From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755378Ab0LJLQp (ORCPT ); Fri, 10 Dec 2010 06:16:45 -0500 Received: from out02.mta.xmission.com ([166.70.13.232]:52674 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751738Ab0LJLQn (ORCPT ); Fri, 10 Dec 2010 06:16:43 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: "Serge E. Hallyn" Cc: LSM , containers@lists.linux-foundation.org, Kees Cook , kernel list References: <20101209172027.GA10085@mail.hallyn.com> <20101209172843.GA10155@mail.hallyn.com> <20101209173050.GA10206@mail.hallyn.com> <20101209173245.GB10206@mail.hallyn.com> Date: Fri, 10 Dec 2010 03:16:34 -0800 In-Reply-To: <20101209173245.GB10206@mail.hallyn.com> (Serge E. Hallyn's message of "Thu, 9 Dec 2010 17:32:45 +0000") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-XM-SPF: eid=;;;mid=;;;hst=in02.mta.xmission.com;;;ip=98.207.157.188;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX19m5Mammbwmpgk2hPxABWzRhNay56VvBMQ= X-SA-Exim-Connect-IP: 98.207.157.188 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 1.5 XMNoVowels Alpha-numberic number with no vowels * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -3.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa06 1397; Body=1 Fuz1=1 Fuz2=1] * 1.6 XMSubMetaSx_00 1+ Sexy Words * 0.4 UNTRUSTED_Relay Comes from a non-trusted relay X-Spam-DCC: XMission; sa06 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;"Serge E. Hallyn" X-Spam-Relay-Country: Subject: Re: [RFC PATCH 4/4] allow killing tasks in your own or child userns X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Fri, 06 Aug 2010 16:31:04 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "Serge E. Hallyn" writes: > 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) > +{ Nit: You should just pass in the target task here. Making it abundantly clear where current and tcred come from. ns_capable implicitly uses current which is a little surprising when everything else is being passed in, but makes perfect sense in this context. > + 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);