As recent CVE-2023-2861 (fixed by f6b0de53fb) 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 (preferably in conjunction with its 'mapped' security
model) instead, but now it is time to officially deprecate the 'proxy'
backend.
Signed-off-by: Christian Schoenebeck
Reviewed-by: Greg Kurz
---
v4 -> v5:
- Eliminate repititve use of word 'instead' in text.
- Commit log: mention exact commit which fixed CVE-2023-2861.
MAINTAINERS| 9 -
docs/about/deprecated.rst | 23 +++
docs/tools/virtfs-proxy-helper.rst | 3 +++
fsdev/qemu-fsdev.c | 8
fsdev/virtfs-proxy-helper.c| 9 +
hw/9pfs/9p-proxy.c | 5 +
hw/9pfs/9p-proxy.h | 5 +
meson.build| 2 +-
qemu-options.hx| 6 +-
9 files changed, 67 insertions(+), 3 deletions(-)
diff --git a/MAINTAINERS b/MAINTAINERS
index e07746ac7d..42f2897d5e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2124,13 +2124,20 @@ 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/
-F: docs/tools/virtfs-proxy-helper.rst
+X: fsdev/virtfs-proxy-helper.c
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
+F: docs/tools/virtfs-proxy-helper.rst
+S: Obsolete
+
virtio-blk
M: Stefan Hajnoczi
L: qemu-bl...@nongnu.org
diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
index 0743459862..ddc1e48460 100644
--- a/docs/about/deprecated.rst
+++ b/docs/about/deprecated.rst
@@ -343,6 +343,29 @@ 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 (along with its proxy helper daemon) in a future version of QEMU.
Please
+use ``-fsdev local`` or ``-virtfs local`` for using the 9p ``local`` filesystem
+backend, or alternatively consider deploying virtiofsd 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 by using its 'mapped' security model option.
+
+Nowadays it would make sense to reimplement the ``proxy`` backend by using
+QEMU's ``vhost`` feature, which would eliminate the high latency costs under
+which the 9p ``proxy`` backend currently suffers. However as of to date nobody
+has indicated plans for such kind of reimplemention unfortunately.
+
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..f5c953a710 100644
--- a/fsdev/qemu-fsdev.c
+++ b/fsdev/qemu-fsdev.c
@@ -133,6 +133,14 @@ int qemu_fsdev_add(QemuOpts *opts, Error **errp)
}
if (fsdriver) {
+if (strncmp(fsdriver, "proxy", 5) == 0) {
+warn_report(
+"'-fsdev proxy' and '-virtfs proxy' are deprecated, use "
+"'local' instead of 'proxy, or consider deploying virtiofsd "
+"as alternative to 9p"
+);
+}
+
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..144aaf585a 100644
--- a/fsdev/virtfs-proxy-he
