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Re: [PATCH v3] 9pfs: deprecate 'proxy' backend
From: |
Christian Schoenebeck |
Subject: |
Re: [PATCH v3] 9pfs: deprecate 'proxy' backend |
Date: |
Wed, 21 Jun 2023 15:32:39 +0200 |
On Thursday, June 15, 2023 11:35:05 AM CEST Christian Schoenebeck wrote:
> On Saturday, June 10, 2023 3:39:44 PM CEST Christian Schoenebeck wrote:
> > As recent CVE-2023-2861 once again showed, the 9p 'proxy' fs driver is in
> > bad shape. Using the 'proxy' backend was already discouraged for safety
> > reasons before and we recommended to use the 'local' backend instead,
> > but now it is time to officially deprecate the 'proxy' backend.
> >
> > Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Ping
> > ---
> > v2 -> v3:
> > * Fix copy wasted typo (-> 'backend').
> >
> > MAINTAINERS | 7 +++++++
> > docs/about/deprecated.rst | 17 +++++++++++++++++
> > docs/tools/virtfs-proxy-helper.rst | 3 +++
> > fsdev/qemu-fsdev.c | 5 +++++
> > fsdev/virtfs-proxy-helper.c | 5 +++++
> > hw/9pfs/9p-proxy.c | 5 +++++
> > hw/9pfs/9p-proxy.h | 5 +++++
> > meson.build | 2 +-
> > qemu-options.hx | 6 +++++-
> > softmmu/vl.c | 5 +++++
> > 10 files changed, 58 insertions(+), 2 deletions(-)
>
> Or would it be better to split this up, e.g. into 3 separate patches (runtime
> messages, docs, MAINTAINERS)?
>
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 436b3f0afe..185d694b2e 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -2118,13 +2118,20 @@ S: Odd Fixes
> > W: https://wiki.qemu.org/Documentation/9p
> > F: hw/9pfs/
> > X: hw/9pfs/xen-9p*
> > +X: hw/9pfs/9p-proxy*
> > F: fsdev/
> > +X: fsdev/virtfs-proxy-helper.c
> > F: docs/tools/virtfs-proxy-helper.rst
>
> I missed virtfs-proxy-helper.rst here. That should be moved to the new 'proxy'
> section below as well.
>
> > F: tests/qtest/virtio-9p-test.c
> > F: tests/qtest/libqos/virtio-9p*
> > T: git https://gitlab.com/gkurz/qemu.git 9p-next
> > T: git https://github.com/cschoenebeck/qemu.git 9p.next
> >
> > +virtio-9p-proxy
> > +F: hw/9pfs/9p-proxy*
> > +F: fsdev/virtfs-proxy-helper.c
> > +S: Obsolete
> > +
> > virtio-blk
> > M: Stefan Hajnoczi <stefanha@redhat.com>
> > L: qemu-block@nongnu.org
> > diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
> > index 0743459862..9b2c780365 100644
> > --- a/docs/about/deprecated.rst
> > +++ b/docs/about/deprecated.rst
> > @@ -343,6 +343,23 @@ the addition of volatile memory support, it is now
> > necessary to distinguish
> > between persistent and volatile memory backends. As such, memdev is
> > deprecated
> > in favor of persistent-memdev.
> >
> > +``-fsdev proxy`` and ``-virtfs proxy`` (since 8.1)
> > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > +
> > +The 9p ``proxy`` filesystem backend driver has been deprecated and will be
> > +removed in a future version of QEMU. Please use ``-fsdev local`` or
> > +``-virtfs local`` for using the ``local`` 9p filesystem backend instead.
> > +
> > +The 9p ``proxy`` backend was originally developed as an alternative to the
> > 9p
> > +``local`` backend. The idea was to enhance security by dispatching actual
> > low
> > +level filesystem operations from 9p server (QEMU process) over to a
> > separate
> > +process (the virtfs-proxy-helper binary). However this alternative never
> > gained
> > +momentum. The proxy backend is much slower than the local backend, hasn't
> > seen
> > +any development in years, and showed to be less secure, especially due to
> > the
> > +fact that its helper daemon must be run as root, whereas with the local
> > backend
> > +QEMU is typically run as unprivileged user and allows to tighten behaviour
> > by
> > +mapping permissions et al.
> > +
> >
> > Block device options
> > ''''''''''''''''''''
> > diff --git a/docs/tools/virtfs-proxy-helper.rst
> > b/docs/tools/virtfs-proxy-helper.rst
> > index 6cdeedf8e9..bd310ebb07 100644
> > --- a/docs/tools/virtfs-proxy-helper.rst
> > +++ b/docs/tools/virtfs-proxy-helper.rst
> > @@ -9,6 +9,9 @@ Synopsis
> > Description
> > -----------
> >
> > +NOTE: The 9p 'proxy' backend is deprecated (since QEMU 8.1) and will be
> > +removed, along with this daemon, in a future version of QEMU!
> > +
> > Pass-through security model in QEMU 9p server needs root privilege to do
> > few file operations (like chown, chmod to any mode/uid:gid). There are two
> > issues in pass-through security model:
> > diff --git a/fsdev/qemu-fsdev.c b/fsdev/qemu-fsdev.c
> > index 3da64e9f72..242f54ab49 100644
> > --- a/fsdev/qemu-fsdev.c
> > +++ b/fsdev/qemu-fsdev.c
> > @@ -133,6 +133,11 @@ int qemu_fsdev_add(QemuOpts *opts, Error **errp)
> > }
> >
> > if (fsdriver) {
> > + if (strncmp(fsdriver, "proxy", 5) == 0) {
> > + warn_report("'-fsdev proxy' is deprecated, use '-fsdev local' "
> > + "instead");
> > + }
> > +
> > for (i = 0; i < ARRAY_SIZE(FsDrivers); i++) {
> > if (strcmp(FsDrivers[i].name, fsdriver) == 0) {
> > break;
> > diff --git a/fsdev/virtfs-proxy-helper.c b/fsdev/virtfs-proxy-helper.c
> > index d9511f429c..5dd5d99284 100644
> > --- a/fsdev/virtfs-proxy-helper.c
> > +++ b/fsdev/virtfs-proxy-helper.c
> > @@ -9,6 +9,11 @@
> > * the COPYING file in the top-level directory.
> > */
> >
> > +/*
> > + * NOTE: The 9p 'proxy' backend is deprecated (since QEMU 8.1) and will be
> > + * removed in a future version of QEMU!
> > + */
> > +
> > #include "qemu/osdep.h"
> > #include <glib/gstdio.h>
> > #include <sys/resource.h>
> > diff --git a/hw/9pfs/9p-proxy.c b/hw/9pfs/9p-proxy.c
> > index 99d115ff0d..905cae6992 100644
> > --- a/hw/9pfs/9p-proxy.c
> > +++ b/hw/9pfs/9p-proxy.c
> > @@ -15,6 +15,11 @@
> > * https://wiki.qemu.org/Documentation/9p
> > */
> >
> > +/*
> > + * NOTE: The 9p 'proxy' backend is deprecated (since QEMU 8.1) and will be
> > + * removed in a future version of QEMU!
> > + */
> > +
> > #include "qemu/osdep.h"
> > #include <sys/socket.h>
> > #include <sys/un.h>
> > diff --git a/hw/9pfs/9p-proxy.h b/hw/9pfs/9p-proxy.h
> > index b84301d001..9be4718d3e 100644
> > --- a/hw/9pfs/9p-proxy.h
> > +++ b/hw/9pfs/9p-proxy.h
> > @@ -10,6 +10,11 @@
> > * the COPYING file in the top-level directory.
> > */
> >
> > +/*
> > + * NOTE: The 9p 'proxy' backend is deprecated (since QEMU 8.1) and will be
> > + * removed in a future version of QEMU!
> > + */
> > +
> > #ifndef QEMU_9P_PROXY_H
> > #define QEMU_9P_PROXY_H
> >
> > diff --git a/meson.build b/meson.build
> > index 34306a6205..05c01b72bb 100644
> > --- a/meson.build
> > +++ b/meson.build
> > @@ -4170,7 +4170,7 @@ if have_block
> > summary_info += {'Block whitelist (ro)':
> > get_option('block_drv_ro_whitelist')}
> > summary_info += {'Use block whitelist in tools':
> > get_option('block_drv_whitelist_in_tools')}
> > summary_info += {'VirtFS (9P) support': have_virtfs}
> > - summary_info += {'VirtFS (9P) Proxy Helper support':
> > have_virtfs_proxy_helper}
> > + summary_info += {'VirtFS (9P) Proxy Helper support (deprecated)':
> > have_virtfs_proxy_helper}
> > summary_info += {'Live block migration':
> > config_host_data.get('CONFIG_LIVE_BLOCK_MIGRATION')}
> > summary_info += {'replication support':
> > config_host_data.get('CONFIG_REPLICATION')}
> > summary_info += {'bochs support': get_option('bochs').allowed()}
> > diff --git a/qemu-options.hx b/qemu-options.hx
> > index b57489d7ca..3a6c7d3ef9 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -1735,7 +1735,9 @@ SRST
> > Accesses to the filesystem are done by QEMU.
> >
> > ``proxy``
> > - Accesses to the filesystem are done by virtfs-proxy-helper(1).
> > + Accesses to the filesystem are done by virtfs-proxy-helper(1). This
> > + option is deprecated (since QEMU 8.1) and will be removed in a
> > future
> > + version of QEMU. Use ``local`` instead.
> >
> > ``synth``
> > Synthetic filesystem, only used by QTests.
> > @@ -1867,6 +1869,8 @@ SRST
> >
> > ``proxy``
> > Accesses to the filesystem are done by virtfs-proxy-helper(1).
> > + This option is deprecated (since QEMU 8.1) and will be removed in a
> > + future version of QEMU. Use ``local`` instead.
> >
> > ``synth``
> > Synthetic filesystem, only used by QTests.
> > diff --git a/softmmu/vl.c b/softmmu/vl.c
> > index b0b96f67fa..e60648b591 100644
> > --- a/softmmu/vl.c
> > +++ b/softmmu/vl.c
> > @@ -3102,6 +3102,11 @@ void qemu_init(int argc, char **argv)
> > error_report("Usage: -virtfs fsdriver,mount_tag=tag");
> > exit(1);
> > }
> > + if (strncmp(qemu_opt_get(opts, "fsdriver"), "proxy", 5) ==
> > 0) {
> > + warn_report("'-virtfs proxy' is deprecated, use "
> > + "'-virtfs local' instead");
> > + }
> > +
> > fsdev = qemu_opts_create(qemu_find_opts("fsdev"),
> > qemu_opts_id(opts) ?:
> > qemu_opt_get(opts, "mount_tag"),
> >
>
>
>
>
Re: [PATCH v3] 9pfs: deprecate 'proxy' backend, Daniel P . Berrangé, 2023/06/21