linux-kernel - Re: [lxc-devel] Kernel bug? Setuid apps and user namespaces

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-next>] [day] [month] [year] [list]

Message-ID: <20140402172049.GA13240@sergelap>
Date:	Wed, 2 Apr 2014 12:20:49 -0500
From:	Serge Hallyn <serge.hallyn@...ntu.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Sean Pajot <sean.pajot@...culink.com>,
	lxc-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [lxc-devel] Kernel bug? Setuid apps and user namespaces

Hi Eric,

(sorry, I don't seem to have the email I actually wanted to reply
to in my mbox, but it is
https://lists.linuxcontainers.org/pipermail/lxc-devel/2013-October/005857.html)

You'd said,
> Someone needs to read and think through all of the corner cases and see
> if we can ever have a time when task_dumpable is false but root in the
> container would not or should not be able to see everything.
> 
> In particular I am worried about the case of a setuid app calling setns,
> and entering a lesser privileged user namespace.  In my foggy mind that
> might be a security problem.  And there might be other similar crazy
> cases.

Can we make use of current->mm->exe_file->f_cred->user_ns?

So either always use 
make_kgid(current->mm->exe_file->f_cred->user_ns, 0)
instead of make_kuid(cred->user_ns, 0), or check that
(current->mm->exe_file->f_cred->user_ns == cred->user_ns)
and, if not, assume that the caller has done a setns?

-serge
--
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/