netdev - [PATCH 1/2] vhost/vsock: fix incorrect used length reported to the guest

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Date:   Mon, 22 Nov 2021 17:35:24 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     virtualization@...ts.linux-foundation.org
Cc:     linux-kernel@...r.kernel.org,
        Stefano Garzarella <sgarzare@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>, netdev@...r.kernel.org,
        Halil Pasic <pasic@...ux.ibm.com>, kvm@...r.kernel.org,
        Asias He <asias@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>
Subject: [PATCH 1/2] 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@...r.kernel.org
Reported-by: Halil Pasic <pasic@...ux.ibm.com>
Suggested-by: Jason Wang <jasowang@...hat.com>
Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
---
 drivers/vhost/vsock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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)));
-- 
2.31.1