shlwapi: return NULL from StrStr if needle is longer than haystack

[Mark Harmstone]

Hi,

This is needed to fix a potential buffer overrun in real_length in 
libs/wine/sortkey.c.

Thanks

---
diff --git a/dlls/shlwapi/string.c b/dlls/shlwapi/string.c
index b4b5b8a..a160021 100644
--- a/dlls/shlwapi/string.c
+++ b/dlls/shlwapi/string.c
@@ -526,6 +526,7 @@ static LPSTR SHLWAPI_StrStrHelperA(LPCSTR lpszStr, 
LPCSTR lpszSearch,
      return NULL;

    iLen = strlen(lpszSearch);
+  if (iLen > strlen(lpszStr)) return NULL;

    while (*lpszStr)
    {
@@ -677,6 +678,7 @@ LPWSTR WINAPI StrStrIW(LPCWSTR lpszStr, LPCWSTR 
lpszSearch)
      return NULL;

    iLen = strlenW(lpszSearch);
+  if (iLen > strlenW(lpszStr)) return NULL;

    while (*lpszStr)
    {