linux-kernel - Re: [GIT PULL] x86/urgent for v5.11-rc7

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 8 Feb 2021 11:33:30 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Dave Hansen <dave.hansen@...el.com>, Borislav Petkov <bp@...e.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>, x86-ml <x86@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] x86/urgent for v5.11-rc7

On Sun, Feb 07, 2021 at 10:31:32AM -0800, Andy Lutomirski wrote:
> 
> > On Feb 7, 2021, at 10:19 AM, Dave Hansen <dave.hansen@...el.com> wrote:
> > 
> > On 2/7/21 9:58 AM, Borislav Petkov wrote:
> >>> On Sun, Feb 07, 2021 at 09:49:18AM -0800, Linus Torvalds wrote:
> >>> On Sun, Feb 7, 2021 at 2:40 AM Borislav Petkov <bp@...e.de> wrote:
> >>>> - Disable CET instrumentation in the kernel so that gcc doesn't add
> >>>> ENDBR64 to kernel code and thus confuse tracing.
> >>> So this is clearly the right thing to do for now, but I wonder if
> >>> people have a plan for actually enabling CET and endbr at cpl0 at some
> >>> point?
> >> It probably is an item on some Intel manager's to-enable list. So far,
> >> the CET enablement concentrates only on userspace but dhansen might know
> >> more about future plans. CCed.
> > 
> > It's definitely on our radar to look at after CET userspace.
> > 
> > The only question for me is whether it will be worth doing with the
> > exiting kernel entry/exit architecture.
> 
> I assume you mean: is anyone sufficiently inspired to try to handle
> NMI correctly?  I have a whole pile of nacks saved up for incorrect
> implementations, although I will try to wrap them in polite
> explanations of precisely what is wrong :)

Yeah, the IST stack recursion possibilities are 'fun'. But IIRC CET-SS
has far more problems than just NMI. It will also run into all the ROP
tricks we pull for return tracing, CALL emulation and other lovely
things.