layer-shell: don't give focus to unmapped layer surfaces

Focused layers are not cleared when destroyed, they are cleared on unmap.
Giving focus to an unmapped layer surface is (1) incorrect and (2) triggers a
use-after-free.

Closes: https://github.com/swaywm/sway/issues/4517

2 files changed, 3 insertions, 1 deletions

diff --git a/sway/desktop/layer_shell.c b/sway/desktop/layer_shell.c
index 60270a42..c881919d 100644
--- a/sway/desktop/layer_shell.c
+++ b/sway/desktop/layer_shell.c
@@ -200,7 +200,8 @@ void arrange_layers(struct sway_output *output) {
         for (size_t i = 0; i < nlayers; ++i) {
                 wl_list_for_each_reverse(layer,
                                 &output->layers[layers_above_shell[i]], link) {
-                        if (layer->layer_surface->current.keyboard_interactive) {
+                        if (layer->layer_surface->current.keyboard_interactive &&
+                                        layer->layer_surface->mapped) {
                                 topmost = layer;
                                 break;
                         }
diff --git a/sway/input/seat.c b/sway/input/seat.c
index 4da8e937..b2243fe3 100644
--- a/sway/input/seat.c
+++ b/sway/input/seat.c
@@ -1095,6 +1095,7 @@ void seat_set_focus_layer(struct sway_seat *seat,
         } else if (!layer || seat->focused_layer == layer) {
                 return;
         }
+        assert(layer->mapped);
         seat_set_focus_surface(seat, layer->surface, true);
         if (layer->layer >= ZWLR_LAYER_SHELL_V1_LAYER_TOP) {
                 seat->focused_layer = layer;