net: Make qdisc_skb_cb upper size bound explicit.

Just like skb->cb[], so that qdisc_skb_cb can be encapsulated inside
of other data structures.

This is intended to be used by IPoIB so that it can remember
addressing information stored at hard_header_ops->create() time that
it can fetch when the packet gets to the transmit routine.

Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 13 insertions, 10 deletions

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index f6bb08b73ca4..55ce96b53b09 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -220,9 +220,16 @@ struct tcf_proto {
 
 struct qdisc_skb_cb {
         unsigned int            pkt_len;
-        long                    data[];
+        unsigned char           data[24];
 };
 
+static inline void qdisc_cb_private_validate(const struct sk_buff *skb, int sz)
+{
+        struct qdisc_skb_cb *qcb;
+        BUILD_BUG_ON(sizeof(skb->cb) < sizeof(unsigned int) + sz);
+        BUILD_BUG_ON(sizeof(qcb->data) < sz);
+}
+
 static inline int qdisc_qlen(const struct Qdisc *q)
 {
         return q->q.qlen;
diff --git a/net/sched/sch_choke.c b/net/sched/sch_choke.c
index e465064d39a3..7e267d7b9c75 100644
--- a/net/sched/sch_choke.c
+++ b/net/sched/sch_choke.c
@@ -148,8 +148,7 @@ struct choke_skb_cb {
 
 static inline struct choke_skb_cb *choke_skb_cb(const struct sk_buff *skb)
 {
-        BUILD_BUG_ON(sizeof(skb->cb) <
-                sizeof(struct qdisc_skb_cb) + sizeof(struct choke_skb_cb));
+        qdisc_cb_private_validate(skb, sizeof(struct choke_skb_cb));
         return (struct choke_skb_cb *)qdisc_skb_cb(skb)->data;
 }
 
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 2776012132ea..e83d61ca78ca 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -130,8 +130,7 @@ struct netem_skb_cb {
 
 static inline struct netem_skb_cb *netem_skb_cb(struct sk_buff *skb)
 {
-        BUILD_BUG_ON(sizeof(skb->cb) <
-                sizeof(struct qdisc_skb_cb) + sizeof(struct netem_skb_cb));
+        qdisc_cb_private_validate(skb, sizeof(struct netem_skb_cb));
         return (struct netem_skb_cb *)qdisc_skb_cb(skb)->data;
 }
 
diff --git a/net/sched/sch_sfb.c b/net/sched/sch_sfb.c
index 96e42cae4c7a..d7eea99333e9 100644
--- a/net/sched/sch_sfb.c
+++ b/net/sched/sch_sfb.c
@@ -94,8 +94,7 @@ struct sfb_skb_cb {
 
 static inline struct sfb_skb_cb *sfb_skb_cb(const struct sk_buff *skb)
 {
-        BUILD_BUG_ON(sizeof(skb->cb) <
-                sizeof(struct qdisc_skb_cb) + sizeof(struct sfb_skb_cb));
+        qdisc_cb_private_validate(skb, sizeof(struct sfb_skb_cb));
         return (struct sfb_skb_cb *)qdisc_skb_cb(skb)->data;
 }
 
diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
index 67494aef9acf..60d47180f043 100644
--- a/net/sched/sch_sfq.c
+++ b/net/sched/sch_sfq.c
@@ -166,9 +166,8 @@ struct sfq_skb_cb {
 
 static inline struct sfq_skb_cb *sfq_skb_cb(const struct sk_buff *skb)
 {
-       BUILD_BUG_ON(sizeof(skb->cb) <
-               sizeof(struct qdisc_skb_cb) + sizeof(struct sfq_skb_cb));
-       return (struct sfq_skb_cb *)qdisc_skb_cb(skb)->data;
+        qdisc_cb_private_validate(skb, sizeof(struct sfq_skb_cb));
+        return (struct sfq_skb_cb *)qdisc_skb_cb(skb)->data;
 }
 
 static unsigned int sfq_hash(const struct sfq_sched_data *q,