[IshKebab]

Why would you use ownership data for disk quotas? That's crazy. It should be based on file location. Anything in the user's home directory comes out of their quota. I assume that's how it does work surely?

[kazinator]

What if Alice leave her home directory permissions open? Mallory can then move a large file there and have it assigned to Alice's quota.

I suppose it could work, but Mallory would then risk Alice blowing that file away (perhaps innocently, not even realizing it was Mallory's file).

[IshKebab]

If I leave my front door unlocked and you put a large cow in my house, it's taking up space in my house.

[Izkata]

Not if the file is in the shared /tmp/