[Bug 2043711] Re: Open3.pm tries to run code in /tmp when preconfiguring packages

[Julian Andres Klode]

This issue only occurs in a highly unusual system configuration where

1. /tmp is a separate mount point from / (before oracular, it usually is a directory in /)
2. Said mountpoint is mounted noexec (even the tmpfs in oracular is not mounted noexec)

Given that there is an easy workaround to set an option in apt.conf,
users who have gone to the trouble of doing those two modifications to
their system also drop a snippet into apt.conf.d.

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https://bugs.launchpad.net/bugs/2043711

Title:
  Open3.pm tries to run code in /tmp when preconfiguring packages

Status in debconf package in Ubuntu:
  Fix Released
Status in debconf source package in Focal:
  New
Status in debconf source package in Jammy:
  New
Status in debconf source package in Noble:
  Fix Released
Status in debconf source package in Oracular:
  Fix Released
Status in debconf source package in Plucky:
  Fix Released
Status in debconf package in Debian:
  Unknown

Bug description:
  During update of ubuntu-drivers-common:

    Can't exec "/tmp/ubuntu-drivers-common.config.55GJ8b": Permission denied at /usr/lib/x86_64-linux-gnu/perl-base/IPC/Open3.pm line 178, <GEN0> line 1.
  open2: exec of /tmp/ubuntu-drivers-common.config.55GJ8b configure 1:0.9.6.2~0.22.04.4 failed: Permission 
    denied at /usr/share/perl5/Debconf/ConfModule.pm line 59.
    Preconfiguring packages ...
    Can't exec "/tmp/ubuntu-drivers-common.config.uSPrCH": Permission denied at /usr/lib/x86_64-linux-gnu/perl-base/IPC/Open3.pm line 178, <GEN0> line 1.
    open2: exec of /tmp/ubuntu-drivers-common.config.uSPrCH configure 1:0.9.6.2~0.22.04.4 failed: Permission 
    denied at /usr/share/perl5/Debconf/ConfModule.pm line 59.

  /tmp is mounted with noexec because running code from /tmp has been a
  vulnerability vector for several decades, hence reporting this as a
  vulnerability in perl-base.

  This error did not appear to prevent the update of ubuntu-drivers-
  common and "dpkg --verify ubuntu-drivers-common" returns 0.

  ___________________________________________________________________________________________________________

  Attempting to use the package search on this form by clicking the 🔍
  created a modal in which there is an error

    Sorry, something went wrong with your search. We've recorded what
  happened, and we'll fix it as soon as possible. (Error ID:
  OOPS-c80f71590b02908a1187b9f743c53eac)

  which is repeated with any attempt to search for a package.

  ___________________________________________________________________________________________________________

  Submitting this form gives an error

    "perl-base" does not exist in Ubuntu. Please choose a different
  package. If you're unsure, please select "I don't know"

    $ dpkg -S /usr/lib/x86_64-linux-gnu/perl-base/IPC/Open3.pm
    perl-base: /usr/lib/x86_64-linux-gnu/perl-base/IPC/Open3.pm
    $ dpkg -l perl-base
    Desired=Unknown/Install/Remove/Purge/Hold
    | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
    |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
    ||/ Name           Version           Architecture Description
    +++-==============-=================-============-=============================>
    ii  perl-base      5.34.0-3ubuntu1.2 amd64        minimal Perl system

  Looks like a package to me. Nevertheless, using "Did you mean..."
  offers "perl".

  ProblemType: Bug
  DistroRelease: Ubuntu 22.04
  Package: perl-base 5.34.0-3ubuntu1.2
  ProcVersionSignature: Ubuntu 6.5.0-1007.7-oem 6.5.3
  Uname: Linux 6.5.0-1007-oem x86_64
  ApportVersion: 2.20.11-0ubuntu82.5
  Architecture: amd64
  CasperMD5CheckResult: unknown
  CurrentDesktop: ubuntu:GNOME
  Date: Thu Nov 16 10:08:48 2023
  InstallationDate: Installed on 2016-04-23 (2763 days ago)
  InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
  ProcEnviron:
   TERM=rxvt
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: perl
  UpgradeStatus: Upgraded to jammy on 2022-08-19 (453 days ago)

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