linux-cve-announce - CVE-2023-53843: net: openvswitch: reject negative ifindex

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Message-ID: <2025120958-CVE-2023-53843-195d@gregkh>
Date: Tue,  9 Dec 2025 10:31:27 +0900
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53843: net: openvswitch: reject negative ifindex

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

net: openvswitch: reject negative ifindex

Recent changes in net-next (commit 759ab1edb56c ("net: store netdevs
in an xarray")) refactored the handling of pre-assigned ifindexes
and let syzbot surface a latent problem in ovs. ovs does not validate
ifindex, making it possible to create netdev ports with negative
ifindex values. It's easy to repro with YNL:

$ ./cli.py --spec netlink/specs/ovs_datapath.yaml \
         --do new \
	 --json '{"upcall-pid": 1, "name":"my-dp"}'
$ ./cli.py --spec netlink/specs/ovs_vport.yaml \
	 --do new \
	 --json '{"upcall-pid": "00000001", "name": "some-port0", "dp-ifindex":3,"ifindex":4294901760,"type":2}'

$ ip link show
-65536: some-port0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 7a:48:21:ad:0b:fb brd ff:ff:ff:ff:ff:ff
...

Validate the inputs. Now the second command correctly returns:

$ ./cli.py --spec netlink/specs/ovs_vport.yaml \
	 --do new \
	 --json '{"upcall-pid": "00000001", "name": "some-port0", "dp-ifindex":3,"ifindex":4294901760,"type":2}'

lib.ynl.NlError: Netlink error: Numerical result out of range
nl_len = 108 (92) nl_flags = 0x300 nl_type = 2
	error: -34	extack: {'msg': 'integer out of range', 'unknown': [[type:4 len:36] b'\x0c\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x0c\x00\x03\x00\xff\xff\xff\x7f\x00\x00\x00\x00\x08\x00\x01\x00\x08\x00\x00\x00'], 'bad-attr': '.ifindex'}

Accept 0 since it used to be silently ignored.

The Linux kernel CVE team has assigned CVE-2023-53843 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.1 with commit 54c4ef34c4b6f9720fded620e2893894f9f2c554 and fixed in 6.1.47 with commit c965a58376146dcfdda186819462e8eb3aadef3a
	Issue introduced in 6.1 with commit 54c4ef34c4b6f9720fded620e2893894f9f2c554 and fixed in 6.4.12 with commit 881faff9e548a7ddfb11595be7c1c649217d27db
	Issue introduced in 6.1 with commit 54c4ef34c4b6f9720fded620e2893894f9f2c554 and fixed in 6.5 with commit a552bfa16bab4ce901ee721346a28c4e483f4066

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2023-53843
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/openvswitch/datapath.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/c965a58376146dcfdda186819462e8eb3aadef3a
	https://git.kernel.org/stable/c/881faff9e548a7ddfb11595be7c1c649217d27db
	https://git.kernel.org/stable/c/a552bfa16bab4ce901ee721346a28c4e483f4066