Re: [PATCH v4 33/39] x86: Prevent 32 bit operations for 64 bit shstk tasks

Andy Lutomirski
2022-12-03T22:50:17Z

On Fri, Dec 2, 2022 at 4:44 PM Rick Edgecombe
<rick.p.edgecombe@intel.com> wrote:
>

> So since 32 bit is not easy to support, and there are likely not many
> users. More cleanly don't support 32 bit signals in a 64 bit address
> space by not allowing 32 bit ABI signal handlers when shadow stack is
> enabled. Do this by clearing any 32 bit ABI signal handlers when shadow
> stack is enabled, and disallow any further 32 bit ABI signal handlers.
> Also, return an error code for the clone operations when in a 32 bit
> syscall.
>

This seems unfortunate. The result will be a highly incomprehensible
crash. Maybe instead deny enabling shadow stack in the first place?
Or at least pr_warn_once if anything gets flushed.