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Date: Tue, 06 Dec 2022 15:17:42 +0000
From: Xen.org security team <security@....org>
To: xen-announce@...ts.xen.org, xen-devel@...ts.xen.org,
 xen-users@...ts.xen.org, oss-security@...ts.openwall.com
CC: Xen.org security team <security-team-members@....org>
Subject: Xen Security Advisory 424 v1 (CVE-2022-42328,CVE-2022-42329) -
 Guests can trigger deadlock in Linux netback driver

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

     Xen Security Advisory CVE-2022-42328,CVE-2022-42329 / XSA-424

          Guests can trigger deadlock in Linux netback driver

ISSUE DESCRIPTION
=================

The patch for XSA-392 introduced another issue which might result in
a deadlock when trying to free the SKB of a packet dropped due to
the XSA-392 handling (CVE-2022-42328).

Additionally when dropping packages for other reasons the same
deadlock could occur in case of netpoll being active for the interface
the xen-netback driver is connected to (CVE-2022-42329).

IMPACT
======

A malicious guest could cause Denial of Service (DoS) of the host via
the paravirtualized network interface.

VULNERABLE SYSTEMS
==================

All systems using the Linux kernel based network backend xen-netback
are vulnerable.

MITIGATION
==========

Using another PV network backend (e.g. the qemu based "qnic" backend)
will mitigate the problem.

Using a dedicated network driver domain per guest will mitigate the
problem.

NOTE REGARDING LACK OF EMBARGO
==============================

This issue was discussed in public already.

RESOLUTION
==========

Applying the attached patch resolves this issue.

xsa424-linux.patch     Linux 6.0, 6.1-rc

$ sha256sum xsa424*
89db7cad9694f498c4ac450356932fb69fb514162e07aea0343776effa821fc8  xsa424-linux.patch
$

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Download attachment "xsa424-linux.patch" of type "application/octet-stream" (3524 bytes)

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