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Re: [Xen-devel] [PATCH 2/3] x86: relax LDT check in arch_set_info_guest()

On 06.12.2019 11:33, Andrew Cooper wrote:
> On 06/12/2019 10:14, Jan Beulich wrote:
>> It is wrong for us to check the base address when there's no LDT in the
>> first place.
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> ---
>> TBD: I also wonder whether we wouldn't better set v->arch.pv.ldt_base to
>>      zero for an empty LDT, just like do_mmuext_op() does.
> My query with patch 1 is also applicable here.

As is my answer there.

> As for setting it to zero, we should use something non-canonical
> instead.  Doing so would have saved us from XSA-298, which was only a
> problem in guests because the base falling to 0.

I can certainly do so (in do_mmuext_op() then as well).


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