qemu: fix CVE-2021-3748

(From OE-Core rev: 6fe3b1002a273808fe4caf6f2e1ecd54729b954d)

Signed-off-by: Sakib Sajal <sakib.sajal@windriver.com>
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

2 files changed, 128 insertions, 0 deletions

diff --git a/meta/recipes-devtools/qemu/qemu.inc b/meta/recipes-devtools/qemu/qemu.inc
index 3aad41088a..5c1c88db25 100644
--- a/meta/recipes-devtools/qemu/qemu.inc
+++ b/meta/recipes-devtools/qemu/qemu.inc
@@ -71,6 +71,7 @@ SRC_URI = "https://download.qemu.org/${BPN}-${PV}.tar.xz \
            file://CVE-2021-3608.patch \
            file://CVE-2021-3682.patch \
            file://CVE-2021-3713.patch \
+           file://CVE-2021-3748.patch \
            "
 UPSTREAM_CHECK_REGEX = "qemu-(?P<pver>\d+(\.\d+)+)\.tar"
 
diff --git a/meta/recipes-devtools/qemu/qemu/CVE-2021-3748.patch b/meta/recipes-devtools/qemu/qemu/CVE-2021-3748.patch
new file mode 100644
index 0000000000..4765f24739
--- /dev/null
+++ b/meta/recipes-devtools/qemu/qemu/CVE-2021-3748.patch
@@ -0,0 +1,127 @@
+From bacc200f623647632258f7efc0f098ac30dd4225 Mon Sep 17 00:00:00 2001
+From: Jason Wang <jasowang@redhat.com>
+Date: Thu, 2 Sep 2021 13:44:12 +0800
+Subject: [PATCH 09/12] 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>
+
+Upstream-Status: Backport [bedd7e93d01961fcb16a97ae45d93acf357e11f6]
+CVE: CVE-2021-3748
+
+Signed-off-by: Sakib Sajal <sakib.sajal@windriver.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 9179013ac..df1d30e2c 100644
+--- a/hw/net/virtio-net.c
++++ b/hw/net/virtio-net.c
+@@ -1665,10 +1665,13 @@ 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;
+@@ -1699,6 +1702,12 @@ 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) {
+@@ -1710,7 +1719,8 @@ 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) {
+@@ -1718,7 +1728,8 @@ 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;
+@@ -1755,12 +1766,13 @@ 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) {
+@@ -1770,10 +1782,23 @@ 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,
+-- 
+2.31.1
+