netdev - [PATCH net-next] net: sched: fallback to qdisc noqueue if default qdisc setup fail

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <158807197021.1980046.17172496536132159811.stgit@firesoul>
Date:   Tue, 28 Apr 2020 13:06:10 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     netdev@...r.kernel.org
Cc:     Jesper Dangaard Brouer <brouer@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Stephen Hemminger <stephen@...workplumber.org>,
        David Ahern <dsahern@...il.com>
Subject: [PATCH net-next] net: sched: fallback to qdisc noqueue if default
 qdisc setup fail

Currently if the default qdisc setup/init fails, the device ends up with
qdisc "noop", which causes all TX packets to get dropped.

With the introduction of sysctl net/core/default_qdisc it is possible
to change the default qdisc to be more advanced, which opens for the
possibility that Qdisc_ops->init() can fail.

This patch detect these kind of failures, and choose to fallback to
qdisc "noqueue", which is so simple that its init call will not fail.
This allows the interface to continue functioning.

Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
---
 net/sched/sch_generic.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 2efd5b61acef..275b1347265e 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -1037,10 +1037,9 @@ static void attach_one_default_qdisc(struct net_device *dev,
 		ops = &pfifo_fast_ops;
 
 	qdisc = qdisc_create_dflt(dev_queue, ops, TC_H_ROOT, NULL);
-	if (!qdisc) {
-		netdev_info(dev, "activation failed\n");
+	if (!qdisc)
 		return;
-	}
+
 	if (!netif_is_multiqueue(dev))
 		qdisc->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT;
 	dev_queue->qdisc_sleeping = qdisc;
@@ -1055,6 +1054,7 @@ static void attach_default_qdiscs(struct net_device *dev)
 
 	if (!netif_is_multiqueue(dev) ||
 	    dev->priv_flags & IFF_NO_QUEUE) {
+init_each_txq:
 		netdev_for_each_tx_queue(dev, attach_one_default_qdisc, NULL);
 		dev->qdisc = txq->qdisc_sleeping;
 		qdisc_refcount_inc(dev->qdisc);
@@ -1065,6 +1065,15 @@ static void attach_default_qdiscs(struct net_device *dev)
 			qdisc->ops->attach(qdisc);
 		}
 	}
+
+	/* Detect default qdisc setup/init failed and fallback to "noqueue" */
+	if (dev->qdisc == &noop_qdisc) {
+		netdev_warn(dev, "default qdisc (%s) fail, fallback to %s\n",
+			    default_qdisc_ops->id, noqueue_qdisc_ops.id);
+		dev->priv_flags |= IFF_NO_QUEUE;
+		goto init_each_txq;
+	}
+
 #ifdef CONFIG_NET_SCHED
 	if (dev->qdisc != &noop_qdisc)
 		qdisc_hash_add(dev->qdisc, false);