limit the number of buses and connections per user

10 files changed, 140 insertions, 4 deletions

diff --git a/TODO b/TODO
index 62c257bc292..47273bb7ab4 100644
--- a/TODO
+++ b/TODO
@@ -21,9 +21,6 @@ Features:
     for another connection, like a connection can have a maximum of 100
     messages in-flight, but only 10 of them for the same connection
 
-  - limit the number of buses an ordinary user can create
-  - limit the number of connections per uid
-
   - allow to update the metadata subscription bit mask
 
   - support the creation of anonymous buses
diff --git a/bus.c b/bus.c
index 757c260f7cb..fdc4a1c77e2 100644
--- a/bus.c
+++ b/bus.c
@@ -57,6 +57,10 @@ static void __kdbus_bus_free(struct kref *kref)
 	struct kdbus_bus *bus = container_of(kref, struct kdbus_bus, kref);
 
 	kdbus_bus_disconnect(bus);
+
+	atomic_dec(&bus->user->buses);
+	kdbus_ns_user_unref(bus->user);
+
 	if (bus->name_registry)
 		kdbus_name_registry_free(bus->name_registry);
 	kdbus_ns_unref(bus->ns);
@@ -237,6 +241,21 @@ int kdbus_bus_new(struct kdbus_ns *ns,
 	if (ret < 0)
 		goto exit;
 
+	/* account the bus against the user */
+	b->user = kdbus_ns_user_ref(ns, uid);
+	if (!b->user) {
+		ret = -ENOMEM;
+		goto exit;
+	}
+
+	if (!capable(CAP_IPC_OWNER) &&
+	    atomic_inc_return(&b->user->buses) > KDBUS_USER_MAX_BUSES) {
+		atomic_dec(&b->user->buses);
+		b->user = kdbus_ns_user_unref(b->user);
+		ret = -EMFILE;
+		goto exit;
+	}
+
 	/* link into namespace */
 	mutex_lock(&ns->lock);
 	b->id = ++ns->bus_seq_last;
diff --git a/bus.h b/bus.h
index 15c0af4648f..2a2a859ed5b 100644
--- a/bus.h
+++ b/bus.h
@@ -38,6 +38,7 @@
  * @ns_entry:		Namespace's list of buses
  * @monitors_list:	Connections that monitor this bus
  * @id128:		Unique random 128 bit ID of this bus
+ * @user:		Owner of the connection;
  *
  * A bus provides a "bus" endpoint / device node.
  *
@@ -64,6 +65,7 @@ struct kdbus_bus {
 	struct list_head ns_entry;
 	struct list_head monitors_list;
 	u8 id128[16];
+	struct kdbus_ns_user *user;
 };
 
 int kdbus_bus_make_user(void __user *buf, struct kdbus_cmd_make **make,
diff --git a/connection.c b/connection.c
index b952b4e4854..0bbdb182d41 100644
--- a/connection.c
+++ b/connection.c
@@ -1359,6 +1359,10 @@ static void __kdbus_conn_free(struct kref *kref)
 	struct kdbus_conn_reply_entry *reply, *reply_tmp;
 
 	kdbus_conn_disconnect(conn, false);
+
+	atomic_dec(&conn->user->connections);
+	kdbus_ns_user_unref(conn->user);
+
 	if (conn->ep->policy_db)
 		kdbus_policy_db_remove_conn(conn->ep->policy_db, conn);
 
@@ -1824,6 +1828,20 @@ int kdbus_conn_new(struct kdbus_ep *ep,
 		conn->meta = meta;
 	}
 
+	/* account the connection against the user */
+	conn->user = kdbus_ns_user_ref(ep->bus->ns, ep->bus->uid_owner);
+	if (!conn->user) {
+		ret = -ENOMEM;
+		goto exit_free_meta;
+	}
+
+	if (!capable(CAP_IPC_OWNER) &&
+	    atomic_inc_return(&conn->user->connections) > KDBUS_USER_MAX_CONN) {
+		atomic_dec(&conn->user->connections);
+		ret = -EMFILE;
+		goto exit_unref_user;
+	}
+
 	/* link into bus */
 	mutex_lock(&bus->lock);
 	hash_add(bus->conn_hash, &conn->hentry, conn->id);
@@ -1832,6 +1850,8 @@ int kdbus_conn_new(struct kdbus_ep *ep,
 	*c = conn;
 	return 0;
 
+exit_unref_user:
+	kdbus_ns_user_unref(conn->user);
 exit_free_meta:
 	kdbus_meta_free(conn->owner_meta);
 exit_release_names:
@@ -1850,7 +1870,7 @@ exit_free_conn:
 }
 
 /**
- * kdbus_conn_has_name() - check if a connection owns a name
+ * kdbus_conn_has_name() - check if a connection owns r name
  * @conn:		Connection
  * @name:		Well-know name to check for
  *
diff --git a/connection.h b/connection.h
index f55b3b57ba8..624cbd0de4e 100644
--- a/connection.h
+++ b/connection.h
@@ -49,6 +49,7 @@
  *			HELLO
  * @msg_count:		Number of queued messages
  * @pool:		The user's buffer to receive messages
+ * @user:		Owner of the connection;
  */
 struct kdbus_conn {
 	struct kref kref;
@@ -76,6 +77,7 @@ struct kdbus_conn {
 	struct kdbus_meta *owner_meta;
 	unsigned int msg_count;
 	struct kdbus_pool *pool;
+	struct kdbus_ns_user *user;
 };
 
 struct kdbus_kmsg;
diff --git a/defaults.h b/defaults.h
index da6b83c986e..683b4e2c56b 100644
--- a/defaults.h
+++ b/defaults.h
@@ -52,4 +52,10 @@
 /* maximum number of queud requests waiting ot a reply */
 #define KDBUS_CONN_MAX_REQUESTS_PENDING	64
 
+/* maximum number of connections per user in one namespace */
+#define KDBUS_USER_MAX_CONN		256
+
+/* maximum number of buses per user in one namespace */
+#define KDBUS_USER_MAX_BUSES		16
+
 #endif
diff --git a/handle.c b/handle.c
index 4517cf5744c..c11195a6937 100644
--- a/handle.c
+++ b/handle.c
@@ -401,6 +401,12 @@ static long kdbus_handle_ioctl_ep(struct file *file, unsigned int cmd,
 		kgid_t gid = KGIDT_INIT(0);
 		char *name;
 
+		/* creating custom endpoints is a privileged operation */
+		if (!kdbus_bus_uid_is_privileged(handle->ep->bus)) {
+			ret = -EFAULT;
+			break;
+		}
+
 		if (!KDBUS_IS_ALIGNED8((uintptr_t)buf)) {
 			ret = -EFAULT;
 			break;
diff --git a/kdbus.h b/kdbus.h
index c0a539149f1..36b362d449a 100644
--- a/kdbus.h
+++ b/kdbus.h
@@ -864,6 +864,8 @@ enum kdbus_ioctl_type {
  *			refused to send as KDBUS_MSG_PAYLOAD_MEMFD.
  * @EMFILE:		Too many file descriptors have been supplied with a
  *			message.
+ *			Too many connections or buses are created for a given
+ *			user.
  * @EMLINK:		Too many requests from this connection to other peers
  *			are queued and waiting for a reply
  * @EMSGSIZE:		The supplied data is larger than the allowed maximum
diff --git a/namespace.c b/namespace.c
index 56e32c734c2..66af3b6a875 100644
--- a/namespace.c
+++ b/namespace.c
@@ -392,3 +392,61 @@ exit:
 	kfree(m);
 	return ret;
 }
+
+struct kdbus_ns_user *kdbus_ns_user_ref(struct kdbus_ns *ns, kuid_t uid)
+{
+	struct kdbus_ns_user *u;
+
+	/* find uid and reference it */
+	mutex_lock(&ns->lock);
+	hash_for_each_possible(ns->user_hash, u, hentry, uid) {
+		if (u->uid != uid)
+			continue;
+
+		kref_get(&u->kref);
+		mutex_unlock(&ns->lock);
+		return u;
+	}
+	mutex_unlock(&ns->lock);
+
+	/* allocate a new user */
+	u = kzalloc(GFP_KERNEL, sizeof(struct kdbus_ns_user));
+	if (!u)
+		return NULL;
+
+	kref_init(&u->kref);
+	u->ns = kdbus_ns_ref(ns);
+	u->uid = uid;
+	atomic_set(&u->buses, 0);
+	atomic_set(&u->connections, 0);
+
+	/* link into namespace */
+	mutex_lock(&ns->lock);
+	hash_add(ns->user_hash, &u->hentry, u->uid);
+	mutex_unlock(&ns->lock);
+
+printk("new user %u\n", u->uid);
+	return u;
+}
+
+static void __kdbus_ns_user_free(struct kref *kref)
+{
+	struct kdbus_ns_user *user = container_of(kref, struct kdbus_ns_user,
+						  kref);
+
+	BUG_ON(atomic_read(&user->buses) > 0);
+	BUG_ON(atomic_read(&user->connections) > 0);
+
+	mutex_lock(&user->ns->lock);
+	hash_del(&user->hentry);
+	mutex_unlock(&user->ns->lock);
+	kdbus_ns_unref(user->ns);
+printk("user %u done\n", user->uid);
+	kfree(user);
+}
+
+struct kdbus_ns_user *kdbus_ns_user_unref(struct kdbus_ns_user *user)
+{
+	kref_put(&user->kref, __kdbus_ns_user_free);
+	return NULL;
+}
diff --git a/namespace.h b/namespace.h
index a5dbb9b8ba6..e36ce939d64 100644
--- a/namespace.h
+++ b/namespace.h
@@ -13,6 +13,7 @@
 #ifndef __KDBUS_NS_H
 #define __KDBUS_NS_H
 
+#include <linux/hashtable.h>
 #include <linux/idr.h>
 
 /**
@@ -33,6 +34,7 @@
  * @msg_seq_last:	Last used message id sequence number
  * @ns_entry:		Entry in parent namespace
  * @bus_list:		Buses in this namespace
+ * @user_hash:		Accounting of user resources
  *
  * A namespace provides a "control" device node. Every namespace has its
  * own major number for its endpoint device nodes.
@@ -61,6 +63,25 @@ struct kdbus_ns {
 	atomic64_t msg_seq_last;
 	struct list_head ns_entry;
 	struct list_head bus_list;
+	DECLARE_HASHTABLE(user_hash, 6);
+};
+
+/**
+ * struct kdbus_ns_user - resource accounting for users
+ * @kref:		Reference counter
+ * @ns:			Namespace of the user
+ * @hentry:		Entry in namespace user map
+ * @uid:		UID of the user
+ * @buses:		Number of buses the user has created
+ * @connections:	Number of connections the user has created
+ */
+struct kdbus_ns_user {
+	struct kref kref;
+	struct kdbus_ns *ns;
+	struct hlist_node hentry;
+	kuid_t uid;
+	atomic_t buses;
+	atomic_t connections;
 };
 
 extern struct kdbus_ns *kdbus_ns_init;
@@ -74,4 +95,7 @@ int kdbus_ns_new(struct kdbus_ns *parent, const char *name,
 int kdbus_ns_make_user(void __user *buf,
 		       struct kdbus_cmd_make **make, char **name);
 struct kdbus_ns *kdbus_ns_find_by_major(unsigned int major);
+
+struct kdbus_ns_user *kdbus_ns_user_ref(struct kdbus_ns *ns, kuid_t uid);
+struct kdbus_ns_user *kdbus_ns_user_unref(struct kdbus_ns_user *user);
 #endif