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Wed, 16 Apr 2025 03:24:48 -0700 (PDT) Received: from exu-caveira.tail33bf8.ts.net ([2804:7f1:e2c3:dc7b:da12:1e53:d800:3508]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-308613cb765sm1193075a91.43.2025.04.16.03.24.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Apr 2025 03:24:47 -0700 (PDT) From: Victor Nogueira To: netdev@vger.kernel.org Cc: jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, toke@redhat.com, gerrard.tai@starlabs.sg, pctammela@mojatatu.com Subject: [PATCH net v2 4/5] net_sched: qfq: Fix double list add in class with netem as child qdisc Date: Wed, 16 Apr 2025 07:24:26 -0300 Message-ID: <20250416102427.3219655-5-victor@mojatatu.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250416102427.3219655-1-victor@mojatatu.com> References: <20250416102427.3219655-1-victor@mojatatu.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit As described in Gerrard's report [1], there are use cases where a netem child qdisc will make the parent qdisc's enqueue callback reentrant. In the case of qfq, there won't be a UAF, but the code will add the same classifier to the list twice, which will cause memory corruption. This patch checks whether the class was already added to the agg->active list (cl_is_initialised) before doing the addition to cater for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/ Fixes: 37d9cf1a3ce3 ("sched: Fix detection of empty queues in child qdiscs") Acked-by: Jamal Hadi Salim Signed-off-by: Victor Nogueira --- net/sched/sch_qfq.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/net/sched/sch_qfq.c b/net/sched/sch_qfq.c index 687a932eb9b2..b7767b105506 100644 --- a/net/sched/sch_qfq.c +++ b/net/sched/sch_qfq.c @@ -202,6 +202,11 @@ struct qfq_sched { */ enum update_reason {enqueue, requeue}; +static bool cl_is_initialised(struct qfq_class *cl) +{ + return !list_empty(&cl->alist); +} + static struct qfq_class *qfq_find_class(struct Qdisc *sch, u32 classid) { struct qfq_sched *q = qdisc_priv(sch); @@ -1260,6 +1265,9 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch, == cl && cl->deficit < len) list_move_tail(&cl->alist, &agg->active); + return err; + /* cater for reentrant call */ + } else if (cl_is_initialised(cl)) { return err; } -- 2.34.1