As additional information, I tested if using the Eoan kernel with Focal would do any difference on this - it didn't, so this seems not to be dependent on the kernel version in Focal.
** Description changed: Hello, in Focal the behaviour has changed when a program running as root tries to modify a file which belongs to a user/group other than root in a directory with sticky bit set. I'm not sure if this is a bug or the behaviour is intentional (for certain security reasons). Steps to reproduce: - Boot current Focal daily iso - Open terminal - Create a directory with sticky bit set (chmod o+t; or use an existing directory with sticky bit, e.g. /var/crash ) - - Create an empty file with user:group set to anything different that root (e.g. ubuntu:ubuntu, ubuntu:whoospie, ...) + - Create an empty file with user:group set to anything different than root (e.g. ubuntu:ubuntu, ubuntu:whoopsie, ...) - Open the file with nano running as root (sudo nano testfile.txt), write something in it, and try to save it. This won't work and gives a "permission denied" error message. This behaviour is different than in previous Ubuntu versions. In Eoan it is possible to modify the file as root in the scenario described above. I discovered this because after changing my main installation to Eoan I noticed that I got weird error messages from rsync when backing up my root subvolume. In my backup script rsync runs as root, and can't update backed up contents of /var/crash or /var/spool/cups/tmp anymore because it isn't allowed to modify the respective files anymore. For me personally this is a regression compared to previous Ubuntu versions where I never saw such errors during backup. Whether PAM is the appropriate package to report this bug against I'm not sure, so please feel free to assign it to the correct package. If this is intentional, does anybody have a clue how to work around this for use cases like backup with rsync? Kind regards, Jan ProblemType: Bug DistroRelease: Ubuntu 20.04 Package: libpam-runtime 1.3.1-5ubuntu4 ProcVersionSignature: Ubuntu 5.4.0-24.28-generic 5.4.30 Uname: Linux 5.4.0-24-generic x86_64 ApportVersion: 2.20.11-0ubuntu27 Architecture: amd64 CasperMD5CheckResult: skip CurrentDesktop: KDE Date: Mon Apr 20 12:11:32 2020 InstallationDate: Installed on 2020-04-08 (11 days ago) InstallationMedia: Kubuntu 20.04 LTS "Focal Fossa" - Beta amd64 (20200408) PackageArchitecture: all SourcePackage: pam UpgradeStatus: No upgrade log present (probably fresh install) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1873785 Title: Root can't modify files of other users in directories with sticky bit anymore To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/pam/+bug/1873785/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
