Re: [cxenstored] Potential bug in special watch event firing

[Juergen Gross <jgross@xxxxxxxx>]

Hi Raphael,

On 26.04.22 19:02, Raphael Ning wrote:
> While reading C xenstored code, I noticed that it may send special events like 
> @releaseDomain to (privileged) clients that only watch the root node (/). 
> That's probably not the intended behaviour.
>
> For example, when firing @releaseDomain, fire_watches() is called with exact == 
> false:
>
> https://github.com/xen-project/xen/blob/2419a159fb943c24a6f2439604b9fdb1478fcd08/tools/xenstore/xenstored_domain.c#L234
>
> As a result, it will check whether @releaseDomain is a child of the path being 
> watched:
>
> https://github.com/xen-project/xen/blob/2419a159fb943c24a6f2439604b9fdb1478fcd08/tools/xenstore/xenstored_watch.c#L195
>
> And when the parent path is /, is_child() unconditionally returns true:
>
> https://github.com/xen-project/xen/blob/2419a159fb943c24a6f2439604b9fdb1478fcd08/tools/xenstore/xenstored_watch.c#L66
>
> The xenstore documentation is not clear about whether @<wspecial> should be 
> considered children of /. But I find it counterintuitive that clients may be notified 
> about a special event without explicitly subscribing to it. Is it a bug?
I agree this is a bug.


Juergen

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