[PATCH AUTOSEL 4.19 194/209] net: sched: avoid writing on noop_qdisc

Sasha Levin
2019-11-13T02:18:13Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit f98ebd47fd0da1717267ce1583a105d8cc29a16a ]

While noop_qdisc.gso_skb and noop_qdisc.skb_bad_txq are not used
in other places, it seems not correct to overwrite their fields
in dev_init_scheduler_queue().

noop_qdisc is essentially a shared and read-only object, even if
it is not marked as const because of some implementation detail.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sched/sch_generic.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 30e32df5f84a7..8a4d01e427a22 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -577,6 +577,18 @@ struct Qdisc noop_qdisc = {
.dev_queue = &noop_netdev_queue,
.running = SEQCNT_ZERO(noop_qdisc.running),
.busylock = __SPIN_LOCK_UNLOCKED(noop_qdisc.busylock),
+ .gso_skb = {
+ .next = (struct sk_buff *)&noop_qdisc.gso_skb,
+ .prev = (struct sk_buff *)&noop_qdisc.gso_skb,
+ .qlen = 0,
+ .lock = __SPIN_LOCK_UNLOCKED(noop_qdisc.gso_skb.lock),
+ },
+ .skb_bad_txq = {
+ .next = (struct sk_buff *)&noop_qdisc.skb_bad_txq,
+ .prev = (struct sk_buff *)&noop_qdisc.skb_bad_txq,
+ .qlen = 0,
+ .lock = __SPIN_LOCK_UNLOCKED(noop_qdisc.skb_bad_txq.lock),
+ },
};
EXPORT_SYMBOL(noop_qdisc);

@@ -1253,8 +1265,6 @@ static void dev_init_scheduler_queue(struct net_device *dev,

rcu_assign_pointer(dev_queue->qdisc, qdisc);
dev_queue->qdisc_sleeping = qdisc;
- __skb_queue_head_init(&qdisc->gso_skb);
- __skb_queue_head_init(&qdisc->skb_bad_txq);
}

void dev_init_scheduler(struct net_device *dev)
--
2.20.1