Re: [Xen-users] Xen Security Advisory 240 (CVE-2017-15595) - Unlimited recursion in linear pagetable de-typing

[James Dingwall <james-xen@xxxxxxxxxxxxxx>]

On Thu, Nov 16, 2017 at 03:11:39PM +0100, Juergen Gross wrote:
> On 16/11/17 14:58, James Dingwall wrote:
> > On Wed, Nov 15, 2017 at 05:13:22PM +0000, Xen.org security team wrote:
> >> -----BEGIN PGP SIGNED MESSAGE-----
> >> Hash: SHA256
> >>
> >>             Xen Security Advisory CVE-2017-15595 / XSA-240
> >>                                version 5
> >>
> >>            Unlimited recursion in linear pagetable de-typing
> > <snip>
> >>
> >> c0c624f51fb1bd9e31a2c120343164d545ab6e709ed4bb9e5dd89b5c4c4e49f8  
> >> xsa240-4.8/0001-x86-limit-linear-page-table-use-to-a-single-level.patch
> >> 7e3c2c4a4d0ee0a29abaa7aceffbb774b1f92aa81dfa4c5d1c5c5156b6bb0a3a  
> >> xsa240-4.8/0002-x86-mm-Disable-PV-linear-pagetables-by-default.patch
> >> f174ee608a7f7f0601ae46edafbf443c90a87632609c1b4145fb0e2e5c4b1b51  
> >> xsa240-4.8/0003-x86-dont-wrongly-trigger-linear-page-table-assertion.patch
> > <snip>
> > 
> > I'm trying to apply patch 0003 to a 4.8.2 branch but it is rejected (patch 
> > --verbose -p1).  The hunk it is 
> > trying to remove does not exist in the stable-4.8 branch or at tag 
> > RELEASE-4.8.2.  Trying to find 
> > CONFIG_PV_LINEAR_PT in git does not show this in stable-4.8 or stable-4.9 
> > branches (but it is present in the 
> > staging branches.)  It looks like the patch issued for 4.6 would apply, is 
> > this satisfactory for 4.8.2?
> 
> What about applying above patches 0001 and 0002 first?

I have, this is all on top of a checkout of xen-4.8.2.  0001 and 0002 don't 
appear to have been changed, only 
0003 added.  e1fa1c6ee152105c9adf5fb5ff4507028a87d2a3 on staging-4.8 introduces 
the CONFIG_PV_LINEAR_PT option 
so the patch doesn't apply unless using code not on the stable-4.8 branch.  I 
think it is is small enough that I 
could modify it for 4.8.2 but I'd prefer not to get it wrong:)

Thanks,
James

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