CVE-2026-64530: net/sched: cls_api: Handle TC_ACT_CONSUMED in tcf_qevent_handle

From: Greg Kroah-Hartman <[email protected]>

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

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

net/sched: cls_api: Handle TC_ACT_CONSUMED in tcf_qevent_handle

tcf_classify() can return TC_ACT_CONSUMED while the skb is held by the
defragmentation engine (e.g. act_ct on out-of-order fragments). When
that happens the skb is no longer owned by the caller and must not be
touched again.

tcf_qevent_handle() did not handle TC_ACT_CONSUMED: it fell through the
switch and returned the skb to the caller as if classification had
passed. The only qdisc that wires up qevents today is RED, via three call sites
(qe_mark on RED_PROB_MARK/HARD_MARK, qe_early_drop on congestion_drop)
red_enqueue() was continuing to operate on an skb it no longer owns  in this
case -- enqueueing it, dropping it, or updating statistics. Resulting in a UAF.

  tc qdisc add dev eth0 root handle 1: red ... qevent early_drop block 10
  tc filter add block 10 ... action ct

  (with ct defrag enabled and traffic that produces out-of-order
  fragments, e.g. a fragmented UDP stream)

Handle TC_ACT_CONSUMED in tcf_qevent_handle() the same way the ingress
and egress fast paths do: treat it as stolen and return NULL without
touching the skb. Unlike the TC_ACT_STOLEN case, the skb must not be
dropped/freed here, as it is no longer owned by us.

The Linux kernel CVE team has assigned CVE-2026-64530 to this issue.


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

	Issue introduced in 5.15.148 with commit 172ba7d46c202e679f3ccb10264c67416aaeb1c4 and fixed in 5.15.212 with commit 5ed3d6f85991656667059d3fa5a1d683ac58c447
	Issue introduced in 6.1.75 with commit 0b5b831122fc3789fff75be433ba3e4dd7b779d4 and fixed in 6.1.178 with commit f42e8134a3a1074b834a574d404352f867ba994a
	Issue introduced in 6.6.14 with commit 73f7da5fd124f2cda9161e2e46114915e6e82e97 and fixed in 6.6.145 with commit 447d493034a9cf7bf13a2abac86d0573d907ec2f
	Issue introduced in 6.8 with commit 3f14b377d01d8357eba032b4cabc8c1149b458b6 and fixed in 6.12.97 with commit e1270e69dcf2c3512c453484178f2e9dc0db3f05
	Issue introduced in 6.8 with commit 3f14b377d01d8357eba032b4cabc8c1149b458b6 and fixed in 6.18.40 with commit 2140c2f3f2e7b066e1ae616ede8856cafd8015e9
	Issue introduced in 6.8 with commit 3f14b377d01d8357eba032b4cabc8c1149b458b6 and fixed in 7.1.5 with commit e28aedab9488343924d227b5a896faed67ce84d5
	Issue introduced in 6.8 with commit 3f14b377d01d8357eba032b4cabc8c1149b458b6 and fixed in 7.2-rc1 with commit a8a02897f2b479127db261de05cbf0c28b98d159
	Issue introduced in 6.7.2 with commit f5346df0591d10bc948761ca854b1fae6d2ef441

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-2026-64530
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/sched/cls_api.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/5ed3d6f85991656667059d3fa5a1d683ac58c447
	https://git.kernel.org/stable/c/f42e8134a3a1074b834a574d404352f867ba994a
	https://git.kernel.org/stable/c/447d493034a9cf7bf13a2abac86d0573d907ec2f
	https://git.kernel.org/stable/c/e1270e69dcf2c3512c453484178f2e9dc0db3f05
	https://git.kernel.org/stable/c/2140c2f3f2e7b066e1ae616ede8856cafd8015e9
	https://git.kernel.org/stable/c/e28aedab9488343924d227b5a896faed67ce84d5
	https://git.kernel.org/stable/c/a8a02897f2b479127db261de05cbf0c28b98d159