linux-hardening - RE: [PATCH] m68k: Implement "current_stack

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Message-ID: <95b9c3e8227a4892b26cc0384d1782c2@AcuMS.aculab.com>
Date:   Thu, 24 Feb 2022 09:54:04 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Geert Uytterhoeven' <geert@...ux-m68k.org>
CC:     Kees Cook <keescook@...omium.org>,
        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"

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.

	David

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