Re: [KERNEL] Re: [KERNEL] Re: [KERNEL] Re: Kernel 4.3 breaks security in systems using capabilities

[Christoph Lameter <cl@linux.com>]

On Tue, 10 Nov 2015, Theodore Ts'o wrote:

> If you want to create a patch, my recommendation would be to do one
> that turns off ambient capabilities as a CONFIG option, and hide it
> under CONFIG_EXPERT.  Or maybe adding a new securebit which disables
> ambient capabilities.  Whether or not that will be acceptable
> upstream, I don't know, mainly because I think a strong case can be

That is already available and was submitted with the patch.

commit 746bf6d64275be0c65b0631d8a72b16f1454cfa1
Author: Andy Lutomirski <luto@kernel.org>
Date:   Fri Sep 4 15:42:51 2015 -0700

    capabilities: add a securebit to disable PR_CAP_AMBIENT_RAISE

    Per Andrew Morgan's request, add a securebit to allow admins to disable
    PR_CAP_AMBIENT_RAISE.  This securebit will prevent processes from adding
    capabilities to their ambient set.

    For simplicity, this disables PR_CAP_AMBIENT_RAISE entirely rather than
    just disabling setting previously cleared bits.

    Signed-off-by: Andy Lutomirski <luto@kernel.org>
    Acked-by: Andrew G. Morgan <morgan@kernel.org>
    Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
    Cc: Kees Cook <keescook@chromium.org>
    Cc: Christoph Lameter <cl@linux.com>
    Cc: Serge Hallyn <serge.hallyn@canonical.com>
    Cc: Jonathan Corbet <corbet@lwn.net>
    Cc: Aaron Jones <aaronmdjones@gmail.com>
    Cc: Ted Ts'o <tytso@mit.edu>
    Cc: Andrew G. Morgan <morgan@kernel.org>
    Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
    Cc: Austin S Hemmelgarn <ahferroin7@gmail.com>
    Cc: Markku Savela <msa@moth.iki.fi>
    Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    Cc: Michael Kerrisk <mtk.manpages@gmail.com>
    Cc: James Morris <james.l.morris@oracle.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>