Em Mon, 26 Jul 2021 18:36:52 +0200
Roberto Sassu [off-list ref] escreveu:

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

+
+#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