linux-kernel - Re: [PATCH] m68k: Implement "current_stack

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Message-ID: <CAMuHMdU6msvi0j=mS28GFYbm+uMRk7PkYe+zOM4sDmOVxeibLQ@mail.gmail.com>
Date:   Thu, 24 Feb 2022 10:56:09 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     David Laight <David.Laight@...lab.com>,
        Kees Cook <keescook@...omium.org>
Cc:     linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>
Subject: Re: [PATCH] m68k: Implement "current_stack_pointer"

Hi David, Kees,

On Thu, Feb 24, 2022 at 10:54 AM David Laight <David.Laight@...lab.com> wrote:
> From: Geert Uytterhoeven <geert@...ux-m68k.org>
> > Sent: 24 February 2022 09:17
> >
> > On Thu, Feb 24, 2022 at 10:12 AM David Laight <David.Laight@...lab.com> wrote:
> > > From: Geert Uytterhoeven
> > > > Sent: 24 February 2022 08:59
> > > ...
> > > > > +register unsigned long current_stack_pointer __asm__("sp");
> > > >
> > > > I don't know what HARDENED_USERCOPY does, so I don't know if you need
> > > > "usp" (see rdusp()) or "sp"?
> > >
> > > HARDENED_USERCOPY significantly slows down some systems calls
> > > (especially things like sendmsg()) by trying to run-time verify
> > > that the kernel buffer doesn't overrun a stack frame or kmalloc()ed
> >
> > Kernel stack frame of user stack frame?
>
> Kernel, the kernel doesn't care if the user stack gets trashed.

OK.

Reviewed-by: Geert Uytterhoeven <geert@...ux-m68k.org>

Kees: Do you want me to queue this in the m68k for-v5.18 branch, or do
you want to take it yourself, together with the HARDENED_USERCOPY work?
In case of the latter:
Acked-by: Geert Uytterhoeven <geert@...ux-m68k.org>

Please let me know. Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds