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

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Message-ID: <20af3021fa4e9f1d9a322678b7ce1737d1931fee.camel@intel.com>
Date:   Sun, 4 Dec 2022 20:51:22 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "Lutomirski, Andy" <luto@...nel.org>
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Subject: Re: [PATCH v4 33/39] x86: Prevent 32 bit operations for 64 bit shstk
 tasks

On Sat, 2022-12-03 at 14:49 -0800, Andy Lutomirski wrote:
> On Fri, Dec 2, 2022 at 4:44 PM Rick Edgecombe
> <rick.p.edgecombe@...el.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.

Thanks for the suggestion! Denying seems much better, I'll change it.