On March 27, 2024 9:21:59 AM MDT, "Luck, Tony" <[email protected]> wrote: >This e-mail is to check you on whether that __randomize_layout can shuffle the >fields inside that nested union/structure. I tried some experiments, and in a >few kernel builds I saw the whole block move to different offsets, but the >order >of x86_vendor, x86, x86_model, and x86_reserved was preserved. Yes, this is an intentional behavior: __randomize_layout will only apply to the struct it is attached to, and is not enabled for any substructs (anonymous or otherwise). >But experiments aren't proof. Nor defense against future versions of >scripts/gcc-plugins/randomize_layout_plugin.c becoming smarter or >more aggressive about changing layout. The behavior is also supported natively by Clang -- neither implementation is likely to ever change its treatment of substructs as it would kind of cause chaos. So you're all good! :) -- Kees Cook
