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

[Kevin Wolf]

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 <address@hidden>
> Reviewed-by: Eric Blake <address@hidden>
> Message-Id: <address@hidden>

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.

Kevin