Re: [Xen-devel] [PATCH v3 2/2] xsm: hide detailed Xen version from unprivileged guests

[Julien Grall <julien@xxxxxxx>]

On 22/01/2020 10:01, Sergey Dyasli wrote:
> On 20/01/2020 10:01, Jan Beulich wrote:
> > On 17.01.2020 17:44, Sergey Dyasli wrote:
> > > v2 --> v3:
> > > - Remove hvmloader filtering
> > Why? Seeing the prior discussion, how about adding XENVER_denied to
> > return the "denied" string, allowing components which want to filter
> > to know exactly what to look for? And then re-add the filtering you
> > had? (The help text of the config option should then perhaps be
> > extended to make very clear that the chosen string should not match
> > anything that could potentially be returned by any of the XENVER_
> > sub-ops.)
> I had the following reasoning:
>
> 1. Most real-world users would set CONFIG_XSM_DENIED_STRING="" anyway.
>
> 2. Filtering in DMI tables is not a complete solution, since denied
> string leaks elsewhere through the hypercall (PV guests, sysfs, driver
> logs) as Andrew has pointed out in the previous discussion.
>
> On the other hand, SMBios filtering slightly improves the situation for
> HVM domains, so I can return it if maintainers find it worthy.
While I am not a maintainer of this code, my concern is you impose the 
conversion from "denied" to "" to all the users (include those who wants 
to keep "denied").
If you were doing any filtering in hvmloader, then it would be best if 
this is configurable. But this is a bit pointless if you already allow 
the user to configure the string at the hypervisor level :).
Cheers,

--
Julien Grall

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