vhost: vsock: add weight support

commit e79b431fb901ba1106670bcc80b9b617b25def7d upstream.

This patch will check the weight and exit the loop if we exceeds the
weight. This is useful for preventing vsock kthread from hogging cpu
which is guest triggerable. The weight can help to avoid starving the
request from on direction while another direction is being processed.

The value of weight is picked from vhost-net.

This addresses CVE-2019-3900.

Cc: Stefan Hajnoczi <stefanha@redhat.com>
Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 58c5c82bc0beb8527214134bf97e22250ccbb61e..bab495d73195f985ef30b26c36f5ddb0b33a5ec3 100644 (file)
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -86,6 +86,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
                            struct vhost_virtqueue *vq)
 {
        struct vhost_virtqueue *tx_vq = &vsock->vqs[VSOCK_VQ_TX];
+       int pkts = 0, total_len = 0;
        bool added = false;
        bool restart_tx = false;
 
@@ -97,7 +98,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
        /* Avoid further vmexits, we're already processing the virtqueue */
        vhost_disable_notify(&vsock->dev, vq);
 
-       for (;;) {
+       do {
                struct virtio_vsock_pkt *pkt;
                struct iov_iter iov_iter;
                unsigned out, in;
@@ -182,8 +183,9 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
                 */
                virtio_transport_deliver_tap_pkt(pkt);
 
+               total_len += pkt->len;
                virtio_transport_free_pkt(pkt);
-       }
+       } while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));
        if (added)
                vhost_signal(&vsock->dev, vq);
 
@@ -358,7 +360,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
        struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
                                                 dev);
        struct virtio_vsock_pkt *pkt;
-       int head;
+       int head, pkts = 0, total_len = 0;
        unsigned int out, in;
        bool added = false;
 
@@ -368,7 +370,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
                goto out;
 
        vhost_disable_notify(&vsock->dev, vq);
-       for (;;) {
+       do {
                u32 len;
 
                if (!vhost_vsock_more_replies(vsock)) {
@@ -409,9 +411,11 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
                else
                        virtio_transport_free_pkt(pkt);
 
-               vhost_add_used(vq, head, sizeof(pkt->hdr) + len);
+               len += sizeof(pkt->hdr);
+               vhost_add_used(vq, head, len);
+               total_len += len;
                added = true;
-       }
+       } while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));
 
 no_more_replies:
        if (added)