xwayland: move config reading up

Doing any kind of memory allocation calls between fork() and exec() in
the child process is prone to deadlocks and explosions. In general, only
async-signal-safe functions are safe there.

Move the config access to the parent process before fork() to avoid
problems.

See also:
https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/941#note_1457053

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

compositor/xwayland.c

@@ -140,13 +140,13 @@ spawn_xserver(void *user_data, const char *display, int abstract_fd, int unix_fd
 		return 1;
 	}
 
+	section = weston_config_get_section(config, "xwayland", NULL, NULL);
+	weston_config_section_get_string(section, "path",
+					 &xserver, XSERVER_PATH);
+
 	pid = fork();
 	switch (pid) {
 	case 0:
-		section = weston_config_get_section(config,
-						    "xwayland", NULL, NULL);
-		weston_config_section_get_string(section, "path",
-						 &xserver, XSERVER_PATH);
 
 		/* SOCK_CLOEXEC closes both ends, so we need to unset
 		 * the flag on the client fd. */
@@ -205,6 +205,8 @@ spawn_xserver(void *user_data, const char *display, int abstract_fd, int unix_fd
 		break;
 	}
 
+	free(xserver);
+
 	return pid;
 }