[PATCH net-next 13/14] vsock: prevent transport modules unloading

Stefano Garzarella
2019-10-23T09:58:41Z

This patch adds 'module' member in the 'struct vsock_transport'
in order to get/put the transport module. This prevents the
module unloading while sockets are assigned to it.

We increase the module refcnt when a socket is assigned to a
transport, and we decrease the module refcnt when the socket
is destructed.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
RFC -> v1:
- fixed typo 's/tranport/transport/' in a comment (Stefan)
---
drivers/vhost/vsock.c | 2 ++
include/net/af_vsock.h | 2 ++
net/vmw_vsock/af_vsock.c | 20 ++++++++++++++++----
net/vmw_vsock/hyperv_transport.c | 2 ++
net/vmw_vsock/virtio_transport.c | 2 ++
net/vmw_vsock/vmci_transport.c | 1 +
6 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index b235f4bbe8ea..fdda9ec625ad 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -386,6 +386,8 @@ static bool vhost_vsock_more_replies(struct vhost_vsock *vsock)

static struct virtio_transport vhost_transport = {
.transport = {
+ .module = THIS_MODULE,
+
.get_local_cid = vhost_transport_get_local_cid,

.init = virtio_transport_do_socket_init,
diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index 27a3463e4892..269e2f034789 100644
--- a/include/net/af_vsock.h
+++ b/include/net/af_vsock.h
@@ -100,6 +100,8 @@ struct vsock_transport_send_notify_data {
#define VSOCK_TRANSPORT_F_DGRAM 0x00000004

struct vsock_transport {
+ struct module *module;
+
/* Initialize/tear-down socket. */
int (*init)(struct vsock_sock *, struct vsock_sock *);
void (*destruct)(struct vsock_sock *);
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index dddd85d9a147..1f2e707cae66 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -380,6 +380,16 @@ void vsock_enqueue_accept(struct sock *listener, struct sock *connected)
}
EXPORT_SYMBOL_GPL(vsock_enqueue_accept);

+static void vsock_deassign_transport(struct vsock_sock *vsk)
+{
+ if (!vsk->transport)
+ return;
+
+ vsk->transport->destruct(vsk);
+ module_put(vsk->transport->module);
+ vsk->transport = NULL;
+}
+
/* Assign a transport to a socket and call the .init transport callback.
*
* Note: for stream socket this must be called when vsk->remote_addr is set
@@ -413,10 +423,13 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
return 0;

vsk->transport->release(vsk);
- vsk->transport->destruct(vsk);
+ vsock_deassign_transport(vsk);
}

- if (!new_transport)
+ /* We increase the module refcnt to prevent the transport unloading
+ * while there are open sockets assigned to it.
+ */
+ if (!new_transport || !try_module_get(new_transport->module))
return -ENODEV;

vsk->transport = new_transport;
@@ -737,8 +750,7 @@ static void vsock_sk_destruct(struct sock *sk)
{
struct vsock_sock *vsk = vsock_sk(sk);

- if (vsk->transport)
- vsk->transport->destruct(vsk);
+ vsock_deassign_transport(vsk);

/* When clearing these addresses, there's no need to set the family and
* possibly register the address family with the kernel.
diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
index 0ea66d87af39..d0a349d85414 100644
--- a/net/vmw_vsock/hyperv_transport.c
+++ b/net/vmw_vsock/hyperv_transport.c
@@ -857,6 +857,8 @@ int hvs_notify_send_post_enqueue(struct vsock_sock *vsk, ssize_t written,
}

static struct vsock_transport hvs_transport = {
+ .module = THIS_MODULE,
+
.get_local_cid = hvs_get_local_cid,

.init = hvs_sock_init,
diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index 83ad85050384..1458c5c8b64d 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -462,6 +462,8 @@ static void virtio_vsock_rx_done(struct virtqueue *vq)

static struct virtio_transport virtio_transport = {
.transport = {
+ .module = THIS_MODULE,
+
.get_local_cid = virtio_transport_get_local_cid,

.init = virtio_transport_do_socket_init,
diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
index 04437f822d82..0cbf023fae11 100644
--- a/net/vmw_vsock/vmci_transport.c
+++ b/net/vmw_vsock/vmci_transport.c
@@ -2019,6 +2019,7 @@ static u32 vmci_transport_get_local_cid(void)
}

static struct vsock_transport vmci_transport = {
+ .module = THIS_MODULE,
.init = vmci_transport_socket_init,
.destruct = vmci_transport_destruct,
.release = vmci_transport_release,
--
2.21.0