ofz#2287 check multiply

Change-Id: Ibc4c93ac1f5686a476b5e303347dc951daa58e33
Reviewed-on: https://gerrit.libreoffice.org/38909Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

vcl/headless/svpbmp.cxx

@@ -132,8 +132,10 @@ BitmapBuffer* ImplCreateDIB(
         pDIB->maPalette.SetEntryCount( nColors );
     }
 
-    const size_t size = pDIB->mnScanlineSize * pDIB->mnHeight;
-    if (size > SAL_MAX_INT32/2)
+    size_t size;
+    bFail = o3tl::checked_multiply<size_t>(pDIB->mnHeight, pDIB->mnScanlineSize, size);
+    SAL_WARN_IF(bFail, "vcl.gdi", "checked multiply failed");
+    if (bFail || size > SAL_MAX_INT32/2)
     {
         delete pDIB;
         return nullptr;