linux-kernel - [PATCH v3 3/4] Allow unprivileged CLONE_NEWUTS and CLONE_NEWIPC with no_new

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Message-Id: <9a520b74ad5dc14a3d6950b6d63a64714adbdd7d.1327858005.git.luto@amacapital.net>
Date:	Mon, 30 Jan 2012 08:17:28 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Will Drewry <wad@...omium.org>, linux-kernel@...r.kernel.org
Cc:	Casey Schaufler <casey@...aufler-ca.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jamie Lokier <jamie@...reable.org>, keescook@...omium.org,
	john.johansen@...onical.com, serge.hallyn@...onical.com,
	coreyb@...ux.vnet.ibm.com, pmoore@...hat.com, eparis@...hat.com,
	djm@...drot.org, segoon@...nwall.com, rostedt@...dmis.org,
	jmorris@...ei.org, scarybeasts@...il.com, avi@...hat.com,
	penberg@...helsinki.fi, viro@...iv.linux.org.uk, mingo@...e.hu,
	akpm@...ux-foundation.org, khilman@...com, borislav.petkov@....com,
	amwang@...hat.com, oleg@...hat.com, ak@...ux.intel.com,
	eric.dumazet@...il.com, gregkh@...e.de, dhowells@...hat.com,
	daniel.lezcano@...e.fr, linux-fsdevel@...r.kernel.org,
	linux-security-module@...r.kernel.org, olofj@...omium.org,
	mhalcrow@...gle.com, dlaor@...hat.com, corbet@....net,
	alan@...rguk.ukuu.org.uk, Al Viro <viro@...IV.linux.org.uk>,
	Andy Lutomirski <luto@...capital.net>
Subject: [PATCH v3 3/4] Allow unprivileged CLONE_NEWUTS and CLONE_NEWIPC with no_new_privs

They are normally disallowed because they could be used to subvert
setuid programs.  But if setuid is disabled, then they are safe.

Signed-off-by: Andy Lutomirski <luto@...capital.net>
---
 kernel/nsproxy.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index b576f7f..47cf873 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -191,7 +191,13 @@ int unshare_nsproxy_namespaces(unsigned long unshare_flags,
 			       CLONE_NEWNET)))
 		return 0;
 
-	if (!capable(CAP_SYS_ADMIN))
+	/* We require either no_new_privs or CAP_SYS_ADMIN for all modes */
+	if (!current->no_new_privs && !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	/* NEWNS and NEWNET always require CAP_SYS_ADMIN. */
+	if ((unshare_flags & (CLONE_NEWNS | CLONE_NEWNET)) &&
+	    !capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
 	*new_nsp = create_new_namespaces(unshare_flags, current,
-- 
1.7.7.6

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