[Pvfs2-developers] Batch create in sys-symlink.sm

[Walter Ligon]

You are right.  Currently we aren't focusing on resource abuse issues, 
but obviously the guys are trying to think ahead, and in doing so should 
consider that point.

The only thing I have right now is that we have no way to know if a user 
is requesting excess dfiles when creating a file.  We do know he doesn't 
need them when creating other things.  We could implement a set of 
attributes that set limits on a user and check those as part of the 
process.  If we want to do that, then we need to have a serious talk 
about how to implement, how to manage it, what people outside would 
expect - like should it integrate into existing quota systems, etc.  I 
see that as a future task at the moment.

Walt

Rob Ross wrote:
> I'm not sure how important the bulk-create issue is either, but I 
> thought I'd bring up the file creation as a related place where a 
> malicious user could consume lots of resources quickly. Seems like if 
> we're going to try to address one then we need to try to address the other?
> 
> Rob
> 
> On Jun 25, 2009, at 11:04 AM, Walter Ligon wrote:
> 
>> up until now it has been the user's prerogative to create files with 
>> as many dfiles as he wants - I assume a user is limited to some max by 
>> the configuration (is he?) but that could be large - so he could 
>> allocate 100 dfiles and only use 2 (if he only uses 1 the stuffing 
>> will come into play).  I'm open to discussion of how to deal with that 
>> in terms of interface and such.  If we need that we can work on a way 
>> to do it.
>>
>> Over the last year I've found David & Nick to be very thorough in 
>> trying to design so that users can only do what they are supposed to 
>> do.  It may be that it really isn't that bid a deal if users can 
>> allocate extra object - as long as they can't link anything to them.  
>> I fully suspect that we can improve beyond the basic level of security 
>> we are working on now and we can discuss that.  What I'm saying is I'm 
>> not sure how important this bulk-create issue really is - but there 
>> are ways to deal with it.
>>
>> Walt
>>
>> Rob Ross wrote:
>>> On Jun 25, 2009, at 9:45 AM, Nicholas Mills wrote:
>>>> Rob -
>>>>
>>>> You're absolutely correct. The capabilities are trusted and can only 
>>>> come from servers. If a client gets a hold of one it's assumed that 
>>>> some server determined the client had a need for the capability. 
>>>> Servers are able to create capabilities for themselves that allow 
>>>> them to do anything.
>>>>
>>>> Everyone -
>>>>
>>>> Right now I haven't had a need to differentiate between client and 
>>>> server requests. However, in the case of batch create I'd really 
>>>> like to prevent a client from having access to this capability. For 
>>>> the moment the only client state machine to use batch create is 
>>>> sys-symlink, and even then the state machine only creates one handle.
>>> Walt suggested perhaps limiting clients to a single create by use of 
>>> some sort of differentiator in the capability. This would avoid the 
>>> need to change how PVFS is working today, but means you'd have to do 
>>> a little parameter checking; how awkward would that be? Seems to me 
>>> you might want to similarly be restricting the *types* of objects 
>>> that a client could create, if you're going to try to minimize the 
>>> potential damage from this particular call. Since clients would only 
>>> be using this to create a symlink object (if I understand the earlier 
>>> discussion correctly), you could limit clients to only creating 
>>> symlink objects and only one at a time.
>>> Otherwise a client might be able to use this facility to create a 
>>> metadata object, populate it with something that makes it look like 
>>> it should have permission to access the associated datafiles, and 
>>> then point at some datafiles it would like to access? I dunno the 
>>> bigger picture, so I don't know if you have already handled this 
>>> possibility in some other way...
>>> Ok, so all that leads me to agree that you don't ideally want clients 
>>> to be given permission to use this operation :).
>>>> Above all I want everyone to know that I'm very open to suggestion. 
>>>> Of course I realize that in the future new client state machines 
>>>> could make use of the batch create request. But for now, at least, 
>>>> only the servers have a legitimate need for this request.
>>> Now that I'm looking at this, why aren't you equally worried about a 
>>> user using the new create request and specifying some ridiculously 
>>> large num_dfiles_req? Doesn't that have the same problem with respect 
>>> to resource consumption?
>>> Rob