Re: [Xen-devel] [PATCH V5 3/3] xen/vm_event: Deny register writes if refused by vm_event reply

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.07.15 at 15:45, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
> On 07/14/2015 03:35 PM, Jan Beulich wrote:
>>>>> On 13.07.15 at 19:14, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>>> --- a/xen/arch/x86/vm_event.c
>>> +++ b/xen/arch/x86/vm_event.c
>>> @@ -22,11 +22,19 @@
>>>  
>>>  #include <xen/sched.h>
>>>  #include <asm/hvm/hvm.h>
>>> +#include <asm/vm_event.h>
>>>  
>>>  int vm_event_init_domain(struct domain *d)
>>>  {
>>>      struct vcpu *v;
>>>  
>>> +    if ( !d->arch.event_write_data )
>>> +        d->arch.event_write_data = xzalloc_array(struct monitor_write_data,
>>> +                                                 d->max_vcpus);
>> 
>> Looking at this again I wonder why the data isn't being made part of
>> struct arch_vcpu's vm_event sub-structure. That would also address
>> the complaint I have here about this not being a guaranteed maximum
>> page size runtime allocation.
> 
> I think this is just how the initial suggestion was worded, I'll change it.

Right - after having sent the reply I started wondering whether
maybe I had asked for this. But if I did, then surely not with
xzalloc_array(), but vzalloc().

If you moved this into struct arch_vcpu (again), then its size would
likely call for the whole vm_event structure to become indirectly
accessed and allocated.

Jan


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