Currently there is concurrent reset and enqueue operation for the same lockless qdisc when there is no lock to synchronize the q->enqueue() in __dev_xmit_skb() with the qdisc reset operation in qdisc_deactivate() called by dev_deactivate_queue(), which may cause out-of-bounds access for priv->ring[] in hns3 driver if user has requested a smaller queue num when __dev_xmit_skb() still enqueue a skb with a larger queue_mapping after the corresponding qdisc is reset, and call hns3_nic_net_xmit() with that skb later.
Avoid the above concurrent op by calling synchronize_rcu_tasks() after assigning new qdisc to dev_queue->qdisc and before calling qdisc_deactivate() to make sure skb with larger queue_mapping enqueued to old qdisc will always be reset when qdisc_deactivate() is called. Signed-off-by: Yunsheng Lin <linyunsh...@huawei.com> --- net/sched/sch_generic.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index 265a61d..6e42237 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -1160,8 +1160,13 @@ static void dev_deactivate_queue(struct net_device *dev, qdisc = rtnl_dereference(dev_queue->qdisc); if (qdisc) { - qdisc_deactivate(qdisc); rcu_assign_pointer(dev_queue->qdisc, qdisc_default); + + /* Make sure lockless qdisc enqueuing is done with the + * old qdisc in __dev_xmit_skb(). + */ + synchronize_rcu_tasks(); + qdisc_deactivate(qdisc); } } -- 2.8.1