On Sat, Oct 12, 2019 at 02:33:36PM +0800, Wang Shilong wrote: > Steps to reproduce: > [wangsl@localhost tmp]$ mkdir project > [wangsl@localhost tmp]$ lsattr -p project -d > 0 ------------------ project > [wangsl@localhost tmp]$ chattr -p 1 project > [wangsl@localhost tmp]$ lsattr -p -d project > 1 ------------------ project > [wangsl@localhost tmp]$ chattr -p 2 project > [wangsl@localhost tmp]$ lsattr -p -d project > 2 ------------------ project > [wangsl@localhost tmp]$ df -Th . > Filesystem Type Size Used Avail Use% Mounted on > /dev/sda3 xfs 36G 4.1G 32G 12% / > [wangsl@localhost tmp]$ uname -r > 5.4.0-rc2+ > > As above you could see file owner could change project ID of file its self. Perfectly legal to do this. Working as designed, and intended. Project quotas have allowed this since they were introduced in the late 1980s on Irix... > As my understanding, we could set project ID and inherit attribute to account > Directory usage, and implement a similar 'Directory Quota' based on this. Yes, that is a -use- of project quotas, but not the -only- use. Users have always been allowed to select what project their files belong to - it's a method of accounting space even when users cannot access all of the project information. > But Directories could easily break this limit by change its file to > other project ID. Yes. But then users are using the project quotas as traditional project quotas, which is just fine. There are users out there that use this mix of behaviours - users have a default directory quota to limit unbound space usage of home directories, but for files that belong to a specific project they simply change the project ID and now the space in their home directory those project files take up is accounted to the project rather than the user. > And we used vfs_ioc_fssetxattr_check() to only allow init userspace to > change project quota: Right, that's so directory quotas can be enforced for container use cases, preventing the users inside a container from modifying the project quota and escaping the space usage limit set for the container. This means project quotas are unavailable for use inside user namespaces as they are used for container resource usage limiting. > Shall we have something like following to limit admin change for > Project state too? As per above, that will break many existing use cases for project quotas, so I don't think we will be doing that. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
