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[129.219.8.64]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b38f060165csm4839089a12.10.2025.07.05.14.21.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 05 Jul 2025 14:21:53 -0700 (PDT) From: Xiang Mei To: xiyou.wangcong@gmail.com Cc: netdev@vger.kernel.org, gregkh@linuxfoundation.org, jhs@mojatatu.com, jiri@resnulli.us, security@kernel.org, Xiang Mei Subject: [PATCH v3] net/sched: sch_qfq: Fix null-deref in agg_dequeue Date: Sat, 5 Jul 2025 14:21:43 -0700 Message-ID: <20250705212143.3982664-1-xmei5@asu.edu> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit To prevent a potential crash in agg_dequeue (net/sched/sch_qfq.c) when cl->qdisc->ops->peek(cl->qdisc) returns NULL, we check the return value before using it, similar to the existing approach in sch_hfsc.c. To avoid code duplication, the following changes are made: 1. Changed qdisc_warn_nonwc(include/net/pkt_sched.h) into a static inline function. 2. Moved qdisc_peek_len from net/sched/sch_hfsc.c to include/net/pkt_sched.h so that sch_qfq can reuse it. 3. Applied qdisc_peek_len in agg_dequeue to avoid crashing. Signed-off-by: Xiang Mei --- v3: - Move qdisc_warn_nonwc and qdisc_peek_len to pkt_sched.h v2: - Use real name in signed-off-by v1: - Move qdisc_warn_nonwc to include/net/sch_generic.h - Move qdisc_peek_len from net/sched/sch_hfsc.c to include/net/sch_generic.h - Replace cl->qdisc->ops->peek() with qdisc_peek_len() in sch_qfq.c include/net/pkt_sched.h | 25 ++++++++++++++++++++++++- net/sched/sch_api.c | 10 ---------- net/sched/sch_hfsc.c | 16 ---------------- net/sched/sch_qfq.c | 2 +- 4 files changed, 25 insertions(+), 28 deletions(-) diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h index 15960564e0c3..4d72d24b1f33 100644 --- a/include/net/pkt_sched.h +++ b/include/net/pkt_sched.h @@ -112,7 +112,6 @@ struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r, struct netlink_ext_ack *extack); void qdisc_put_rtab(struct qdisc_rate_table *tab); void qdisc_put_stab(struct qdisc_size_table *tab); -void qdisc_warn_nonwc(const char *txt, struct Qdisc *qdisc); bool sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q, struct net_device *dev, struct netdev_queue *txq, spinlock_t *root_lock, bool validate); @@ -306,4 +305,28 @@ static inline bool tc_qdisc_stats_dump(struct Qdisc *sch, return true; } +static inline void qdisc_warn_nonwc(const char *txt, struct Qdisc *qdisc) +{ + if (!(qdisc->flags & TCQ_F_WARN_NONWC)) { + pr_warn("%s: %s qdisc %X: is non-work-conserving?\n", + txt, qdisc->ops->id, qdisc->handle >> 16); + qdisc->flags |= TCQ_F_WARN_NONWC; + } +} + +static inline unsigned int qdisc_peek_len(struct Qdisc *sch) +{ + struct sk_buff *skb; + unsigned int len; + + skb = sch->ops->peek(sch); + if (unlikely(skb == NULL)) { + qdisc_warn_nonwc("qdisc_peek_len", sch); + return 0; + } + len = qdisc_pkt_len(skb); + + return len; +} + #endif diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index df89790c459a..6518fdc63dc2 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -594,16 +594,6 @@ void __qdisc_calculate_pkt_len(struct sk_buff *skb, qdisc_skb_cb(skb)->pkt_len = pkt_len; } -void qdisc_warn_nonwc(const char *txt, struct Qdisc *qdisc) -{ - if (!(qdisc->flags & TCQ_F_WARN_NONWC)) { - pr_warn("%s: %s qdisc %X: is non-work-conserving?\n", - txt, qdisc->ops->id, qdisc->handle >> 16); - qdisc->flags |= TCQ_F_WARN_NONWC; - } -} -EXPORT_SYMBOL(qdisc_warn_nonwc); - static enum hrtimer_restart qdisc_watchdog(struct hrtimer *timer) { struct qdisc_watchdog *wd = container_of(timer, struct qdisc_watchdog, diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c index afcb83d469ff..751b1e2c35b3 100644 --- a/net/sched/sch_hfsc.c +++ b/net/sched/sch_hfsc.c @@ -835,22 +835,6 @@ update_vf(struct hfsc_class *cl, unsigned int len, u64 cur_time) } } -static unsigned int -qdisc_peek_len(struct Qdisc *sch) -{ - struct sk_buff *skb; - unsigned int len; - - skb = sch->ops->peek(sch); - if (unlikely(skb == NULL)) { - qdisc_warn_nonwc("qdisc_peek_len", sch); - return 0; - } - len = qdisc_pkt_len(skb); - - return len; -} - static void hfsc_adjust_levels(struct hfsc_class *cl) { diff --git a/net/sched/sch_qfq.c b/net/sched/sch_qfq.c index 5e557b960bde..e0cefa21ce21 100644 --- a/net/sched/sch_qfq.c +++ b/net/sched/sch_qfq.c @@ -992,7 +992,7 @@ static struct sk_buff *agg_dequeue(struct qfq_aggregate *agg, if (cl->qdisc->q.qlen == 0) /* no more packets, remove from list */ list_del_init(&cl->alist); - else if (cl->deficit < qdisc_pkt_len(cl->qdisc->ops->peek(cl->qdisc))) { + else if (cl->deficit < qdisc_peek_len(cl->qdisc)) { cl->deficit += agg->lmax; list_move_tail(&cl->alist, &agg->active); } -- 2.43.0