1 files changed, 111 insertions, 39 deletions

diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index 15eb5d3d4750..0815d1357861 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * virtio transport for vsock
  *
@@ -7,8 +8,6 @@
  *
  * Some of the code is take from Gerd Hoffmann <kraxel@redhat.com>'s
  * early virtio-vsock proof-of-concept bits.
- *
- * This work is licensed under the terms of the GNU GPL, version 2.
  */
 #include <linux/spinlock.h>
 #include <linux/module.h>
@@ -39,6 +38,7 @@ struct virtio_vsock {
 	 * must be accessed with tx_lock held.
 	 */
 	struct mutex tx_lock;
+	bool tx_run;
 
 	struct work_struct send_pkt_work;
 	spinlock_t send_pkt_list_lock;
@@ -54,6 +54,7 @@ struct virtio_vsock {
 	 * must be accessed with rx_lock held.
 	 */
 	struct mutex rx_lock;
+	bool rx_run;
 	int rx_buf_nr;
 	int rx_buf_max_nr;
 
@@ -61,24 +62,28 @@ struct virtio_vsock {
 	 * vqs[VSOCK_VQ_EVENT] must be accessed with event_lock held.
 	 */
 	struct mutex event_lock;
+	bool event_run;
 	struct virtio_vsock_event event_list[8];
 
 	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)
@@ -92,6 +97,10 @@ static void virtio_transport_loopback_work(struct work_struct *work)
 	spin_unlock_bh(&vsock->loopback_list_lock);
 
 	mutex_lock(&vsock->rx_lock);
+
+	if (!vsock->rx_run)
+		goto out;
+
 	while (!list_empty(&pkts)) {
 		struct virtio_vsock_pkt *pkt;
 
@@ -100,6 +109,7 @@ static void virtio_transport_loopback_work(struct work_struct *work)
 
 		virtio_transport_recv_pkt(pkt);
 	}
+out:
 	mutex_unlock(&vsock->rx_lock);
 }
 
@@ -128,6 +138,9 @@ virtio_transport_send_pkt_work(struct work_struct *work)
 
 	mutex_lock(&vsock->tx_lock);
 
+	if (!vsock->tx_run)
+		goto out;
+
 	vq = vsock->vqs[VSOCK_VQ_TX];
 
 	for (;;) {
@@ -186,6 +199,7 @@ virtio_transport_send_pkt_work(struct work_struct *work)
 	if (added)
 		virtqueue_kick(vq);
 
+out:
 	mutex_unlock(&vsock->tx_lock);
 
 	if (restart_rx)
@@ -198,14 +212,18 @@ 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);
@@ -215,6 +233,9 @@ 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;
 }
 
@@ -223,12 +244,14 @@ 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);
@@ -256,7 +279,11 @@ 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)
@@ -308,6 +335,10 @@ static void virtio_transport_tx_work(struct work_struct *work)
 
 	vq = vsock->vqs[VSOCK_VQ_TX];
 	mutex_lock(&vsock->tx_lock);
+
+	if (!vsock->tx_run)
+		goto out;
+
 	do {
 		struct virtio_vsock_pkt *pkt;
 		unsigned int len;
@@ -318,6 +349,8 @@ static void virtio_transport_tx_work(struct work_struct *work)
 			added = true;
 		}
 	} while (!virtqueue_enable_cb(vq));
+
+out:
 	mutex_unlock(&vsock->tx_lock);
 
 	if (added)
@@ -346,6 +379,9 @@ static void virtio_transport_rx_work(struct work_struct *work)
 
 	mutex_lock(&vsock->rx_lock);
 
+	if (!vsock->rx_run)
+		goto out;
+
 	do {
 		virtqueue_disable_cb(vq);
 		for (;;) {
@@ -455,6 +491,9 @@ static void virtio_transport_event_work(struct work_struct *work)
 
 	mutex_lock(&vsock->event_lock);
 
+	if (!vsock->event_run)
+		goto out;
+
 	do {
 		struct virtio_vsock_event *event;
 		unsigned int len;
@@ -469,7 +508,7 @@ static void virtio_transport_event_work(struct work_struct *work)
 	} while (!virtqueue_enable_cb(vq));
 
 	virtqueue_kick(vsock->vqs[VSOCK_VQ_EVENT]);
-
+out:
 	mutex_unlock(&vsock->event_lock);
 }
 
@@ -566,7 +605,8 @@ 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;
 	}
@@ -591,8 +631,6 @@ 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);
@@ -606,14 +644,23 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
 	INIT_WORK(&vsock->send_pkt_work, virtio_transport_send_pkt_work);
 	INIT_WORK(&vsock->loopback_work, virtio_transport_loopback_work);
 
+	mutex_lock(&vsock->tx_lock);
+	vsock->tx_run = true;
+	mutex_unlock(&vsock->tx_lock);
+
 	mutex_lock(&vsock->rx_lock);
 	virtio_vsock_rx_fill(vsock);
+	vsock->rx_run = true;
 	mutex_unlock(&vsock->rx_lock);
 
 	mutex_lock(&vsock->event_lock);
 	virtio_vsock_event_fill(vsock);
+	vsock->event_run = true;
 	mutex_unlock(&vsock->event_lock);
 
+	vdev->priv = vsock;
+	rcu_assign_pointer(the_virtio_vsock, vsock);
+
 	mutex_unlock(&the_virtio_vsock_mutex);
 	return 0;
 
@@ -628,15 +675,33 @@ static void virtio_vsock_remove(struct virtio_device *vdev)
 	struct virtio_vsock *vsock = vdev->priv;
 	struct virtio_vsock_pkt *pkt;
 
-	flush_work(&vsock->loopback_work);
-	flush_work(&vsock->rx_work);
-	flush_work(&vsock->tx_work);
-	flush_work(&vsock->event_work);
-	flush_work(&vsock->send_pkt_work);
+	mutex_lock(&the_virtio_vsock_mutex);
+
+	vdev->priv = NULL;
+	rcu_assign_pointer(the_virtio_vsock, NULL);
+	synchronize_rcu();
 
 	/* Reset all connected sockets when the device disappear */
 	vsock_for_each_connected_socket(virtio_vsock_reset_sock);
 
+	/* Stop all work handlers to make sure no one is accessing the device,
+	 * so we can safely call vdev->config->reset().
+	 */
+	mutex_lock(&vsock->rx_lock);
+	vsock->rx_run = false;
+	mutex_unlock(&vsock->rx_lock);
+
+	mutex_lock(&vsock->tx_lock);
+	vsock->tx_run = false;
+	mutex_unlock(&vsock->tx_lock);
+
+	mutex_lock(&vsock->event_lock);
+	vsock->event_run = false;
+	mutex_unlock(&vsock->event_lock);
+
+	/* Flush all device writes and interrupts, device will not use any
+	 * more buffers.
+	 */
 	vdev->config->reset(vdev);
 
 	mutex_lock(&vsock->rx_lock);
@@ -667,12 +732,20 @@ 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);
-
+	/* Delete virtqueues and flush outstanding callbacks if any */
 	vdev->config->del_vqs(vdev);
 
+	/* Other works can be queued before 'config->del_vqs()', so we flush
+	 * all works before to free the vsock object to avoid use after free.
+	 */
+	flush_work(&vsock->loopback_work);
+	flush_work(&vsock->rx_work);
+	flush_work(&vsock->tx_work);
+	flush_work(&vsock->event_work);
+	flush_work(&vsock->send_pkt_work);
+
+	mutex_unlock(&the_virtio_vsock_mutex);
+
 	kfree(vsock);
 }
 
@@ -702,28 +775,27 @@ static int __init virtio_vsock_init(void)
 	if (!virtio_vsock_workqueue)
 		return -ENOMEM;
 
-	ret = register_virtio_driver(&virtio_vsock_driver);
+	ret = vsock_core_init(&virtio_transport.transport);
 	if (ret)
 		goto out_wq;
 
-	ret = vsock_core_init(&virtio_transport.transport);
+	ret = register_virtio_driver(&virtio_vsock_driver);
 	if (ret)
-		goto out_vdr;
+		goto out_vci;
 
 	return 0;
 
-out_vdr:
-	unregister_virtio_driver(&virtio_vsock_driver);
+out_vci:
+	vsock_core_exit();
 out_wq:
 	destroy_workqueue(virtio_vsock_workqueue);
 	return ret;
-
 }
 
 static void __exit virtio_vsock_exit(void)
 {
-	vsock_core_exit();
 	unregister_virtio_driver(&virtio_vsock_driver);
+	vsock_core_exit();
 	destroy_workqueue(virtio_vsock_workqueue);
 }