[PATCH 3.16 120/305] net: sched: gred: pass the right attribute to gred_change_table_def()

From: Ben Hutchings
Date: Sun Feb 03 2019 - 09:32:30 EST


3.16.63-rc1 review patch. If anyone has any objections, please let me know.

------------------

From: Jakub Kicinski <jakub.kicinski@xxxxxxxxxxxxx>

commit 38b4f18d56372e1e21771ab7b0357b853330186c upstream.

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: f62d6b936df5 ("[PKT_SCHED]: GRED: Use central VQ change procedure")
Signed-off-by: Jakub Kicinski <jakub.kicinski@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
net/sched/sch_gred.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sched/sch_gred.c
+++ b/net/sched/sch_gred.c
@@ -437,7 +437,7 @@ static int gred_change(struct Qdisc *sch
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)