From 2220e8189fb94068dbad333228659fbac819abb0 Mon Sep 17 00:00:00 2001
From: Jason Wang <jasowang@redhat.com>
Date: Tue, 2 Jan 2024 11:29:01 +0800
Subject: [PATCH] virtio-net: correctly copy vnet header when flushing TX

When HASH_REPORT is negotiated, the guest_hdr_len might be larger than
the size of the mergeable rx buffer header. Using
virtio_net_hdr_mrg_rxbuf during the header swap might lead a stack
overflow in this case. Fixing this by using virtio_net_hdr_v1_hash
instead.

Reported-by: Xiao Lei <leixiao.nop@zju.edu.cn>
Cc: Yuri Benditovich <yuri.benditovich@daynix.com>
Cc: qemu-stable@nongnu.org
Cc: Mauro Matteo Cascella <mcascell@redhat.com>
Fixes: CVE-2023-6693
Fixes: e22f0603fb2f ("virtio-net: reference implementation of hash report")
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Jason Wang <jasowang@redhat.com>

Upstream-Status: Backport [https://gitlab.com/qemu-project/qemu/-/commit/2220e8189fb94068dbad333228659fbac819abb0]
CVE: CVE-2023-6693
Signed-off-by: Vivek Kumbhar <vkumbhar@mvista.com>
---
 hw/net/virtio-net.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index e1f474883..42e66697f 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -600,6 +600,11 @@ static void virtio_net_set_mrg_rx_bufs(VirtIONet *n, int mergeable_rx_bufs,

     n->mergeable_rx_bufs = mergeable_rx_bufs;

+    /*
+     * Note: when extending the vnet header, please make sure to
+     * change the vnet header copying logic in virtio_net_flush_tx()
+     * as well.
+     */
     if (version_1) {
         n->guest_hdr_len = hash_report ?
             sizeof(struct virtio_net_hdr_v1_hash) :
@@ -2520,7 +2525,7 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
         ssize_t ret;
         unsigned int out_num;
         struct iovec sg[VIRTQUEUE_MAX_SIZE], sg2[VIRTQUEUE_MAX_SIZE + 1], *out_sg;
-        struct virtio_net_hdr_mrg_rxbuf mhdr;
+        struct virtio_net_hdr_v1_hash vhdr;

         elem = virtqueue_pop(q->tx_vq, sizeof(VirtQueueElement));
         if (!elem) {
@@ -2537,7 +2542,7 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
         }

         if (n->has_vnet_hdr) {
-            if (iov_to_buf(out_sg, out_num, 0, &mhdr, n->guest_hdr_len) <
+            if (iov_to_buf(out_sg, out_num, 0, &vhdr, n->guest_hdr_len) <
                 n->guest_hdr_len) {
                 virtio_error(vdev, "virtio-net header incorrect");
                 virtqueue_detach_element(q->tx_vq, elem, 0);
@@ -2545,8 +2550,8 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
                 return -EINVAL;
             }
             if (n->needs_vnet_hdr_swap) {
-                virtio_net_hdr_swap(vdev, (void *) &mhdr);
-                sg2[0].iov_base = &mhdr;
+                virtio_net_hdr_swap(vdev, (void *) &vhdr);
+                sg2[0].iov_base = &vhdr;
                 sg2[0].iov_len = n->guest_hdr_len;
                 out_num = iov_copy(&sg2[1], ARRAY_SIZE(sg2) - 1,
                                    out_sg, out_num,
--
2.34.1
