Re: Per-process flag set via prctl() to deny module loading?

[Tycho Andersen]

On Mon, Apr 10, 2023 at 01:06:00PM +0300, Topi Miettinen wrote:
> I'd propose to add a per-process flag to irrevocably deny any loading of
> kernel modules for the process and its children. The flag could be set (but
> not unset) via prctl() and for unprivileged processes, only when
> NoNewPrivileges is also set. This would be similar to CAP_SYS_MODULE, but
> unlike capabilities, there would be no issues with namespaces since the flag
> isn't namespaced.
> 
> The implementation should be very simple.
> 
> Preferably the flag, when configured, would be set by systemd, Firejail and
> maybe also container managers. The expectation would be that the permission
> to load modules would be retained only by udev and where SUID needs to be
> allowed (NoNewPrivileges unset).

You can do something like this today via STATIC_USERMODEHELPER without
the need for kernel patches. It is a bit heavyweight for a
general-purpose system though.

Tycho