From: Stan Ulbrych <stan@python.org>
Date: Mon, 6 Apr 2026 11:56:36 +0000 (+0100)
Subject:  gh-148157: Check for `_PyPegen_add_type_comment_to_arg` fail in `_PyPegen_name_defau... 
X-Git-Tag: v3.15.0a8~19
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=1795fccfbc7ccb89ead5c529b2f55f54622d1314;p=thirdparty%2FPython%2Fcpython.git

 gh-148157: Check for `_PyPegen_add_type_comment_to_arg` fail in `_PyPegen_name_default_pair` (#148158)
---

diff --git a/Lib/test/test_type_comments.py b/Lib/test/test_type_comments.py
index dd2e67841651..d827ac271085 100644
--- a/Lib/test/test_type_comments.py
+++ b/Lib/test/test_type_comments.py
@@ -398,6 +398,9 @@ class TypeCommentTests(unittest.TestCase):
         with self.assertRaises(UnicodeDecodeError):
             _testcapi.Py_CompileStringExFlags(
                 b"a=1 # type: \x80", "<test>", 256, flags)
+        with self.assertRaises(UnicodeDecodeError):
+            _testcapi.Py_CompileStringExFlags(
+                b"def a(f=8, #type: \x80\n\x80", "<test>", 256, flags)
 
     def test_func_type_input(self):
 
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-04-06-11-15-46.gh-issue-148157.JFnZDn.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-06-11-15-46.gh-issue-148157.JFnZDn.rst
new file mode 100644
index 000000000000..6565291eb998
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-06-11-15-46.gh-issue-148157.JFnZDn.rst
@@ -0,0 +1,2 @@
+Fix an unlikely crash when parsing an invalid type comments for function
+parameters. Found by OSS Fuzz in :oss-fuzz:`492782951`.
diff --git a/Parser/action_helpers.c b/Parser/action_helpers.c
index 1f5b6220ba1b..5e52bb838719 100644
--- a/Parser/action_helpers.c
+++ b/Parser/action_helpers.c
@@ -435,6 +435,9 @@ _PyPegen_name_default_pair(Parser *p, arg_ty arg, expr_ty value, Token *tc)
         return NULL;
     }
     a->arg = _PyPegen_add_type_comment_to_arg(p, arg, tc);
+    if (!a->arg) {
+        return NULL;
+    }
     a->value = value;
     return a;
 }