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virtio-net: fix use after unmap/free for sg

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When mergeable buffer is enabled, we try to set the num_buffers after
the virtqueue elem has been unmapped. This will lead several issues,
E.g a use after free when the descriptor has an address which belongs
to the non direct access region. In this case we use bounce buffer
that is allocated during address_space_map() and freed during
address_space_unmap().

Fixing this by storing the elems temporarily in an array and delay the
unmap after we set the the num_buffers.

This addresses CVE-2021-3748.

Reported-by: Alexander Bulekov <alxndr@bu.edu>
Fixes: fbe78f4f55c6 ("virtio-net support")
Cc: qemu-stable@nongnu.org
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: imxcc <xingchaochao@huawei.com>
This commit is contained in:
Chen Qun 2021-09-02 13:44:12 +08:00
parent 9b3e5f5993
commit d22f4b0b0c
1 changed files with 123 additions and 0 deletions
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123
virtio-net-fix-use-after-unmap-free-for-sg.patch Normal file
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@ -0,0 +1,123 @@
From 662633f388c5cead35b6ba5428dc9ab88710a471 Mon Sep 17 00:00:00 2001
From: Jason Wang <jasowang@redhat.com>
Date: Thu, 2 Sep 2021 13:44:12 +0800
Subject: [PATCH] virtio-net: fix use after unmap/free for sg
When mergeable buffer is enabled, we try to set the num_buffers after
the virtqueue elem has been unmapped. This will lead several issues,
E.g a use after free when the descriptor has an address which belongs
to the non direct access region. In this case we use bounce buffer
that is allocated during address_space_map() and freed during
address_space_unmap().
Fixing this by storing the elems temporarily in an array and delay the
unmap after we set the the num_buffers.
This addresses CVE-2021-3748.
Reported-by: Alexander Bulekov <alxndr@bu.edu>
Fixes: fbe78f4f55c6 ("virtio-net support")
Cc: qemu-stable@nongnu.org
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: imxcc <xingchaochao@huawei.com>
---
hw/net/virtio-net.c | 39 ++++++++++++++++++++++++++++++++-------
1 file changed, 32 insertions(+), 7 deletions(-)
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 63f1bae99c..f93823d06d 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1265,10 +1265,13 @@ static ssize_t virtio_net_receive_rcu(NetClientState *nc, const uint8_t *buf,
VirtIONet *n = qemu_get_nic_opaque(nc);
VirtIONetQueue *q = virtio_net_get_subqueue(nc);
VirtIODevice *vdev = VIRTIO_DEVICE(n);
+ VirtQueueElement *elems[VIRTQUEUE_MAX_SIZE];
+ size_t lens[VIRTQUEUE_MAX_SIZE];
struct iovec mhdr_sg[VIRTQUEUE_MAX_SIZE];
struct virtio_net_hdr_mrg_rxbuf mhdr;
unsigned mhdr_cnt = 0;
- size_t offset, i, guest_offset;
+ size_t offset, i, guest_offset, j;
+ ssize_t err;
if (!virtio_net_can_receive(nc)) {
return -1;
@@ -1291,6 +1294,12 @@ static ssize_t virtio_net_receive_rcu(NetClientState *nc, const uint8_t *buf,
total = 0;
+ if (i == VIRTQUEUE_MAX_SIZE) {
+ virtio_error(vdev, "virtio-net unexpected long buffer chain");
+ err = size;
+ goto err;
+ }
+
elem = virtqueue_pop(q->rx_vq, sizeof(VirtQueueElement));
if (!elem) {
if (i) {
@@ -1302,7 +1311,8 @@ static ssize_t virtio_net_receive_rcu(NetClientState *nc, const uint8_t *buf,
n->guest_hdr_len, n->host_hdr_len,
vdev->guest_features);
}
- return -1;
+ err = -1;
+ goto err;
}
if (elem->in_num < 1) {
@@ -1310,7 +1320,8 @@ static ssize_t virtio_net_receive_rcu(NetClientState *nc, const uint8_t *buf,
"virtio-net receive queue contains no in buffers");
virtqueue_detach_element(q->rx_vq, elem, 0);
g_free(elem);
- return -1;
+ err = -1;
+ goto err;
}
sg = elem->in_sg;
@@ -1342,12 +1353,13 @@ static ssize_t virtio_net_receive_rcu(NetClientState *nc, const uint8_t *buf,
if (!n->mergeable_rx_bufs && offset < size) {
virtqueue_unpop(q->rx_vq, elem, total);
g_free(elem);
- return size;
+ err = size;
+ goto err;
}
- /* signal other side */
- virtqueue_fill(q->rx_vq, elem, total, i++);
- g_free(elem);
+ elems[i] = elem;
+ lens[i] = total;
+ i++;
}
if (mhdr_cnt) {
@@ -1357,10 +1369,23 @@ static ssize_t virtio_net_receive_rcu(NetClientState *nc, const uint8_t *buf,
&mhdr.num_buffers, sizeof mhdr.num_buffers);
}
+ for (j = 0; j < i; j++) {
+ /* signal other side */
+ virtqueue_fill(q->rx_vq, elems[j], lens[j], j);
+ g_free(elems[j]);
+ }
+
virtqueue_flush(q->rx_vq, i);
virtio_notify(vdev, q->rx_vq);
return size;
+
+err:
+ for (j = 0; j < i; j++) {
+ g_free(elems[j]);
+ }
+
+ return err;
}
static ssize_t virtio_net_do_receive(NetClientState *nc, const uint8_t *buf,
--
2.27.0