[Bug 2064685] Re: write says write: effective gid does not match group of /dev/pts/5

[Alex Murray]

For context, this change was introduced in
https://ubuntu.com/security/notices/USN-6719-2

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Title:
  write says write: effective gid does not match group of /dev/pts/5

Status in util-linux package in Ubuntu:
  Confirmed

Bug description:
  I am logged in as 'nanook', I am in the tty group:
  id
  uid=2000(nanook) gid=1000(shell) groups=1000(shell),4(adm),5(tty),24(cdrom),27(sudo),30(dip),46(plugdev),118(lpadmin),128(sambashare),135(lxd)
  Yet when I say,
  write nanook
  I get
  write: effective gid does not match group of /dev/pts/5
  ls -l /dev/pts/5
  crw--w---- 1 nanook tty 136, 5 May  2 18:51 /dev/pts/5
  So something is wrong.  And since it seems to involve permissions there may be security issues.

  ProblemType: Bug
  DistroRelease: Ubuntu 22.04
  Package: util-linux 2.37.2-4ubuntu3.4
  ProcVersionSignature: Ubuntu 5.15.0-102.112-generic 5.15.148
  Uname: Linux 5.15.0-102-generic x86_64
  ApportVersion: 2.20.11-0ubuntu82.5
  Architecture: amd64
  CasperMD5CheckResult: unknown
  CurrentDesktop: MATE
  Date: Thu May  2 18:47:55 2024
  SourcePackage: util-linux
  UpgradeStatus: No upgrade log present (probably fresh install)

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