Re: [Xen-devel] [PATCH] x86/emulate: Check current->arch.vm_event in hvmemul_virtual_to_linear()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.04.16 at 19:54, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
> On 04/07/16 20:27, Jan Beulich wrote:
>>>>> On 07.04.16 at 10:39, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>>> Theoretically it is possible for mem_access_emulate_each_rep to be
>>> true even when current->arch.vm_event == NULL, so add an extra
>>> check to hvmemul_virtual_to_linear().
>> 
>> Mind saying what those theoretical conditions are when this might
>> happen?
> 
> This could happen if someone were to call xc_monitor_emulate_each_rep(),
> but not xc_monitor_enable() (when current->arch.vm_event gets
> allocated), or after someone called both, but afterwards called
> xc_monitor_disable() (when current->arch.vm_event gets freed).

Then wouldn't the correct action be to fail
xc_monitor_emulate_each_rep() (i.e. whatever hypercall this
resolves to) when the monitor is not enabled? (You did already
clarify that the other variant isn't applicable)?

Jan


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