Re: [Qemu-devel] QMP accepts double dict keys

[Eric Blake]

On 12/3/18 10:30 AM, Max Reitz wrote:
> Hi,
>
> QMP accepts double keys in dicts without complaining.  The value it is
> using is apparently the last one specified:
JSON says it is undefined what happens when a client passes double keys. 
 We are probably best off if we teach our parser to be strict and 
reject doubled keys in QMP as invalid.
Hmm - can a client abuse QMP with duplicate keys to cause qemu to leak 
memory?
> $ qemu-system-x86_64 -qmp stdio
> {"QMP": {"version": {"qemu": {"micro": 93, "minor": 0, "major": 3},
> "package": "v3.1.0-rc3-7-g87a45d86ed"}, "capabilities": []}}
> {'execute':'qmp_capabilities'}
> {"return": {}}
> {'execute':'blockdev-add','arguments':{'driver':'null-co',
>   'node-name':'foo','node-name':'bar'}}
> {"return": {}}
> {'execute':'query-named-block-nodes'}
> {"return": [{ [...] "node-name": "bar" [...] }]}
>
> Another test case is iotest 229 which specifies both mode=absolute-paths
> and mode=existing (it wants the latter).
>
> Max
--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org