[PATCH 5.4 23/43] net: sch_generic: aviod concurrent reset and enqueue op for lockless qdisc

Greg Kroah-Hartman
2020-09-25T12:51:58Z

From: Yunsheng Lin <linyunsheng@huawei.com>

[ Upstream commit 2fb541c862c987d02dfdf28f1545016deecfa0d5 ]

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.

Reused the existing synchronize_net() in dev_deactivate_many() to
make sure skb with larger queue_mapping enqueued to old qdisc(which
is saved in dev_queue->qdisc_sleeping) will always be reset when
dev_reset_queue() is called.

Fixes: 6b3ba9146fe6 ("net: sched: allow qdiscs to handle locking")
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sched/sch_generic.c | 49 ++++++++++++++++++++++++++++++++----------------
1 file changed, 33 insertions(+), 16 deletions(-)

--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -1126,27 +1126,36 @@ static void dev_deactivate_queue(struct
struct netdev_queue *dev_queue,
void *_qdisc_default)
{
- struct Qdisc *qdisc_default = _qdisc_default;
- struct Qdisc *qdisc;
+ struct Qdisc *qdisc = rtnl_dereference(dev_queue->qdisc);

- qdisc = rtnl_dereference(dev_queue->qdisc);
if (qdisc) {
- bool nolock = qdisc->flags & TCQ_F_NOLOCK;
-
- if (nolock)
- spin_lock_bh(&qdisc->seqlock);
- spin_lock_bh(qdisc_lock(qdisc));
-
if (!(qdisc->flags & TCQ_F_BUILTIN))
set_bit(__QDISC_STATE_DEACTIVATED, &qdisc->state);
+ }
+}

- rcu_assign_pointer(dev_queue->qdisc, qdisc_default);
- qdisc_reset(qdisc);
+static void dev_reset_queue(struct net_device *dev,
+ struct netdev_queue *dev_queue,
+ void *_unused)
+{
+ struct Qdisc *qdisc;
+ bool nolock;

- spin_unlock_bh(qdisc_lock(qdisc));
- if (nolock)
- spin_unlock_bh(&qdisc->seqlock);
- }
+ qdisc = dev_queue->qdisc_sleeping;
+ if (!qdisc)
+ return;
+
+ nolock = qdisc->flags & TCQ_F_NOLOCK;
+
+ if (nolock)
+ spin_lock_bh(&qdisc->seqlock);
+ spin_lock_bh(qdisc_lock(qdisc));
+
+ qdisc_reset(qdisc);
+
+ spin_unlock_bh(qdisc_lock(qdisc));
+ if (nolock)
+ spin_unlock_bh(&qdisc->seqlock);
}

static bool some_qdisc_is_busy(struct net_device *dev)
@@ -1207,12 +1216,20 @@ void dev_deactivate_many(struct list_hea
dev_watchdog_down(dev);
}

- /* Wait for outstanding qdisc-less dev_queue_xmit calls.
+ /* Wait for outstanding qdisc-less dev_queue_xmit calls or
+ * outstanding qdisc enqueuing calls.
* This is avoided if all devices are in dismantle phase :
* Caller will call synchronize_net() for us
*/
synchronize_net();

+ list_for_each_entry(dev, head, close_list) {
+ netdev_for_each_tx_queue(dev, dev_reset_queue, NULL);
+
+ if (dev_ingress_queue(dev))
+ dev_reset_queue(dev, dev_ingress_queue(dev), NULL);
+ }
+
/* Wait for outstanding qdisc_run calls. */
list_for_each_entry(dev, head, close_list) {
while (some_qdisc_is_busy(dev))