Re: [PATCH v2] 9pfs: deprecate 'proxy' backend
On Saturday, June 10, 2023 1:07:27 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
> ---
> v1 -> v2:
> * Add deprecation notice also to virtfs-proxy-helper.rst,
>qemu-options.hx and to the 'proxy' source files
>(virtfs-proxy-helper.c, 9p-proxy.c, 9p-proxy.h).
>
> 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(-)
>
> 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
> 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
> L: qemu-bl...@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..f5051130e2 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' nackend 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..87e358376a 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' nackend is deprecated (since QEMU 8.1) and will be
> + * removed in a future version of QEMU!
> + */
> +
> #include "qemu/osdep.h"
> #include
> #include
>
[PATCH v2] 9pfs: deprecate 'proxy' backend
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
---
v1 -> v2:
* Add deprecation notice also to virtfs-proxy-helper.rst,
qemu-options.hx and to the 'proxy' source files
(virtfs-proxy-helper.c, 9p-proxy.c, 9p-proxy.h).
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(-)
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
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
L: qemu-bl...@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..f5051130e2 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' nackend 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..87e358376a 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' nackend is deprecated (since QEMU 8.1) and will be
+ * removed in a future version of QEMU!
+ */
+
#include "qemu/osdep.h"
#include
#include
diff --git a/hw/9pfs/9p-proxy.c b/hw/9pfs/9p-proxy.c
index 99d115ff0d..ab489cdd40 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' nackend is deprecated (since QEMU 8.1) and will be
+ * removed in a future version of QEMU!
+ */
+
