Re: [Qemu-devel] [PULL v2 18/32] qmp: Don't let JSON errors jump the queue

[Markus Armbruster <armbru@redhat.com>]

Kevin Wolf <kwolf@redhat.com> writes:

> Am 10.07.2018 um 16:02 hat Marc-André Lureau geschrieben:
>> Hi
>> 
>> On Tue, Jul 10, 2018 at 3:20 PM, Kevin Wolf <kwolf@redhat.com> wrote:
>> > Am 03.07.2018 um 23:35 hat Markus Armbruster geschrieben:
>> >> handle_qmp_command() reports JSON syntax errors right away.  This is
>> >> wrong when OOB is enabled, because the errors can "jump the queue"
>> >> then.
>> >>
>> >> The previous commit fixed the same bug for semantic errors, by
>> >> delaying the checking until dispatch.  We can't delay the checking, so
>> >> delay the reporting.
>> >>
>> >> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>> >> Reviewed-by: Eric Blake <eblake@redhat.com>
>> >> Message-Id: <20180703085358.13941-19-armbru@redhat.com>
>> >
>> > I'm observing a qemu crash in qemu-iotests 153 (which does however not
>> > seem to make the test case fail). git bisect points me to this patch.
>> >
>> > I'm getting output like this:
>> >
>> > *** Error in `/home/kwolf/source/qemu/tests/qemu-iotests/qemu': free(): invalid pointer: 0x0000555f7870f7e0 ***
>> > ======= Backtrace: =========
>> > /lib64/libc.so.6(+0x7cbac)[0x7fa9b29a2bac]
>> > /lib64/libc.so.6(+0x87a59)[0x7fa9b29ada59]
>> > /lib64/libc.so.6(cfree+0x16e)[0x7fa9b29b33be]
>> > /lib64/libglib-2.0.so.0(g_free+0xe)[0x7fa9ce462b4e]
>> > /home/kwolf/source/qemu/tests/qemu-iotests/qemu(+0x6eb9dc)[0x555f76f489dc]
>> > /home/kwolf/source/qemu/tests/qemu-iotests/qemu(+0x30ae4b)[0x555f76b67e4b]
>> > /home/kwolf/source/qemu/tests/qemu-iotests/qemu(+0x311558)[0x555f76b6e558]
>> > /home/kwolf/source/qemu/tests/qemu-iotests/qemu(+0x6e2d4e)[0x555f76f3fd4e]
>> > /home/kwolf/source/qemu/tests/qemu-iotests/qemu(+0x6e5fa0)[0x555f76f42fa0]
>> > /home/kwolf/source/qemu/tests/qemu-iotests/qemu(+0x6e2c2e)[0x555f76f3fc2e]
>> > /lib64/libglib-2.0.so.0(g_main_context_dispatch+0x157)[0x7fa9ce45d257]
>> > /home/kwolf/source/qemu/tests/qemu-iotests/qemu(+0x6e526e)[0x555f76f4226e]
>> > /home/kwolf/source/qemu/tests/qemu-iotests/qemu(+0x42349e)[0x555f76c8049e]
>> > /home/kwolf/source/qemu/tests/qemu-iotests/qemu(+0x2c27ef)[0x555f76b1f7ef]
>> > /lib64/libc.so.6(__libc_start_main+0xea)[0x7fa9b294688a]
>> > /home/kwolf/source/qemu/tests/qemu-iotests/qemu(+0x2c5b8a)[0x555f76b22b8a]
>> >
>> > Interestingly, this doesn't want to produce a core dump for me, so no
>> > backtrace with usable function names here. But I assume that you can
>> > easily reproduce this yourself.
>> >
>> 
>> Looks like the double-free regression, you could try: "[PATCH]
>> monitor: fix double-free of request error"
>
> Thanks, that does fix it. Looks like it missed -rc0, though?

Yes.  I'll work on a pull request for -rc1.