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FreeBSD-SA-19:21.bhyve Security Advisory
The FreeBSD Project

Topic: Insufficient validation of guest-supplied data (e1000 device)

Category: core
Module: bhyve
Announced: 2019-08-06
Credits: Reno Robert
Affects: All supported versions of FreeBSD.
Corrected: 2019-08-05 22:04:16 UTC (stable/12, 12.0-STABLE)
2019-08-06 17:13:17 UTC (releng/12.0, 12.0-RELEASE-p9)
2019-08-05 22:04:16 UTC (stable/11, 11.3-STABLE)
2019-08-06 17:13:17 UTC (releng/11.3, 11.3-RELEASE-p2)
2019-08-06 17:13:17 UTC (releng/11.2, 11.2-RELEASE-p13)
CVE Name: CVE-2019-5609

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://security.FreeBSD.org/>.

I. Background

bhyve(8) is a hypervisor that supports running a variety of guest operating
systems in virtual machines. bhyve(8) includes an emulated Intel 82545
network interface adapter (“e1000”).

II. Problem Description

The e1000 network adapters permit a variety of modifications to an Ethernet
packet when it is being transmitted. These include the insertion of IP and
TCP checksums, insertion of an Ethernet VLAN header, and TCP segmentation
offload (“TSO”). The e1000 device model uses an on-stack buffer to generate
the modified packet header when simulating these modifications on transmitted
packets.

When TCP segmentation offload is requested for a transmitted packet, the
e1000 device model used a guest-provided value to determine the size of the
on-stack buffer without validation. The subsequent header generation could
overflow an incorrectly sized buffer or indirect a pointer composed of stack
garbage.

III. Impact

A misbehaving bhyve guest could overwrite memory in the bhyve process on the
host.

IV. Workaround

Only the e1000 device model is affected; the virtio-net device is not
affected by this issue. If supported by the guest operating system
presenting only the virtio-net device to the guest is a suitable workaround.
No workaround is available if the e1000 device model is required.

V. Solution

Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date,
and restart any affected virtual machines.

1) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

2) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch https://security.FreeBSD.org/patches/SA-19:21/bhyve.patch
# fetch https://security.FreeBSD.org/patches/SA-19:21/bhyve.patch.asc
# gpg –verify bhyve.patch.asc

b) Apply the patch. Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

Restart the applicable virtual machines, or reboot the system.

VI. Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path Revision
– ————————————————————————-
stable/12/ r350619
releng/12.0/ r350647
stable/11/ r350619
releng/11.3/ r350647
releng/11.2/ r350647
– ————————————————————————-

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN –summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-5609>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-19:21.bhyve.asc>
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