[3.9] bpo-46110: Add a recursion check to avoid stack overflow in the PEG parser (GH-30177)

Co-authored-by: Batuhan Taskaya <isidentical@gmail.com>.
(cherry picked from commit e9898bf)

Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>

Author: pablogsal

Lib/test/test_syntax.py

@@ -1004,6 +1004,14 @@ def test_syntax_error_on_deeply_nested_blocks(self):
 """
         self._check_error(source, "too many statically nested blocks")
 
+    @support.cpython_only
+    def test_error_on_parser_stack_overflow(self):
+        source = "-" * 100000 + "4"
+        for mode in ["exec", "eval", "single"]:
+            with self.subTest(mode=mode):
+                with self.assertRaises(MemoryError):
+                    compile(source, "<string>", mode)
+
 
 def test_main():
     support.run_unittest(SyntaxTestCase)

Misc/NEWS.d/next/Core and Builtins/2021-12-18-02-37-07.bpo-46110.B6hAfu.rst

@@ -0,0 +1,2 @@
+Add a maximum recursion check to the PEG parser to avoid stack overflow.
+Patch by Pablo Galindo