The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 49d8c5ffad07ca014cfae72a1b9b8c52b6ad9cb8 Mon Sep 17 00:00:00 2001

From: Stefano Garzarella sgarzare@redhat.com Date: Mon, 22 Nov 2021 17:35:24 +0100 Subject: [PATCH] vhost/vsock: fix incorrect used length reported to the guest

The "used length" reported by calling vhost_add_used() must be the number of bytes written by the device (using "in" buffers).

In vhost_vsock_handle_tx_kick() the device only reads the guest buffers (they are all "out" buffers), without writing anything, so we must pass 0 as "used length" to comply virtio spec.

Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") Cc: stable@vger.kernel.org Reported-by: Halil Pasic pasic@linux.ibm.com Suggested-by: Jason Wang jasowang@redhat.com Signed-off-by: Stefano Garzarella sgarzare@redhat.com Link: https://lore.kernel.org/r/20211122163525.294024-2-sgarzare@redhat.com Signed-off-by: Michael S. Tsirkin mst@redhat.com Reviewed-by: Stefan Hajnoczi stefanha@redhat.com Reviewed-by: Halil Pasic pasic@linux.ibm.com

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c index 938aefbc75ec..4e3b95af7ee4 100644 --- a/drivers/vhost/vsock.c +++ b/drivers/vhost/vsock.c @@ -554,7 +554,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work) virtio_transport_free_pkt(pkt);

len += sizeof(pkt->hdr); - vhost_add_used(vq, head, len); + vhost_add_used(vq, head, 0); total_len += len; added = true; } while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));