From: Eric W. Biederman <ebiederm@xmission.com>
Date: Fri, 22 Mar 2013 11:08:05 +0000 (-0700)
Subject: vfs: Carefully propogate mounts across user namespaces
X-Git-Tag: v3.9-rc5~21^2~2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=132c94e31b8bca8ea921f9f96a57d684fa4ae0a9;p=pandora-kernel.git

vfs: Carefully propogate mounts across user namespaces

As a matter of policy MNT_READONLY should not be changable if the
original mounter had more privileges than creator of the mount
namespace.

Add the flag CL_UNPRIVILEGED to note when we are copying a mount from
a mount namespace that requires more privileges to a mount namespace
that requires fewer privileges.

When the CL_UNPRIVILEGED flag is set cause clone_mnt to set MNT_NO_REMOUNT
if any of the mnt flags that should never be changed are set.

This protects both mount propagation and the initial creation of a less
privileged mount namespace.

Cc: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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