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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Yunjian Wang <wangyunjian@huawei.com>,
        Willem de Bruijn <willemb@google.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Jakub Kicinski <kuba@kernel.org>
Subject: [PATCH 5.4 43/92] vhost_net: fix ubuf refcount incorrectly when sendmsg fails
Date:   Mon, 11 Jan 2021 14:01:47 +0100
Message-Id: <20210111130041.220554024@linuxfoundation.org>
In-Reply-To: <20210111130039.165470698@linuxfoundation.org>
References: <20210111130039.165470698@linuxfoundation.org>
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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
@@ -860,6 +860,7 @@ static void handle_tx_zerocopy(struct vh
 	size_t len, total_len = 0;
 	int err;
 	struct vhost_net_ubuf_ref *uninitialized_var(ubufs);
+	struct ubuf_info *ubuf;
 	bool zcopy_used;
 	int sent_pkts = 0;
 
@@ -892,9 +893,7 @@ static void handle_tx_zerocopy(struct vh
 
 		/* 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;
@@ -924,7 +923,8 @@ static void handle_tx_zerocopy(struct vh
 		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;
 			}