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@xxxxxxxxxx>
---
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 20b8ea1e3518..e2acd8894ea7 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -174,18 +174,39 @@ struct fscrypt_symlink_data {
char encrypted_path[];
} __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;
}
--
2.41.0
|