Re: [RFC PATCH 3/3] add listmnt(2) syscall

From: Christian Brauner
Date: Mon Sep 18 2023 - 12:52:37 EST


On Sun, Sep 17, 2023 at 04:32:04PM +0200, Miklos Szeredi wrote:
> On Sun, Sep 17, 2023 at 2:54 AM Matthew House <mattlloydhouse@xxxxxxxxx> wrote:
>
> > > + list_for_each_entry(r, &m->mnt_mounts, mnt_child) {
> > > + if (!capable(CAP_SYS_ADMIN) &&


> Good point. That issue was nagging at the back of my mind. Having an
> explicit flag nicely solves the issue.

Ideally we avoid multiple capable(CAP_SYS_ADMIN) calls by only doing it
once and saving the return value. capable() call's aren't that cheap.
Plus, we should decide whether this should trigger an audit event or
not: capable(CAP_SYS_ADMIN) triggers an audit event,
ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN) wouldn't.