[PATCH net V5] virtio-net: fix the race between refill work and close
From: Jason Wang <jasowang@redhat.com>
Date: 2022-07-04 07:49:15
Also in:
lkml, virtualization
Subsystem:
networking drivers, the rest, virtio net driver · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, "Michael S. Tsirkin", Jason Wang
We try using cancel_delayed_work_sync() to prevent the work from
enabling NAPI. This is insufficient since we don't disable the source
of the refill work scheduling. This means an NAPI poll callback after
cancel_delayed_work_sync() can schedule the refill work then can
re-enable the NAPI that leads to use-after-free [1].
Since the work can enable NAPI, we can't simply disable NAPI before
calling cancel_delayed_work_sync(). So fix this by introducing a
dedicated boolean to control whether or not the work could be
scheduled from NAPI.
[1]
==================================================================
BUG: KASAN: use-after-free in refill_work+0x43/0xd4
Read of size 2 at addr ffff88810562c92e by task kworker/2:1/42
CPU: 2 PID: 42 Comm: kworker/2:1 Not tainted 5.19.0-rc1+ #480
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
Workqueue: events refill_work
Call Trace:
<TASK>
dump_stack_lvl+0x34/0x44
print_report.cold+0xbb/0x6ac
? _printk+0xad/0xde
? refill_work+0x43/0xd4
kasan_report+0xa8/0x130
? refill_work+0x43/0xd4
refill_work+0x43/0xd4
process_one_work+0x43d/0x780
worker_thread+0x2a0/0x6f0
? process_one_work+0x780/0x780
kthread+0x167/0x1a0
? kthread_exit+0x50/0x50
ret_from_fork+0x22/0x30
</TASK>
...
Fixes: b2baed69e605c ("virtio_net: set/cancel work on ndo_open/ndo_stop")
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
Changes since V4:
- Tweak the variable name (using delayed_refill)
Changes since V3:
- rebase to -net
Changes since V2:
- use spin_unlock()/lock_bh() in open/stop to synchronize with bh
Changes since V1:
- Tweak the changelog
---
drivers/net/virtio_net.c | 35 +++++++++++++++++++++++++++++++++--
1 file changed, 33 insertions(+), 2 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 356cf8dd4164..b9ac4431becb 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c@@ -245,6 +245,12 @@ struct virtnet_info { /* Work struct for refilling if we run low on memory. */ struct delayed_work refill; + /* Is delayed refill enabled? */ + bool delayed_refill_enabled; + + /* The lock to synchronize the access to delayed_refill_enabled */ + spinlock_t refill_lock; + /* Work struct for config space updates */ struct work_struct config_work;
@@ -348,6 +354,20 @@ static struct page *get_a_page(struct receive_queue *rq, gfp_t gfp_mask) return p; } +static void enable_delayed_refill(struct virtnet_info *vi) +{ + spin_lock_bh(&vi->refill_lock); + vi->delayed_refill_enabled = true; + spin_unlock_bh(&vi->refill_lock); +} + +static void disable_delayed_refill(struct virtnet_info *vi) +{ + spin_lock_bh(&vi->refill_lock); + vi->delayed_refill_enabled = false; + spin_unlock_bh(&vi->refill_lock); +} + static void virtqueue_napi_schedule(struct napi_struct *napi, struct virtqueue *vq) {
@@ -1527,8 +1547,12 @@ static int virtnet_receive(struct receive_queue *rq, int budget, } if (rq->vq->num_free > min((unsigned int)budget, virtqueue_get_vring_size(rq->vq)) / 2) { - if (!try_fill_recv(vi, rq, GFP_ATOMIC)) - schedule_delayed_work(&vi->refill, 0); + if (!try_fill_recv(vi, rq, GFP_ATOMIC)) { + spin_lock(&vi->refill_lock); + if (vi->delayed_refill_enabled) + schedule_delayed_work(&vi->refill, 0); + spin_unlock(&vi->refill_lock); + } } u64_stats_update_begin(&rq->stats.syncp);
@@ -1651,6 +1675,8 @@ static int virtnet_open(struct net_device *dev) struct virtnet_info *vi = netdev_priv(dev); int i, err; + enable_delayed_refill(vi); + for (i = 0; i < vi->max_queue_pairs; i++) { if (i < vi->curr_queue_pairs) /* Make sure we have some buffers: if oom use wq. */
@@ -2033,6 +2059,8 @@ static int virtnet_close(struct net_device *dev) struct virtnet_info *vi = netdev_priv(dev); int i; + /* Make sure NAPI doesn't schedule refill work */ + disable_delayed_refill(vi); /* Make sure refill_work doesn't re-enable napi! */ cancel_delayed_work_sync(&vi->refill);
@@ -2792,6 +2820,8 @@ static int virtnet_restore_up(struct virtio_device *vdev) virtio_device_ready(vdev); + enable_delayed_refill(vi); + if (netif_running(vi->dev)) { err = virtnet_open(vi->dev); if (err)
@@ -3535,6 +3565,7 @@ static int virtnet_probe(struct virtio_device *vdev) vdev->priv = vi; INIT_WORK(&vi->config_work, virtnet_config_changed_work); + spin_lock_init(&vi->refill_lock); /* If we can receive ANY GSO packets, we must allocate large ones. */ if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||
--
2.25.1