Re: [PATCH v2 3/3] iotests: Add new nbd-robustness test

[Eric Blake <eblake@redhat.com>]

On Mon, Nov 09, 2026 at 08:36:22AM -0700, Stefan Hajnoczi wrote:
> On Sat, Nov 07, 2026 at 04:54:38PM -0600, Eric Blake wrote:
> > Convert the proof of concept test by Sunday Jiang into an iotest. I
> > tried to get libnbd to trigger the situation, but forcing a block
> > status command when no status has been initiated is not something that
> > libnbd is willing to do. So this results in a hard-coded sequence of
> > bytes sent over a raw socket.  Swapping the order with the previous
> > patch shows the assertion failure that was previously reachable.
> > 
> > Based-on: https://gitlab.com/qemu-project/qemu/-/work_items/4091
> > Signed-off-by: Eric Blake <eblake@redhat.com>
> > ---
> >  tests/qemu-iotests/tests/nbd-robustness     | 137 ++++++++++++++++++++
> >  tests/qemu-iotests/tests/nbd-robustness.out |   5 +
> >  2 files changed, 142 insertions(+)
> >  create mode 100755 tests/qemu-iotests/tests/nbd-robustness
> >  create mode 100644 tests/qemu-iotests/tests/nbd-robustness.out
> > 
> > diff --git a/tests/qemu-iotests/tests/nbd-robustness b/tests/qemu-iotests/tests/nbd-robustness
> > new file mode 100755
> > index 00000000000..602b7060854
> > --- /dev/null
> > +++ b/tests/qemu-iotests/tests/nbd-robustness
> > @@ -0,0 +1,137 @@
> > +#!/usr/bin/env python3
> > +# group: rw auto quick
> > +#
> > +# Test cases for NBD robustness against malicious clients
> > +#
> > +# Copyright (C) 2026 Red Hat, Inc.
> > +#
> > +# SPDX-License-Identifier: GPL-2.0-or-later
> > +
> > +import os
> > +from contextlib import contextmanager
> > +
> > +import iotests
> > +from iotests import qemu_img_create, qemu_io
> > +
> > +import socket
> > +import struct
> > +
> > +
> > +disk = os.path.join(iotests.test_dir, 'disk')
> > +size = '4M'
> > +nbd_sock = os.path.join(iotests.sock_dir, 'nbd_sock')
> > +nbd_uri = 'nbd+unix:///{}?socket=' + nbd_sock
> > +nbd: ModuleType
> 
> nbd is never used and ModuleType is in the types stdlib package, which
> is not included here. This looks like it can be removed.

Indeed, it was leftover copy-paste from nbd-commands when I was first
trying to use libnbd to drive the reproducer, before figuring out that
libnbd can't trigger it. Will fix.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization:  qemu.org | libguestfs.org