From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755787Ab0LIRco (ORCPT ); Thu, 9 Dec 2010 12:32:44 -0500 Received: from 184-106-158-135.static.cloud-ips.com ([184.106.158.135]:57745 "EHLO mail" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754332Ab0LIRcn (ORCPT ); Thu, 9 Dec 2010 12:32:43 -0500 Date: Thu, 9 Dec 2010 17:32:45 +0000 From: "Serge E. Hallyn" To: LSM Cc: containers@lists.linux-foundation.org, Kees Cook , "Eric W. Biederman" , kernel list Subject: [RFC PATCH 4/4] allow killing tasks in your own or child userns Message-ID: <20101209173245.GB10206@mail.hallyn.com> References: <20101209172027.GA10085@mail.hallyn.com> <20101209172843.GA10155@mail.hallyn.com> <20101209173050.GA10206@mail.hallyn.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101209173050.GA10206@mail.hallyn.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Changelog: Dec 8: Fixed bug in my check_kill_permission pointed out by Eric Biederman. To test: 1. Test killing tasks as usual. No change. 2. Clone a new user namespace without a new pidns. a. You CAN kill -CONT tasks in your thread group but outside your user ns. b. You can NOT otherwise kill tasks outside your user_ns. c. Inside your new userns, signal semantics are as normal with respect to userids, CAP_KILL, and thread groups. Signed-off-by: Serge E. Hallyn --- kernel/signal.c | 27 ++++++++++++++++++++++----- 1 files changed, 22 insertions(+), 5 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index 4e3cff1..677025c 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -635,6 +635,27 @@ static inline bool si_fromuser(const struct siginfo *info) (!is_si_special(info) && SI_FROMUSER(info)); } +static inline int kill_ok_by_cred(struct cred *cred, struct cred *tcred) +{ + if (cred->user->user_ns != tcred->user->user_ns) { + /* userids are not equivalent - either you have the + capability to the target user ns or you don't */ + if (ns_capable(tcred->user->user_ns, CAP_KILL)) + return 1; + return 0; + } + + /* same user namespace - usual credentials checks apply */ + if ((cred->euid ^ tcred->suid) && + (cred->euid ^ tcred->uid) && + (cred->uid ^ tcred->suid) && + (cred->uid ^ tcred->uid) && + !ns_capable(tcred->user->user_ns, CAP_KILL)) + return 0; + + return 1; +} + /* * Bad permissions for sending the signal * - the caller must hold the RCU read lock @@ -659,11 +680,7 @@ static int check_kill_permission(int sig, struct siginfo *info, cred = current_cred(); tcred = __task_cred(t); if (!same_thread_group(current, t) && - (cred->euid ^ tcred->suid) && - (cred->euid ^ tcred->uid) && - (cred->uid ^ tcred->suid) && - (cred->uid ^ tcred->uid) && - !capable(CAP_KILL)) { + !kill_ok_by_cred(cred, tcred)) { switch (sig) { case SIGCONT: sid = task_session(t); -- 1.7.2.3