policy.v2.flags &
-- 
2.40.1

[PATCH v5 4/8] fscrypt: move dirhash key setup away from IO key setup

[Sweet Tea Dorminy]

The function named fscrypt_setup_v2_file_key() has as its main focus the
setting up of the fscrypt_info's ci_enc_key member, the prepared key
with which filenames or file contents are encrypted or decrypted.
However, it currently also sets up the dirhash key, used by some
directories, based on a parameter. There are no dependencies on
setting up the dirhash key beyond having the master key locked, and it's
clearer having fscrypt_setup_file_key() be only about setting up the
prepared key for IO.

Thus, move dirhash key setup to fscrypt_setup_encryption_info(), which
calls out to each function setting up parts of the fscrypt_info, and
stop passing the need_dirhash_key parameter around.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
---
 fs/crypto/keysetup.c | 37 +++++++++++++++++++++----------------
 1 file changed, 21 insertions(+), 16 deletions(-)

diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 06deac6f4487..430e2455ea2d 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -343,8 +343,7 @@ static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_info *ci,
 }
 
 static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
-				     struct fscrypt_master_key *mk,
-				     bool need_dirhash_key)
+				     struct fscrypt_master_key *mk)
 {
 	int err;
 
@@ -386,25 +385,15 @@ static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
 		err = fscrypt_set_per_file_enc_key(ci, derived_key);
 		memzero_explicit(derived_key, ci->ci_mode->keysize);
 	}
-	if (err)
-		return err;
 
-	/* Derive a secret dirhash key for directories that need it. */
-	if (need_dirhash_key) {
-		err = fscrypt_derive_dirhash_key(ci, mk);
-		if (err)
-			return err;
-	}
-
-	return 0;
+	return err;
 }
 
 /*
  * Find or create the appropriate prepared key for an info.
  */
 static int fscrypt_setup_file_key(struct fscrypt_info *ci,
-				  struct fscrypt_master_key *mk,
-				  bool need_dirhash_key)
+				  struct fscrypt_master_key *mk)
 {
 	int err;
 
@@ -426,7 +415,7 @@ static int fscrypt_setup_file_key(struct fscrypt_info *ci,
 		err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
 		break;
 	case FSCRYPT_POLICY_V2:
-		err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key);
+		err = fscrypt_setup_v2_file_key(ci, mk);
 		break;
 	default:
 		WARN_ON_ONCE(1);
@@ -620,10 +609,26 @@ fscrypt_setup_encryption_info(struct inode *inode,
 	if (res)
 		goto out;
 
-	res = fscrypt_setup_file_key(crypt_info, mk, need_dirhash_key);
+	res = fscrypt_setup_file_key(crypt_info, mk);
 	if (res)
 		goto out;
 
+	/*
+	 * Derive a secret dirhash key for directories that need it. It
+	 * should be impossible to set flags such that a v1 policy sets
+	 * need_dirhash_key, but check it anyway.
+	 */
+	if (need_dirhash_key) {
+		if (WARN_ON_ONCE(policy->version == FSCRYPT_POLICY_V1)) {
+			res = -EINVAL;
+			goto out;
+		}
+
+		res = fscrypt_derive_dirhash_key(crypt_info, mk);
+		if (res)
+			goto out;
+	}
+
 	/*
 	 * For existing inodes, multiple tasks may race to set ->i_crypt_info.
 	 * So use cmpxchg_release().  This pairs with the smp_load_acquire() in
-- 
2.40.1

[PATCH v5 5/8] fscrypt: reduce special-casing of IV_INO_LBLK_32

[Sweet Tea Dorminy]

Right now, the IV_INO_LBLK_32 policy is handled by its own function
called in fscrypt_setup_v2_file_key(), different from all other policies
which just call find_mode_prepared_key() with various parameters. The
function additionally sets up the relevant inode hashing key in the
master key, and uses it to hash the inode number if possible. This is
not particularly relevant to setting up a prepared key, so this change
tries to make it clear that every non-default policy uses basically the
same setup mechanism for its prepared key. The other setup is moved to
be called from the top crypt_info setup function.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
---
 fs/crypto/keysetup.c | 62 +++++++++++++++++++++++---------------------
 1 file changed, 32 insertions(+), 30 deletions(-)

diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 430e2455ea2d..8b201b91c036 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -302,44 +302,30 @@ void fscrypt_hash_inode_number(struct fscrypt_info *ci,
 					      &mk->mk_ino_hash_key);
 }
 
-static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_info *ci,
-					    struct fscrypt_master_key *mk)
+static int fscrypt_setup_ino_hash_key(struct fscrypt_master_key *mk)
 {
 	int err;
 
-	err = find_mode_prepared_key(ci, mk, mk->mk_iv_ino_lblk_32_keys,
-				     HKDF_CONTEXT_IV_INO_LBLK_32_KEY, true);
-	if (err)
-		return err;
-
 	/* pairs with smp_store_release() below */
-	if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) {
+	if (smp_load_acquire(&mk->mk_ino_hash_key_initialized))
+		return 0;
 
-		mutex_lock(&fscrypt_mode_key_setup_mutex);
+	mutex_lock(&fscrypt_mode_key_setup_mutex);
 
-		if (mk->mk_ino_hash_key_initialized)
-			goto unlock;
+	if (mk->mk_ino_hash_key_initialized)
+		goto unlock;
 
-		err = fscrypt_derive_siphash_key(mk,
-						 HKDF_CONTEXT_INODE_HASH_KEY,
-						 NULL, 0, &mk->mk_ino_hash_key);
-		if (err)
-			goto unlock;
-		/* pairs with smp_load_acquire() above */
-		smp_store_release(&mk->mk_ino_hash_key_initialized, true);
+	err = fscrypt_derive_siphash_key(mk,
+					 HKDF_CONTEXT_INODE_HASH_KEY,
+					 NULL, 0, &mk->mk_ino_hash_key);
+	if (err)
+		goto unlock;
+	/* pairs with smp_load_acquire() above */
+	smp_store_release(&mk->mk_ino_hash_key_initialized, true);
 unlock:
-		mutex_unlock(&fscrypt_mode_key_setup_mutex);
-		if (err)
-			return err;
-	}
+	mutex_unlock(&fscrypt_mode_key_setup_mutex);
 
-	/*
-	 * New inodes may not have an inode number assigned yet.
-	 * Hashing their inode number is delayed until later.
-	 */
-	if (ci->ci_inode->i_ino)
-		fscrypt_hash_inode_number(ci, mk);
-	return 0;
+	return err;
 }
 
 static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
@@ -371,7 +357,9 @@ static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
 					     true);
 	} else if (ci->ci_policy.v2.flags &
 		   FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) {
-		err = fscrypt_setup_iv_ino_lblk_32_key(ci, mk);
+		err = find_mode_prepared_key(ci, mk, mk->mk_iv_ino_lblk_32_keys,
+					     HKDF_CONTEXT_IV_INO_LBLK_32_KEY,
+					     true);
 	} else {
 		u8 derived_key[FSCRYPT_MAX_KEY_SIZE];
 
@@ -629,6 +617,20 @@ fscrypt_setup_encryption_info(struct inode *inode,
 			goto out;
 	}
 
+	/*
+	 * The IV_INO_LBLK_32 policy needs a hashed inode number, but new
+	 * inodes may not have an inode number assigned yet.
+	 */
+	if (policy->version == FSCRYPT_POLICY_V2 &&
+	    (policy->v2.flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) {
+		res = fscrypt_setup_ino_hash_key(mk);
+		if (res)
+			goto out;
+
+		if (inode->i_ino)
+			fscrypt_hash_inode_number(crypt_info, mk);
+	}
+
 	/*
 	 * For existing inodes, multiple tasks may race to set ->i_crypt_info.
 	 * So use cmpxchg_release().  This pairs with the smp_load_acquire() in
-- 
2.40.1

[PATCH v5 6/8] fscrypt: move all the shared mode key setup deeper

[Sweet Tea Dorminy]

Currently, fscrypt_setup_v2_file_key() has a set of ifs which encode
various information about how to set up a new mode key if necessary for
a shared-key policy (DIRECT or IV_INO_LBLK_*). This is somewhat awkward
-- this information is only needed at the point that we need to setup a
new key, which is not the common case; the setup details are recorded as
function parameters relatively far from where they're actually used; and
at the point we use the parameters, we can derive the information
equally well.

So this moves mode and policy checking as deep into the callstack as
possible. mk_prepared_key_for_mode_policy() deals with the array lookup
within a master key. And fill_hkdf_info_for mode_key() deals with
filling in the hkdf info as necessary for a particular policy. These
seem a little clearer in broad strokes, emphasizing the similarities
between the policies, but it does spread out the information on how the
key is derived for a particular policy more.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
---
 fs/crypto/keysetup.c | 131 +++++++++++++++++++++++++++++--------------
 1 file changed, 88 insertions(+), 43 deletions(-)

diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 8b201b91c036..7dd12c1821dd 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -13,6 +13,17 @@
 
 #include "fscrypt_private.h"
 
+#define MAX_MODE_KEY_HKDF_INFO_SIZE 17
+
+/*
+ * Constant defining the various policy flags which require a non-default key
+ * policy.
+ */
+#define FSCRYPT_POLICY_FLAGS_KEY_MASK		\
+	(FSCRYPT_POLICY_FLAG_DIRECT_KEY		\
+	 | FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64	\
+	 | FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)
+
 struct fscrypt_mode fscrypt_modes[] = {
 	[FSCRYPT_MODE_AES_256_XTS] = {
 		.friendly_name = "AES-256-XTS",
@@ -184,20 +195,83 @@ int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key)
 	return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci);
 }
 
+static struct fscrypt_prepared_key *
+mk_prepared_key_for_mode_policy(struct fscrypt_master_key *mk,
+				union fscrypt_policy *policy,
+				struct fscrypt_mode *mode)
+{
+	const u8 mode_num = mode - fscrypt_modes;
+
+	switch (policy->v2.flags & FSCRYPT_POLICY_FLAGS_KEY_MASK) {
+	case FSCRYPT_POLICY_FLAG_DIRECT_KEY:
+		return &mk->mk_direct_keys[mode_num];
+	case FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64:
+		return &mk->mk_iv_ino_lblk_64_keys[mode_num];
+	case FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32:
+		return &mk->mk_iv_ino_lblk_32_keys[mode_num];
+	default:
+		return ERR_PTR(-EINVAL);
+	}
+}
+
+static size_t
+fill_hkdf_info_for_mode_key(const struct fscrypt_info *ci,
+			    u8 hkdf_info[MAX_MODE_KEY_HKDF_INFO_SIZE])
+{
+	const u8 mode_num = ci->ci_mode - fscrypt_modes;
+	const struct super_block *sb = ci->ci_inode->i_sb;
+	u8 hkdf_infolen = 0;
+
+	hkdf_info[hkdf_infolen++] = mode_num;
+	if (!(ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY)) {
+		memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid,
+				sizeof(sb->s_uuid));
+		hkdf_infolen += sizeof(sb->s_uuid);
+	}
+	return hkdf_infolen;
+}
+
 static int setup_new_mode_prepared_key(struct fscrypt_master_key *mk,
 				       struct fscrypt_prepared_key *prep_key,
-				       const struct fscrypt_info *ci,
-				       u8 hkdf_context, bool include_fs_uuid)
+				       const struct fscrypt_info *ci)
 {
 	const struct inode *inode = ci->ci_inode;
 	const struct super_block *sb = inode->i_sb;
+	unsigned int policy_flags = fscrypt_policy_flags(&ci->ci_policy);
 	struct fscrypt_mode *mode = ci->ci_mode;
 	const u8 mode_num = mode - fscrypt_modes;
 	u8 mode_key[FSCRYPT_MAX_KEY_SIZE];
 	u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)];
 	unsigned int hkdf_infolen = 0;
+	u8 hkdf_context = 0;
 	int err = 0;
 
+	switch (policy_flags & FSCRYPT_POLICY_FLAGS_KEY_MASK) {
+	case FSCRYPT_POLICY_FLAG_DIRECT_KEY:
+		hkdf_context = HKDF_CONTEXT_DIRECT_KEY;
+		break;
+	case FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64:
+		hkdf_context = HKDF_CONTEXT_IV_INO_LBLK_64_KEY;
+		break;
+	case FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32:
+		hkdf_context = HKDF_CONTEXT_IV_INO_LBLK_32_KEY;
+		break;
+	}
+
+	/*
+	 * For DIRECT_KEY policies: instead of deriving per-file encryption
+	 * keys, the per-file nonce will be included in all the IVs.  But
+	 * unlike v1 policies, for v2 policies in this case we don't encrypt
+	 * with the master key directly but rather derive a per-mode encryption
+	 * key.  This ensures that the master key is consistently used only for
+	 * HKDF, avoiding key reuse issues.
+	 *
+	 * For IV_INO_LBLK policies: encryption keys are derived from
+	 * (master_key, mode_num, filesystem_uuid), and inode number is
+	 * included in the IVs.  This format is optimized for use with inline
+	 * encryption hardware compliant with the UFS standard.
+	 */
+
 	mutex_lock(&fscrypt_mode_key_setup_mutex);
 
 	if (fscrypt_is_key_prepared(prep_key, ci))
@@ -205,13 +279,9 @@ static int setup_new_mode_prepared_key(struct fscrypt_master_key *mk,
 
 	BUILD_BUG_ON(sizeof(mode_num) != 1);
 	BUILD_BUG_ON(sizeof(sb->s_uuid) != 16);
-	BUILD_BUG_ON(sizeof(hkdf_info) != 17);
-	hkdf_info[hkdf_infolen++] = mode_num;
-	if (include_fs_uuid) {
-		memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid,
-		       sizeof(sb->s_uuid));
-		hkdf_infolen += sizeof(sb->s_uuid);
-	}
+	BUILD_BUG_ON(sizeof(hkdf_info) != MAX_MODE_KEY_HKDF_INFO_SIZE);
+	hkdf_infolen = fill_hkdf_info_for_mode_key(ci, hkdf_info);
+
 	err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
 				  hkdf_context, hkdf_info, hkdf_infolen,
 				  mode_key, mode->keysize);
@@ -225,10 +295,8 @@ static int setup_new_mode_prepared_key(struct fscrypt_master_key *mk,
 	return err;
 }
 
-static int find_mode_prepared_key(struct fscrypt_info *ci,
-				  struct fscrypt_master_key *mk,
-				  struct fscrypt_prepared_key *keys,
-				  u8 hkdf_context, bool include_fs_uuid)
+static int setup_mode_prepared_key(struct fscrypt_info *ci,
+				  struct fscrypt_master_key *mk)
 {
 	struct fscrypt_mode *mode = ci->ci_mode;
 	const u8 mode_num = mode - fscrypt_modes;
@@ -238,13 +306,15 @@ static int find_mode_prepared_key(struct fscrypt_info *ci,
 	if (WARN_ON_ONCE(mode_num > FSCRYPT_MODE_MAX))
 		return -EINVAL;
 
-	prep_key = &keys[mode_num];
+	prep_key = mk_prepared_key_for_mode_policy(mk, &ci->ci_policy, mode);
+	if (IS_ERR(prep_key))
+		return PTR_ERR(prep_key);
+
 	if (fscrypt_is_key_prepared(prep_key, ci)) {
 		ci->ci_enc_key = *prep_key;
 		return 0;
 	}
-	err = setup_new_mode_prepared_key(mk, prep_key, ci, hkdf_context,
-					  include_fs_uuid);
+	err = setup_new_mode_prepared_key(mk, prep_key, ci);
 	if (err)
 		return err;
 
@@ -333,33 +403,8 @@ static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
 {
 	int err;
 
-	if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
-		/*
-		 * DIRECT_KEY: instead of deriving per-file encryption keys, the
-		 * per-file nonce will be included in all the IVs.  But unlike
-		 * v1 policies, for v2 policies in this case we don't encrypt
-		 * with the master key directly but rather derive a per-mode
-		 * encryption key.  This ensures that the master key is
-		 * consistently used only for HKDF, avoiding key reuse issues.
-		 */
-		err = find_mode_prepared_key(ci, mk, mk->mk_direct_keys,
-					     HKDF_CONTEXT_DIRECT_KEY, false);
-	} else if (ci->ci_policy.v2.flags &
-		   FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) {
-		/*
-		 * IV_INO_LBLK_64: encryption keys are derived from (master_key,
-		 * mode_num, filesystem_uuid), and inode number is included in
-		 * the IVs.  This format is optimized for use with inline
-		 * encryption hardware compliant with the UFS standard.
-		 */
-		err = find_mode_prepared_key(ci, mk, mk->mk_iv_ino_lblk_64_keys,
-					     HKDF_CONTEXT_IV_INO_LBLK_64_KEY,
-					     true);
-	} else if (ci->ci_policy.v2.flags &
-		   FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) {
-		err = find_mode_prepared_key(ci, mk, mk->mk_iv_ino_lblk_32_keys,
-					     HKDF_CONTEXT_IV_INO_LBLK_32_KEY,
-					     true);
+	if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAGS_KEY_MASK) {
+		err = setup_mode_prepared_key(ci, mk);
 	} else {
 		u8 derived_key[FSCRYPT_MAX_KEY_SIZE];
 
-- 
2.40.1

[PATCH v5 7/8] fscrypt: make infos have a pointer to prepared keys

[Sweet Tea Dorminy]

At present, it's not entirely clear who owns a prepared key. Under
default policies, infos own the prepared key; but under any of the
policy flag key policies, or with some v1 policies, the info merely has
a copy of the authoritative prepared key; the authoritative copy of the
prepared key lives in the master key or the direct key, but the info has
no way to get to the authoritative key or get updates from it.

A scenario which could occur is the following:

-A directory tree is set up to use v2 policy DIRECT_KEY, mode adiantum.
-One directory is opened, gets a prepared key with a crypto_skcipher.
-A file within it is opened, sets up and gets the 'same' prepared key,
 but it's set up the blk_crypto_key in the prepared key.
-Another directory in the tree is opened, and gets the 'same' prepared
 key, but it's now got a pointer to the blk_crypto_key too.
-The two directories' ci_enc_key values are different, even though for
 practical purposes they are the same.

While it has no correctness implications, it's confusing for debugging
when two directories with the same mode/policy have different prepared
key contents depending on what else happened.

Adding a layer of indirection makes everything clearer at the cost of
another pointer. Now everyone sharing a prepared key within a direct key
or a master key have the same pointer to the single prepared key.
Followups move information from the crypt_info into the prepared key,
which ends up reducing memory usage slightly. And, it makes using
pooled, pre-allocated objects which could be stolen from a dormant
fscrypt_info much easier.

So this change makes crypt_info->ci_enc_key a pointer and updates all
users thereof.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
---
 fs/crypto/crypto.c          |  2 +-
 fs/crypto/fname.c           |  4 ++--
 fs/crypto/fscrypt_private.h |  2 +-
 fs/crypto/inline_crypt.c    |  4 ++--
 fs/crypto/keysetup.c        | 16 +++++++++++-----
 fs/crypto/keysetup_v1.c     |  2 +-
 6 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
index 6a837e4b80dc..9f3bda18c797 100644
--- a/fs/crypto/crypto.c
+++ b/fs/crypto/crypto.c
@@ -108,7 +108,7 @@ int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
 	DECLARE_CRYPTO_WAIT(wait);
 	struct scatterlist dst, src;
 	struct fscrypt_info *ci = inode->i_crypt_info;
-	struct crypto_skcipher *tfm = ci->ci_enc_key.tfm;
+	struct crypto_skcipher *tfm = ci->ci_enc_key->tfm;
 	int res = 0;
 
 	if (WARN_ON_ONCE(len <= 0))
diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
index 6eae3f12ad50..edb78cd1b0e7 100644
--- a/fs/crypto/fname.c
+++ b/fs/crypto/fname.c
@@ -101,7 +101,7 @@ int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname,
 	struct skcipher_request *req = NULL;
 	DECLARE_CRYPTO_WAIT(wait);
 	const struct fscrypt_info *ci = inode->i_crypt_info;
-	struct crypto_skcipher *tfm = ci->ci_enc_key.tfm;
+	struct crypto_skcipher *tfm = ci->ci_enc_key->tfm;
 	union fscrypt_iv iv;
 	struct scatterlist sg;
 	int res;
@@ -158,7 +158,7 @@ static int fname_decrypt(const struct inode *inode,
 	DECLARE_CRYPTO_WAIT(wait);
 	struct scatterlist src_sg, dst_sg;
 	const struct fscrypt_info *ci = inode->i_crypt_info;
-	struct crypto_skcipher *tfm = ci->ci_enc_key.tfm;
+	struct crypto_skcipher *tfm = ci->ci_enc_key->tfm;
 	union fscrypt_iv iv;
 	int res;
 
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 7ab5a7b7eef8..5011737b60b3 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -198,7 +198,7 @@ struct fscrypt_prepared_key {
 struct fscrypt_info {
 
 	/* The key in a form prepared for actual encryption/decryption */
-	struct fscrypt_prepared_key ci_enc_key;
+	struct fscrypt_prepared_key *ci_enc_key;
 
 	/* True if ci_enc_key should be freed when this fscrypt_info is freed */
 	bool ci_owns_key;
diff --git a/fs/crypto/inline_crypt.c b/fs/crypto/inline_crypt.c
index 8bfb3ce86476..2063f7941ce6 100644
--- a/fs/crypto/inline_crypt.c
+++ b/fs/crypto/inline_crypt.c
@@ -273,7 +273,7 @@ void fscrypt_set_bio_crypt_ctx(struct bio *bio, const struct inode *inode,
 	ci = inode->i_crypt_info;
 
 	fscrypt_generate_dun(ci, first_lblk, dun);
-	bio_crypt_set_ctx(bio, ci->ci_enc_key.blk_key, dun, gfp_mask);
+	bio_crypt_set_ctx(bio, ci->ci_enc_key->blk_key, dun, gfp_mask);
 }
 EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx);
 
@@ -360,7 +360,7 @@ bool fscrypt_mergeable_bio(struct bio *bio, const struct inode *inode,
 	 * uses the same pointer.  I.e., there's currently no need to support
 	 * merging requests where the keys are the same but the pointers differ.
 	 */
-	if (bc->bc_key != inode->i_crypt_info->ci_enc_key.blk_key)
+	if (bc->bc_key != inode->i_crypt_info->ci_enc_key->blk_key)
 		return false;
 
 	fscrypt_generate_dun(inode->i_crypt_info, next_lblk, next_dun);
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 7dd12c1821dd..4f04999ecfd1 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -192,7 +192,11 @@ void fscrypt_destroy_prepared_key(struct super_block *sb,
 int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key)
 {
 	ci->ci_owns_key = true;
-	return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci);
+	ci->ci_enc_key = kzalloc(sizeof(*ci->ci_enc_key), GFP_KERNEL);
+	if (!ci->ci_enc_key)
+		return -ENOMEM;
+
+	return fscrypt_prepare_key(ci->ci_enc_key, raw_key, ci);
 }
 
 static struct fscrypt_prepared_key *
@@ -311,14 +315,14 @@ static int setup_mode_prepared_key(struct fscrypt_info *ci,
 		return PTR_ERR(prep_key);
 
 	if (fscrypt_is_key_prepared(prep_key, ci)) {
-		ci->ci_enc_key = *prep_key;
+		ci->ci_enc_key = prep_key;
 		return 0;
 	}
 	err = setup_new_mode_prepared_key(mk, prep_key, ci);
 	if (err)
 		return err;
 
-	ci->ci_enc_key = *prep_key;
+	ci->ci_enc_key = prep_key;
 	return 0;
 }
 
@@ -582,9 +586,11 @@ static void put_crypt_info(struct fscrypt_info *ci)
 
 	if (ci->ci_direct_key)
 		fscrypt_put_direct_key(ci->ci_direct_key);
-	else if (ci->ci_owns_key)
+	else if (ci->ci_owns_key) {
 		fscrypt_destroy_prepared_key(ci->ci_inode->i_sb,
-					     &ci->ci_enc_key);
+					     ci->ci_enc_key);
+		kfree_sensitive(ci->ci_enc_key);
+	}
 
 	mk = ci->ci_master_key;
 	if (mk) {
diff --git a/fs/crypto/keysetup_v1.c b/fs/crypto/keysetup_v1.c
index 75dabd9b27f9..e1d761e8067f 100644
--- a/fs/crypto/keysetup_v1.c
+++ b/fs/crypto/keysetup_v1.c
@@ -259,7 +259,7 @@ static int setup_v1_file_key_direct(struct fscrypt_info *ci,
 	if (IS_ERR(dk))
 		return PTR_ERR(dk);
 	ci->ci_direct_key = dk;
-	ci->ci_enc_key = dk->dk_key;
+	ci->ci_enc_key = &dk->dk_key;
 	return 0;
 }
 
-- 
2.40.1

[PATCH v5 8/8] fscrypt: make prepared keys record their type

[Sweet Tea Dorminy]

Right now fscrypt_infos have two fields dedicated solely to recording
what type of prepared key the info has: whether it solely owns the
prepared key, or has borrowed it from a master key, or from a direct
key.

The ci_direct_key field is only used for v1 direct key policies,
recording the direct key that needs to have its refcount reduced when
the crypt_info is freed. However, now that crypt_info->ci_enc_key is a
pointer to the authoritative prepared key -- embedded in the direct key,
in this case, we no longer need to keep a full pointer to the direct key
-- we can use container_of() to go from the prepared key to its
surrounding direct key.

The key ownership information doesn't change during the lifetime of a
prepared key.  Since at worst there's a prepared key per info, and at
best many infos share a single prepared key, it can be slightly more
efficient to store this ownership info in the prepared key instead of in
the fscrypt_info, especially since we can squash both fields down into
a single enum.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
---
 fs/crypto/fscrypt_private.h | 31 +++++++++++++++++++++++--------
 fs/crypto/keysetup.c        | 21 +++++++++++++--------
 fs/crypto/keysetup_v1.c     |  7 +++++--
 3 files changed, 41 insertions(+), 18 deletions(-)

diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index 5011737b60b3..e726a1fb9f7e 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -174,18 +174,39 @@ struct fscrypt_symlink_data {
 	char encrypted_path[1];
 } __packed;
 
+/**
+ * enum fscrypt_prepared_key_type - records a prepared key's ownership
+ *
+ * @FSCRYPT_KEY_PER_INFO: this prepared key is allocated for a specific info
+ *		          and is never shared.
+ * @FSCRYPT_KEY_DIRECT_V1: this prepared key is embedded in a fscrypt_direct_key
+ *		           used in v1 direct key policies.
+ * @FSCRYPT_KEY_MASTER_KEY: this prepared key is a per-mode and policy key,
+ *			    part of a fscrypt_master_key, shared between all
+ *			    users of this master key having this mode and
+ *			    policy.
+ */
+enum fscrypt_prepared_key_type {
+	FSCRYPT_KEY_PER_INFO = 1,
+	FSCRYPT_KEY_DIRECT_V1,
+	FSCRYPT_KEY_MASTER_KEY,
+} __packed;
+
 /**
  * struct fscrypt_prepared_key - a key prepared for actual encryption/decryption
  * @tfm: crypto API transform object
  * @blk_key: key for blk-crypto
+ * @type: records the ownership type of the prepared key
  *
- * Normally only one of the fields will be non-NULL.
+ * Normally only one of @tfm and @blk_key will be non-NULL, although it is
+ * possible if @type is FSCRYPT_KEY_MASTER_KEY.
  */
 struct fscrypt_prepared_key {
 	struct crypto_skcipher *tfm;
 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
 	struct blk_crypto_key *blk_key;
 #endif
+	enum fscrypt_prepared_key_type type;
 };
 
 /*
@@ -233,12 +254,6 @@ struct fscrypt_info {
 	 */
 	struct list_head ci_master_key_link;
 
-	/*
-	 * If non-NULL, then encryption is done using the master key directly
-	 * and ci_enc_key will equal ci_direct_key->dk_key.
-	 */
-	struct fscrypt_direct_key *ci_direct_key;
-
 	/*
 	 * This inode's hash key for filenames.  This is a 128-bit SipHash-2-4
 	 * key.  This is only set for directories that use a keyed dirhash over
@@ -641,7 +656,7 @@ static inline int fscrypt_require_key(struct inode *inode)
 
 /* keysetup_v1.c */
 
-void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
+void fscrypt_put_direct_key(struct fscrypt_prepared_key *prep_key);
 
 int fscrypt_setup_v1_file_key(struct fscrypt_info *ci,
 			      const u8 *raw_master_key);
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 4f04999ecfd1..a19650f954e2 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -191,11 +191,11 @@ void fscrypt_destroy_prepared_key(struct super_block *sb,
 /* Given a per-file encryption key, set up the file's crypto transform object */
 int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key)
 {
-	ci->ci_owns_key = true;
 	ci->ci_enc_key = kzalloc(sizeof(*ci->ci_enc_key), GFP_KERNEL);
 	if (!ci->ci_enc_key)
 		return -ENOMEM;
 
+	ci->ci_enc_key->type = FSCRYPT_KEY_PER_INFO;
 	return fscrypt_prepare_key(ci->ci_enc_key, raw_key, ci);
 }
 
@@ -290,7 +290,8 @@ static int setup_new_mode_prepared_key(struct fscrypt_master_key *mk,
 				  hkdf_context, hkdf_info, hkdf_infolen,
 				  mode_key, mode->keysize);
 	if (err)
-		goto out_unlock;
+		return err;
+	prep_key->type = FSCRYPT_KEY_MASTER_KEY;
 	err = fscrypt_prepare_key(prep_key, mode_key, ci);
 	memzero_explicit(mode_key, mode->keysize);
 
@@ -584,12 +585,16 @@ static void put_crypt_info(struct fscrypt_info *ci)
 	if (!ci)
 		return;
 
-	if (ci->ci_direct_key)
-		fscrypt_put_direct_key(ci->ci_direct_key);
-	else if (ci->ci_owns_key) {
-		fscrypt_destroy_prepared_key(ci->ci_inode->i_sb,
-					     ci->ci_enc_key);
-		kfree_sensitive(ci->ci_enc_key);
+	if (ci->ci_enc_key) {
+		enum fscrypt_prepared_key_type type = ci->ci_enc_key->type;
+
+		if (type == FSCRYPT_KEY_DIRECT_V1)
+			fscrypt_put_direct_key(ci->ci_enc_key);
+		if (type == FSCRYPT_KEY_PER_INFO) {
+			fscrypt_destroy_prepared_key(ci->ci_inode->i_sb,
+						     ci->ci_enc_key);
+			kfree_sensitive(ci->ci_enc_key);
+		}
 	}
 
 	mk = ci->ci_master_key;
diff --git a/fs/crypto/keysetup_v1.c b/fs/crypto/keysetup_v1.c
index e1d761e8067f..1e785cedead0 100644
--- a/fs/crypto/keysetup_v1.c
+++ b/fs/crypto/keysetup_v1.c
@@ -160,8 +160,11 @@ static void free_direct_key(struct fscrypt_direct_key *dk)
 	}
 }
 
-void fscrypt_put_direct_key(struct fscrypt_direct_key *dk)
+void fscrypt_put_direct_key(struct fscrypt_prepared_key *prep_key)
 {
+	struct fscrypt_direct_key *dk =
+		container_of(prep_key, struct fscrypt_direct_key, dk_key);
+
 	if (!refcount_dec_and_lock(&dk->dk_refcount, &fscrypt_direct_keys_lock))
 		return;
 	hash_del(&dk->dk_node);
@@ -235,6 +238,7 @@ fscrypt_get_direct_key(const struct fscrypt_info *ci, const u8 *raw_key)
 	dk->dk_sb = ci->ci_inode->i_sb;
 	refcount_set(&dk->dk_refcount, 1);
 	dk->dk_mode = ci->ci_mode;
+	dk->dk_key.type = FSCRYPT_KEY_DIRECT_V1;
 	err = fscrypt_prepare_key(&dk->dk_key, raw_key, ci);
 	if (err)
 		goto err_free_dk;
@@ -258,7 +262,6 @@ static int setup_v1_file_key_direct(struct fscrypt_info *ci,
 	dk = fscrypt_get_direct_key(ci, raw_master_key);
 	if (IS_ERR(dk))
 		return PTR_ERR(dk);
-	ci->ci_direct_key = dk;
 	ci->ci_enc_key = &dk->dk_key;
 	return 0;
 }
-- 
2.40.1

Re: [PATCH v5 8/8] fscrypt: make prepared keys record their type

[Luís Henriques]

Sweet Tea Dorminy <sweettea-kernel@dorminy.me> writes:

> Right now fscrypt_infos have two fields dedicated solely to recording
> what type of prepared key the info has: whether it solely owns the
> prepared key, or has borrowed it from a master key, or from a direct
> key.
>
> The ci_direct_key field is only used for v1 direct key policies,
> recording the direct key that needs to have its refcount reduced when
> the crypt_info is freed. However, now that crypt_info->ci_enc_key is a
> pointer to the authoritative prepared key -- embedded in the direct key,
> in this case, we no longer need to keep a full pointer to the direct key
> -- we can use container_of() to go from the prepared key to its
> surrounding direct key.
>
> The key ownership information doesn't change during the lifetime of a
> prepared key.  Since at worst there's a prepared key per info, and at
> best many infos share a single prepared key, it can be slightly more
> efficient to store this ownership info in the prepared key instead of in
> the fscrypt_info, especially since we can squash both fields down into
> a single enum.
>
> Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
> ---
>  fs/crypto/fscrypt_private.h | 31 +++++++++++++++++++++++--------
>  fs/crypto/keysetup.c        | 21 +++++++++++++--------
>  fs/crypto/keysetup_v1.c     |  7 +++++--
>  3 files changed, 41 insertions(+), 18 deletions(-)
>
> diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
> index 5011737b60b3..e726a1fb9f7e 100644
> --- a/fs/crypto/fscrypt_private.h
> +++ b/fs/crypto/fscrypt_private.h
> @@ -174,18 +174,39 @@ struct fscrypt_symlink_data {
>  	char encrypted_path[1];
>  } __packed;
>  
> +/**
> + * enum fscrypt_prepared_key_type - records a prepared key's ownership
> + *
> + * @FSCRYPT_KEY_PER_INFO: this prepared key is allocated for a specific info
> + *		          and is never shared.
> + * @FSCRYPT_KEY_DIRECT_V1: this prepared key is embedded in a fscrypt_direct_key
> + *		           used in v1 direct key policies.
> + * @FSCRYPT_KEY_MASTER_KEY: this prepared key is a per-mode and policy key,
> + *			    part of a fscrypt_master_key, shared between all
> + *			    users of this master key having this mode and
> + *			    policy.
> + */
> +enum fscrypt_prepared_key_type {
> +	FSCRYPT_KEY_PER_INFO = 1,
> +	FSCRYPT_KEY_DIRECT_V1,
> +	FSCRYPT_KEY_MASTER_KEY,
> +} __packed;
> +
>  /**
>   * struct fscrypt_prepared_key - a key prepared for actual encryption/decryption
>   * @tfm: crypto API transform object
>   * @blk_key: key for blk-crypto
> + * @type: records the ownership type of the prepared key
>   *
> - * Normally only one of the fields will be non-NULL.
> + * Normally only one of @tfm and @blk_key will be non-NULL, although it is
> + * possible if @type is FSCRYPT_KEY_MASTER_KEY.
>   */
>  struct fscrypt_prepared_key {
>  	struct crypto_skcipher *tfm;
>  #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
>  	struct blk_crypto_key *blk_key;
>  #endif
> +	enum fscrypt_prepared_key_type type;
>  };
>  
>  /*
> @@ -233,12 +254,6 @@ struct fscrypt_info {
>  	 */
>  	struct list_head ci_master_key_link;
>  
> -	/*
> -	 * If non-NULL, then encryption is done using the master key directly
> -	 * and ci_enc_key will equal ci_direct_key->dk_key.
> -	 */
> -	struct fscrypt_direct_key *ci_direct_key;
> -
>  	/*
>  	 * This inode's hash key for filenames.  This is a 128-bit SipHash-2-4
>  	 * key.  This is only set for directories that use a keyed dirhash over
> @@ -641,7 +656,7 @@ static inline int fscrypt_require_key(struct inode *inode)
>  
>  /* keysetup_v1.c */
>  
> -void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
> +void fscrypt_put_direct_key(struct fscrypt_prepared_key *prep_key);
>  
>  int fscrypt_setup_v1_file_key(struct fscrypt_info *ci,
>  			      const u8 *raw_master_key);
> diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
> index 4f04999ecfd1..a19650f954e2 100644
> --- a/fs/crypto/keysetup.c
> +++ b/fs/crypto/keysetup.c
> @@ -191,11 +191,11 @@ void fscrypt_destroy_prepared_key(struct super_block *sb,
>  /* Given a per-file encryption key, set up the file's crypto transform object */
>  int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key)
>  {
> -	ci->ci_owns_key = true;
>  	ci->ci_enc_key = kzalloc(sizeof(*ci->ci_enc_key), GFP_KERNEL);
>  	if (!ci->ci_enc_key)
>  		return -ENOMEM;
>  
> +	ci->ci_enc_key->type = FSCRYPT_KEY_PER_INFO;
>  	return fscrypt_prepare_key(ci->ci_enc_key, raw_key, ci);
>  }
>  
> @@ -290,7 +290,8 @@ static int setup_new_mode_prepared_key(struct fscrypt_master_key *mk,
>  				  hkdf_context, hkdf_info, hkdf_infolen,
>  				  mode_key, mode->keysize);
>  	if (err)
> -		goto out_unlock;
> +		return err;

Is this change really intended?  I guess it's a mistake, because if we
simply return we'll leave keysetup mutex locked, which is probably not
what we want here.

Cheers,
-- 
Luís

> +	prep_key->type = FSCRYPT_KEY_MASTER_KEY;
>  	err = fscrypt_prepare_key(prep_key, mode_key, ci);
>  	memzero_explicit(mode_key, mode->keysize);
>