[PATCH 4.14 22/57] vhost_net: fix ubuf refcount incorrectly when sendmsg fails

Greg Kroah-Hartman
2021-01-11T13:56:07Z

From: Yunjian Wang <wangyunjian@huawei.com>

[ Upstream commit 01e31bea7e622f1890c274f4aaaaf8bccd296aa5 ]

Currently the vhost_zerocopy_callback() maybe be called to decrease
the refcount when sendmsg fails in tun. The error handling in vhost
handle_tx_zerocopy() will try to decrease the same refcount again.
This is wrong. To fix this issue, we only call vhost_net_ubuf_put()
when vq->heads[nvq->desc].len == VHOST_DMA_IN_PROGRESS.

Fixes: bab632d69ee4 ("vhost: vhost TX zero-copy support")
Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/1609207308-20544-1-git-send-email-wangyunjian@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/vhost/net.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -466,6 +466,7 @@ static void handle_tx(struct vhost_net *
size_t hdr_size;
struct socket *sock;
struct vhost_net_ubuf_ref *uninitialized_var(ubufs);
+ struct ubuf_info *ubuf;
bool zcopy, zcopy_used;
int sent_pkts = 0;

@@ -532,9 +533,7 @@ static void handle_tx(struct vhost_net *

/* use msg_control to pass vhost zerocopy ubuf info to skb */
if (zcopy_used) {
- struct ubuf_info *ubuf;
ubuf = nvq->ubuf_info + nvq->upend_idx;
-
vq->heads[nvq->upend_idx].id = cpu_to_vhost32(vq, head);
vq->heads[nvq->upend_idx].len = VHOST_DMA_IN_PROGRESS;
ubuf->callback = vhost_zerocopy_callback;
@@ -563,7 +562,8 @@ static void handle_tx(struct vhost_net *
err = sock->ops->sendmsg(sock, &msg, len);
if (unlikely(err < 0)) {
if (zcopy_used) {
- vhost_net_ubuf_put(ubufs);
+ 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;
}