[PATCH 5.10 01/63] net/sched: sch_taprio: reset child qdiscs before freeing them

Greg Kroah-Hartman
2021-01-04T16:09:01Z

From: Davide Caratti <dcaratti@redhat.com>

[ Upstream commit 44d4775ca51805b376a8db5b34f650434a08e556 ]

syzkaller shows that packets can still be dequeued while taprio_destroy()
is running. Let sch_taprio use the reset() function to cancel the advance
timer and drop all skbs from the child qdiscs.

Fixes: 5a781ccbd19e ("tc: Add support for configuring the taprio scheduler")
Link: https://syzkaller.appspot.com/bug?id=f362872379bf8f0017fb667c1ab158f2d1e764ae
Reported-by: syzbot+8971da381fb5a31f542d@syzkaller.appspotmail.com
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Link: https://lore.kernel.org/r/63b6d79b0e830ebb0283e020db4df3cdfdfb2b94.1608142843.git.dcaratti@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sched/sch_taprio.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)

--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1596,6 +1596,21 @@ free_sched:
return err;
}

+static void taprio_reset(struct Qdisc *sch)
+{
+ struct taprio_sched *q = qdisc_priv(sch);
+ struct net_device *dev = qdisc_dev(sch);
+ int i;
+
+ hrtimer_cancel(&q->advance_timer);
+ if (q->qdiscs) {
+ for (i = 0; i < dev->num_tx_queues && q->qdiscs[i]; i++)
+ qdisc_reset(q->qdiscs[i]);
+ }
+ sch->qstats.backlog = 0;
+ sch->q.qlen = 0;
+}
+
static void taprio_destroy(struct Qdisc *sch)
{
struct taprio_sched *q = qdisc_priv(sch);
@@ -1606,7 +1621,6 @@ static void taprio_destroy(struct Qdisc
list_del(&q->taprio_list);
spin_unlock(&taprio_list_lock);

- hrtimer_cancel(&q->advance_timer);

taprio_disable_offload(dev, q, NULL);

@@ -1953,6 +1967,7 @@ static struct Qdisc_ops taprio_qdisc_ops
.init = taprio_init,
.change = taprio_change,
.destroy = taprio_destroy,
+ .reset = taprio_reset,
.peek = taprio_peek,
.dequeue = taprio_dequeue,
.enqueue = taprio_enqueue,