bug#48039: xorg-server might be vulnerable to CVE-2021-3472

[Nicolò Balzarotti]

Hi, just found this [fn:1]:

A flaw was found in xorg-x11-server in versions before 1.20.11. An
integer underflow can occur in xserver which can lead to a local
privilege escalation.

The commit fixing the bug should be the one at [fn:2], and latest tagged
version (1.20.11) should be fixed.

On a side note, the redhat issue tracker says that [fn:3]:

Xorg server does not run with root privileges in Red Hat Enterprise
Linux 8, therefore this flaw has been rated as having moderate impact
for Red Hat Enterprise linux 8.

Is it possible for guix too not to run the server as root?  I've no idea
myself

guix refresh -l xorg-server
Building the following 73 packages would ensure 121

I just rebuilt xorg-server itself with the attached patch, and building
other packages now but it might take some time on my server.  I'll let
you know how it goes.

[fn:1] https://nvd.nist.gov/vuln/detail/CVE-2021-3472
[fn:2]
https://gitlab.freedesktop.org/xorg/xserver/-/commit/7aaf54a1884f71dc363f0b884e57bcb67407a6cd
[fn:3] https://bugzilla.redhat.com/show_bug.cgi?id=1944167

0001-gnu-xorg-server-Update-to-1.20.11.patch
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