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Xen Security Advisory XSA-457
version 2
Linux/xen-netfront: Memory leak due to missing cleanup function
UPDATES IN VERSION 2
====================
* Clarify the XSA is in netfront and *not* netback
* Clarify the impact: only the guest may crash
ISSUE DESCRIPTION
=================
In netfront, xennet_alloc_one_rx_buffer() failed to call the
appropriate clean-up function, resulting in a memory leak.
IMPACT
======
A malicious guest userspace process can exhaust memory resources
within the guest kernel, potentially leading to a guest crash (Denial
of Service). It is not known whether it can be triggered remotely.
VULNERABLE SYSTEMS
==================
Systems with guests running Linux 5.9 and later with Xen PV network
devices are affected.
MITIGATION
==========
For HVM guests, using emulated network devices will avoid this issue.
RESOLUTION
==========
The following patch in Linux resolves the issue:
https://git.kernel.org/torvalds/c/037965402a010898d34f4e35327d22c0a95cd51f
A copy of which is attached.
xsa457.patch Linux 5.9
$ sha256sum xsa457*
9d6ae3da27f1ff92f9f45c800822beecda603d6dea6726207cee6c768416114c xsa457.patch
$
NOTE ON THE LACK OF EMBARGO
===========================
The issue was reported initially on a public bug tracker and fixed in
public before it was realized that there was a security aspect.
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