Re: [Xen-devel] [PATCH 2/2] xen/physmap: Do not permit a guest to populate PoD pages for itself

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 19.08.16 at 17:02, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 19/08/16 15:58, Jan Beulich wrote:
>>>>> On 19.08.16 at 16:12, <andrew.cooper3@xxxxxxxxxx> wrote:
>>> --- a/xen/common/memory.c
>>> +++ b/xen/common/memory.c
>>> @@ -903,7 +903,16 @@ long do_memory_op(unsigned long cmd, 
> XEN_GUEST_HANDLE_PARAM(void) arg)
>>>  
>>>          if ( op == XENMEM_populate_physmap
>>>               && (reservation.mem_flags & XENMEMF_populate_on_demand) )
>>> +        {
>>> +            /* Disallow populating PoD pages on oneself. */
>>> +            if ( d == curr_d )
>>> +            {
>>> +                rcu_unlock_domain(d);
>>> +                return start_extent;
>>> +            }
>>> +
>>>              args.memflags |= MEMF_populate_on_demand;
>>> +        }
>>>  
>>>          if ( xsm_memory_adjust_reservation(XSM_TARGET, curr_d, d) )
>>>          {
>> Considering the code continues
>>
>>             rcu_unlock_domain(d);
>>             return start_extent;
>>         }
>>
>>         switch ( op )
>>         {
>>         case XENMEM_increase_reservation:
>>             increase_reservation(&args);
>>             break;
>>         case XENMEM_decrease_reservation:
>>             decrease_reservation(&args);
>>             break;
>>         default: /* XENMEM_populate_physmap */
>>             populate_physmap(&args);
>>             break;
>>         }
>>
>> I think it is time to move this XENMEM_populate_physmap specific
>> code chunk into populate_physmap(), at once eliminating the need
>> for another not entirely trivial error exit path here.
> 
> Do you mean just my code addition, or the whole if condition?  The
> former is easy, but the latter is hard as reservation is specifically
> not passed into populate_physmap().

Oh, I didn't realize that - just your addition then.

Jan


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