[PATCH net-next v8 07/14] vhost/vsock: add netns support

[Bobby Eshleman <bobbyeshleman@gmail.com>]

From: Bobby Eshleman <bobbyeshleman@meta.com>

Add the ability to isolate vhost-vsock flows using namespaces.

The VM, via the vhost_vsock struct, inherits its namespace from the
process that opens the vhost-vsock device. vhost_vsock lookup functions
are modified to take into account the mode (e.g., if CIDs are matching
but modes don't align, then return NULL).

vhost_vsock now acquires a reference to the namespace.

Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
---
Changes in v7:
- remove the check_global flag of vhost_vsock_get(), that logic was both
  wrong and not necessary, reuse vsock_net_check_mode() instead
- remove 'delete me' comment
Changes in v5:
- respect pid namespaces when assigning namespace to vhost_vsock
---
 drivers/vhost/vsock.c | 44 ++++++++++++++++++++++++++++++++++----------
 1 file changed, 34 insertions(+), 10 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 34adf0cf9124..df6136633cd8 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -46,6 +46,11 @@ static DEFINE_READ_MOSTLY_HASHTABLE(vhost_vsock_hash, 8);
 struct vhost_vsock {
 	struct vhost_dev dev;
 	struct vhost_virtqueue vqs[2];
+	struct net *net;
+	netns_tracker ns_tracker;
+
+	/* The ns mode at the time vhost_vsock was created */
+	enum vsock_net_mode net_mode;
 
 	/* Link to global vhost_vsock_hash, writes use vhost_vsock_mutex */
 	struct hlist_node hash;
@@ -67,7 +72,8 @@ static u32 vhost_transport_get_local_cid(void)
 /* Callers that dereference the return value must hold vhost_vsock_mutex or the
  * RCU read lock.
  */
-static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
+static struct vhost_vsock *vhost_vsock_get(u32 guest_cid, struct net *net,
+					   enum vsock_net_mode mode)
 {
 	struct vhost_vsock *vsock;
 
@@ -78,9 +84,9 @@ static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
 		if (other_cid == 0)
 			continue;
 
-		if (other_cid == guest_cid)
+		if (other_cid == guest_cid &&
+		    vsock_net_check_mode(net, mode, vsock->net, vsock->net_mode))
 			return vsock;
-
 	}
 
 	return NULL;
@@ -271,14 +277,16 @@ static void vhost_transport_send_pkt_work(struct vhost_work *work)
 static int
 vhost_transport_send_pkt(struct sk_buff *skb)
 {
+	enum vsock_net_mode mode = virtio_vsock_skb_net_mode(skb);
 	struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
+	struct net *net = virtio_vsock_skb_net(skb);
 	struct vhost_vsock *vsock;
 	int len = skb->len;
 
 	rcu_read_lock();
 
 	/* Find the vhost_vsock according to guest context id  */
-	vsock = vhost_vsock_get(le64_to_cpu(hdr->dst_cid));
+	vsock = vhost_vsock_get(le64_to_cpu(hdr->dst_cid), net, mode);
 	if (!vsock) {
 		rcu_read_unlock();
 		kfree_skb(skb);
@@ -305,7 +313,8 @@ vhost_transport_cancel_pkt(struct vsock_sock *vsk)
 	rcu_read_lock();
 
 	/* Find the vhost_vsock according to guest context id  */
-	vsock = vhost_vsock_get(vsk->remote_addr.svm_cid);
+	vsock = vhost_vsock_get(vsk->remote_addr.svm_cid,
+				sock_net(sk_vsock(vsk)), vsk->net_mode);
 	if (!vsock)
 		goto out;
 
@@ -327,7 +336,7 @@ vhost_transport_cancel_pkt(struct vsock_sock *vsk)
 }
 
 static struct sk_buff *
-vhost_vsock_alloc_skb(struct vhost_virtqueue *vq,
+vhost_vsock_alloc_skb(struct vhost_vsock *vsock, struct vhost_virtqueue *vq,
 		      unsigned int out, unsigned int in)
 {
 	struct virtio_vsock_hdr *hdr;
@@ -353,6 +362,9 @@ vhost_vsock_alloc_skb(struct vhost_virtqueue *vq,
 	if (!skb)
 		return NULL;
 
+	virtio_vsock_skb_set_net(skb, vsock->net);
+	virtio_vsock_skb_set_net_mode(skb, vsock->net_mode);
+
 	iov_iter_init(&iov_iter, ITER_SOURCE, vq->iov, out, len);
 
 	hdr = virtio_vsock_hdr(skb);
@@ -462,11 +474,12 @@ static struct virtio_transport vhost_transport = {
 
 static bool vhost_transport_seqpacket_allow(struct vsock_sock *vsk, u32 remote_cid)
 {
+	struct net *net = sock_net(sk_vsock(vsk));
 	struct vhost_vsock *vsock;
 	bool seqpacket_allow = false;
 
 	rcu_read_lock();
-	vsock = vhost_vsock_get(remote_cid);
+	vsock = vhost_vsock_get(remote_cid, net, vsk->net_mode);
 
 	if (vsock)
 		seqpacket_allow = vsock->seqpacket_allow;
@@ -520,7 +533,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
 			break;
 		}
 
-		skb = vhost_vsock_alloc_skb(vq, out, in);
+		skb = vhost_vsock_alloc_skb(vsock, vq, out, in);
 		if (!skb) {
 			vq_err(vq, "Faulted on pkt\n");
 			continue;
@@ -652,8 +665,10 @@ static void vhost_vsock_free(struct vhost_vsock *vsock)
 
 static int vhost_vsock_dev_open(struct inode *inode, struct file *file)
 {
+
 	struct vhost_virtqueue **vqs;
 	struct vhost_vsock *vsock;
+	struct net *net;
 	int ret;
 
 	/* This struct is large and allocation could fail, fall back to vmalloc
@@ -669,6 +684,14 @@ static int vhost_vsock_dev_open(struct inode *inode, struct file *file)
 		goto out;
 	}
 
+	net = current->nsproxy->net_ns;
+	vsock->net = get_net_track(net, &vsock->ns_tracker, GFP_KERNEL);
+
+	/* Cache the mode of the namespace so that if that netns mode changes,
+	 * the vhost_vsock will continue to function as expected.
+	 */
+	vsock->net_mode = vsock_net_mode(net);
+
 	vsock->guest_cid = 0; /* no CID assigned yet */
 	vsock->seqpacket_allow = false;
 
@@ -708,7 +731,7 @@ static void vhost_vsock_reset_orphans(struct sock *sk)
 	 */
 
 	/* If the peer is still valid, no need to reset connection */
-	if (vhost_vsock_get(vsk->remote_addr.svm_cid))
+	if (vhost_vsock_get(vsk->remote_addr.svm_cid, sock_net(sk), vsk->net_mode))
 		return;
 
 	/* If the close timeout is pending, let it expire.  This avoids races
@@ -753,6 +776,7 @@ static int vhost_vsock_dev_release(struct inode *inode, struct file *file)
 	virtio_vsock_skb_queue_purge(&vsock->send_pkt_queue);
 
 	vhost_dev_cleanup(&vsock->dev);
+	put_net_track(vsock->net, &vsock->ns_tracker);
 	kfree(vsock->dev.vqs);
 	vhost_vsock_free(vsock);
 	return 0;
@@ -779,7 +803,7 @@ static int vhost_vsock_set_cid(struct vhost_vsock *vsock, u64 guest_cid)
 
 	/* Refuse if CID is already in use */
 	mutex_lock(&vhost_vsock_mutex);
-	other = vhost_vsock_get(guest_cid);
+	other = vhost_vsock_get(guest_cid, vsock->net, vsock->net_mode);
 	if (other && other != vsock) {
 		mutex_unlock(&vhost_vsock_mutex);
 		return -EADDRINUSE;

-- 
2.47.3