| Re: [PATCH 03/08] allow sethostname in a container [message #41524] |
Fri, 04 February 2011 15:56 |
serge
Messages: 72
Registered: January 2007
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Member |
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Quoting Serge E. Hallyn (serge@hallyn.com):
> Quoting Serge E. Hallyn (serge@hallyn.com):
> > Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
> > ---
> > kernel/sys.c | 2 +-
> > 1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/kernel/sys.c b/kernel/sys.c
> > index 2745dcd..9b9b03b 100644
> > --- a/kernel/sys.c
> > +++ b/kernel/sys.c
> > @@ -1171,7 +1171,7 @@ SYSCALL_DEFINE2(sethostname, char __user *, name, int, len)
> > int errno;
> > char tmp[__NEW_UTS_LEN];
> >
> > - if (!capable(CAP_SYS_ADMIN))
> > + if (!ns_capable(current->nsproxy->uts_ns->user_ns, CAP_SYS_ADMIN))
> > return -EPERM;
> > if (len < 0 || len > __NEW_UTS_LEN)
> > return -EINVAL;
> > --
> > 1.7.0.4
>
> An interesting note here is that since the task doing ns_exec (and
> therefore in the init_user_ns) requires CAP_SYS_ADMIN to unshare,
> this check will actually always be true if uts_ns was not unshared.
Noone ever called me on this, so for the sake of posterity reading the
m-l archives: what I said above is not true. If uts_ns was not
unshared, then current->nsproxy->uts_ns->user_ns != current_user_ns(),
so current should not have ns_capable(current->nsproxy->uts_ns->user_ns,
CAP_SYS_ADMIN). So the check will always return false.
> If uts is unshared, then regular capabilities semantics in the
> child user_ns apply (that is, root can do sethostname, unpriv user
> cannot) The intent is that user namespaces will eventually allow
> unprivileged users to unshare, after which this will make much more
> sense.
>
> -serge
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