kdbus: add name registry implementation

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Daniel Mack <daniel@zonque.org>

This patch adds the name registry implementation.

Each bus instantiates a name registry to resolve well-known names
into unique connection IDs for message delivery. The registry will
be queried when a message is sent with kdbus_msg.dst_id set to
KDBUS_DST_ID_NAME, or when a registry dump is requested.

It's important to have this registry implemented in the kernel to
implement lookups and take-overs in a race-free way.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 ipc/kdbus/names.c | 921 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 ipc/kdbus/names.h |  81 +++++
 2 files changed, 1002 insertions(+)
 create mode 100644 ipc/kdbus/names.c
 create mode 100644 ipc/kdbus/names.h

diff --git a/ipc/kdbus/names.c b/ipc/kdbus/names.c
new file mode 100644
index 000000000000..552309bd6716
--- /dev/null
+++ b/ipc/kdbus/names.c
@@ -0,0 +1,921 @@
+/*
+ * Copyright (C) 2013-2014 Kay Sievers
+ * Copyright (C) 2013-2014 Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+ * Copyright (C) 2013-2014 Daniel Mack <daniel@zonque.org>
+ * Copyright (C) 2013-2014 David Herrmann <dh.herrmann@gmail.com>
+ * Copyright (C) 2013-2014 Linux Foundation
+ * Copyright (C) 2014 Djalal Harouni
+ *
+ * kdbus is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation; either version 2.1 of the License, or (at
+ * your option) any later version.
+ */
+
+#include <linux/ctype.h>
+#include <linux/fs.h>
+#include <linux/hash.h>
+#include <linux/idr.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/rwsem.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#include "bus.h"
+#include "connection.h"
+#include "endpoint.h"
+#include "item.h"
+#include "names.h"
+#include "notify.h"
+#include "policy.h"
+
+/**
+ * struct kdbus_name_queue_item - a queue item for a name
+ * @conn:		The associated connection
+ * @entry:		Name entry queuing up for
+ * @entry_entry:	List element for the list in @entry
+ * @conn_entry:		List element for the list in @conn
+ * @flags:		The queuing flags
+ */
+struct kdbus_name_queue_item {
+	struct kdbus_conn *conn;
+	struct kdbus_name_entry *entry;
+	struct list_head entry_entry;
+	struct list_head conn_entry;
+	u64 flags;
+};
+
+static void kdbus_name_entry_free(struct kdbus_name_entry *e)
+{
+	hash_del(&e->hentry);
+	kfree(e->name);
+	kfree(e);
+}
+
+/**
+ * kdbus_name_registry_free() - drop a name reg's reference
+ * @reg:		The name registry, may be %NULL
+ *
+ * Cleanup the name registry's internal structures.
+ */
+void kdbus_name_registry_free(struct kdbus_name_registry *reg)
+{
+	struct kdbus_name_entry *e;
+	struct hlist_node *tmp;
+	unsigned int i;
+
+	if (!reg)
+		return;
+
+	hash_for_each_safe(reg->entries_hash, i, tmp, e, hentry)
+		kdbus_name_entry_free(e);
+
+	kfree(reg);
+}
+
+/**
+ * kdbus_name_registry_new() - create a new name registry
+ *
+ * Return: a new kdbus_name_registry on success, ERR_PTR on failure.
+ */
+struct kdbus_name_registry *kdbus_name_registry_new(void)
+{
+	struct kdbus_name_registry *r;
+
+	r = kzalloc(sizeof(*r), GFP_KERNEL);
+	if (!r)
+		return ERR_PTR(-ENOMEM);
+
+	hash_init(r->entries_hash);
+	init_rwsem(&r->rwlock);
+
+	return r;
+}
+
+static struct kdbus_name_entry *
+kdbus_name_lookup(struct kdbus_name_registry *reg, u32 hash, const char *name)
+{
+	struct kdbus_name_entry *e;
+
+	hash_for_each_possible(reg->entries_hash, e, hentry, hash)
+		if (strcmp(e->name, name) == 0)
+			return e;
+
+	return NULL;
+}
+
+static void kdbus_name_queue_item_free(struct kdbus_name_queue_item *q)
+{
+	list_del(&q->entry_entry);
+	list_del(&q->conn_entry);
+	kfree(q);
+}
+
+/*
+ * The caller must hold the lock so we decrement the counter and
+ * delete the entry.
+ *
+ * The caller needs to hold its own reference, so the connection does not go
+ * away while the entry's reference is dropped under lock.
+ */
+static void kdbus_name_entry_remove_owner(struct kdbus_name_entry *e)
+{
+	BUG_ON(!e->conn);
+	BUG_ON(!mutex_is_locked(&e->conn->lock));
+
+	atomic_dec(&e->conn->name_count);
+	list_del(&e->conn_entry);
+	e->conn = kdbus_conn_unref(e->conn);
+}
+
+static void kdbus_name_entry_set_owner(struct kdbus_name_entry *e,
+				       struct kdbus_conn *conn)
+{
+	BUG_ON(e->conn);
+	BUG_ON(!mutex_is_locked(&conn->lock));
+
+	e->conn = kdbus_conn_ref(conn);
+	atomic_inc(&conn->name_count);
+	list_add_tail(&e->conn_entry, &e->conn->names_list);
+}
+
+static int kdbus_name_replace_owner(struct kdbus_name_entry *e,
+				    struct kdbus_conn *conn, u64 flags)
+{
+	struct kdbus_conn *conn_old = kdbus_conn_ref(e->conn);
+	int ret;
+
+	BUG_ON(conn == conn_old);
+	BUG_ON(!conn_old);
+
+	/* take lock of both connections in a defined order */
+	if (conn < conn_old) {
+		mutex_lock(&conn->lock);
+		mutex_lock_nested(&conn_old->lock, 1);
+	} else {
+		mutex_lock(&conn_old->lock);
+		mutex_lock_nested(&conn->lock, 1);
+	}
+
+	if (!kdbus_conn_active(conn)) {
+		ret = -ECONNRESET;
+		goto exit_unlock;
+	}
+
+	ret = kdbus_notify_name_change(conn->ep->bus, KDBUS_ITEM_NAME_CHANGE,
+				       e->conn->id, conn->id,
+				       e->flags, flags, e->name);
+	if (ret < 0)
+		goto exit_unlock;
+
+	/* hand over name ownership */
+	kdbus_name_entry_remove_owner(e);
+	kdbus_name_entry_set_owner(e, conn);
+	e->flags = flags;
+
+exit_unlock:
+	mutex_unlock(&conn_old->lock);
+	mutex_unlock(&conn->lock);
+
+	kdbus_conn_unref(conn_old);
+	return ret;
+}
+
+static int kdbus_name_entry_release(struct kdbus_name_entry *e,
+				    struct kdbus_bus *bus)
+{
+	struct kdbus_conn *conn;
+
+	/* give it to first active waiter in the queue */
+	while (!list_empty(&e->queue_list)) {
+		struct kdbus_name_queue_item *q;
+		int ret;
+
+		q = list_first_entry(&e->queue_list,
+				     struct kdbus_name_queue_item,
+				     entry_entry);
+
+		ret = kdbus_name_replace_owner(e, q->conn, q->flags);
+		if (ret < 0)
+			continue;
+
+		kdbus_name_queue_item_free(q);
+		return 0;
+	}
+
+	/* hand it back to an active activator connection */
+	if (e->activator && e->activator != e->conn) {
+		u64 flags = KDBUS_NAME_ACTIVATOR;
+		int ret;
+
+		/*
+		 * Move messages still queued in the old connection
+		 * and addressed to that name to the new connection.
+		 * This allows a race and loss-free name and message
+		 * takeover and exit-on-idle services.
+		 */
+		ret = kdbus_conn_move_messages(e->activator, e->conn,
+					       e->name_id);
+		if (ret < 0)
+			goto exit_release;
+
+		return kdbus_name_replace_owner(e, e->activator, flags);
+	}
+
+exit_release:
+	/* release the name */
+	kdbus_notify_name_change(e->conn->ep->bus, KDBUS_ITEM_NAME_REMOVE,
+				 e->conn->id, 0,
+				 e->flags, 0, e->name);
+
+	conn = kdbus_conn_ref(e->conn);
+	mutex_lock(&conn->lock);
+	kdbus_name_entry_remove_owner(e);
+	mutex_unlock(&conn->lock);
+	kdbus_conn_unref(conn);
+
+	kdbus_conn_unref(e->activator);
+	kdbus_name_entry_free(e);
+
+	return 0;
+}
+
+static int kdbus_name_release(struct kdbus_name_registry *reg,
+			      struct kdbus_conn *conn,
+			      const char *name)
+{
+	struct kdbus_name_queue_item *q_tmp, *q;
+	struct kdbus_name_entry *e = NULL;
+	u32 hash;
+	int ret = 0;
+
+	hash = kdbus_str_hash(name);
+
+	/* lock order: domain -> bus -> ep -> names -> connection */
+	mutex_lock(&conn->ep->bus->lock);
+	down_write(&reg->rwlock);
+
+	e = kdbus_name_lookup(reg, hash, name);
+	if (!e) {
+		ret = -ESRCH;
+		goto exit_unlock;
+	}
+
+	/* Is the connection already the real owner of the name? */
+	if (e->conn == conn) {
+		ret = kdbus_name_entry_release(e, conn->ep->bus);
+	} else {
+		/*
+		 * Otherwise, walk the list of queued entries and search
+		 * for items for connection.
+		 */
+
+		/* In case the name belongs to somebody else */
+		ret = -EADDRINUSE;
+
+		list_for_each_entry_safe(q, q_tmp,
+					 &e->queue_list,
+					 entry_entry) {
+			if (q->conn != conn)
+				continue;
+
+			kdbus_name_queue_item_free(q);
+			ret = 0;
+			break;
+		}
+	}
+
+	/*
+	 * Now that the connection has lost a name, purge all cached policy
+	 * entries, so upon the next message, TALK access will be checked
+	 * against the names the connection actually owns.
+	 */
+	if (ret == 0)
+		kdbus_conn_purge_policy_cache(conn);
+
+exit_unlock:
+	up_write(&reg->rwlock);
+	mutex_unlock(&conn->ep->bus->lock);
+
+	return ret;
+}
+
+/**
+ * kdbus_name_remove_by_conn() - remove all name entries of a given connection
+ * @reg:		The name registry
+ * @conn:		The connection which entries to remove
+ *
+ * This function removes all name entry held by a given connection.
+ */
+void kdbus_name_remove_by_conn(struct kdbus_name_registry *reg,
+			       struct kdbus_conn *conn)
+{
+	struct kdbus_name_queue_item *q_tmp, *q;
+	struct kdbus_conn *activator = NULL;
+	struct kdbus_name_entry *e_tmp, *e;
+	LIST_HEAD(names_queue_list);
+	LIST_HEAD(names_list);
+
+	/* lock order: domain -> bus -> ep -> names -> conn */
+	mutex_lock(&conn->ep->bus->lock);
+	down_write(&reg->rwlock);
+
+	mutex_lock(&conn->lock);
+	list_splice_init(&conn->names_list, &names_list);
+	list_splice_init(&conn->names_queue_list, &names_queue_list);
+	mutex_unlock(&conn->lock);
+
+	if (kdbus_conn_is_activator(conn)) {
+		activator = conn->activator_of->activator;
+		conn->activator_of->activator = NULL;
+	}
+	list_for_each_entry_safe(q, q_tmp, &names_queue_list, conn_entry)
+		kdbus_name_queue_item_free(q);
+	list_for_each_entry_safe(e, e_tmp, &names_list, conn_entry)
+		kdbus_name_entry_release(e, conn->ep->bus);
+
+	up_write(&reg->rwlock);
+	mutex_unlock(&conn->ep->bus->lock);
+
+	kdbus_conn_unref(activator);
+	kdbus_notify_flush(conn->ep->bus);
+}
+
+/**
+ * kdbus_name_lock() - look up a name in a name registry and lock it
+ * @reg:		The name registry
+ * @name:		The name to look up
+ *
+ * Search for a name in a given name registry and return it with the
+ * registry-lock held. If the object is not found, the lock is not acquired and
+ * NULL is returned. The caller is responsible of unlocking the name via
+ * kdbus_name_unlock() again. Note that kdbus_name_unlock() can be safely called
+ * with NULL as name. In this case, it's a no-op as nothing was locked.
+ *
+ * The *_lock() + *_unlock() logic is only required for callers that need to
+ * protect their code against concurrent activator/implementor name changes.
+ * Multiple readers can lock names concurrently. However, you may not change
+ * name-ownership while holding a name-lock.
+ *
+ * Return: NULL if name is unknown, otherwise return a pointer to the name
+ *         entry with the name-lock held (reader lock only).
+ */
+struct kdbus_name_entry *kdbus_name_lock(struct kdbus_name_registry *reg,
+					 const char *name)
+{
+	struct kdbus_name_entry *e = NULL;
+	u32 hash = kdbus_str_hash(name);
+
+	down_read(&reg->rwlock);
+	e = kdbus_name_lookup(reg, hash, name);
+	if (e)
+		return e;
+	up_read(&reg->rwlock);
+
+	return NULL;
+}
+
+/**
+ * kdbus_name_unlock() - unlock one name in a name registry
+ * @reg:		The name registry
+ * @entry:		The locked name entry or NULL
+ *
+ * This is the unlock-counterpart of kdbus_name_lock(). It unlocks a name that
+ * was previously successfully locked. You can safely pass NULL as entry and
+ * this will become a no-op. Therefore, it's safe to always call this on the
+ * return-value of kdbus_name_lock().
+ *
+ * Return: This always returns NULL.
+ */
+struct kdbus_name_entry *kdbus_name_unlock(struct kdbus_name_registry *reg,
+					   struct kdbus_name_entry *entry)
+{
+	if (entry) {
+		BUG_ON(!rwsem_is_locked(&reg->rwlock));
+		up_read(&reg->rwlock);
+	}
+
+	return NULL;
+}
+
+static int kdbus_name_queue_conn(struct kdbus_conn *conn, u64 flags,
+				 struct kdbus_name_entry *e)
+{
+	struct kdbus_name_queue_item *q;
+
+	q = kzalloc(sizeof(*q), GFP_KERNEL);
+	if (!q)
+		return -ENOMEM;
+
+	q->conn = conn;
+	q->flags = flags;
+	q->entry = e;
+
+	list_add_tail(&q->entry_entry, &e->queue_list);
+	list_add_tail(&q->conn_entry, &conn->names_queue_list);
+
+	return 0;
+}
+
+/**
+ * kdbus_name_is_valid() - check if a name is valid
+ * @p:			The name to check
+ * @allow_wildcard:	Whether or not to allow a wildcard name
+ *
+ * A name is valid if all of the following criterias are met:
+ *
+ *  - The name has two or more elements separated by a period ('.') character.
+ *  - All elements must contain at least one character.
+ *  - Each element must only contain the ASCII characters "[A-Z][a-z][0-9]_-"
+ *    and must not begin with a digit.
+ *  - The name must not exceed KDBUS_NAME_MAX_LEN.
+ *  - If @allow_wildcard is true, the name may end on '.*'
+ */
+bool kdbus_name_is_valid(const char *p, bool allow_wildcard)
+{
+	bool dot, found_dot = false;
+	const char *q;
+
+	for (dot = true, q = p; *q; q++) {
+		if (*q == '.') {
+			if (dot)
+				return false;
+
+			found_dot = true;
+			dot = true;
+		} else {
+			bool good;
+
+			good = isalpha(*q) || (!dot && isdigit(*q)) ||
+				*q == '_' || *q == '-' ||
+				(allow_wildcard && dot &&
+					*q == '*' && *(q + 1) == '\0');
+
+			if (!good)
+				return false;
+
+			dot = false;
+		}
+	}
+
+	if (q - p > KDBUS_NAME_MAX_LEN)
+		return false;
+
+	if (dot)
+		return false;
+
+	if (!found_dot)
+		return false;
+
+	return true;
+}
+
+/**
+ * kdbus_name_acquire() - acquire a name
+ * @reg:		The name registry
+ * @conn:		The connection to pin this entry to
+ * @name:		The name to acquire
+ * @flags:		Acquisition flags (KDBUS_NAME_*)
+ *
+ * Callers must ensure that @conn is either a privileged bus user or has
+ * sufficient privileges in the policy-db to own the well-known name @name.
+ *
+ * Return: 0 success, negative error number on failure.
+ */
+int kdbus_name_acquire(struct kdbus_name_registry *reg,
+		       struct kdbus_conn *conn,
+		       const char *name, u64 *flags)
+{
+	struct kdbus_name_entry *e = NULL;
+	u32 hash;
+	int ret = 0;
+
+	/* lock order: domain -> bus -> ep -> names -> conn */
+	mutex_lock(&conn->ep->bus->lock);
+	down_write(&reg->rwlock);
+
+	hash = kdbus_str_hash(name);
+	e = kdbus_name_lookup(reg, hash, name);
+	if (e) {
+		/* connection already owns that name */
+		if (e->conn == conn) {
+			ret = -EALREADY;
+			goto exit_unlock;
+		}
+
+		if (kdbus_conn_is_activator(conn)) {
+			/* An activator can only own a single name */
+			if (conn->activator_of) {
+				if (conn->activator_of == e)
+					ret = -EALREADY;
+				else
+					ret = -EINVAL;
+			} else if (!e->activator && !conn->activator_of) {
+				/*
+				 * Activator registers for name that is
+				 * already owned
+				 */
+				e->activator = kdbus_conn_ref(conn);
+				conn->activator_of = e;
+			}
+
+			goto exit_unlock;
+		}
+
+		/* take over the name of an activator connection */
+		if (e->flags & KDBUS_NAME_ACTIVATOR) {
+			/*
+			 * Take over the messages queued in the activator
+			 * connection, the activator itself never reads them.
+			 */
+			ret = kdbus_conn_move_messages(conn, e->activator, 0);
+			if (ret < 0)
+				goto exit_unlock;
+
+			ret = kdbus_name_replace_owner(e, conn, *flags);
+			goto exit_unlock;
+		}
+
+		/* take over the name if both parties agree */
+		if ((*flags & KDBUS_NAME_REPLACE_EXISTING) &&
+		    (e->flags & KDBUS_NAME_ALLOW_REPLACEMENT)) {
+			/*
+			 * Move name back to the queue, in case we take it away
+			 * from a connection which asked for queuing.
+			 */
+			if (e->flags & KDBUS_NAME_QUEUE) {
+				ret = kdbus_name_queue_conn(e->conn,
+							    e->flags, e);
+				if (ret < 0)
+					goto exit_unlock;
+			}
+
+			ret = kdbus_name_replace_owner(e, conn, *flags);
+			goto exit_unlock;
+		}
+
+		/* add it to the queue waiting for the name */
+		if (*flags & KDBUS_NAME_QUEUE) {
+			ret = kdbus_name_queue_conn(conn, *flags, e);
+
+			/* tell the caller that we queued it */
+			*flags |= KDBUS_NAME_IN_QUEUE;
+
+			goto exit_unlock;
+		}
+
+		/* the name is busy, return a failure */
+		ret = -EEXIST;
+		goto exit_unlock;
+	} else {
+		/* An activator can only own a single name */
+		if (kdbus_conn_is_activator(conn) &&
+		    conn->activator_of) {
+			ret = -EINVAL;
+			goto exit_unlock;
+		}
+	}
+
+	/* new name entry */
+	e = kzalloc(sizeof(*e), GFP_KERNEL);
+	if (!e) {
+		ret = -ENOMEM;
+		goto exit_unlock;
+	}
+
+	e->name = kstrdup(name, GFP_KERNEL);
+	if (!e->name) {
+		kfree(e);
+		ret = -ENOMEM;
+		goto exit_unlock;
+	}
+
+	if (kdbus_conn_is_activator(conn)) {
+		e->activator = kdbus_conn_ref(conn);
+		conn->activator_of = e;
+	}
+
+	e->flags = *flags;
+	INIT_LIST_HEAD(&e->queue_list);
+	e->name_id = ++reg->name_seq_last;
+
+	mutex_lock(&conn->lock);
+	if (!kdbus_conn_active(conn)) {
+		mutex_unlock(&conn->lock);
+		kfree(e);
+		ret = -ECONNRESET;
+		goto exit_unlock;
+	}
+	hash_add(reg->entries_hash, &e->hentry, hash);
+	kdbus_name_entry_set_owner(e, conn);
+	mutex_unlock(&conn->lock);
+
+	kdbus_notify_name_change(e->conn->ep->bus, KDBUS_ITEM_NAME_ADD,
+				 0, e->conn->id,
+				 0, e->flags, e->name);
+
+exit_unlock:
+	up_write(&reg->rwlock);
+	mutex_unlock(&conn->ep->bus->lock);
+	kdbus_notify_flush(conn->ep->bus);
+	return ret;
+}
+
+/**
+ * kdbus_cmd_name_acquire() - acquire a name from a ioctl command buffer
+ * @reg:		The name registry
+ * @conn:		The connection to pin this entry to
+ * @cmd:		The command as passed in by the ioctl
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int kdbus_cmd_name_acquire(struct kdbus_name_registry *reg,
+			   struct kdbus_conn *conn,
+			   struct kdbus_cmd_name *cmd)
+{
+	const char *name;
+	int ret;
+
+	name = kdbus_items_get_str(cmd->items, KDBUS_ITEMS_SIZE(cmd, items),
+				   KDBUS_ITEM_NAME);
+	if (IS_ERR(name))
+		return -EINVAL;
+
+	if (!kdbus_name_is_valid(name, false))
+		return -EINVAL;
+
+	/*
+	 * Do atomic_inc_return here to reserve our slot, then decrement
+	 * it before returning.
+	 */
+	if (atomic_inc_return(&conn->name_count) > KDBUS_CONN_MAX_NAMES) {
+		ret = -E2BIG;
+		goto out_dec;
+	}
+
+	ret = kdbus_ep_policy_check_own_access(conn->ep, conn, name);
+	if (ret < 0)
+		goto out_dec;
+
+	ret = kdbus_name_acquire(reg, conn, name, &cmd->flags);
+	kdbus_notify_flush(conn->ep->bus);
+
+out_dec:
+	/* Decrement the previous allocated slot */
+	atomic_dec(&conn->name_count);
+	return ret;
+}
+
+/**
+ * kdbus_cmd_name_release() - release a name entry from a ioctl command buffer
+ * @reg:		The name registry
+ * @conn:		The connection that holds the name
+ * @cmd:		The command as passed in by the ioctl
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int kdbus_cmd_name_release(struct kdbus_name_registry *reg,
+			   struct kdbus_conn *conn,
+			   const struct kdbus_cmd_name *cmd)
+{
+	int ret;
+	const char *name;
+
+	name = kdbus_items_get_str(cmd->items, KDBUS_ITEMS_SIZE(cmd, items),
+				   KDBUS_ITEM_NAME);
+	if (IS_ERR(name))
+		return -EINVAL;
+
+	if (!kdbus_name_is_valid(name, false))
+		return -EINVAL;
+
+	ret = kdbus_ep_policy_check_see_access(conn->ep, conn, name);
+	if (ret < 0)
+		return ret;
+
+	ret = kdbus_name_release(reg, conn, name);
+
+	kdbus_notify_flush(conn->ep->bus);
+	return ret;
+}
+
+static int kdbus_name_list_write(struct kdbus_conn *conn,
+				 struct kdbus_conn *c,
+				 struct kdbus_pool_slice *slice,
+				 size_t *pos,
+				 struct kdbus_name_entry *e,
+				 bool write)
+{
+	const size_t len = sizeof(struct kdbus_name_info);
+	size_t p = *pos;
+	size_t name_item_size = 0;
+
+	if (e) {
+		name_item_size = offsetof(struct kdbus_item, name.name) +
+				 KDBUS_ALIGN8(strlen(e->name) + 1);
+
+		if (kdbus_ep_policy_check_see_access_unlocked(conn->ep, conn,
+							      e->name) < 0)
+			return 0;
+	}
+
+	if (write) {
+		int ret;
+		struct kdbus_name_info info = {
+			.size = len,
+			.owner_id = c->id,
+			.conn_flags = c->flags,
+		};
+
+		info.size += name_item_size;
+
+		/* write record */
+		ret = kdbus_pool_slice_copy(slice, p, &info, len);
+		if (ret < 0)
+			return ret;
+		p += len;
+
+		/* append name */
+		if (e) {
+			/* fake the header of a kdbus_name item */
+			struct {
+				__u64 size;
+				__u64 type;
+				__u64 flags;
+			} h;
+			size_t nlen;
+
+			h.size = name_item_size;
+			h.type = KDBUS_ITEM_OWNED_NAME;
+			h.flags = e->flags;
+
+			ret = kdbus_pool_slice_copy(slice, p, &h, sizeof(h));
+			if (ret < 0)
+				return ret;
+
+			p += sizeof(h);
+
+			nlen = name_item_size - sizeof(h);
+			ret = kdbus_pool_slice_copy(slice, p, e->name, nlen);
+			if (ret < 0)
+				return ret;
+
+			p += nlen;
+		}
+	} else {
+		p += len + name_item_size;
+	}
+
+	*pos = p;
+	return 0;
+}
+
+static int kdbus_name_list_all(struct kdbus_conn *conn, u64 flags,
+			       struct kdbus_pool_slice *slice,
+			       size_t *pos, bool write)
+{
+	struct kdbus_conn *c;
+	size_t p = *pos;
+	int ret, i;
+
+	hash_for_each(conn->ep->bus->conn_hash, i, c, hentry) {
+		bool added = false;
+
+		/* skip activators */
+		if (!(flags & KDBUS_NAME_LIST_ACTIVATORS) &&
+		    kdbus_conn_is_activator(c))
+			continue;
+
+		/* all names the connection owns */
+		if (flags & (KDBUS_NAME_LIST_NAMES |
+			     KDBUS_NAME_LIST_ACTIVATORS)) {
+			struct kdbus_name_entry *e;
+
+			mutex_lock(&c->lock);
+			list_for_each_entry(e, &c->names_list, conn_entry) {
+				struct kdbus_conn *a = e->activator;
+
+				if ((flags & KDBUS_NAME_LIST_ACTIVATORS) &&
+				    a && a != c) {
+					ret = kdbus_name_list_write(conn, a,
+							slice, &p, e, write);
+					if (ret < 0) {
+						mutex_unlock(&c->lock);
+						return ret;
+					}
+
+					added = true;
+				}
+
+				if (flags & KDBUS_NAME_LIST_NAMES ||
+				    kdbus_conn_is_activator(c)) {
+					ret = kdbus_name_list_write(conn, c,
+							slice, &p, e, write);
+					if (ret < 0) {
+						mutex_unlock(&c->lock);
+						return ret;
+					}
+
+					added = true;
+				}
+			}
+			mutex_unlock(&c->lock);
+		}
+
+		/* queue of names the connection is currently waiting for */
+		if (flags & KDBUS_NAME_LIST_QUEUED) {
+			struct kdbus_name_queue_item *q;
+
+			mutex_lock(&c->lock);
+			list_for_each_entry(q, &c->names_queue_list,
+					    conn_entry) {
+				ret = kdbus_name_list_write(conn, c,
+						slice, &p, q->entry, write);
+				if (ret < 0) {
+					mutex_unlock(&c->lock);
+					return ret;
+				}
+
+				added = true;
+			}
+			mutex_unlock(&c->lock);
+		}
+
+		/* nothing added so far, just add the unique ID */
+		if (!added && flags & KDBUS_NAME_LIST_UNIQUE) {
+			ret = kdbus_name_list_write(conn, c,
+					slice, &p, NULL, write);
+			if (ret < 0)
+				return ret;
+		}
+	}
+
+	*pos = p;
+	return 0;
+}
+
+/**
+ * kdbus_cmd_name_list() - list names of a connection
+ * @reg:		The name registry
+ * @conn:		The connection holding the name entries
+ * @cmd:		The command as passed in by the ioctl
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int kdbus_cmd_name_list(struct kdbus_name_registry *reg,
+			struct kdbus_conn *conn,
+			struct kdbus_cmd_name_list *cmd)
+{
+	struct kdbus_policy_db *policy_db;
+	struct kdbus_name_list list = {};
+	struct kdbus_pool_slice *slice;
+	size_t pos;
+	int ret;
+
+	policy_db = &conn->ep->policy_db;
+
+	/* lock order: domain -> bus -> ep -> names -> conn */
+	down_read(&reg->rwlock);
+	down_read(&conn->ep->bus->conn_rwlock);
+	down_read(&policy_db->entries_rwlock);
+
+	/* size of header + records */
+	pos = sizeof(struct kdbus_name_list);
+	ret = kdbus_name_list_all(conn, cmd->flags, NULL, &pos, false);
+	if (ret < 0)
+		goto exit_unlock;
+
+	slice = kdbus_pool_slice_alloc(conn->pool, pos);
+	if (IS_ERR(slice)) {
+		ret = PTR_ERR(slice);
+		goto exit_unlock;
+	}
+
+	/* copy the header, specifying the overall size */
+	list.size = pos;
+	ret = kdbus_pool_slice_copy(slice, 0, &list, sizeof(list));
+	if (ret < 0)
+		goto exit_pool_free;
+
+	/* copy the records */
+	pos = sizeof(struct kdbus_name_list);
+	ret = kdbus_name_list_all(conn, cmd->flags, slice, &pos, true);
+	if (ret < 0)
+		goto exit_pool_free;
+
+	cmd->offset = kdbus_pool_slice_offset(slice);
+	kdbus_pool_slice_flush(slice);
+	kdbus_pool_slice_make_public(slice);
+
+exit_pool_free:
+	if (ret < 0)
+		kdbus_pool_slice_free(slice);
+exit_unlock:
+	up_read(&policy_db->entries_rwlock);
+	up_read(&conn->ep->bus->conn_rwlock);
+	up_read(&reg->rwlock);
+	return ret;
+}
diff --git a/ipc/kdbus/names.h b/ipc/kdbus/names.h
new file mode 100644
index 000000000000..a4d732a38782
--- /dev/null
+++ b/ipc/kdbus/names.h
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2013-2014 Kay Sievers
+ * Copyright (C) 2013-2014 Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+ * Copyright (C) 2013-2014 Daniel Mack <daniel@zonque.org>
+ * Copyright (C) 2013-2014 David Herrmann <dh.herrmann@gmail.com>
+ * Copyright (C) 2013-2014 Linux Foundation
+ *
+ * kdbus is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation; either version 2.1 of the License, or (at
+ * your option) any later version.
+ */
+
+#ifndef __KDBUS_NAMES_H
+#define __KDBUS_NAMES_H
+
+#include <linux/hashtable.h>
+#include <linux/rwsem.h>
+
+/**
+ * struct kdbus_name_registry - names registered for a bus
+ * @entries_hash:	Map of entries
+ * @lock:		Registry data lock
+ * @name_seq_last:	Last used sequence number to assign to a name entry
+ */
+struct kdbus_name_registry {
+	DECLARE_HASHTABLE(entries_hash, 8);
+	struct rw_semaphore rwlock;
+	u64 name_seq_last;
+};
+
+/**
+ * struct kdbus_name_entry - well-know name entry
+ * @name:		The well-known name
+ * @name_id:		Sequence number of name entry to be able to uniquely
+ *			identify a name over its registration lifetime
+ * @flags:		KDBUS_NAME_* flags
+ * @queue_list:		List of queued waiters for the well-known name
+ * @conn_entry:		Entry in connection
+ * @hentry:		Entry in registry map
+ * @conn:		Connection owning the name
+ * @activator:		Connection of the activator queuing incoming messages
+ */
+struct kdbus_name_entry {
+	char *name;
+	u64 name_id;
+	u64 flags;
+	struct list_head queue_list;
+	struct list_head conn_entry;
+	struct hlist_node hentry;
+	struct kdbus_conn *conn;
+	struct kdbus_conn *activator;
+};
+
+struct kdbus_name_registry *kdbus_name_registry_new(void);
+void kdbus_name_registry_free(struct kdbus_name_registry *reg);
+
+int kdbus_name_acquire(struct kdbus_name_registry *reg,
+		       struct kdbus_conn *conn,
+		       const char *name, u64 *flags);
+int kdbus_cmd_name_acquire(struct kdbus_name_registry *reg,
+			   struct kdbus_conn *conn,
+			   struct kdbus_cmd_name *cmd);
+int kdbus_cmd_name_release(struct kdbus_name_registry *reg,
+			   struct kdbus_conn *conn,
+			   const struct kdbus_cmd_name *cmd);
+int kdbus_cmd_name_list(struct kdbus_name_registry *reg,
+			struct kdbus_conn *conn,
+			struct kdbus_cmd_name_list *cmd);
+
+struct kdbus_name_entry *kdbus_name_lock(struct kdbus_name_registry *reg,
+					 const char *name);
+struct kdbus_name_entry *kdbus_name_unlock(struct kdbus_name_registry *reg,
+					   struct kdbus_name_entry *entry);
+
+void kdbus_name_remove_by_conn(struct kdbus_name_registry *reg,
+			       struct kdbus_conn *conn);
+
+bool kdbus_name_is_valid(const char *p, bool allow_wildcard);
+
+#endif
-- 
2.1.3