linux-kernel - 3.0: user namespace problem with capabilities

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Message-Id: <201107211422.23861.a.miskiewicz@gmail.com>
Date:	Thu, 21 Jul 2011 14:22:23 +0200
From:	Arkadiusz Miskiewicz <a.miskiewicz@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	"Serge E. Hallyn" <serge.hallyn@...onical.com>,
	Herbert Poetzl <herbert@...hfloor.at>
Subject: 3.0: user namespace problem with capabilities


Hi,

linux-vserver guys think that there is a problem with user namespace in 
upcoming 3.0

"this is a mainline/upstream bug, which basically happens
when unsharing the USER namespace. what happens is that
all capabilities are dropped, and as result, the userspace
tool cannot issue Linux-VServer syscall commands anymore
(because of missing CAP_CONTEXT)"

"this can be verified on vanilla linux-3.0 kernels with
http://vserver.13thfloor.at/Stuff/clone_newuser.c
in the following way:

gcc -o clone_newuser clone_newuser.c
./clone_newuser ls /root/

assuming that /root does not have any right for 'other'
this will result in a permission denied (when the USER
namespace is compiled into the kernel)"

Whole post:

http://list.linux-vserver.org/archive?msp:5151:ekldgndhkgmehnehiegi

What's maintainers opinion on this?
-- 
Arkadiusz Miśkiewicz        PLD/Linux Team
arekm / maven.pl            http://ftp.pld-linux.org/
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