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

[Christian Brauner]

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 at gmail.com> 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.