Re: [PATCH 1/1] Add a new sysctl to disable io_uring system-wide

[Matteo Rizzo]

On Tue, 27 Jun 2023 at 19:10, Bart Van Assche <bvanassche@xxxxxxx> wrote:
> I'm using fio + io_uring all the time on Android devices. I think we need a
> better solution than disabling io_uring system-wide, e.g. a mechanism based
> on SELinux that disables io_uring for apps and that keeps io_uring enabled
> for processes started via 'adb root && adb shell ...'

Android already uses seccomp to prevent untrusted applications from using
io_uring. This patch is aimed at server/desktop environments where there is
no easy way to set a system-wide seccomp policy and right now the only way
to disable io_uring system-wide is to compile it out of the kernel entirely
(not really feasible for e.g. a general-purpose distro).

I thought about adding a capability check that lets privileged processes
bypass this sysctl, but it wasn't clear to me which capability I should use.
For userfaultfd the kernel uses CAP_SYS_PTRACE, but I wasn't sure that's
the best choice here since io_uring has nothing to do with ptrace.
If anyone has any suggestions please let me know. A LSM hook also sounds
like an option but it would be more complicated to implement and use.