netdev - [PATCH net 1/2] sch_htb: Fix select

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Message-ID: <20210311144206.2135872-2-maximmi@nvidia.com>
Date:   Thu, 11 Mar 2021 16:42:05 +0200
From:   Maxim Mikityanskiy <maximmi@...dia.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>
CC:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Tariq Toukan <tariqt@...dia.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        <netdev@...r.kernel.org>, Maxim Mikityanskiy <maximmi@...dia.com>,
        <syzbot+b53a709f04722ca12a3c@...kaller.appspotmail.com>
Subject: [PATCH net 1/2] sch_htb: Fix select_queue for non-offload mode

htb_select_queue assumes it's always the offload mode, and it ends up in
calling ndo_setup_tc without any checks. It may lead to a NULL pointer
dereference if ndo_setup_tc is not implemented, or to an error returned
from the driver, which will prevent attaching qdiscs to HTB classes in
the non-offload mode.

This commit fixes the bug by adding the missing check to
htb_select_queue. In the non-offload mode it will return sch->dev_queue,
mimicking tc_modify_qdisc's behavior for the case where select_queue is
not implemented.

Reported-by: syzbot+b53a709f04722ca12a3c@...kaller.appspotmail.com
Fixes: d03b195b5aa0 ("sch_htb: Hierarchical QoS hardware offload")
Signed-off-by: Maxim Mikityanskiy <maximmi@...dia.com>
Reviewed-by: Tariq Toukan <tariqt@...dia.com>
---
 net/sched/sch_htb.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index dff3adf5a915..b23203159996 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -1340,8 +1340,12 @@ htb_select_queue(struct Qdisc *sch, struct tcmsg *tcm)
 {
 	struct net_device *dev = qdisc_dev(sch);
 	struct tc_htb_qopt_offload offload_opt;
+	struct htb_sched *q = qdisc_priv(sch);
 	int err;
 
+	if (!q->offload)
+		return sch->dev_queue;
+
 	offload_opt = (struct tc_htb_qopt_offload) {
 		.command = TC_HTB_LEAF_QUERY_QUEUE,
 		.classid = TC_H_MIN(tcm->tcm_parent),
-- 
2.25.1