Re: [Qemu-devel] [PATCH v2] qapi: fix memory leak in QmpOutputVisitor

[Eric Blake <eblake@redhat.com>]

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On 10/21/2016 10:39 AM, Eric Blake wrote:
> On 10/21/2016 09:01 AM, Markus Armbruster wrote:
>> Pino Toscano <ptoscano@redhat.com> writes:
>>
>>> qmp_output_start_struct() and qmp_output_start_list() create a new
>>> QObject (QDict, QList) and push it to the stack of the QmpOutputVisitor,
>>> where it is saved as 'value'.  When freeing the iterator in
>>> qmp_output_free(), these values are never freed properly.
>>>
>>> The simple solution is to qobject_decref() them.
>>>
>>> Signed-off-by: Pino Toscano <ptoscano@redhat.com>

>>
>> Hmm.  The patch looks correct, even though it adds a decref very similar
>> to the one deleted by commit f24582d "qapi: fix double free in
>> qmp_output_visitor_cleanup()".
> 

In fact, applying this patch regresses to the very state that f24582d
tried to prevent.  However, I'm unable to see a difference in valgrind
on tests/test-qmp-output-visitor either with or without this patch,
which sadly means our testsuite is not actually testing this scenario.

>> Should this go into -stable?
> 
> I'm still not convinced this patch makes sense.

NACK.

As mentioned in the v1 thread, the leak that Pino was seeing is fixed by
http://lists.nongnu.org/archive/html/qemu-devel/2016-10/msg04023.html
I don't think we don't want this patch.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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