kdbus: add connection, queue handling and message validation code

This patch adds code to create and destroy connections, to validate
incoming messages and to maintain the queue of messages that are
associated with a connection.

Note that connection and queue have a 1:1 relation, the code is only
split in two parts for cleaner separation and better readability.

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>

1 files changed, 259 insertions, 0 deletions

diff --git a/ipc/kdbus/reply.c b/ipc/kdbus/reply.c
new file mode 100644
index 00000000000..6b3bd81bbb4
--- /dev/null
+++ b/ipc/kdbus/reply.c
@@ -0,0 +1,259 @@
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/uio.h>
+
+#include "bus.h"
+#include "connection.h"
+#include "endpoint.h"
+#include "message.h"
+#include "metadata.h"
+#include "names.h"
+#include "domain.h"
+#include "item.h"
+#include "notify.h"
+#include "policy.h"
+#include "reply.h"
+#include "util.h"
+
+/**
+ * kdbus_reply_new() - Allocate and set up a new kdbus_reply object
+ * @reply_src:		The connection a reply is expected from
+ * @reply_dst:		The connection this reply object belongs to
+ * @msg:		Message associated with the reply
+ * @name_entry:		Name entry used to send the message
+ * @sync:		Whether or not to make this reply synchronous
+ *
+ * Allocate and fill a new kdbus_reply object.
+ *
+ * Return: New kdbus_conn object on success, ERR_PTR on error.
+ */
+struct kdbus_reply *kdbus_reply_new(struct kdbus_conn *reply_src,
+				    struct kdbus_conn *reply_dst,
+				    const struct kdbus_msg *msg,
+				    struct kdbus_name_entry *name_entry,
+				    bool sync)
+{
+	struct kdbus_reply *r;
+	int ret = 0;
+
+	if (atomic_inc_return(&reply_dst->request_count) >
+	    KDBUS_CONN_MAX_REQUESTS_PENDING) {
+		ret = -EMLINK;
+		goto exit_dec_request_count;
+	}
+
+	r = kzalloc(sizeof(*r), GFP_KERNEL);
+	if (!r) {
+		ret = -ENOMEM;
+		goto exit_dec_request_count;
+	}
+
+	kref_init(&r->kref);
+	INIT_LIST_HEAD(&r->entry);
+	r->reply_src = kdbus_conn_ref(reply_src);
+	r->reply_dst = kdbus_conn_ref(reply_dst);
+	r->cookie = msg->cookie;
+	r->name_id = name_entry ? name_entry->name_id : 0;
+	r->deadline_ns = msg->timeout_ns;
+
+	if (sync) {
+		r->sync = true;
+		r->waiting = true;
+	}
+
+exit_dec_request_count:
+	if (ret < 0) {
+		atomic_dec(&reply_dst->request_count);
+		return ERR_PTR(ret);
+	}
+
+	return r;
+}
+
+static void __kdbus_reply_free(struct kref *kref)
+{
+	struct kdbus_reply *reply =
+		container_of(kref, struct kdbus_reply, kref);
+
+	atomic_dec(&reply->reply_dst->request_count);
+	kdbus_conn_unref(reply->reply_src);
+	kdbus_conn_unref(reply->reply_dst);
+	kfree(reply);
+}
+
+/**
+ * kdbus_reply_ref() - Increase reference on kdbus_reply
+ * @r:		The reply, may be %NULL
+ *
+ * Return: The reply object with an extra reference
+ */
+struct kdbus_reply *kdbus_reply_ref(struct kdbus_reply *r)
+{
+	if (r)
+		kref_get(&r->kref);
+	return r;
+}
+
+/**
+ * kdbus_reply_unref() - Decrease reference on kdbus_reply
+ * @r:		The reply, may be %NULL
+ *
+ * Return: NULL
+ */
+struct kdbus_reply *kdbus_reply_unref(struct kdbus_reply *r)
+{
+	if (r)
+		kref_put(&r->kref, __kdbus_reply_free);
+	return NULL;
+}
+
+/**
+ * kdbus_reply_link() - Link reply object into target connection
+ * @r:		Reply to link
+ */
+void kdbus_reply_link(struct kdbus_reply *r)
+{
+	if (WARN_ON(!list_empty(&r->entry)))
+		return;
+
+	list_add(&r->entry, &r->reply_dst->reply_list);
+	kdbus_reply_ref(r);
+}
+
+/**
+ * kdbus_reply_unlink() - Unlink reply object from target connection
+ * @r:		Reply to unlink
+ */
+void kdbus_reply_unlink(struct kdbus_reply *r)
+{
+	if (!list_empty(&r->entry)) {
+		list_del_init(&r->entry);
+		kdbus_reply_unref(r);
+	}
+}
+
+/**
+ * kdbus_sync_reply_wakeup() - Wake a synchronously blocking reply
+ * @reply:	The reply object
+ * @err:	Error code to set on the remote side
+ *
+ * Remove the synchronous reply object from its connection reply_list, and
+ * wake up remote peer (method origin) with the appropriate synchronous reply
+ * code.
+ */
+void kdbus_sync_reply_wakeup(struct kdbus_reply *reply, int err)
+{
+	if (WARN_ON(!reply->sync))
+		return;
+
+	reply->waiting = false;
+	reply->err = err;
+	wake_up_interruptible(&reply->reply_dst->wait);
+}
+
+/**
+ * kdbus_reply_find() - Find the corresponding reply object
+ * @replying:	The replying connection or NULL
+ * @reply_dst:	The connection the reply will be sent to
+ *		(method origin)
+ * @cookie:	The cookie of the requesting message
+ *
+ * Lookup a reply object that should be sent as a reply by
+ * @replying to @reply_dst with the given cookie.
+ *
+ * Callers must take the @reply_dst lock.
+ *
+ * Return: the corresponding reply object or NULL if not found
+ */
+struct kdbus_reply *kdbus_reply_find(struct kdbus_conn *replying,
+				     struct kdbus_conn *reply_dst,
+				     u64 cookie)
+{
+	struct kdbus_reply *r, *reply = NULL;
+
+	list_for_each_entry(r, &reply_dst->reply_list, entry) {
+		if (r->cookie == cookie &&
+		    (!replying || r->reply_src == replying)) {
+			reply = r;
+			break;
+		}
+	}
+
+	return reply;
+}
+
+/**
+ * kdbus_reply_list_scan_work() - Worker callback to scan the replies of a
+ *				  connection for exceeded timeouts
+ * @work:		Work struct of the connection to scan
+ *
+ * Walk the list of replies stored with a connection and look for entries
+ * that have exceeded their timeout. If such an entry is found, a timeout
+ * notification is sent to the waiting peer, and the reply is removed from
+ * the list.
+ *
+ * The work is rescheduled to the nearest timeout found during the list
+ * iteration.
+ */
+void kdbus_reply_list_scan_work(struct work_struct *work)
+{
+	struct kdbus_conn *conn =
+		container_of(work, struct kdbus_conn, work.work);
+	struct kdbus_reply *reply, *reply_tmp;
+	u64 deadline = ~0ULL;
+	struct timespec64 ts;
+	u64 now;
+
+	ktime_get_ts64(&ts);
+	now = timespec64_to_ns(&ts);
+
+	mutex_lock(&conn->lock);
+	if (!kdbus_conn_active(conn)) {
+		mutex_unlock(&conn->lock);
+		return;
+	}
+
+	list_for_each_entry_safe(reply, reply_tmp, &conn->reply_list, entry) {
+		/*
+		 * If the reply block is waiting for synchronous I/O,
+		 * the timeout is handled by wait_event_*_timeout(),
+		 * so we don't have to care for it here.
+		 */
+		if (reply->sync && !reply->interrupted)
+			continue;
+
+		WARN_ON(reply->reply_dst != conn);
+
+		if (reply->deadline_ns > now) {
+			/* remember next timeout */
+			if (deadline > reply->deadline_ns)
+				deadline = reply->deadline_ns;
+
+			continue;
+		}
+
+		/*
+		 * A zero deadline means the connection died, was
+		 * cleaned up already and the notification was sent.
+		 * Don't send notifications for reply trackers that were
+		 * left in an interrupted syscall state.
+		 */
+		if (reply->deadline_ns != 0 && !reply->interrupted)
+			kdbus_notify_reply_timeout(conn->ep->bus, conn->id,
+						   reply->cookie);
+
+		kdbus_reply_unlink(reply);
+	}
+
+	/* rearm delayed work with next timeout */
+	if (deadline != ~0ULL)
+		schedule_delayed_work(&conn->work,
+				      nsecs_to_jiffies(deadline - now));
+
+	mutex_unlock(&conn->lock);
+
+	kdbus_notify_flush(conn->ep->bus);
+}