linux-kernel - Re: For review: user

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <5411B5F5.2090500@gmail.com>
Date:	Thu, 11 Sep 2014 07:47:17 -0700
From:	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:	Andy Lutomirski <luto@...capital.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	mtk.manpages@...il.com, lkml <linux-kernel@...r.kernel.org>,
	"linux-man@...r.kernel.org" <linux-man@...r.kernel.org>,
	Linux Containers <containers@...ts.linux-foundation.org>,
	richard -rw- weinberger <richard.weinberger@...il.com>,
	"Serge E. Hallyn" <serge@...lyn.com>
Subject: Re: For review: user_namespace(7) man page

Hi Andy,

On 09/09/2014 12:26 PM, Andy Lutomirski wrote:
> On Tue, Sep 9, 2014 at 9:05 AM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
>>
>> We may also want to discuss the specific restrictions on chroot.
>>
>> The text about chroot at least gives people a strong hint that the
>> chroot rules are affected by user namespaces.
>>
>> The restrictions that we have settled on to avoid chroot being a problem
>> are the creator of a user namespace must not be chrooted in their
>> current mount namespace, and the creator of the user namespace must not
>> be threaded.
>>
>> Andy can you check me on this it looks like unshare is currently buggy
>> in that it will allow a threaded application to create a user namespace.
> 
> I think it's this code in unshare:
> 
>     /*
>      * If unsharing a user namespace must also unshare the thread.
>      */
>     if (unshare_flags & CLONE_NEWUSER)
>         unshare_flags |= CLONE_THREAD | CLONE_FS;
> 
> I suppose that this should be documented.
> 
> CLONE_FS prevents the chroot from leaking out of the namespace.  (But
> see the other thread that I'm about to start...)

So, in the current draft of the setns(2) page, there is

    CLONE_NEWNS
        ...
        Since  Linux 3.9, CLONE_NEWUSER also automatically  implies
        CLONE_FS.

Does that cover your point? Or did you mean that more needs to be said?

Thanks,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
--
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/