lkml.org 
[lkml]   [2011]   [Sep]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] user namespace: make signal.c respect user namespaces
Quoting Oleg Nesterov (oleg@redhat.com):
> On 09/19, Serge E. Hallyn wrote:
> >
> > __send_signal: convert the uid being sent in SI_USER to the target task's
> > user namespace.
> >
> > do_notify_parent and do_notify_parent_cldstop: map task's uid to parent's
> > user namespace
> >
> > ptrace_signal: map parent's uid into current's user namespace before
> > including in signal to current.
>
> And all of them follow the same pattern,
>
> > @@ -1073,7 +1074,8 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
> > q->info.si_code = SI_USER;
> > q->info.si_pid = task_tgid_nr_ns(current,
> > task_active_pid_ns(t));
> > - q->info.si_uid = current_uid();
> > + q->info.si_uid = user_ns_map_uid(task_cred_xxx(t, user_ns),
> > + current_cred(), current_uid());
>
> Up to you, but may be we can add a helper? Something like
>
> static inline uid_t good_name(struct task_struct *from, struct task_struct *to)
> {
> // the caller does rcu_read_lock() if needed
> const struct cred *from_cred = __task_cred(from);
> return user_ns_map_uid(task_cred_xxx(to, user_ns),
> from_cred, from_cred->uid);
> }
>
> As for __send_signal() in particular, I guess we could do
>
> q->info.si_uid = from_ancestor_ns ? 0 : current_uid();

But wait - can't __send_signal end up being triggered through fcntl
F_SETSIG+F_SETOWN to another but none-ancestor namespace? So we
do actually need to call the full user_ns_map_uid() there. However,
the uid sent in ptrace_signal() can (if i'm thinking right) be set
using

info->si_uid = (current_user_ns() == parent_user_ns()) ?
0 : current_uid();

Not much of a win performance-wise, but perhaps better by making it
clear that those are the only possibilities (and overflowuid is not
possible).

thanks,
-serge


\
 
 \ /
  Last update: 2011-09-20 17:41    [W:0.411 / U:0.308 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site