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vsock/virtio: use RCU to avoid use-after-free on the_virtio_vsock

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Some callbacks used by the upper layers can run while we are in the
.remove(). A potential use-after-free can happen, because we free
the_virtio_vsock without knowing if the callbacks are over or not.

To solve this issue we move the assignment of the_virtio_vsock at the
end of .probe(), when we finished all the initialization, and at the
beginning of .remove(), before to release resources.
For the same reason, we do the same also for the vdev->priv.

We use RCU to be sure that all callbacks that use the_virtio_vsock
ended before freeing it. This is not required for callbacks that
use vdev->priv, because after the vdev->config->del_vqs() we are sure
that they are ended and will no longer be invoked.

We also take the mutex during the .remove() to avoid that .probe() can
run while we are resetting the device.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Stefano Garzarella 2019-07-05 13:04:52 +02:00 committed by David S. Miller
parent 1a2d405c00
commit 0deab087b1
1 changed files with 46 additions and 24 deletions
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70
net/vmw_vsock/virtio_transport.c
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@ -65,19 +65,22 @@ struct virtio_vsock {
u32 guest_cid;
};
static struct virtio_vsock *virtio_vsock_get(void)
{
return the_virtio_vsock;
}
static u32 virtio_transport_get_local_cid(void)
{
struct virtio_vsock *vsock = virtio_vsock_get();
struct virtio_vsock *vsock;
u32 ret;
if (!vsock)
return VMADDR_CID_ANY;
rcu_read_lock();
vsock = rcu_dereference(the_virtio_vsock);
if (!vsock) {
ret = VMADDR_CID_ANY;
goto out_rcu;
}
return vsock->guest_cid;
ret = vsock->guest_cid;
out_rcu:
rcu_read_unlock();
return ret;
}
static void virtio_transport_loopback_work(struct work_struct *work)
@ -197,14 +200,18 @@ virtio_transport_send_pkt(struct virtio_vsock_pkt *pkt)
struct virtio_vsock *vsock;
int len = pkt->len;
vsock = virtio_vsock_get();
rcu_read_lock();
vsock = rcu_dereference(the_virtio_vsock);
if (!vsock) {
virtio_transport_free_pkt(pkt);
return -ENODEV;
len = -ENODEV;
goto out_rcu;
}
if (le64_to_cpu(pkt->hdr.dst_cid) == vsock->guest_cid)
return virtio_transport_send_pkt_loopback(vsock, pkt);
if (le64_to_cpu(pkt->hdr.dst_cid) == vsock->guest_cid) {
len = virtio_transport_send_pkt_loopback(vsock, pkt);
goto out_rcu;
}
if (pkt->reply)
atomic_inc(&vsock->queued_replies);
@ -214,6 +221,9 @@ virtio_transport_send_pkt(struct virtio_vsock_pkt *pkt)
spin_unlock_bh(&vsock->send_pkt_list_lock);
queue_work(virtio_vsock_workqueue, &vsock->send_pkt_work);
out_rcu:
rcu_read_unlock();
return len;
}
@ -222,12 +232,14 @@ virtio_transport_cancel_pkt(struct vsock_sock *vsk)
{
struct virtio_vsock *vsock;
struct virtio_vsock_pkt *pkt, *n;
int cnt = 0;
int cnt = 0, ret;
LIST_HEAD(freeme);
vsock = virtio_vsock_get();
rcu_read_lock();
vsock = rcu_dereference(the_virtio_vsock);
if (!vsock) {
return -ENODEV;
ret = -ENODEV;
goto out_rcu;
}
spin_lock_bh(&vsock->send_pkt_list_lock);
@ -255,7 +267,11 @@ virtio_transport_cancel_pkt(struct vsock_sock *vsk)
queue_work(virtio_vsock_workqueue, &vsock->rx_work);
}
return 0;
ret = 0;
out_rcu:
rcu_read_unlock();
return ret;
}
static void virtio_vsock_rx_fill(struct virtio_vsock *vsock)
@ -565,7 +581,8 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
return ret;
/* Only one virtio-vsock device per guest is supported */
if (the_virtio_vsock) {
if (rcu_dereference_protected(the_virtio_vsock,
lockdep_is_held(&the_virtio_vsock_mutex))) {
ret = -EBUSY;
goto out;
}
@ -590,8 +607,6 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
vsock->rx_buf_max_nr = 0;
atomic_set(&vsock->queued_replies, 0);
vdev->priv = vsock;
the_virtio_vsock = vsock;
mutex_init(&vsock->tx_lock);
mutex_init(&vsock->rx_lock);
mutex_init(&vsock->event_lock);
@ -613,6 +628,9 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
virtio_vsock_event_fill(vsock);
mutex_unlock(&vsock->event_lock);
vdev->priv = vsock;
rcu_assign_pointer(the_virtio_vsock, vsock);
mutex_unlock(&the_virtio_vsock_mutex);
return 0;
@ -627,6 +645,12 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
struct virtio_vsock *vsock = vdev->priv;
struct virtio_vsock_pkt *pkt;
mutex_lock(&the_virtio_vsock_mutex);
vdev->priv = NULL;
rcu_assign_pointer(the_virtio_vsock, NULL);
synchronize_rcu();
flush_work(&vsock->loopback_work);
flush_work(&vsock->rx_work);
flush_work(&vsock->tx_work);
@ -666,12 +690,10 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
}
spin_unlock_bh(&vsock->loopback_list_lock);
mutex_lock(&the_virtio_vsock_mutex);
the_virtio_vsock = NULL;
mutex_unlock(&the_virtio_vsock_mutex);
vdev->config->del_vqs(vdev);
mutex_unlock(&the_virtio_vsock_mutex);
kfree(vsock);
}