sched: Avoid dereferencing skb pointer after child enqueue

Parent qdiscs may dereference the pointer to the enqueued skb after
enqueue. However, both CAKE and TBF call consume_skb() on the original skb
when splitting GSO packets, leading to a potential use-after-free in the
parent. Fix this by avoiding dereferencing the skb pointer after enqueueing
to the child.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_cbs.c b/net/sched/sch_cbs.c
index e689e11..c6a5029 100644 (file)
--- a/net/sched/sch_cbs.c
+++ b/net/sched/sch_cbs.c
@@ -88,13 +88,14 @@ static int cbs_child_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                             struct Qdisc *child,
                             struct sk_buff **to_free)
 {
+       unsigned int len = qdisc_pkt_len(skb);
        int err;
 
        err = child->ops->enqueue(skb, child, to_free);
        if (err != NET_XMIT_SUCCESS)
                return err;
 
-       qdisc_qstats_backlog_inc(sch, skb);
+       sch->qstats.backlog += len;
        sch->q.qlen++;
 
        return NET_XMIT_SUCCESS;

diff --git a/net/sched/sch_drr.c b/net/sched/sch_drr.c
index cdebaed..feaf471 100644 (file)
--- a/net/sched/sch_drr.c
+++ b/net/sched/sch_drr.c
@@ -350,6 +350,7 @@ static struct drr_class *drr_classify(struct sk_buff *skb, struct Qdisc *sch,
 static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                       struct sk_buff **to_free)
 {
+       unsigned int len = qdisc_pkt_len(skb);
        struct drr_sched *q = qdisc_priv(sch);
        struct drr_class *cl;
        int err = 0;
@@ -376,7 +377,7 @@ static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                cl->deficit = cl->quantum;
        }
 
-       qdisc_qstats_backlog_inc(sch, skb);
+       sch->qstats.backlog += len;
        sch->q.qlen++;
        return err;
 }

diff --git a/net/sched/sch_dsmark.c b/net/sched/sch_dsmark.c
index f6f4807..4247146 100644 (file)
--- a/net/sched/sch_dsmark.c
+++ b/net/sched/sch_dsmark.c
@@ -199,6 +199,7 @@ static struct tcf_block *dsmark_tcf_block(struct Qdisc *sch, unsigned long cl,
 static int dsmark_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                          struct sk_buff **to_free)
 {
+       unsigned int len = qdisc_pkt_len(skb);
        struct dsmark_qdisc_data *p = qdisc_priv(sch);
        int err;
 
@@ -271,7 +272,7 @@ static int dsmark_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                return err;
        }
 
-       qdisc_qstats_backlog_inc(sch, skb);
+       sch->qstats.backlog += len;
        sch->q.qlen++;
 
        return NET_XMIT_SUCCESS;

diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c
index b18ec1f..6bb8f73 100644 (file)
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -1539,6 +1539,7 @@ hfsc_dump_qdisc(struct Qdisc *sch, struct sk_buff *skb)
 static int
 hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 {
+       unsigned int len = qdisc_pkt_len(skb);
        struct hfsc_class *cl;
        int uninitialized_var(err);
 
@@ -1560,8 +1561,6 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
        }
 
        if (cl->qdisc->q.qlen == 1) {
-               unsigned int len = qdisc_pkt_len(skb);
-
                if (cl->cl_flags & HFSC_RSC)
                        init_ed(cl, len);
                if (cl->cl_flags & HFSC_FSC)
@@ -1576,7 +1575,7 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 
        }
 
-       qdisc_qstats_backlog_inc(sch, skb);
+       sch->qstats.backlog += len;
        sch->q.qlen++;
 
        return NET_XMIT_SUCCESS;

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 58b4494..30f9da7 100644 (file)
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -581,6 +581,7 @@ static int htb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                       struct sk_buff **to_free)
 {
        int uninitialized_var(ret);
+       unsigned int len = qdisc_pkt_len(skb);
        struct htb_sched *q = qdisc_priv(sch);
        struct htb_class *cl = htb_classify(skb, sch, &ret);
 
@@ -610,7 +611,7 @@ static int htb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                htb_activate(q, cl);
        }
 
-       qdisc_qstats_backlog_inc(sch, skb);
+       sch->qstats.backlog += len;
        sch->q.qlen++;
        return NET_XMIT_SUCCESS;
 }

diff --git a/net/sched/sch_prio.c b/net/sched/sch_prio.c
index cdf6870..847141c 100644 (file)
--- a/net/sched/sch_prio.c
+++ b/net/sched/sch_prio.c
@@ -72,6 +72,7 @@ prio_classify(struct sk_buff *skb, struct Qdisc *sch, int *qerr)
 static int
 prio_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 {
+       unsigned int len = qdisc_pkt_len(skb);
        struct Qdisc *qdisc;
        int ret;
 
@@ -88,7 +89,7 @@ prio_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 
        ret = qdisc_enqueue(skb, qdisc, to_free);
        if (ret == NET_XMIT_SUCCESS) {
-               qdisc_qstats_backlog_inc(sch, skb);
+               sch->qstats.backlog += len;
                sch->q.qlen++;
                return NET_XMIT_SUCCESS;
        }

diff --git a/net/sched/sch_qfq.c b/net/sched/sch_qfq.c
index dc37c4e..8d5e55d 100644 (file)
--- a/net/sched/sch_qfq.c
+++ b/net/sched/sch_qfq.c
@@ -1210,6 +1210,7 @@ static struct qfq_aggregate *qfq_choose_next_agg(struct qfq_sched *q)
 static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                       struct sk_buff **to_free)
 {
+       unsigned int len = qdisc_pkt_len(skb), gso_segs;
        struct qfq_sched *q = qdisc_priv(sch);
        struct qfq_class *cl;
        struct qfq_aggregate *agg;
@@ -1224,17 +1225,17 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
        }
        pr_debug("qfq_enqueue: cl = %x\n", cl->common.classid);
 
-       if (unlikely(cl->agg->lmax < qdisc_pkt_len(skb))) {
+       if (unlikely(cl->agg->lmax < len)) {
                pr_debug("qfq: increasing maxpkt from %u to %u for class %u",
-                        cl->agg->lmax, qdisc_pkt_len(skb), cl->common.classid);
-               err = qfq_change_agg(sch, cl, cl->agg->class_weight,
-                                    qdisc_pkt_len(skb));
+                        cl->agg->lmax, len, cl->common.classid);
+               err = qfq_change_agg(sch, cl, cl->agg->class_weight, len);
                if (err) {
                        cl->qstats.drops++;
                        return qdisc_drop(skb, sch, to_free);
                }
        }
 
+       gso_segs = skb_is_gso(skb) ? skb_shinfo(skb)->gso_segs : 1;
        err = qdisc_enqueue(skb, cl->qdisc, to_free);
        if (unlikely(err != NET_XMIT_SUCCESS)) {
                pr_debug("qfq_enqueue: enqueue failed %d\n", err);
@@ -1245,8 +1246,9 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                return err;
        }
 
-       bstats_update(&cl->bstats, skb);
-       qdisc_qstats_backlog_inc(sch, skb);
+       cl->bstats.bytes += len;
+       cl->bstats.packets += gso_segs;
+       sch->qstats.backlog += len;
        ++sch->q.qlen;
 
        agg = cl->agg;
@@ -1254,7 +1256,7 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
        if (cl->qdisc->q.qlen != 1) {
                if (unlikely(skb == cl->qdisc->ops->peek(cl->qdisc)) &&
                    list_first_entry(&agg->active, struct qfq_class, alist)
-                   == cl && cl->deficit < qdisc_pkt_len(skb))
+                   == cl && cl->deficit < len)
                        list_move_tail(&cl->alist, &agg->active);
 
                return err;

diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c
index 942dcca..7f272a9 100644 (file)
--- a/net/sched/sch_tbf.c
+++ b/net/sched/sch_tbf.c
@@ -185,6 +185,7 @@ static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                       struct sk_buff **to_free)
 {
        struct tbf_sched_data *q = qdisc_priv(sch);
+       unsigned int len = qdisc_pkt_len(skb);
        int ret;
 
        if (qdisc_pkt_len(skb) > q->max_size) {
@@ -200,7 +201,7 @@ static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                return ret;
        }
 
-       qdisc_qstats_backlog_inc(sch, skb);
+       sch->qstats.backlog += len;
        sch->q.qlen++;
        return NET_XMIT_SUCCESS;
 }