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GSubprocessLauncher: Move cleanup to dispose()

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The GSubprocessLauncher class lacks a dispose() method, and frees
all their resources in the finalize() method.

This is a problem with Javascript because the sockets passed to a
child process using g_subprocess_launcher_take_fd() aren't closed
in the parent space until the object is fully freed. This means
that if the child closes a socket, it won't be detected until the
GSubprocessLauncher object has been freed by the garbage
collector.

Just closing the socket externally is not a valid solution,
because the finalize() method will close it again, and since
another file/pipe/socket could have been opened in the meantime
and use the same FD number, the finalize() method would close
an incorrect FD.

An example is launching a child process that uses its own
socket for Wayland: the parent creates two sockets with
socketpair(), passes one to the Wayland API (wl_client_create()),
and the other is passed to the child process using
g_subprocess_launcher_take_fd(). But now there are two instances
of that second socket: one in the parent, and another one in the
child process. That means that, if the child closes its socket (or
dies), the Wayland server will not detect that until the
GSubprocessLauncher object is fully destroyed. That means that a
GSubprocessLauncher created in Javascript will last for several
seconds after the child dies, and every window or graphical element
will remain in the screen until the Garbage Collector destroys the
GSubprocessLauncher object.

This patch fixes this by moving the resource free code into a
dispose() method, which can be called from Javascript. This allows
to ensure that any socket passed to the child with
g_subprocess_launcher_take_fd() can be closed even from Javascript
just by calling the method run_dispose().

Fix https://gitlab.gnome.org/GNOME/glib/-/merge_requests/1670
This commit is contained in:
Sergio Costas 2020-09-30 22:35:00 +02:00
parent f01ca92821
commit 605cff61da
1 changed files with 22 additions and 13 deletions
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35
gio/gsubprocesslauncher.c
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@ -131,47 +131,52 @@ g_subprocess_launcher_set_property (GObject *object, guint prop_id,
}
static void
g_subprocess_launcher_finalize (GObject *object)
g_subprocess_launcher_dispose (GObject *object)
{
GSubprocessLauncher *self = G_SUBPROCESS_LAUNCHER (object);
#ifdef G_OS_UNIX
guint i;
g_free (self->stdin_path);
g_free (self->stdout_path);
g_free (self->stderr_path);
g_clear_pointer (&self->stdin_path, g_free);
g_clear_pointer (&self->stdout_path, g_free);
g_clear_pointer (&self->stderr_path, g_free);
if (self->stdin_fd != -1)
close (self->stdin_fd);
self->stdin_fd = -1;
if (self->stdout_fd != -1)
close (self->stdout_fd);
self->stdout_fd = -1;
if (self->stderr_fd != -1)
close (self->stderr_fd);
self->stderr_fd = -1;
if (self->basic_fd_assignments)
{
for (i = 0; i < self->basic_fd_assignments->len; i++)
(void) close (g_array_index (self->basic_fd_assignments, int, i));
g_array_unref (self->basic_fd_assignments);
g_clear_pointer (&self->basic_fd_assignments, g_array_unref);
}
if (self->needdup_fd_assignments)
{
for (i = 0; i < self->needdup_fd_assignments->len; i += 2)
(void) close (g_array_index (self->needdup_fd_assignments, int, i));
g_array_unref (self->needdup_fd_assignments);
g_clear_pointer (&self->needdup_fd_assignments, g_array_unref);
}
if (self->child_setup_destroy_notify)
(* self->child_setup_destroy_notify) (self->child_setup_user_data);
self->child_setup_destroy_notify = NULL;
self->child_setup_user_data = NULL;
#endif
g_strfreev (self->envp);
g_free (self->cwd);
g_clear_pointer (&self->envp, g_strfreev);
g_clear_pointer (&self->cwd, g_free);
G_OBJECT_CLASS (g_subprocess_launcher_parent_class)->finalize (object);
G_OBJECT_CLASS (g_subprocess_launcher_parent_class)->dispose (object);
}
static void
@ -194,7 +199,7 @@ g_subprocess_launcher_class_init (GSubprocessLauncherClass *class)
GObjectClass *gobject_class = G_OBJECT_CLASS (class);
gobject_class->set_property = g_subprocess_launcher_set_property;
gobject_class->finalize = g_subprocess_launcher_finalize;
gobject_class->dispose = g_subprocess_launcher_dispose;
g_object_class_install_property (gobject_class, 1,
g_param_spec_flags ("flags", "Flags", "GSubprocessFlags for launched processes",
@ -634,12 +639,16 @@ g_subprocess_launcher_take_fd (GSubprocessLauncher *self,
{
if (source_fd == target_fd)
{
g_array_append_val (self->basic_fd_assignments, source_fd);
if (self->basic_fd_assignments)
g_array_append_val (self->basic_fd_assignments, source_fd);
}
else
{
g_array_append_val (self->needdup_fd_assignments, source_fd);
g_array_append_val (self->needdup_fd_assignments, target_fd);
if (self->needdup_fd_assignments)
{
g_array_append_val (self->needdup_fd_assignments, source_fd);
g_array_append_val (self->needdup_fd_assignments, target_fd);
}
}
}