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[184.144.29.222]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8df826927cesm31178356d6.41.2026.06.20.06.07.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 20 Jun 2026 06:07:52 -0700 (PDT) From: Jamal Hadi Salim To: netdev@vger.kernel.org Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, jiri@resnulli.us, victor@mojatatu.com, zdi-disclosures@trendmicro.c, security@kernel.org, Jamal Hadi Salim , Zero Day Initiative Subject: [PATCH net 1/1] net/sched: cls_api: Handle TC_ACT_CONSUMED in tcf_qevent_handle Date: Sat, 20 Jun 2026 09:07:49 -0400 Message-Id: <20260620130749.226642-1-jhs@mojatatu.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Fixes: 3f14b377d01d ("net/sched: act_ct: fix skb leak and crash on ooo frags") Reported-by: Zero Day Initiative Tested-by: Victor Nogueira Signed-off-by: Jamal Hadi Salim --- net/sched/cls_api.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c index 20f7f9ee0b353..3e67600a4a1a1 100644 --- a/net/sched/cls_api.c +++ b/net/sched/cls_api.c @@ -4049,6 +4049,9 @@ struct sk_buff *tcf_qevent_handle(struct tcf_qevent *qe, struct Qdisc *sch, stru skb_do_redirect(skb); *ret = __NET_XMIT_STOLEN; return NULL; + case TC_ACT_CONSUMED: + *ret = __NET_XMIT_STOLEN; + return NULL; } return skb; -- 2.34.1