linux-kernel - Re: [RFC PATCH 3/4] kmod - add call_usermodehelper

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1417133990.2520.15.camel@pluto.fritz.box>
Date:	Fri, 28 Nov 2014 08:19:50 +0800
From:	Ian Kent <ikent@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Stanislav Kinsbursky <skinsbursky@...allels.com>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	David Howells <dhowells@...hat.com>,
	Benjamin Coddington <bcodding@...hat.com>,
	Al Viro <viro@...IV.linux.org.uk>
Subject: Re: [RFC PATCH 3/4] kmod - add call_usermodehelper_ns() helper

On Tue, 2014-11-25 at 17:27 -0600, Eric W. Biederman wrote:
> 
> > How does one correctly set the namespace in user space since each of
> > the /proc/<pid>/ns/<namespace> will use a slightly different
> > proc_ns_operations install function? 
> >
> > Are we saying that, for example, if open(/proc/<pid>/ns/pid)/setns() is
> > used then the process must not do path lookups if it expects them to be
> > within the namespace and restrict itself to pid related system calls
> > only and so on for each of the other namespaces?
> 
> In userspace you can only set the pid namespace for new children.  You
> can never change your own pid namespace.  Because actually changing a
> processes pid is too nasty to contemplate, or implement and because in a
> login daemon context having your first child be the initial process of
> the pid namespace is actually what is desirable.
> 

Maybe using the pid namespace was a bad example but now it seems I don't
understand the purpose of /proc/<pid>/ns/pid with the use of setns()
either.

I wasn't thinking of changing the process pid here at all, as you say
from the kernel POV that must not happen, I was thinking of changing an
execed userspace process view of pids.

Assuming that <pid> is valid within a callers namespace (and I believe
that's checked along the way) doesn't using this allow the created
userspace process to see pids in the view of the given namespace? Isn't
that the intended use of this?

Ian

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/