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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Jakub Kicinski <jakub.kicinski@netronome.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.9 140/171] net: sched: gred: pass the right attribute to gred_change_table_def()
Date:   Thu,  8 Nov 2018 13:51:50 -0800
Message-Id: <20181108215137.128769187@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Jakub Kicinski <jakub.kicinski@netronome.com>

[ Upstream commit 38b4f18d56372e1e21771ab7b0357b853330186c ]

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@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 |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sched/sch_gred.c
+++ b/net/sched/sch_gred.c
@@ -411,7 +411,7 @@ static int gred_change(struct Qdisc *sch
 	if (tb[TCA_GRED_PARMS] == NULL && tb[TCA_GRED_STAB] == NULL) {
 		if (tb[TCA_GRED_LIMIT] != NULL)
 			sch->limit = nla_get_u32(tb[TCA_GRED_LIMIT]);
-		return gred_change_table_def(sch, opt);
+		return gred_change_table_def(sch, tb[TCA_GRED_DPS]);
 	}
 
 	if (tb[TCA_GRED_PARMS] == NULL ||