On Sun, Sep 19, 2021 at 12:56 AM Thomas Weißschuh <thomas@xxxxxxxx> wrote: > > On 2021-09-18T11:47-0700, Andy Lutomirski wrote: > > On Thu, Sep 16, 2021, at 2:27 AM, Christian Brauner wrote: > > > On Wed, Sep 15, 2021 at 09:47:25AM -0700, Andy Lutomirski wrote: > > > > On Wed, Sep 15, 2021 at 8:50 AM Thomas Weißschuh <thomas@xxxxxxxx> wrote: > > > > > > > > > > Hi, > > > > > > > > > > I would like to propose a new syscall that exposes the functionality of > > > > > request_module() to userspace. > > > > > > > > > > Propsed signature: request_module(char *module_name, char **args, int flags); > > > > > Where args and flags have to be NULL and 0 for the time being. > > > > > > > > > > Rationale: > > > > > > > > > > We are using nested, privileged containers which are loading kernel modules. > > > > > Currently we have to always pass around the contents of /lib/modules from the > > > > > root namespace which contains the modules. > > > > > (Also the containers need to have userspace components for moduleloading > > > > > installed) > > > > > > > > > > The syscall would remove the need for this bookkeeping work. > > > > > > > > I feel like I'm missing something, and I don't understand the purpose > > > > of this syscall. Wouldn't the right solution be for the container to > > > > have a stub module loader (maybe doable with a special /sbin/modprobe > > > > or maybe a kernel patch would be needed, depending on the exact use > > > > case) and have the stub call out to the container manager to request > > > > the module? The container manager would check its security policy and > > > > load the module or not load it as appropriate. > > > > > > I don't see the need for a syscall like this yet either. > > > > > > This should be the job of the container manager. modprobe just calls the > > > init_module() syscall, right? > > > > Not quite so simple. modprobe parses things in /lib/modules and maybe /etc to decide what init_module() calls to do. > > > > But I admit I’m a bit confused. What exactly is the container doing that causes the container’s copy of modprobe to be called? > > The container is running an instance of the docker daemon in swarm mode. > That needs the "ip_vs" module (amongst others) and explicitly tries to load it > via modprobe. > Do you mean it literally invokes /sbin/modprobe? If so, hooking this at /sbin/modprobe and calling out to the container manager seems like a decent solution. > > > If so the seccomp notifier can be used to intercept this system call for > > > the container and verify the module against an allowlist similar to how > > > we currently handle mount. > > > > > > Christian > > >
