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Re: [PATCH v6 00/11] Add support for eXclusive Page Frame Ownership

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Hi Yisheng,

On Mon, Sep 11, 2017 at 06:34:45PM +0800, Yisheng Xie wrote:
> Hi Tycho ,
> 
> On 2017/9/8 1:35, Tycho Andersen wrote:
> > Hi all,
> > 
> > Here is v6 of the XPFO set; see v5 discussion here:
> > https://lkml.org/lkml/2017/8/9/803
> > 
> > Changelogs are in the individual patch notes, but the highlights are:
> > * add primitives for ensuring memory areas are mapped (although these are quite
> >   ugly, using stack allocation; I'm open to better suggestions)
> > * instead of not flushing caches, re-map pages using the above
> > * TLB flushing is much more correct (i.e. we're always flushing everything
> >   everywhere). I suspect we may be able to back this off in some cases, but I'm
> >   still trying to collect performance numbers to prove this is worth doing.
> > 
> > I have no TODOs left for this set myself, other than fixing whatever review
> > feedback people have. Thoughts and testing welcome!
> 
> According to the paper of Vasileios P. Kemerlis et al, the mainline kernel
> will not set the Pro. of physmap(direct map area) to RW(X), so do we really
> need XPFO to protect from ret2dir attack?

I guess you're talking about section 4.3? They mention that that x86
only gets rw, but that aarch64 is rwx still.

But in either case this still provides access protection, similar to
SMAP. Also, if I understand things correctly the protections are
unmanaged, so a page that had the +x bit set at some point, it could
be used for ret2dir.

Cheers,

Tycho

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[PATCH v6 00/11] Add support for eXclusive Page Frame Ownership Tycho Andersen <tycho@docker.com> - 2017-09-07 19:40 +0200
  [PATCH v6 05/11] arm64/mm: Add support for XPFO Tycho Andersen <tycho@docker.com> - 2017-09-07 19:40 +0200
    Re: [PATCH v6 05/11] arm64/mm: Add support for XPFO Christoph Hellwig <hch@infradead.org> - 2017-09-08 10:00 +0200
      Re: [PATCH v6 05/11] arm64/mm: Add support for XPFO Tycho Andersen <tycho@docker.com> - 2017-09-08 19:30 +0200
        Re: [PATCH v6 05/11] arm64/mm: Add support for XPFO Julien Grall <julien.grall@arm.com> - 2017-09-14 12:50 +0200
          Re: [PATCH v6 05/11] arm64/mm: Add support for XPFO Juergen Gross <jgross@suse.com> - 2017-09-14 13:40 +0200
    Re: [kernel-hardening] [PATCH v6 05/11] arm64/mm: Add support for  XPFO Mark Rutland <mark.rutland@arm.com> - 2017-09-14 20:30 +0200
      Re: [kernel-hardening] [PATCH v6 05/11] arm64/mm: Add support for  XPFO Tycho Andersen <tycho@docker.com> - 2017-09-18 23:30 +0200
  [PATCH v6 01/11] mm: add MAP_HUGETLB support to vm_mmap Tycho Andersen <tycho@docker.com> - 2017-09-07 19:40 +0200
    Re: [PATCH v6 01/11] mm: add MAP_HUGETLB support to vm_mmap Christoph Hellwig <hch@infradead.org> - 2017-09-08 09:50 +0200
  [PATCH v6 02/11] x86: always set IF before oopsing from page fault Tycho Andersen <tycho@docker.com> - 2017-09-07 19:40 +0200
  Re: [PATCH v6 00/11] Add support for eXclusive Page Frame Ownership Yisheng Xie <xieyisheng1@huawei.com> - 2017-09-11 12:40 +0200
    Re: [PATCH v6 00/11] Add support for eXclusive Page Frame Ownership Tycho Andersen <tycho@docker.com> - 2017-09-11 17:10 +0200
      Re: [PATCH v6 00/11] Add support for eXclusive Page Frame Ownership Yisheng Xie <xieyisheng1@huawei.com> - 2017-09-12 09:10 +0200
        Re: [PATCH v6 00/11] Add support for eXclusive Page Frame Ownership Juerg Haefliger <juerg.haefliger@canonical.com> - 2017-09-12 09:50 +0200
          Re: [PATCH v6 00/11] Add support for eXclusive Page Frame Ownership Yisheng Xie <xieyisheng1@huawei.com> - 2017-09-12 10:20 +0200

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