CVE-2025-21958

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

Revert openvswitch: switch to per-action label counting in conntrack

Currently, ovs_ct_set_labels() is only called for confirmed conntrack entries (ct) within ovs_ct_commit(). However, if the conntrack entry does not have the labels_ext extension, attempting to allocate it in ovs_ct_get_conn_labels() for a confirmed entry triggers a warning in nf_ct_ext_add():

WARN_ON(nf_ct_is_confirmed(ct));

This happens when the conntrack entry is created externally before OVS increments net->ct.labels_used. The issue has become more likely since commit fcb1aa5163b1 (openvswitch: switch to per-action label counting in conntrack), which changed to use per-action label counting and increment net->ct.labels_used when a flow with ct action is added.

Since there’s no straightforward way to fully resolve this issue at the moment, this reverts the commit to avoid breaking existing use cases.

Affected Software

References

• https://git.kernel.org/stable/c/1063ae07383c0ddc5bcce170260c143825846b03
• https://git.kernel.org/stable/c/9e79fdabd52cfce1a021640a81256878a2c516a2
• https://git.kernel.org/stable/c/d91bfc64a4886102746e74d2c6f3a61e9a77fd7d