Jason Wang
2022-Jul-04 06:32 UTC
[PATCH net V4] virtio-net: fix the race between refill work and close
On Mon, Jul 4, 2022 at 2:19 PM Michael S. Tsirkin <mst at redhat.com> wrote:> > On Mon, Jul 04, 2022 at 12:19:48PM +0800, Jason Wang wrote: > > 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 at redhat.com> > > --- > > 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..68430d7923ac 100644 > > --- a/drivers/net/virtio_net.c > > +++ b/drivers/net/virtio_net.c > > @@ -251,6 +251,12 @@ struct virtnet_info { > > /* Does the affinity hint is set for virtqueues? */ > > bool affinity_hint_set; > > > > + /* Is refill work enabled? */ > > refilling enabledI think it should be reill work, we try refill first, if fail we schedule the work: if (!try_fill_recv(vi, rq, GFP_ATOMIC)) schedule_delayed_work(&vi->refill, 0); Thanks> > > + bool refill_work_enabled; > > > refill_work -> refill? > > > + > > + /* The lock to synchronize the access to refill_work_enabled */ > > .. and refill > > And maybe put these field near the refill field. > > > + spinlock_t refill_lock; > > + > > /* CPU hotplug instances for online & dead */ > > struct hlist_node node; > > struct hlist_node node_dead; > > @@ -348,6 +354,20 @@ static struct page *get_a_page(struct receive_queue *rq, gfp_t gfp_mask) > > return p; > > } > > > > +static void enable_refill_work(struct virtnet_info *vi) > > +{ > > + spin_lock_bh(&vi->refill_lock); > > + vi->refill_work_enabled = true; > > + spin_unlock_bh(&vi->refill_lock); > > +} > > + > > +static void disable_refill_work(struct virtnet_info *vi) > > +{ > > + spin_lock_bh(&vi->refill_lock); > > + vi->refill_work_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->refill_work_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_refill_work(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_refill_work(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_refill_work(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 >
Michael S. Tsirkin
2022-Jul-04 07:03 UTC
[PATCH net V4] virtio-net: fix the race between refill work and close
On Mon, Jul 04, 2022 at 02:32:45PM +0800, Jason Wang wrote:> On Mon, Jul 4, 2022 at 2:19 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > On Mon, Jul 04, 2022 at 12:19:48PM +0800, Jason Wang wrote: > > > 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 at redhat.com> > > > --- > > > 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..68430d7923ac 100644 > > > --- a/drivers/net/virtio_net.c > > > +++ b/drivers/net/virtio_net.c > > > @@ -251,6 +251,12 @@ struct virtnet_info { > > > /* Does the affinity hint is set for virtqueues? */ > > > bool affinity_hint_set; > > > > > > + /* Is refill work enabled? */ > > > > refilling enabled > > I think it should be reill work, we try refill first, if fail we > schedule the work: > > if (!try_fill_recv(vi, rq, GFP_ATOMIC)) > schedule_delayed_work(&vi->refill, 0); > > Thanksmaybe "delayed refill"? It's not "work" it's a work struct. I'm trying to be consistent with: /* Work struct for refilling if we run low on memory. */ struct delayed_work refill;> > > > > + bool refill_work_enabled; > > > > > > refill_work -> refill? > > > > > + > > > + /* The lock to synchronize the access to refill_work_enabled */ > > > > .. and refill > > > > And maybe put these field near the refill field. > > > > > + spinlock_t refill_lock; > > > + > > > /* CPU hotplug instances for online & dead */ > > > struct hlist_node node; > > > struct hlist_node node_dead; > > > @@ -348,6 +354,20 @@ static struct page *get_a_page(struct receive_queue *rq, gfp_t gfp_mask) > > > return p; > > > } > > > > > > +static void enable_refill_work(struct virtnet_info *vi) > > > +{ > > > + spin_lock_bh(&vi->refill_lock); > > > + vi->refill_work_enabled = true; > > > + spin_unlock_bh(&vi->refill_lock); > > > +} > > > + > > > +static void disable_refill_work(struct virtnet_info *vi) > > > +{ > > > + spin_lock_bh(&vi->refill_lock); > > > + vi->refill_work_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->refill_work_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_refill_work(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_refill_work(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_refill_work(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 > >