Re: RANDSTRUCT structs need linux/compiler_types.h (Was: [nfsd4] potentially hardware breaking regression in 4.14-rc and 4.13.11)

[Kees Cook]

On Wed, Feb 21, 2018 at 2:19 PM, Maciej S. Szmigiero
<mail@xxxxxxxxxxxxxxxxxxxxx> wrote:
> One can see that offsets used to access various members of struct path are
> different, and also that the original file from step 3 contains an object
> named "__randomize_layout".
>
> This is caused by a fact that the current version of nfs4xdr.c includes
> linux/fs_struct.h as the very first included header which then includes
> linux/path.h as the very first included header, which then defines
> struct path, but without including any files on its own.
>
> This results in __randomize_layout tag at the end of struct path
> definition being treated as a variable name (since linux/compiler-gcc.h
> that defines it as a type attribute has not been included yet).

Oh, well done! That would explain the code offset I was seeing when
the plugin on, but no-op, since the variable would still exist.

I'll play with Linus's suggestion and see what we get.

Thanks!

-Kees

-- 
Kees Cook
Pixel Security