Re: [Xen-devel] [hypervisor deadlock] Re: [PATCH v9 for Xen 4.7 1/4] xen: enable per-VCPU parameter for RTDS

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 04/04/16 16:58, Chong Li wrote:
> On Mon, Apr 4, 2016 at 10:14 AM, Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 01/04/16 05:59, Chong Li wrote:
>>> diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
>>> index 305889a..e5d15d8 100644
>>> --- a/xen/common/sched_credit.c
>>> +++ b/xen/common/sched_credit.c
>>> @@ -1080,15 +1080,13 @@ csched_dom_cntl(
>>>       * lock. Runq lock not needed anywhere in here. */
>>>      spin_lock_irqsave(&prv->lock, flags);
>>>
>>> -    if ( op->cmd == XEN_DOMCTL_SCHEDOP_getinfo )
>>> +    switch ( op->cmd )
>>>      {
>>> +    case XEN_DOMCTL_SCHEDOP_getinfo:
>>>          op->u.credit.weight = sdom->weight;
>>>          op->u.credit.cap = sdom->cap;
>>> -    }
>>> -    else
>>> -    {
>>> -        ASSERT(op->cmd == XEN_DOMCTL_SCHEDOP_putinfo);
>>> -
>>> +        break;
>>> +    case XEN_DOMCTL_SCHEDOP_putinfo:
>>>          if ( op->u.credit.weight != 0 )
>>>          {
>>>              if ( !list_empty(&sdom->active_sdom_elem) )
>>> @@ -1101,7 +1099,9 @@ csched_dom_cntl(
>>>
>>>          if ( op->u.credit.cap != (uint16_t)~0U )
>>>              sdom->cap = op->u.credit.cap;
>>> -
>>> +        break;
>>> +    default:
>>> +        return -EINVAL;
>>
>> This path returns without unlocking prv->lock.
>>
>>>      }
>>>
>>>      spin_unlock_irqrestore(&prv->lock, flags);
>>> diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
>>> index 7ddad38..d48ed5a 100644
>>> --- a/xen/common/sched_credit2.c
>>> +++ b/xen/common/sched_credit2.c
>>> @@ -1421,14 +1421,12 @@ csched2_dom_cntl(
>>>       * runq lock to update csvcs. */
>>>      spin_lock_irqsave(&prv->lock, flags);
>>>
>>> -    if ( op->cmd == XEN_DOMCTL_SCHEDOP_getinfo )
>>> +    switch ( op->cmd )
>>>      {
>>> +    case XEN_DOMCTL_SCHEDOP_getinfo:
>>>          op->u.credit2.weight = sdom->weight;
>>> -    }
>>> -    else
>>> -    {
>>> -        ASSERT(op->cmd == XEN_DOMCTL_SCHEDOP_putinfo);
>>> -
>>> +        break;
>>> +    case XEN_DOMCTL_SCHEDOP_putinfo:
>>>          if ( op->u.credit2.weight != 0 )
>>>          {
>>>              struct vcpu *v;
>>> @@ -1457,6 +1455,9 @@ csched2_dom_cntl(
>>>                  vcpu_schedule_unlock(lock, svc->vcpu);
>>>              }
>>>          }
>>> +        break;
>>> +    default:
>>> +        return -EINVAL;
>>
>> As does this.
>>
>> Please submit a bugfix ASAP.  This will become a security vulnerability
>> if Xen 4.7 is shipped without it being fixed.
>>
>>>      }
>>>
>>>      spin_unlock_irqrestore(&prv->lock, flags);
>>
> Thanks for pointing this out.
> 
> Dario, do you want to include this bugfix in your cleanup patch, or
> let me submit this?

If you're around and can test it, it's probably better if you can send a
patch right a way.

Thanks,
 -George


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