net_sched: fix ops->bind_class() implementations

The current implementations of ops->bind_class() are merely
searching for classid and updating class in the struct tcf_result,
without invoking either of cl_ops->bind_tcf() or
cl_ops->unbind_tcf(). This breaks the design of them as qdisc's
like cbq use them to count filters too. This is why syzbot triggered
the warning in cbq_destroy_class().

In order to fix this, we have to call cl_ops->bind_tcf() and
cl_ops->unbind_tcf() like the filter binding path. This patch does
so by refactoring out two helper functions __tcf_bind_filter()
and __tcf_unbind_filter(), which are lockless and accept a Qdisc
pointer, then teaching each implementation to call them correctly.

Note, we merely pass the Qdisc pointer as an opaque pointer to
each filter, they only need to pass it down to the helper
functions without understanding it at all.

Fixes: 07d79fc7d94e ("net_sched: add reverse binding for tc class")
Reported-and-tested-by: syzbot+0a0596220218fcb603a8@syzkaller.appspotmail.com
Reported-and-tested-by: syzbot+63bdb6006961d8c917c6@syzkaller.appspotmail.com
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 19 insertions, 14 deletions

diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h
index ce036492986a..a972244ab193 100644
--- a/include/net/pkt_cls.h
+++ b/include/net/pkt_cls.h
@@ -141,31 +141,38 @@ __cls_set_class(unsigned long *clp, unsigned long cl)
 	return xchg(clp, cl);
 }
 
-static inline unsigned long
-cls_set_class(struct Qdisc *q, unsigned long *clp, unsigned long cl)
+static inline void
+__tcf_bind_filter(struct Qdisc *q, struct tcf_result *r, unsigned long base)
 {
-	unsigned long old_cl;
+	unsigned long cl;
 
-	sch_tree_lock(q);
-	old_cl = __cls_set_class(clp, cl);
-	sch_tree_unlock(q);
-	return old_cl;
+	cl = q->ops->cl_ops->bind_tcf(q, base, r->classid);
+	cl = __cls_set_class(&r->class, cl);
+	if (cl)
+		q->ops->cl_ops->unbind_tcf(q, cl);
 }
 
 static inline void
 tcf_bind_filter(struct tcf_proto *tp, struct tcf_result *r, unsigned long base)
 {
 	struct Qdisc *q = tp->chain->block->q;
-	unsigned long cl;
 
 	/* Check q as it is not set for shared blocks. In that case,
 	 * setting class is not supported.
 	 */
 	if (!q)
 		return;
-	cl = q->ops->cl_ops->bind_tcf(q, base, r->classid);
-	cl = cls_set_class(q, &r->class, cl);
-	if (cl)
+	sch_tree_lock(q);
+	__tcf_bind_filter(q, r, base);
+	sch_tree_unlock(q);
+}
+
+static inline void
+__tcf_unbind_filter(struct Qdisc *q, struct tcf_result *r)
+{
+	unsigned long cl;
+
+	if ((cl = __cls_set_class(&r->class, 0)) != 0)
 		q->ops->cl_ops->unbind_tcf(q, cl);
 }
 
@@ -173,12 +180,10 @@ static inline void
 tcf_unbind_filter(struct tcf_proto *tp, struct tcf_result *r)
 {
 	struct Qdisc *q = tp->chain->block->q;
-	unsigned long cl;
 
 	if (!q)
 		return;
-	if ((cl = __cls_set_class(&r->class, 0)) != 0)
-		q->ops->cl_ops->unbind_tcf(q, cl);
+	__tcf_unbind_filter(q, r);
 }
 
 struct tcf_exts {