134 lines
5.0 KiB
Diff
134 lines
5.0 KiB
Diff
From b849ebb5d199da3694e6b6261a931436214f7a0e Mon Sep 17 00:00:00 2001
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From: Philip Withnall <withnall@endlessm.com>
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Date: Mon, 6 Feb 2017 09:41:10 +0100
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Subject: [PATCH] gdbus: Fix race in name watching on connection teardown
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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If g_dbus_unwatch_name() is called from one thread at the same time as
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the GDBusConnection is emitting ::disconnected in another thread, there
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will be a race and the handler for ::disconnected may end up using
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memory after it’s freed.
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Fix this by serialising through the map_id_to_client, so that
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on_connection_disconnected() atomically gets a strong reference to the
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Client, or NULL.
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https://bugzilla.gnome.org/show_bug.cgi?id=777307
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---
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gio/gdbusnamewatching.c | 48 +++++++++++++++++++++++++++++++++++++++++++-----
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1 file changed, 43 insertions(+), 5 deletions(-)
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diff --git a/gio/gdbusnamewatching.c b/gio/gdbusnamewatching.c
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index 3cb2b57b7b0f..148fb41cf025 100644
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--- a/gio/gdbusnamewatching.c
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+++ b/gio/gdbusnamewatching.c
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@@ -249,13 +249,43 @@ call_vanished_handler (Client *client,
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/* ---------------------------------------------------------------------------------------------------- */
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+/* Return a reference to the #Client for @watcher_id, or %NULL if it’s been
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+ * unwatched. This is safe to call from any thread. */
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+static Client *
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+dup_client (guint watcher_id)
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+{
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+ Client *client;
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+
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+ G_LOCK (lock);
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+
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+ g_assert (watcher_id != 0);
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+ g_assert (map_id_to_client != NULL);
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+
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+ client = g_hash_table_lookup (map_id_to_client, GUINT_TO_POINTER (watcher_id));
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+
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+ if (client != NULL)
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+ client_ref (client);
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+
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+ G_UNLOCK (lock);
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+
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+ return client;
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+}
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+
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+/* Could be called from any thread, so it could be called after client_unref()
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+ * has started finalising the #Client. Avoid that by looking up the #Client
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+ * atomically. */
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static void
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on_connection_disconnected (GDBusConnection *connection,
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gboolean remote_peer_vanished,
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GError *error,
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gpointer user_data)
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{
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- Client *client = user_data;
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+ guint watcher_id = GPOINTER_TO_UINT (user_data);
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+ Client *client = NULL;
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+
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+ client = dup_client (watcher_id);
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+ if (client == NULL)
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+ return;
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if (client->name_owner_changed_subscription_id > 0)
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g_dbus_connection_signal_unsubscribe (client->connection, client->name_owner_changed_subscription_id);
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@@ -267,10 +297,13 @@ on_connection_disconnected (GDBusConnection *connection,
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client->connection = NULL;
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call_vanished_handler (client, FALSE);
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+
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+ client_unref (client);
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}
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/* ---------------------------------------------------------------------------------------------------- */
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+/* Will always be called from the thread which acquired client->main_context. */
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static void
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on_name_owner_changed (GDBusConnection *connection,
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const gchar *sender_name,
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@@ -280,11 +313,16 @@ on_name_owner_changed (GDBusConnection *connection,
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GVariant *parameters,
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gpointer user_data)
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{
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- Client *client = user_data;
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+ guint watcher_id = GPOINTER_TO_UINT (user_data);
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+ Client *client = NULL;
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const gchar *name;
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const gchar *old_owner;
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const gchar *new_owner;
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+ client = dup_client (watcher_id);
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+ if (client == NULL)
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+ return;
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+
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if (!client->initialized)
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goto out;
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@@ -319,7 +357,7 @@ on_name_owner_changed (GDBusConnection *connection,
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}
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out:
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- ;
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+ client_unref (client);
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}
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/* ---------------------------------------------------------------------------------------------------- */
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@@ -444,7 +482,7 @@ has_connection (Client *client)
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client->disconnected_signal_handler_id = g_signal_connect (client->connection,
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"closed",
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G_CALLBACK (on_connection_disconnected),
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- client);
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+ GUINT_TO_POINTER (client->id));
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/* start listening to NameOwnerChanged messages immediately */
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client->name_owner_changed_subscription_id = g_dbus_connection_signal_subscribe (client->connection,
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@@ -455,7 +493,7 @@ has_connection (Client *client)
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client->name,
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G_DBUS_SIGNAL_FLAGS_NONE,
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on_name_owner_changed,
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- client,
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+ GUINT_TO_POINTER (client->id),
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NULL);
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if (client->flags & G_BUS_NAME_WATCHER_FLAGS_AUTO_START)
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--
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2.14.3
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