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From: Eric Blake <eblake@redhat.com>
Message-ID: <4dd4e70a-7129-722c-971a-1b9f8b9aa349@redhat.com>
Date: Mon, 3 Dec 2018 10:36:17 -0600
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Subject: Re: [Qemu-devel] QMP accepts double dict keys
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To: Max Reitz <mreitz@redhat.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Markus Armbruster <armbru@redhat.com>

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