On 19.02.2026 00:04, Jason Andryuk wrote:
> On 2026-02-18 14:08, Daniel P. Smith wrote:
>> --- a/xen/common/domain.c
>> +++ b/xen/common/domain.c
>> @@ -210,7 +210,7 @@ static void set_domain_state_info(struct
>> xen_domctl_get_domain_state *info,
>> int get_domain_state(struct xen_domctl_get_domain_state *info, struct
>> domain *d,
>> domid_t *domid)
>> {
>> - unsigned int dom;
>> + unsigned int dom = -1;
>> int rc = -ENOENT;
>> struct domain *hdl;
>>
>> @@ -219,6 +219,10 @@ int get_domain_state(struct xen_domctl_get_domain_state
>> *info, struct domain *d,
>>
>> if ( d )
>> {
>> + rc = xsm_get_domain_state(XSM_XS_PRIV, d);
>> + if ( rc )
>> + return rc;
>> +
>> set_domain_state_info(info, d);
>>
>> return 0;
>> @@ -238,28 +242,39 @@ int get_domain_state(struct
>> xen_domctl_get_domain_state *info, struct domain *d,
>
> Between the two hunks is this:
>
> hdl = lock_dom_exc_handler();
>
> /*
> * Only domain registered for VIRQ_DOM_EXC event is allowed to query
> * domains having changed state.
> */
> if ( current->domain != hdl )
> {
> rc = -EACCES;
> goto out;
> }
>
> So it is only the domain with VIRQ_DOM_EXC that can enter the while loop:
>
>>
>> while ( dom_state_changed )
>> {
>> - dom = find_first_bit(dom_state_changed, DOMID_MASK + 1);
>> + dom = find_next_bit(dom_state_changed, DOMID_MASK + 1, dom + 1);
>> if ( dom >= DOMID_FIRST_RESERVED )
>> break;
>> +
>> + d = rcu_lock_domain_by_id(dom);
>> + if ( d && xsm_get_domain_state(XSM_XS_PRIV, d) )
>
> ... if the VIRQ_DOM_EXC owner is denied for domain d ...
>
>> + {
>> + rcu_unlock_domain(d);
>> + d = NULL;
>> + continue;
>
> ... the caller would continue ...
>
>> + }
>> +
>> if ( test_and_clear_bit(dom, dom_state_changed) )
>
> ... and this bit would never be cleared. Should the VIRQ_DOM_EXC owner
> always get to clear the bit even if it cannot see the result?
I don't think so, no. Whenever a legitimate consumer occurs (the owner of
VIRQ_DOM_EXC can change, after all), it'll then consume the bits as needed.
More generally, I think we're better off not making the code here depend
too much on that special VIRQ_DOM_EXC property.
Jan
