linux-kernel - [PATCH 2/2] user namespaces: require cap_set{ug}id for CLONE

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Message-ID: <20081203191733.GA16652@us.ibm.com>
Date:	Wed, 3 Dec 2008 13:17:33 -0600
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	David Howells <dhowells@...hat.com>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	James Morris <jmorris@...ei.org>
Subject: [PATCH 2/2] user namespaces: require cap_set{ug}id for
	CLONE_NEWUSER

While ideally CLONE_NEWUSER will eventually require no
privilege, the required permission checks are currently
not there.  As a result, CLONE_NEWUSER has the same effect
as a setuid(0)+setgroups(1,"0").  While we already require
CAP_SYS_ADMIN, requiring CAP_SETUID and CAP_SETGID seems
appropriate.

Signed-off-by: Serge E. Hallyn <serue@...ibm.com>
---
 kernel/fork.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 1dd8945..e3a85b3 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1344,7 +1344,8 @@ long do_fork(unsigned long clone_flags,
 		/* hopefully this check will go away when userns support is
 		 * complete
 		 */
-		if (!capable(CAP_SYS_ADMIN))
+		if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
+				!capable(CAP_SETGID))
 			return -EPERM;
 	}
 
-- 
1.5.4.3

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