Fix use after free in transaction code

If we set an instruction as ready twice, it decreases the transaction's
num_waiting a second time and applies the transaction earlier than it
should. This no doubt has undesired effects, probably resulting in a use
after free.

Hopefully fixes the first part of #2207.

1 files changed, 3 insertions, 1 deletions

diff --git a/sway/desktop/transaction.c b/sway/desktop/transaction.c
index 7b670aec..b4d796cb 100644
--- a/sway/desktop/transaction.c
+++ b/sway/desktop/transaction.c
@@ -377,7 +377,9 @@ static void set_instructions_ready(struct sway_view *view, int index) {
         for (int i = 0; i <= index; ++i) {
                 struct sway_transaction_instruction *instruction =
                         view->swayc->instructions->items[i];
-                set_instruction_ready(instruction);
+                if (!instruction->ready) {
+                        set_instruction_ready(instruction);
+                }
         }
 }