Paul Gofman : kernelbase: Fix string size variable overflow in GetModuleFileNameW().

[Alexandre Julliard]

Module: wine
Branch: master
Commit: 7c523f48677abb5d8cf7d2b2f1cff919e57c8e99
URL:    https://source.winehq.org/git/wine.git/?a=commit;h=7c523f48677abb5d8cf7d2b2f1cff919e57c8e99

Author: Paul Gofman <pgofman at codeweavers.com>
Date:   Mon Oct  4 12:21:10 2021 +0300

kernelbase: Fix string size variable overflow in GetModuleFileNameW().

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=51833
Signed-off-by: Paul Gofman <pgofman at codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard at winehq.org>

---

 dlls/kernel32/tests/module.c | 5 +++++
 dlls/kernelbase/loader.c     | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/dlls/kernel32/tests/module.c b/dlls/kernel32/tests/module.c
index 2487b9d65ab..60654754302 100644
--- a/dlls/kernel32/tests/module.c
+++ b/dlls/kernel32/tests/module.c
@@ -190,6 +190,11 @@ static void testGetModuleFileName(const char* name)
 
     ok(len1A / 2 == len2A,
        "Correct length in GetModuleFilenameA with buffer too small (%d/%d)\n", len1A / 2, len2A);
+
+    len1A = GetModuleFileNameA(hMod, bufA, 0x10000);
+    ok(len1A > 0, "Getting module filename for handle %p\n", hMod);
+    len1W = GetModuleFileNameW(hMod, bufW, 0x10000);
+    ok(len1W > 0, "Getting module filename for handle %p\n", hMod);
 }
 
 static void testGetModuleFileName_Wrong(void)
diff --git a/dlls/kernelbase/loader.c b/dlls/kernelbase/loader.c
index 145d721bc26..de9ff2ba1a5 100644
--- a/dlls/kernelbase/loader.c
+++ b/dlls/kernelbase/loader.c
@@ -311,7 +311,7 @@ DWORD WINAPI DECLSPEC_HOTPATCH GetModuleFileNameW( HMODULE module, LPWSTR filena
     }
 
     name.Buffer = filename;
-    name.MaximumLength = size * sizeof(WCHAR);
+    name.MaximumLength = min( size, UNICODE_STRING_MAX_CHARS ) * sizeof(WCHAR);
     status = LdrGetDllFullName( module, &name );
     if (!status || status == STATUS_BUFFER_TOO_SMALL) len = name.Length / sizeof(WCHAR);
     SetLastError( RtlNtStatusToDosError( status ));