Arch Linux

zsx

Member

Registered: 2018-05-10

Posts: 29

[SOLVED] Unprivileged userfaultfd sysctl knob

Hi, everyone!

Starting with the Linux 5.2, there is the new “vm.unprivileged_userfaultfd” sysctl knob to disallow unprivileged access to the userfaultfd syscall. I update the system every day. But from journalctl...

systemd-sysctl[254]: Couldn't write '0' to 'vm/unprivileged_userfaultfd', ignoring: No such file or directory

And...

# sysctl -w vm.unprivileged_userfaultfd=0
sysctl: cannot stat /proc/sys/vm/unprivileged_userfaultfd: No such file or directory

Has anyone else had such a issue? What could be the reason?

Last edited by zsx (2019-10-02 23:08:52)

loqs

Member

Registered: 2014-03-06

Posts: 17,372

Re: [SOLVED] Unprivileged userfaultfd sysctl knob

userfaultfd is not enabled in the kernel build so disabling it for unprivileged users makes no sense.

https://bugs.archlinux.org/task/62780

zsx

Member

Registered: 2018-05-10

Posts: 29

Re: [SOLVED] Unprivileged userfaultfd sysctl knob

loqs, thank you very much for the quick response!