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gdbusconnection: Improve refcount handling of timeout source

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The ref on the timeout source owned by `SendMessageData` was being
dropped just after attaching the source to the main context, leaving it
unowned in that struct. That meant the only ref on the source was held
by the `GMainContext` it was attached to.

This ref was dropped when returning `G_SOURCE_REMOVE` from
`send_message_with_reply_timeout_cb()`. Before that happens,
`send_message_data_deliver_error()` is called, which normally calls
`send_message_with_reply_cleanup()` and destroys the source.

However, if `send_message_data_deliver_error()` is called when the
message has already been delivered, calling
`send_message_with_reply_cleanup()` will be skipped. This leaves the
source pointer in `SendMessageData` dangling, which will cause problems
when `g_source_destroy()` is subsequently called on it.

I’m not sure if it’s possible in practice for this situation to occur,
but the code certainly does nothing to prevent it, and it’s easy enough
to avoid by keeping a strong ref on the source in `SendMessageData`.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

Helps: #1264
This commit is contained in:
Philip Withnall 2023-02-22 14:55:40 +00:00
parent c4055424a4
commit 60e06dd828
1 changed files with 4 additions and 4 deletions
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8
gio/gdbusconnection.c
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@ -1752,7 +1752,7 @@ typedef struct
gulong cancellable_handler_id;
GSource *cancelled_idle_source; /* (owned) (nullable) */
GSource *timeout_source;
GSource *timeout_source; /* (owned) (nullable) */
gboolean delivered;
} SendMessageData;
@ -1761,6 +1761,7 @@ typedef struct
static void
send_message_data_free (SendMessageData *data)
{
/* These should already have been cleared by send_message_with_reply_cleanup(). */
g_assert (data->timeout_source == NULL);
g_assert (data->cancellable_handler_id == 0);
@ -1785,7 +1786,7 @@ send_message_with_reply_cleanup (GTask *task, gboolean remove)
if (data->timeout_source != NULL)
{
g_source_destroy (data->timeout_source);
data->timeout_source = NULL;
g_clear_pointer (&data->timeout_source, g_source_unref);
}
if (data->cancellable_handler_id > 0)
{
@ -1896,7 +1897,7 @@ send_message_with_reply_timeout_cb (gpointer user_data)
send_message_data_deliver_error (task, G_IO_ERROR, G_IO_ERROR_TIMED_OUT,
_("Timeout was reached"));
return FALSE;
return G_SOURCE_REMOVE;
}
/* ---------------------------------------------------------------------------------------------------- */
@ -1957,7 +1958,6 @@ g_dbus_connection_send_message_with_reply_unlocked (GDBusConnection *connect
g_source_set_static_name (data->timeout_source, "[gio] send_message_with_reply_unlocked");
g_task_attach_source (task, data->timeout_source,
(GSourceFunc) send_message_with_reply_timeout_cb);
g_source_unref (data->timeout_source);
}
g_hash_table_insert (connection->map_method_serial_to_task,