linux-kernel - Re: [PATCH 00/18] prevent bounds-check bypass via speculative execution

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Date:   Thu, 11 Jan 2018 10:54:55 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
cc:     Dan Williams <dan.j.williams@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Alan Cox <alan.cox@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Will Deacon <will.deacon@....com>,
        Solomon Peachy <pizza@...ftnet.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Christian Lamparter <chunkeey@...glemail.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        linux-arch@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        linux-scsi <linux-scsi@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>, X86 ML <x86@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Zhang Rui <rui.zhang@...el.com>,
        "Linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>, Jan Kara <jack@...e.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>, qla2xxx-upstream@...gic.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Alan Cox <alan@...ux.intel.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        linux-wireless@...r.kernel.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Netdev <netdev@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: Re: [PATCH 00/18] prevent bounds-check bypass via speculative
 execution

On Tue, 9 Jan 2018, Josh Poimboeuf wrote:

> On Tue, Jan 09, 2018 at 11:44:05AM -0800, Dan Williams wrote:
> > On Tue, Jan 9, 2018 at 11:34 AM, Jiri Kosina <jikos@...nel.org> wrote:
> > > On Fri, 5 Jan 2018, Dan Williams wrote:
> > >
> > > [ ... snip ... ]
> > >> Andi Kleen (1):
> > >>       x86, barrier: stop speculation for failed access_ok
> > >>
> > >> Dan Williams (13):
> > >>       x86: implement nospec_barrier()
> > >>       [media] uvcvideo: prevent bounds-check bypass via speculative execution
> > >>       carl9170: prevent bounds-check bypass via speculative execution
> > >>       p54: prevent bounds-check bypass via speculative execution
> > >>       qla2xxx: prevent bounds-check bypass via speculative execution
> > >>       cw1200: prevent bounds-check bypass via speculative execution
> > >>       Thermal/int340x: prevent bounds-check bypass via speculative execution
> > >>       ipv6: prevent bounds-check bypass via speculative execution
> > >>       ipv4: prevent bounds-check bypass via speculative execution
> > >>       vfs, fdtable: prevent bounds-check bypass via speculative execution
> > >>       net: mpls: prevent bounds-check bypass via speculative execution
> > >>       udf: prevent bounds-check bypass via speculative execution
> > >>       userns: prevent bounds-check bypass via speculative execution
> > >>
> > >> Mark Rutland (4):
> > >>       asm-generic/barrier: add generic nospec helpers
> > >>       Documentation: document nospec helpers
> > >>       arm64: implement nospec_ptr()
> > >>       arm: implement nospec_ptr()
> > >
> > > So considering the recent publication of [1], how come we all of a sudden
> > > don't need the barriers in ___bpf_prog_run(), namely for LD_IMM_DW and
> > > LDX_MEM_##SIZEOP, and something comparable for eBPF JIT?
> > >
> > > Is this going to be handled in eBPF in some other way?
> > >
> > > Without that in place, and considering Jann Horn's paper, it would seem
> > > like PTI doesn't really lock it down fully, right?
> > 
> > Here is the latest (v3) bpf fix:
> > 
> > https://patchwork.ozlabs.org/patch/856645/
> > 
> > I currently have v2 on my 'nospec' branch and will move that to v3 for
> > the next update, unless it goes upstream before then.

Daniel, I guess you're planning to send this still for 4.15?

> That patch seems specific to CONFIG_BPF_SYSCALL.  Is the bpf() syscall
> the only attack vector?  Or are there other ways to run bpf programs
> that we should be worried about?

Seems like Alexei is probably the only person in the whole universe who 
isn't CCed here ... let's fix that.

Thanks,

-- 
Jiri Kosina
SUSE Labs