Re: [Xen-devel] [PATCH] domctl: relax getdomaininfo permissions

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.08.16 at 17:22, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 04/08/16 09:41, Jan Beulich wrote:
>> @@ -817,14 +816,22 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xe
>>  
>>      case XEN_DOMCTL_getdomaininfo:
>>      {
>> -        domid_t dom = op->domain;
>> -
>> -        rcu_read_lock(&domlist_read_lock);
>> +        domid_t dom = DOMID_INVALID;
>>  
>> -        for_each_domain ( d )
>> -            if ( d->domain_id >= dom )
>> +        if ( !d )
>> +        {
>> +            ret = -EINVAL;
>> +            if ( op->domain >= DOMID_FIRST_RESERVED )
>>                  break;
>>  
>> +            rcu_read_lock(&domlist_read_lock);
>> +
>> +            dom = op->domain;
>> +            for_each_domain ( d )
>> +                if ( d->domain_id >= dom )
>> +                    break;
>> +        }
>> +
>>          ret = -ESRCH;
>>          if ( d == NULL )
>>              goto getdomaininfo_out;
>> @@ -839,6 +846,9 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xe
>>          copyback = 1;
>>  
>>      getdomaininfo_out:
>> +        if ( dom == DOMID_INVALID )
>> +            break;
> 
> What is this hunk for?  If you fail the "op->domain >=
> DOMID_FIRST_RESERVED" check we break out of the entire
> XEN_DOMCTL_getdomaininfo case.

If we start out with a non-NULL d, we have to avoid the
rcu_read_unlock() as well as the setting of d to NULL at the
end.

Jan


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