Re: [RFC][PATCH v2 04/12] diglim: Methods

Mauro Carvalho Chehab
2021-07-28T12:19:21Z

Em Mon, 26 Jul 2021 18:36:52 +0200
Roberto Sassu <roberto.sassu@huawei.com> escreveu:

> Introduce the methods requires to manage the three objects defined.
>
> - digest_item methods:
> - digest_add()
> - digest_del()
> - __digest_lookup()
> - diglim_digest_get_info()
>
> - digest_list_item_ref methods:
> - digest_list_ref_add()
> - digest_list_ref_del()
>
> - digest_list_item methods:
> - digest_list_add()
> - digest_list_del()
>
> More information about these functions can be found in
> Documentation/security/diglim/implementation.rst.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
> .../security/diglim/implementation.rst | 9 +
> MAINTAINERS | 2 +
> include/linux/diglim.h | 28 +
> security/integrity/Kconfig | 1 +
> security/integrity/Makefile | 1 +
> security/integrity/diglim/Kconfig | 11 +
> security/integrity/diglim/Makefile | 8 +
> security/integrity/diglim/diglim.h | 20 +-
> security/integrity/diglim/methods.c | 499 ++++++++++++++++++
> 9 files changed, 578 insertions(+), 1 deletion(-)
> create mode 100644 include/linux/diglim.h
> create mode 100644 security/integrity/diglim/Kconfig
> create mode 100644 security/integrity/diglim/Makefile
> create mode 100644 security/integrity/diglim/methods.c
>
> diff --git a/Documentation/security/diglim/implementation.rst b/Documentation/security/diglim/implementation.rst
> index 6002049612a1..54af23b2f5f1 100644
> --- a/Documentation/security/diglim/implementation.rst
> +++ b/Documentation/security/diglim/implementation.rst
> @@ -200,3 +200,12 @@ Similarly:
> the digest can be obtained by summing the address of the digest list buffer
> with ``digest_offset`` (except for the digest lists, where the digest is
> stored in the ``digest`` field of the ``digest_list_item`` structure).
> +
> +
> +Methods
> +-------
> +
> +This section introduces the methods requires to manage the three objects
> +defined.
> +
> +.. kernel-doc:: security/integrity/diglim/methods.c
> diff --git a/MAINTAINERS b/MAINTAINERS
> index f7592d41367d..9e085a36654a 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5461,8 +5461,10 @@ F: Documentation/security/diglim/architecture.rst
> F: Documentation/security/diglim/implementation.rst
> F: Documentation/security/diglim/index.rst
> F: Documentation/security/diglim/introduction.rst
> +F: include/linux/diglim.h
> F: include/uapi/linux/diglim.h
> F: security/integrity/diglim/diglim.h
> +F: security/integrity/diglim/methods.c
>
> DIOLAN U2C-12 I2C DRIVER
> M: Guenter Roeck <linux@roeck-us.net>
> diff --git a/include/linux/diglim.h b/include/linux/diglim.h
> new file mode 100644
> index 000000000000..d4b4548a288b
> --- /dev/null
> +++ b/include/linux/diglim.h
> @@ -0,0 +1,28 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2017-2021 Huawei Technologies Duesseldorf GmbH
> + *
> + * Author: Roberto Sassu <roberto.sassu@huawei.com>
> + *
> + * DIGLIM functions available for use by kernel subsystems.
> + */
> +
> +#ifndef __DIGLIM_H
> +#define __DIGLIM_H
> +
> +#include <crypto/hash_info.h>
> +#include <uapi/linux/diglim.h>
> +
> +#ifdef CONFIG_DIGLIM
> +extern int diglim_digest_get_info(u8 *digest, enum hash_algo algo,
> + enum compact_types type, u16 *modifiers,
> + u8 *actions);
> +#else
> +static inline int diglim_digest_get_info(u8 *digest, enum hash_algo algo,
> + enum compact_types type,
> + u16 *modifiers, u8 *actions)
> +{
> + return -ENOENT;
> +}
> +#endif /*CONFIG_DIGLIM*/
> +#endif /*__DIGLIM_H*/
> diff --git a/security/integrity/Kconfig b/security/integrity/Kconfig
> index 71f0177e8716..8f94f4dcc052 100644
> --- a/security/integrity/Kconfig
> +++ b/security/integrity/Kconfig
> @@ -98,5 +98,6 @@ config INTEGRITY_AUDIT
>
> source "security/integrity/ima/Kconfig"
> source "security/integrity/evm/Kconfig"
> +source "security/integrity/diglim/Kconfig"
>
> endif # if INTEGRITY
> diff --git a/security/integrity/Makefile b/security/integrity/Makefile
> index 7ee39d66cf16..d6166550a6b8 100644
> --- a/security/integrity/Makefile
> +++ b/security/integrity/Makefile
> @@ -19,3 +19,4 @@ integrity-$(CONFIG_LOAD_PPC_KEYS) += platform_certs/efi_parser.o \
> platform_certs/keyring_handler.o
> obj-$(CONFIG_IMA) += ima/
> obj-$(CONFIG_EVM) += evm/
> +obj-$(CONFIG_DIGLIM) += diglim/
> diff --git a/security/integrity/diglim/Kconfig b/security/integrity/diglim/Kconfig
> new file mode 100644
> index 000000000000..436a76a14337
> --- /dev/null
> +++ b/security/integrity/diglim/Kconfig
> @@ -0,0 +1,11 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +# Digest Lists Integrity Module (DIGLIM)
> +#
> +config DIGLIM
> + bool "Digest Lists Integrity Module (DIGLIM)"
> + select SECURITYFS
> + select CRYPTO
> + select CRYPTO_HASH_INFO
> + help
> + DIGLIM provides reference values for file content and metadata,
> + that can be used for measurement and appraisal with IMA.
> diff --git a/security/integrity/diglim/Makefile b/security/integrity/diglim/Makefile
> new file mode 100644
> index 000000000000..b761ed8cfb3e
> --- /dev/null
> +++ b/security/integrity/diglim/Makefile
> @@ -0,0 +1,8 @@
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# Makefile for building Digest Lists Integrity Module (DIGLIM).
> +#
> +
> +obj-$(CONFIG_DIGLIM) += diglim.o
> +
> +diglim-y := methods.o
> diff --git a/security/integrity/diglim/diglim.h b/security/integrity/diglim/diglim.h
> index 578253d7e1d1..25851e7d4906 100644
> --- a/security/integrity/diglim/diglim.h
> +++ b/security/integrity/diglim/diglim.h
> @@ -20,7 +20,7 @@
> #include <linux/audit.h>
> #include <crypto/hash_info.h>
> #include <linux/hash_info.h>
> -#include <uapi/linux/diglim.h>
> +#include <linux/diglim.h>
>
> #define MAX_DIGEST_SIZE 64
> #define HASH_BITS 10
> @@ -81,6 +81,8 @@ static inline unsigned int hash_key(u8 *digest)
> return (digest[0] | digest[1] << 8) % DIGLIM_HTABLE_SIZE;
> }
>
> +extern struct h_table htable[COMPACT__LAST];
> +

it sounds somewhat risky to use just "htable" for a var declared
as external.

> static inline struct compact_list_hdr *get_hdr(
> struct digest_list_item *digest_list,
> loff_t hdr_offset)
> @@ -131,4 +133,20 @@ static inline u8 *get_digest_ref(struct digest_list_item_ref *ref)
>
> return ref->digest_list->buf + ref->digest_offset;
> }
> +
> +struct digest_item *__digest_lookup(u8 *digest, enum hash_algo algo,
> + enum compact_types type, u16 *modifiers,
> + u8 *actions);
> +struct digest_item *digest_add(u8 *digest, enum hash_algo algo,
> + enum compact_types type,
> + struct digest_list_item *digest_list,
> + loff_t digest_offset, loff_t hdr_offset);
> +void digest_del(u8 *digest, enum hash_algo algo, enum compact_types type,
> + struct digest_list_item *digest_list, loff_t digest_offset,
> + loff_t hdr_offset);
> +struct digest_item *digest_list_add(u8 *digest, enum hash_algo algo,
> + loff_t size, u8 *buf, u8 actions,
> + const char *label);
> +void digest_list_del(u8 *digest, enum hash_algo algo, u8 actions,
> + struct digest_list_item *digest_list);
> #endif /*__DIGLIM_INTERNAL_H*/
> diff --git a/security/integrity/diglim/methods.c b/security/integrity/diglim/methods.c
> new file mode 100644
> index 000000000000..7ed61399cfe8
> --- /dev/null
> +++ b/security/integrity/diglim/methods.c
> @@ -0,0 +1,499 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2005,2006,2007,2008 IBM Corporation
> + * Copyright (C) 2017-2021 Huawei Technologies Duesseldorf GmbH
> + *
> + * Author: Roberto Sassu <roberto.sassu@huawei.com>
> + *
> + * Functions to manage digest lists.
> + */
> +
> +#include <linux/vmalloc.h>
> +#include <linux/module.h>
> +#include <linux/fault-inject.h>
> +
> +#include "diglim.h"
> +#include "../integrity.h"
> +
> +/* Define a cache for each object type. */
> +static struct kmem_cache *digest_list_item_cache __read_mostly;
> +static struct kmem_cache *digest_list_item_ref_cache __read_mostly;
> +static struct kmem_cache *digest_item_cache __read_mostly;
> +
> +/* Define a hash table for each digest type. */
> +struct h_table htable[COMPACT__LAST] = {{
> + .queue[0 ... DIGLIM_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
> +}};

> +
> +#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
> +static DECLARE_FAULT_ATTR(fail_diglim);
> +
> +static int __init fail_diglim_debugfs(void)
> +{
> + struct dentry *dir = fault_create_debugfs_attr("fail_diglim", NULL,
> + &fail_diglim);
> +
> + return PTR_ERR_OR_ZERO(dir);
> +}
> +
> +static inline bool should_fail_diglim(void)
> +{
> + return should_fail(&fail_diglim, 1);
> +}
> +
> +late_initcall(fail_diglim_debugfs);
> +#else
> +static inline bool should_fail_diglim(void)
> +{
> + return false;
> +}
> +#endif

I guess this is a matter of personal preference, but, IMO, it is a lot better
to place the debugfs stuff on a separate source file, avoiding ugly #ifdefs
in the middle of the code.

Ok, the current code is too small to deserve a separate file, but
if later patches would add more stuff, then I would opt to have this on
a separate file.

> +
> +/**
> + * __digest_lookup - lookup digest and return associated modifiers and actions
> + * @digest: digest to lookup
> + * @algo: digest algorithm
> + * @type: type of digest to lookup (e.g. file, metadata)
> + * @modifiers: modifiers (attributes) associated to the found digest
> + * @actions: actions performed by IMA on the digest list containing the digest
> + *
> + * This function searches the given digest in the hash table depending on the
> + * passed type and sets the modifiers and actions associated to the digest, if
> + * the pointers are not NULL.
> + *
> + * This function is not intended for external use, as the returned digest item
> + * could be freed at any time after it has been returned.
> + * diglim_digest_get_info() should be used instead by external callers, as it
> + * only returns the modifiers and the actions associated to the digest at the
> + * time the digest is searched.
> + *
> + * RCU protects both the hash table and the linked list of references to the
> + * digest lists containing the found digest.
> + *
> + * Return: a digest_item structure if the digest is found, NULL otherwise.
> + */
> +struct digest_item *__digest_lookup(u8 *digest, enum hash_algo algo,
> + enum compact_types type, u16 *modifiers,
> + u8 *actions)
> +{
> + struct digest_item *d = NULL;
> + struct digest_list_item_ref *ref;
> + int digest_len = hash_digest_size[algo];
> + unsigned int key = hash_key(digest);
> + bool found = false;
> +
> + rcu_read_lock();
> + hlist_for_each_entry_rcu(d, &htable[type].queue[key], hnext) {
> + list_for_each_entry_rcu(ref, &d->refs, list) {
> + if (get_algo_ref(ref) != algo ||
> + memcmp(get_digest_ref(ref), digest, digest_len))
> + break;
> +
> + found = true;
> +
> + /* There is no need to scan all digest list refs. */
> + if (!modifiers || !actions)
> + break;
> +
> + /*
> + * The resulting modifiers and actions are the OR of the
> + * modifiers and actions for each digest list.
> + */
> + *modifiers |= get_hdr_ref(ref)->modifiers;
> + *actions |= ref->digest_list->actions;
> + }
> +
> + if (found)
> + break;
> + }
> +
> + rcu_read_unlock();
> + return d;
> +}
> +
> +/**
> + * diglim_digest_get_info - lookup digest and return modifiers and actions
> + * @digest: digest to lookup
> + * @algo: digest algorithm
> + * @type: type of digest to lookup (e.g. file, metadata)
> + * @modifiers: modifiers (attributes) associated to the found digest
> + * @actions: actions performed by IMA on the digest lists containing the digest
> + *
> + * This function searches the given digest in the hash table depending on the
> + * passed type and sets the modifiers and actions associated to the digest, if
> + * the pointers are not NULL.
> + *
> + * This function is safe for external use, as it does not return pointers of
> + * objects that can be freed without the caller notices it.
> + *
> + * Return: 0 if the digest is found, -ENOENT otherwise.
> + */
> +int diglim_digest_get_info(u8 *digest, enum hash_algo algo,
> + enum compact_types type, u16 *modifiers, u8 *actions)
> +{
> + struct digest_item *d;
> +
> + d = __digest_lookup(digest, algo, type, modifiers, actions);
> + if (!d)
> + return -ENOENT;
> +
> + return 0;
> +}
> +
> +/**
> + * digest_list_ref_add - add reference to a digest list
> + * @d: digest a new reference is added to
> + * @digest_list: digest list whose reference is being added
> + * @digest_offset: offset of the digest in the buffer of the digest list
> + * @hdr_offset: offset of the header within the digest list the digest refers to
> + *
> + * This function adds a new reference to an existing digest list for a given
> + * digest. The reference is described by the digest_list_item_ref structure and
> + * consists of a pointer of the digest list, the offset of the digest to the
> + * beginning of the digest list buffer and the offset of the header the digest
> + * refers to (each digest list might be composed of several digest blocks, each
> + * prefixed by a header describing the attributes of those digests).
> + *
> + * Return: 0 if a new digest list reference was successfully added, a negative
> + * value otherwise.
> + */
> +static int digest_list_ref_add(struct digest_item *d,
> + struct digest_list_item *digest_list,
> + loff_t digest_offset, loff_t hdr_offset)
> +{
> + struct digest_list_item_ref *new_ref = NULL;
> + u8 *digest = get_digest(digest_list, digest_offset, hdr_offset);
> + enum hash_algo algo = get_algo(digest_list, digest_offset, hdr_offset);
> + int digest_len = hash_digest_size[algo];
> +
> + /* Allocate a new reference. */
> + if (!should_fail_diglim())
> + new_ref = kmem_cache_alloc(digest_list_item_ref_cache,
> + GFP_KERNEL);
> + if (!new_ref) {
> + print_hex_dump(KERN_ERR, "digest list ref allocation failed: ",
> + DUMP_PREFIX_NONE, digest_len, 1, digest,
> + digest_len, true);
> + return -ENOMEM;
> + }
> +
> + /* Set the new reference. */
> + new_ref->digest_list = digest_list;
> + /* Converting loff_t -> u32 is fine as long as the digest list < 4G. */
> + new_ref->digest_offset = digest_offset;
> + new_ref->hdr_offset = hdr_offset;
> +
> + list_add_tail_rcu(&new_ref->list, &d->refs);
> +
> + print_hex_dump_debug("add digest list ref: ", DUMP_PREFIX_NONE,
> + digest_len, 1, digest, digest_len, true);
> + return 0;
> +}
> +
> +/**
> + * digest_list_ref_del - del reference to a digest list
> + * @d: digest a reference is deleted from
> + * @digest_list: digest list whose reference is being deleted
> + * @digest_offset: offset of the digest in the buffer of the digest list
> + * @hdr_offset: offset of the header within the digest list the digest refers to
> + *
> + * This function searches the reference to an already loaded digest list in the
> + * linked list of references stored for each digest item. If the reference is
> + * found (if not, it is a bug), the function deletes it from the linked list.
> + */
> +static void digest_list_ref_del(struct digest_item *d,
> + struct digest_list_item *digest_list,
> + loff_t digest_offset, loff_t hdr_offset)
> +{
> + struct digest_list_item_ref *ref;
> + u8 *digest = get_digest(digest_list, digest_offset, hdr_offset);
> + enum hash_algo algo = get_algo(digest_list, digest_offset, hdr_offset);
> + int digest_len = hash_digest_size[algo];
> +
> + /* Search for a digest list reference. */
> + list_for_each_entry(ref, &d->refs, list)
> + if (ref->digest_list == digest_list)
> + break;
> +
> + if (!ref) {
> + print_hex_dump(KERN_ERR, "digest list ref not found: ",
> + DUMP_PREFIX_NONE, digest_len, 1, digest,
> + digest_len, true);
> + return;
> + }
> +
> + list_del_rcu(&ref->list);
> + kmem_cache_free(digest_list_item_ref_cache, ref);
> +
> + print_hex_dump_debug("del digest list ref: ", DUMP_PREFIX_NONE,
> + digest_len, 1, digest, digest_len, true);
> +}
> +
> +/**
> + * digest_add - add a new digest
> + * @digest: digest in binary form
> + * @algo: digest algorithm
> + * @type: digest type
> + * @digest_list: digest list the new digest belongs to
> + * @digest_offset: offset of the digest in the buffer of the digest list
> + * @hdr_offset: offset of the header within the digest list the digest refers to
> + *
> + * This function first searches if the digest is already in the hash table for
> + * the given type. The digest is searched by comparing the passed digest and
> + * algorithm with the digest obtained from the first digest list reference
> + * (buffer + digest_offset), or from the digest field of a digest list item,
> + * for a digest list.
> + *
> + * If the digest exists, only a new reference is added (there might be multiple
> + * references to the same digest list).
> + *
> + * If the digest is not found, a new digest item is allocated and a reference to
> + * the passed digest list is added to that item. The digest item is finally
> + * added to the hash table for the given type.
> + *
> + * Proper locking must be provided by the caller.
> + *
> + * Return: a new or the found digest item on success, an error pointer
> + * otherwise.
> + */
> +struct digest_item *digest_add(u8 *digest, enum hash_algo algo,
> + enum compact_types type,
> + struct digest_list_item *digest_list,
> + loff_t digest_offset, loff_t hdr_offset)
> +{
> + int digest_len = hash_digest_size[algo];
> + struct digest_item *d;
> + int ret;
> +
> + /* Search the digest. */
> + d = __digest_lookup(digest, algo, type, NULL, NULL);
> + if (d) {
> + /*
> + * Add a new digest list reference to the existing digest item.
> + */
> + ret = digest_list_ref_add(d, digest_list, digest_offset,
> + hdr_offset);
> + if (ret < 0)
> + return ERR_PTR(ret);
> +
> + print_hex_dump_debug("digest add duplicate: ", DUMP_PREFIX_NONE,
> + digest_len, 1, digest, digest_len, true);
> + return d;
> + }
> +
> + /* Allocate a new digest item. */
> + if (!should_fail_diglim())
> + d = kmem_cache_alloc(digest_item_cache, GFP_KERNEL);
> + if (!d) {
> + print_hex_dump_debug("digest allocation failed: ",
> + DUMP_PREFIX_NONE, digest_len, 1, digest,
> + digest_len, true);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + INIT_LIST_HEAD(&d->refs);
> +
> + /* Add a new digest list reference to the new digest item. */
> + ret = digest_list_ref_add(d, digest_list, digest_offset, hdr_offset);
> + if (ret < 0) {
> + kmem_cache_free(digest_item_cache, d);
> + return ERR_PTR(ret);
> + }
> +
> + /* Add the new digest item to the hash table for the given type. */
> + hlist_add_head_rcu(&d->hnext, &htable[type].queue[hash_key(digest)]);
> + htable[type].len++;
> +
> + print_hex_dump_debug("digest add: ", DUMP_PREFIX_NONE, digest_len, 1,
> + digest, digest_len, true);
> + return d;
> +}
> +
> +/**
> + * digest_del - delete a digest with one reference, or just a reference
> + * @digest: digest in binary form
> + * @algo: digest algorithm
> + * @type: digest type
> + * @digest_list: digest list the digest belongs to
> + * @digest_offset: offset of the digest in the buffer of the digest list
> + * @hdr_offset: offset of the header within the digest list the digest refers to
> + *
> + * This function is called when a digest list is being removed. The digest is
> + * first searched in the hash table for the given type. If it is found (if not,
> + * it is a bug, because digest lists can be deleted only if they were added
> + * previously), a reference of the passed digest list is deleted from the linked
> + * list of references of the digest item.
> + *
> + * If the last reference was deleted, the digest item is also deleted and
> + * removed from the hash table.
> + *
> + * Proper locking must be provided by the caller.
> + */
> +void digest_del(u8 *digest, enum hash_algo algo, enum compact_types type,
> + struct digest_list_item *digest_list, loff_t digest_offset,
> + loff_t hdr_offset)
> +{
> + struct digest_item *d;
> + int digest_len = hash_digest_size[algo];
> +
> + /* Search the digest. */
> + d = __digest_lookup(digest, algo, type, NULL, NULL);
> + if (!d) {
> + print_hex_dump(KERN_ERR, "digest not found: ", DUMP_PREFIX_NONE,
> + digest_len, 1, digest, digest_len, true);
> + return;
> + }
> +
> + /* Delete a reference of the passed digest list. */
> + digest_list_ref_del(d, digest_list, digest_offset, hdr_offset);
> +
> + print_hex_dump_debug(!list_empty(&d->refs) ?
> + "digest del duplicate: " : "digest del: ",
> + DUMP_PREFIX_NONE, digest_len, 1, digest,
> + digest_len, true);
> +
> + /* Return if there are still references. */
> + if (!list_empty(&d->refs))
> + return;
> +
> + /*
> + * Remove the digest item from the hash table and free it if there are
> + * no more references left.
> + */
> + hlist_del_rcu(&d->hnext);
> + htable[type].len--;
> + kmem_cache_free(digest_item_cache, d);
> +}
> +
> +/**
> + * digest_list_add - add a new digest list
> + * @digest: digest of the digest list in binary form
> + * @algo: digest algorithm
> + * @size: digest list size
> + * @buf: digest list buffer
> + * @actions: actions (measure/appraise) performed by IMA on the digest list
> + * @label: label to be used to identify the digest list
> + *
> + * This function allocates a new digest list item, which contains the buffer,
> + * size, actions performed by IMA and a label. Each digest list item is
> + * associated to a digest item representing the digest of the digest list.
> + *
> + * This function prevents the same digest list to be added multiple times by
> + * searching its digest in the hash table for the COMPACT_DIGEST_LIST type.
> + *
> + * The passed buffer is copied in a new memory area, to avoid to reference
> + * memory that could be freed by the caller.
> + *
> + * If allocation of a new digest list and the associated buffer was successful,
> + * its digest is added to the hash table for the COMPACT_DIGEST_LIST type.
> + *
> + * Proper locking must be provided by the caller.
> + *
> + * Return: the digest item associated to the digest list item on success, an
> + * error pointer otherwise.
> + */
> +struct digest_item *digest_list_add(u8 *digest, enum hash_algo algo,
> + loff_t size, u8 *buf, u8 actions,
> + const char *label)
> +{
> + struct digest_item *d;
> + struct digest_list_item *digest_list = NULL;
> + int digest_len = hash_digest_size[algo];
> +
> + /* Search the digest of the digest list. */
> + d = __digest_lookup(digest, algo, COMPACT_DIGEST_LIST, NULL, NULL);
> + if (d) {
> + print_hex_dump(KERN_ERR, "digest list already uploaded: ",
> + DUMP_PREFIX_NONE, digest_len, 1, digest,
> + digest_len, true);
> + return ERR_PTR(-EEXIST);
> + }
> +
> + /* Allocate a new digest list. */
> + if (!should_fail_diglim())
> + digest_list = kmem_cache_alloc(digest_list_item_cache,
> + GFP_KERNEL);
> + if (!digest_list) {
> + print_hex_dump(KERN_ERR, "digest list allocation failed: ",
> + DUMP_PREFIX_NONE, digest_len, 1, digest,
> + digest_len, true);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + digest_list->buf = NULL;
> + digest_list->size = size;
> +
> + if (!should_fail_diglim())
> + digest_list->buf = kmemdup(buf, size, GFP_KERNEL);
> + if (!digest_list->buf) {
> + print_hex_dump(KERN_ERR, "digest list allocation failed: ",
> + DUMP_PREFIX_NONE, digest_len, 1, digest,
> + digest_len, true);
> + kmem_cache_free(digest_list_item_cache, digest_list);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + digest_list->actions = actions;
> + memcpy(digest_list->digest, digest, hash_digest_size[algo]);
> + digest_list->algo = algo;
> + digest_list->label = label;
> +
> + /* Add the digest of the digest list to the hash table. */
> + d = digest_add(digest, algo, COMPACT_DIGEST_LIST, digest_list, 0, 0);
> + if (IS_ERR(d)) {
> + kfree(digest_list->buf);
> + kmem_cache_free(digest_list_item_cache, digest_list);
> + }
> +
> + return d;
> +}
> +
> +/**
> + * digest_list_del - delete an existing digest list
> + * @digest: digest of the digest list in binary form
> + * @algo: digest algorithm
> + * @actions: actions (measure/appraise) performed by IMA on the digest list
> + * @digest_list: digest list to delete
> + *
> + * This function searches the digest of the digest list in the hash table for
> + * the COMPACT_DIGEST_LIST type. If it is found, this function frees the buffer
> + * and the digest list item allocated in digest_list_add().
> + *
> + * This function will be executed only for digest lists that were previously
> + * added.
> + *
> + * Proper locking must be provided by the caller.
> + */
> +void digest_list_del(u8 *digest, enum hash_algo algo, u8 actions,
> + struct digest_list_item *digest_list)
> +{
> + /* Delete the digest item associated to the digest list. */
> + digest_del(digest, algo, COMPACT_DIGEST_LIST, digest_list, 0, 0);
> +
> + /*
> + * Free the buffer and the digest list item allocated when the digest
> + * list was added.
> + */
> + kfree(digest_list->buf);
> + kmem_cache_free(digest_list_item_cache, digest_list);
> +}
> +
> +static int __init digest_list_cache_init(void)
> +{
> + digest_list_item_cache = kmem_cache_create("digest_list_item_cache",
> + sizeof(struct digest_list_item),
> + 0, SLAB_PANIC, NULL);
> +
> + digest_list_item_ref_cache = kmem_cache_create(
> + "digest_list_item_ref_cache",
> + sizeof(struct digest_list_item_ref), 0,
> + SLAB_PANIC, NULL);
> +
> + digest_item_cache = kmem_cache_create("digest_item_cache",
> + sizeof(struct digest_item), 0,
> + SLAB_PANIC, NULL);
> +
> + return 0;
> +}
> +
> +late_initcall(digest_list_cache_init)

Thanks,
Mauro