commit 0b290dd2171e745d94f48298cafb2327eb2de17c
author Miss Skeleton (bot) <31488909+miss-islington@users.noreply.github.com> Sun Oct 25 16:24:56 2020 -0700
committer GitHub <noreply@github.com> Sun Oct 25 16:24:56 2020 -0700
tree 9d0bb1f152397b70e2f1ddab56dcf9aa947f92c7
parent 83c86cf54b36a7325f615f5adf22b28e48f0e72d

bpo-42150: Avoid buffer overflow in the new parser (GH-22978)

(cherry picked from commit e68c67805e6a4c4ec80bea64be0e8373cc02d322)

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

Parser/pegen/pegen.c

diff --git a/Parser/pegen/pegen.c b/Parser/pegen/pegen.c
index 2c435fb..a7643fc 100644
--- a/Parser/pegen/pegen.c
+++ b/Parser/pegen/pegen.c
@@ -989,7 +989,8 @@
 
     /* Newlines are allowed if preceded by a line continuation character
        or if they appear inside a string. */
-    if (!cur || *(cur - 1) == '\\' || newline_in_string(p, cur)) {
+    if (!cur || (cur != p->tok->buf && *(cur - 1) == '\\')
+             || newline_in_string(p, cur)) {
         return 0;
     }
     char c = *cur;