diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index 4263cac24b32..0053b5c45412 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -496,6 +496,19 @@ fscrypt_is_key_prepared(const struct fscrypt_prepared_key *prep_key, /* keyring.c */ +/* + * fscrypt_master_key_user - a user's claim to a master key + */ +struct fscrypt_master_key_user { + struct list_head link; + kuid_t uid; + /* + * This 'struct key' contains no secret. It exists solely to charge the + * appropriate user's key quota. + */ + struct key *quota_key; +}; + /* * fscrypt_master_key_secret - secret key material of an in-use master key */ @@ -611,19 +624,18 @@ struct fscrypt_master_key { struct fscrypt_key_specifier mk_spec; /* - * Keyring which contains a key of type 'key_type_fscrypt_user' for each - * user who has added this key. Normally each key will be added by just - * one user, but it's possible that multiple users share a key, and in - * that case we need to keep track of those users so that one user can't - * remove the key before the others want it removed too. + * List of user claims to this key (struct fscrypt_master_key_user). + * Normally each key will be added by just one user, but it's possible + * that multiple users share a key, and in that case we need to keep + * track of those users so that one user can't remove the key before the + * others want it removed too. * - * This is NULL for v1 policy keys; those can only be added by root. + * Used only for v2 policy keys. v1 policy keys can be added only by + * root, so user tracking doesn't apply to them. * - * Locking: protected by ->mk_sem. (We don't just rely on the keyrings - * subsystem semaphore ->mk_users->sem, as we need support for atomic - * search+insert along with proper synchronization with other fields.) + * Locking: protected by ->mk_sem. */ - struct key *mk_users; + struct list_head mk_users; /* * List of inodes that were unlocked using this key. This allows the diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c index 5fe0d985a58d..38b73e703073 100644 --- a/fs/crypto/keyring.c +++ b/fs/crypto/keyring.c @@ -65,22 +65,19 @@ static void fscrypt_free_master_key(struct rcu_head *head) kfree_sensitive(mk); } +static void clear_mk_users(struct fscrypt_master_key *mk); + void fscrypt_put_master_key(struct fscrypt_master_key *mk) { if (!refcount_dec_and_test(&mk->mk_struct_refs)) return; /* - * No structural references left, so free ->mk_users, and also free the + * No structural references left, so clear ->mk_users, and also free the * fscrypt_master_key struct itself after an RCU grace period ensures * that concurrent keyring lookups can no longer find it. */ WARN_ON_ONCE(refcount_read(&mk->mk_active_refs) != 0); - if (mk->mk_users) { - /* Clear the keyring so the quota gets released right away. */ - keyring_clear(mk->mk_users); - key_put(mk->mk_users); - mk->mk_users = NULL; - } + clear_mk_users(mk); call_rcu(&mk->mk_rcu_head, fscrypt_free_master_key); } @@ -165,8 +162,8 @@ static void fscrypt_user_key_describe(const struct key *key, struct seq_file *m) } /* - * Type of key in ->mk_users. Each key of this type represents a particular - * user who has added a particular master key. + * Type of fscrypt_master_key_user::quota_key. This contains no secret; it + * exists solely to charge a user's key quota. * * Note that the name of this key type really should be something like * ".fscrypt-user" instead of simply ".fscrypt". But the shorter name is chosen @@ -180,30 +177,9 @@ static struct key_type key_type_fscrypt_user = { .describe = fscrypt_user_key_describe, }; -#define FSCRYPT_MK_USERS_DESCRIPTION_SIZE \ - (CONST_STRLEN("fscrypt-") + 2 * FSCRYPT_KEY_IDENTIFIER_SIZE + \ - CONST_STRLEN("-users") + 1) - #define FSCRYPT_MK_USER_DESCRIPTION_SIZE \ (2 * FSCRYPT_KEY_IDENTIFIER_SIZE + CONST_STRLEN(".uid.") + 10 + 1) -static void format_mk_users_keyring_description( - char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE], - const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]) -{ - sprintf(description, "fscrypt-%*phN-users", - FSCRYPT_KEY_IDENTIFIER_SIZE, mk_identifier); -} - -static void format_mk_user_description( - char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE], - const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]) -{ - - sprintf(description, "%*phN.uid.%u", FSCRYPT_KEY_IDENTIFIER_SIZE, - mk_identifier, __kuid_val(current_fsuid())); -} - /* Create ->s_master_keys if needed. Synchronized by fscrypt_add_key_mutex. */ static int allocate_filesystem_keyring(struct super_block *sb) { @@ -338,91 +314,94 @@ fscrypt_find_master_key(struct super_block *sb, return mk; } -static int allocate_master_key_users_keyring(struct fscrypt_master_key *mk) +/* Find the current user's claim in ->mk_users. ->mk_sem must be held. */ +static struct fscrypt_master_key_user * +find_master_key_user(struct fscrypt_master_key *mk) { - char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE]; - struct key *keyring; + struct fscrypt_master_key_user *mk_user; + kuid_t uid = current_fsuid(); - format_mk_users_keyring_description(description, - mk->mk_spec.u.identifier); - keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, - current_cred(), KEY_POS_SEARCH | - KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW, - KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL); - if (IS_ERR(keyring)) - return PTR_ERR(keyring); - - mk->mk_users = keyring; - return 0; -} - -/* - * Find the current user's "key" in the master key's ->mk_users. - * Returns ERR_PTR(-ENOKEY) if not found. - */ -static struct key *find_master_key_user(struct fscrypt_master_key *mk) -{ - char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE]; - key_ref_t keyref; - - format_mk_user_description(description, mk->mk_spec.u.identifier); - - /* - * We need to mark the keyring reference as "possessed" so that we - * acquire permission to search it, via the KEY_POS_SEARCH permission. - */ - keyref = keyring_search(make_key_ref(mk->mk_users, true /*possessed*/), - &key_type_fscrypt_user, description, false); - if (IS_ERR(keyref)) { - if (PTR_ERR(keyref) == -EAGAIN || /* not found */ - PTR_ERR(keyref) == -EKEYREVOKED) /* recently invalidated */ - keyref = ERR_PTR(-ENOKEY); - return ERR_CAST(keyref); + list_for_each_entry(mk_user, &mk->mk_users, link) { + if (uid_eq(mk_user->uid, uid)) + return mk_user; } - return key_ref_to_ptr(keyref); + return NULL; } /* - * Give the current user a "key" in ->mk_users. This charges the user's quota + * Give the current user a claim in ->mk_users. This charges the user's quota * and marks the master key as added by the current user, so that it cannot be * removed by another user with the key. Either ->mk_sem must be held for * write, or the master key must be still undergoing initialization. */ static int add_master_key_user(struct fscrypt_master_key *mk) { + kuid_t uid = current_fsuid(); char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE]; - struct key *mk_user; + struct key *quota_key; + struct fscrypt_master_key_user *mk_user; int err; - format_mk_user_description(description, mk->mk_spec.u.identifier); - mk_user = key_alloc(&key_type_fscrypt_user, description, - current_fsuid(), current_gid(), current_cred(), - KEY_POS_SEARCH | KEY_USR_VIEW, 0, NULL); - if (IS_ERR(mk_user)) - return PTR_ERR(mk_user); + snprintf(description, sizeof(description), "%*phN.uid.%u", + FSCRYPT_KEY_IDENTIFIER_SIZE, mk->mk_spec.u.identifier, + __kuid_val(uid)); + quota_key = key_alloc(&key_type_fscrypt_user, description, uid, + current_gid(), current_cred(), + KEY_POS_SEARCH | KEY_USR_VIEW, 0, NULL); + if (IS_ERR(quota_key)) + return PTR_ERR(quota_key); - err = key_instantiate_and_link(mk_user, NULL, 0, mk->mk_users, NULL); - key_put(mk_user); - return err; + err = key_instantiate_and_link(quota_key, NULL, 0, NULL, NULL); + if (err) { + key_put(quota_key); + return err; + } + + mk_user = kzalloc_obj(*mk_user); + if (!mk_user) { + key_put(quota_key); + return -ENOMEM; + } + mk_user->uid = uid; + mk_user->quota_key = quota_key; + list_add(&mk_user->link, &mk->mk_users); + return 0; +} + +static void unlink_and_free_mk_user(struct fscrypt_master_key_user *mk_user) +{ + list_del(&mk_user->link); + key_put(mk_user->quota_key); + kfree(mk_user); } /* - * Remove the current user's "key" from ->mk_users. + * Remove the current user's claim from ->mk_users. * ->mk_sem must be held for write. * - * Returns 0 if removed, -ENOKEY if not found, or another -errno code. + * Returns 0 if removed or -ENOKEY if not found. */ static int remove_master_key_user(struct fscrypt_master_key *mk) { - struct key *mk_user; - int err; + struct fscrypt_master_key_user *mk_user; mk_user = find_master_key_user(mk); - if (IS_ERR(mk_user)) - return PTR_ERR(mk_user); - err = key_unlink(mk->mk_users, mk_user); - key_put(mk_user); - return err; + if (!mk_user) + return -ENOKEY; + unlink_and_free_mk_user(mk_user); + return 0; +} + +/* + * Clear ->mk_users. Either ->mk_sem must be held for write, or 'mk' must have + * no structural references left. + */ +static void clear_mk_users(struct fscrypt_master_key *mk) +{ + struct fscrypt_master_key_user *mk_user, *tmp; + + list_for_each_entry_safe(mk_user, tmp, &mk->mk_users, link) + unlink_and_free_mk_user(mk_user); } /* @@ -445,15 +424,14 @@ static int add_new_master_key(struct super_block *sb, refcount_set(&mk->mk_struct_refs, 1); mk->mk_spec = *mk_spec; + INIT_LIST_HEAD(&mk->mk_users); + INIT_LIST_HEAD(&mk->mk_decrypted_inodes); spin_lock_init(&mk->mk_decrypted_inodes_lock); INIT_LIST_HEAD(&mk->mk_mode_keys); if (mk_spec->type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) { - err = allocate_master_key_users_keyring(mk); - if (err) - goto out_put; err = add_master_key_user(mk); if (err) goto out_put; @@ -482,19 +460,13 @@ static int add_existing_master_key(struct fscrypt_master_key *mk, int err; /* - * If the current user is already in ->mk_users, then there's nothing to - * do. Otherwise, we need to add the user to ->mk_users. (Neither is - * applicable for v1 policy keys, which have NULL ->mk_users.) + * For v2 policy keys (FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER): If the current + * user is already in ->mk_users, then there's nothing to do. + * Otherwise, add the user to ->mk_users. */ - if (mk->mk_users) { - struct key *mk_user = find_master_key_user(mk); - - if (mk_user != ERR_PTR(-ENOKEY)) { - if (IS_ERR(mk_user)) - return PTR_ERR(mk_user); - key_put(mk_user); + if (mk->mk_spec.type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) { + if (find_master_key_user(mk) != NULL) return 0; - } err = add_master_key_user(mk); if (err) return err; @@ -893,7 +865,6 @@ int fscrypt_verify_key_added(struct super_block *sb, { struct fscrypt_key_specifier mk_spec; struct fscrypt_master_key *mk; - struct key *mk_user; int err; mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER; @@ -905,13 +876,10 @@ int fscrypt_verify_key_added(struct super_block *sb, goto out; } down_read(&mk->mk_sem); - mk_user = find_master_key_user(mk); - if (IS_ERR(mk_user)) { - err = PTR_ERR(mk_user); - } else { - key_put(mk_user); + if (find_master_key_user(mk) != NULL) err = 0; - } + else + err = -ENOKEY; up_read(&mk->mk_sem); fscrypt_put_master_key(mk); out: @@ -1103,16 +1071,18 @@ static int do_remove_key(struct file *filp, void __user *_uarg, bool all_users) down_write(&mk->mk_sem); /* If relevant, remove current user's (or all users) claim to the key */ - if (mk->mk_users && mk->mk_users->keys.nr_leaves_on_tree != 0) { - if (all_users) - err = keyring_clear(mk->mk_users); - else + if (!list_empty(&mk->mk_users)) { + if (all_users) { + clear_mk_users(mk); + err = 0; + } else { err = remove_master_key_user(mk); + } if (err) { up_write(&mk->mk_sem); goto out_put_key; } - if (mk->mk_users->keys.nr_leaves_on_tree != 0) { + if (!list_empty(&mk->mk_users)) { /* * Other users have still added the key too. We removed * the current user's claim to the key, but we still @@ -1198,6 +1168,8 @@ int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg) struct super_block *sb = file_inode(filp)->i_sb; struct fscrypt_get_key_status_arg arg; struct fscrypt_master_key *mk; + kuid_t uid; + const struct fscrypt_master_key_user *mk_user; int err; if (copy_from_user(&arg, uarg, sizeof(arg))) @@ -1230,19 +1202,13 @@ int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg) } arg.status = FSCRYPT_KEY_STATUS_PRESENT; - if (mk->mk_users) { - struct key *mk_user; - arg.user_count = mk->mk_users->keys.nr_leaves_on_tree; - mk_user = find_master_key_user(mk); - if (!IS_ERR(mk_user)) { + uid = current_fsuid(); + list_for_each_entry(mk_user, &mk->mk_users, link) { + arg.user_count++; + if (uid_eq(mk_user->uid, uid)) arg.status_flags |= FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF; - key_put(mk_user); - } else if (mk_user != ERR_PTR(-ENOKEY)) { - err = PTR_ERR(mk_user); - goto out_release_key; - } } err = 0; out_release_key: