htb: fix sign extension bug

When userspace passes a large priority value
the assignment of the unsigned value hopt->prio
to  signed int cl->prio causes cl->prio to become negative and the
comparison is with TC_HTB_NUMPRIO is always false.

The result is that HTB crashes by referencing outside
the array when processing packets. With this patch the large value
wraps around like other values outside the normal range.

See: https://bugzilla.kernel.org/show_bug.cgi?id=60669

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_htb.c

@@ -100,7 +100,7 @@ struct htb_class {
 	struct psched_ratecfg	ceil;
 	s64			buffer, cbuffer;/* token bucket depth/rate */
 	s64			mbuffer;	/* max wait time */
-	int			prio;		/* these two are used only by leaves... */
+	u32			prio;		/* these two are used only by leaves... */
 	int			quantum;	/* but stored for parent-to-leaf return */
 
 	struct tcf_proto	*filter_list;	/* class attached filters */