net: sched: gred: pass the right attribute to gred_change_table_def()

[ Upstream commit 38b4f18 ]

gred_change_table_def() takes a pointer to TCA_GRED_DPS attribute,
and expects it will be able to interpret its contents as
struct tc_gred_sopt.  Pass the correct gred attribute, instead of
TCA_OPTIONS.

This bug meant the table definition could never be changed after
Qdisc was initialized (unless whatever TCA_OPTIONS contained both
passed netlink validation and was a valid struct tc_gred_sopt...).

Old behaviour:
$ ip link add type dummy
$ tc qdisc replace dev dummy0 parent root handle 7: \
     gred setup vqs 4 default 0
$ tc qdisc replace dev dummy0 parent root handle 7: \
     gred setup vqs 4 default 0
RTNETLINK answers: Invalid argument

Now:
$ ip link add type dummy
$ tc qdisc replace dev dummy0 parent root handle 7: \
     gred setup vqs 4 default 0
$ tc qdisc replace dev dummy0 parent root handle 7: \
     gred setup vqs 4 default 0
$ tc qdisc replace dev dummy0 parent root handle 7: \
     gred setup vqs 4 default 0

Fixes: f62d6b9 ("[PKT_SCHED]: GRED: Use central VQ change procedure")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/sched/sch_gred.c

@@ -437,7 +437,7 @@ static int gred_change(struct Qdisc *sch, struct nlattr *opt)
 		return err;
 
 	if (tb[TCA_GRED_PARMS] == NULL && tb[TCA_GRED_STAB] == NULL)
-		return gred_change_table_def(sch, opt);
+		return gred_change_table_def(sch, tb[TCA_GRED_DPS]);
 
 	if (tb[TCA_GRED_PARMS] == NULL ||
 	    tb[TCA_GRED_STAB] == NULL)