vhost_net: revert upend_idx only on retriable error

[ Upstream commit 1f5d2e3bab16369d5d4b4020a25db4ab1f4f082c ]

Fix possible virtqueue used buffers leak and corresponding stuck
in case of temporary -EIO from sendmsg() which is produced by
tun driver while backend device is not up.

In case of no-retriable error and zcopy do not revert upend_idx
to pass packet data (that is update used_idx in corresponding
vhost_zerocopy_signal_used()) as if packet data has been
transferred successfully.

v2: set vq->heads[ubuf->desc].len equal to VHOST_DMA_DONE_LEN
in case of fake successful transmit.

Signed-off-by: Andrey Smetanin <asmetanin@yandex-team.ru>
Message-Id: <20230424204411.24888-1-asmetanin@yandex-team.ru>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Andrey Smetanin <asmetanin@yandex-team.ru>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 4c538b3..4418192 100644 (file)
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -934,13 +934,18 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
 
                err = sock->ops->sendmsg(sock, &msg, len);
                if (unlikely(err < 0)) {
+                       bool retry = err == -EAGAIN || err == -ENOMEM || err == -ENOBUFS;
+
                        if (zcopy_used) {
                                if (vq->heads[ubuf->desc].len == VHOST_DMA_IN_PROGRESS)
                                        vhost_net_ubuf_put(ubufs);
-                               nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
-                                       % UIO_MAXIOV;
+                               if (retry)
+                                       nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
+                                               % UIO_MAXIOV;
+                               else
+                                       vq->heads[ubuf->desc].len = VHOST_DMA_DONE_LEN;
                        }
-                       if (err == -EAGAIN || err == -ENOMEM || err == -ENOBUFS) {
+                       if (retry) {
                                vhost_discard_vq_desc(vq, 1);
                                vhost_net_enable_vq(net, vq);
                                break;