net_sched: Flush gso_skb list too during ->change()

Previously, when reducing a qdisc's limit via the ->change() operation, only
the main skb queue was trimmed, potentially leaving packets in the gso_skb
list. This could result in NULL pointer dereference when we only check
sch->limit against sch->q.qlen.

This patch introduces a new helper, qdisc_dequeue_internal(), which ensures
both the gso_skb list and the main queue are properly flushed when trimming
excess packets. All relevant qdiscs (codel, fq, fq_codel, fq_pie, hhf, pie)
are updated to use this helper in their ->change() routines.

Fixes: 76e3cc126bb2 ("codel: Controlled Delay AQM")
Fixes: 4b549a2ef4be ("fq_codel: Fair Queue Codel AQM")
Fixes: afe4fd062416 ("pkt_sched: fq: Fair Queue packet scheduler")
Fixes: ec97ecf1ebe4 ("net: sched: add Flow Queue PIE packet scheduler")
Fixes: 10239edf86f1 ("net-qdisc-hhf: Heavy-Hitter Filter (HHF) qdisc")
Fixes: d4b36210c2e6 ("net: pkt_sched: PIE AQM scheme")
Reported-by: Will <willsroot@protonmail.com>
Reported-by: Savy <savy@syst3mfailure.io>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index d48c657191cd01e4d278c2dd6e162d14ed45e2d6..1c05fed05f2bc2087842898683af8da4a06ddc3e 100644 (file)
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -1031,6 +1031,21 @@ static inline struct sk_buff *__qdisc_dequeue_head(struct qdisc_skb_head *qh)
        return skb;
 }
 
+static inline struct sk_buff *qdisc_dequeue_internal(struct Qdisc *sch, bool direct)
+{
+       struct sk_buff *skb;
+
+       skb = __skb_dequeue(&sch->gso_skb);
+       if (skb) {
+               sch->q.qlen--;
+               return skb;
+       }
+       if (direct)
+               return __qdisc_dequeue_head(&sch->q);
+       else
+               return sch->dequeue(sch);
+}
+
 static inline struct sk_buff *qdisc_dequeue_head(struct Qdisc *sch)
 {
        struct sk_buff *skb = __qdisc_dequeue_head(&sch->q);

diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
index 12dd71139da396f799298627655879dfb689538d..c93761040c6e7797e58d24032adcfce4272efb10 100644 (file)
--- a/net/sched/sch_codel.c
+++ b/net/sched/sch_codel.c
@@ -144,7 +144,7 @@ static int codel_change(struct Qdisc *sch, struct nlattr *opt,
 
        qlen = sch->q.qlen;
        while (sch->q.qlen > sch->limit) {
-               struct sk_buff *skb = __qdisc_dequeue_head(&sch->q);
+               struct sk_buff *skb = qdisc_dequeue_internal(sch, true);
 
                dropped += qdisc_pkt_len(skb);
                qdisc_qstats_backlog_dec(sch, skb);

diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index 2ca5332cfcc5c52bf30e6f8337814a656b919b17..902ff54706072b4d5a064caf0f4be27a703d0939 100644 (file)
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -1136,7 +1136,7 @@ static int fq_change(struct Qdisc *sch, struct nlattr *opt,
                sch_tree_lock(sch);
        }
        while (sch->q.qlen > sch->limit) {
-               struct sk_buff *skb = fq_dequeue(sch);
+               struct sk_buff *skb = qdisc_dequeue_internal(sch, false);
 
                if (!skb)
                        break;

diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
index 6c9029f71e88d3e348f537a42d345c82cee256a4..2a0f3a513bfaa1c2a130c57fa3caf3e781efc4e6 100644 (file)
--- a/net/sched/sch_fq_codel.c
+++ b/net/sched/sch_fq_codel.c
@@ -441,7 +441,7 @@ static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt,
 
        while (sch->q.qlen > sch->limit ||
               q->memory_usage > q->memory_limit) {
-               struct sk_buff *skb = fq_codel_dequeue(sch);
+               struct sk_buff *skb = qdisc_dequeue_internal(sch, false);
 
                q->cstats.drop_len += qdisc_pkt_len(skb);
                rtnl_kfree_skbs(skb, skb);

diff --git a/net/sched/sch_fq_pie.c b/net/sched/sch_fq_pie.c
index f3b8203d3e855b98afa7a73bbdfb61e6eec62ae0..df7fac95ab15138bc55cf73bad27fd2bf41d1da9 100644 (file)
--- a/net/sched/sch_fq_pie.c
+++ b/net/sched/sch_fq_pie.c
@@ -366,7 +366,7 @@ static int fq_pie_change(struct Qdisc *sch, struct nlattr *opt,
 
        /* Drop excess packets if new limit is lower */
        while (sch->q.qlen > sch->limit) {
-               struct sk_buff *skb = fq_pie_qdisc_dequeue(sch);
+               struct sk_buff *skb = qdisc_dequeue_internal(sch, false);
 
                len_dropped += qdisc_pkt_len(skb);
                num_dropped += 1;

diff --git a/net/sched/sch_hhf.c b/net/sched/sch_hhf.c
index 44d9efe1a96a89bdb44a6d48071b3eed90fd5554..5aa434b4670738e4cb5d0843b44c0c99959e01fc 100644 (file)
--- a/net/sched/sch_hhf.c
+++ b/net/sched/sch_hhf.c
@@ -564,7 +564,7 @@ static int hhf_change(struct Qdisc *sch, struct nlattr *opt,
        qlen = sch->q.qlen;
        prev_backlog = sch->qstats.backlog;
        while (sch->q.qlen > sch->limit) {
-               struct sk_buff *skb = hhf_dequeue(sch);
+               struct sk_buff *skb = qdisc_dequeue_internal(sch, false);
 
                rtnl_kfree_skbs(skb, skb);
        }

diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c
index 3771d000b30d080601c7e2363daa7a5299c7af0b..ff49a6c97033aa43f680657b7798d4da050d8e71 100644 (file)
--- a/net/sched/sch_pie.c
+++ b/net/sched/sch_pie.c
@@ -195,7 +195,7 @@ static int pie_change(struct Qdisc *sch, struct nlattr *opt,
        /* Drop excess packets if new limit is lower */
        qlen = sch->q.qlen;
        while (sch->q.qlen > sch->limit) {
-               struct sk_buff *skb = __qdisc_dequeue_head(&sch->q);
+               struct sk_buff *skb = qdisc_dequeue_internal(sch, true);
 
                dropped += qdisc_pkt_len(skb);
                qdisc_qstats_backlog_dec(sch, skb);