From 940bbd2e02e1e8112e0284655c9bf06ef7d4ab7e Mon Sep 17 00:00:00 2001
From: Thamatip Chitpong <tangaming123456@outlook.com>
Date: Mon, 6 Feb 2023 23:43:45 +0700
Subject: [PATCH] [WINMM] Fixed boundary condition in mmioOpen file name
 parsing

Wine commit: 4431c32c91206040d59d3eb82a971245594d1243

author: Alexander Puzankov <alxpnv@gmail.com>
Sun, 5 Dec 2010 14:24:59 +0000 (17:24 +0300)

committer: Alexandre Julliard <julliard@winehq.org>
Sun, 5 Dec 2010 15:44:28 +0000 (16:44 +0100)
---
 dll/win32/winmm/mmio.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/dll/win32/winmm/mmio.c b/dll/win32/winmm/mmio.c
index 899b990d994..a0043d6627e 100644
--- a/dll/win32/winmm/mmio.c
+++ b/dll/win32/winmm/mmio.c
@@ -385,13 +385,13 @@ static FOURCC MMIO_ParseExtA(LPCSTR szFileName)
     } else {
         /* Find the first '.' before '+' */
         extStart = extEnd - 1;
-        while (*extStart != '.') {
-            if (extStart == szFileName) {
-                ERR("No extension in szFileName: %s\n", debugstr_a(szFileName));
-                return ret;
-            }
+        while (extStart >= szFileName && *extStart != '.') {
             extStart--;
         }
+        if (extStart < szFileName) {
+            ERR("No extension in szFileName: %s\n", debugstr_a(szFileName));
+            return ret;
+        }
     }
 
     if (extEnd - extStart - 1 > 4)