fix timing issue

Before setting `@lock_file`, remote client can send stop request to the parent process and it can cause data race issue.
ruby · Sep 16, 2022 · 19b4dde · 19b4dde
1 parent 2cb4448
commit 19b4dde
Showing 1 changed file with 5 additions and 3 deletions.
diff --git a/lib/debug/session.rb b/lib/debug/session.rb
@@ -1893,9 +1893,11 @@ def multi_process!
 
     def after_fork child: true
       if child || !@lock_file
-        @m = Mutex.new
-        @lock_level = 0
-        @lock_file = open(@lock_tempfile.path, 'w')
+        @m = Mutex.new unless @m
+        @m.synchronize do
+          @lock_level = 0
+          @lock_file = open(@lock_tempfile.path, 'w')
+        end
       end
     end