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

Jiri Kosina
2018-01-11T09:54:55Z

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@kernel.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