From 746bf6d64275be0c65b0631d8a72b16f1454cfa1 Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <luto@kernel.org>
Date: Fri, 4 Sep 2015 15:42:51 -0700
Subject: 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>
---
 security/commoncap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'security')

diff --git a/security/commoncap.c b/security/commoncap.c
index 1f74dde1063e..1832cf701c3d 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -993,7 +993,8 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
 			if (arg2 == PR_CAP_AMBIENT_RAISE &&
 			    (!cap_raised(current_cred()->cap_permitted, arg3) ||
 			     !cap_raised(current_cred()->cap_inheritable,
-					 arg3)))
+					 arg3) ||
+			     issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
 				return -EPERM;
 
 			new = prepare_creds();
-- 
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