From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753413Ab1AAXKa (ORCPT ); Sat, 1 Jan 2011 18:10:30 -0500 Received: from out01.mta.xmission.com ([166.70.13.231]:43316 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750973Ab1AAXK2 (ORCPT ); Sat, 1 Jan 2011 18:10:28 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: "Serge E. Hallyn" Cc: LSM , James Morris , Kees Cook , containers@lists.linux-foundation.org, kernel list , Alexey Dobriyan , Michael Kerrisk References: <20101217152246.GA8221@mail.hallyn.com> <20101217152458.GA11162@mail.hallyn.com> <20101217152547.GB11162@mail.hallyn.com> <20101217152625.GC11162@mail.hallyn.com> <20101217152659.GD11162@mail.hallyn.com> <20101217200903.GA15528@mail.hallyn.com> <20110101044522.GA26476@mail.hallyn.com> Date: Sat, 01 Jan 2011 15:10:19 -0800 In-Reply-To: <20110101044522.GA26476@mail.hallyn.com> (Serge E. Hallyn's message of "Sat, 1 Jan 2011 04:45:22 +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=in01.mta.xmission.com;;;ip=98.207.157.188;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1+xcEdKcHyz8g5z9duBwdLk0Ch/0TM4fC4= 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 * [sa02 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; sa02 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;"Serge E. Hallyn" X-Spam-Relay-Country: Subject: Re: [RFC 4/5] user namespaces: 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 in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "Serge E. Hallyn" writes: > Quoting Eric W. Biederman (ebiederm@xmission.com): >> "Serge E. Hallyn" writes: >> >> > Quoting Eric W. Biederman (ebiederm@xmission.com): >> >> > --- a/kernel/signal.c >> >> > +++ b/kernel/signal.c >> >> > @@ -659,11 +686,7 @@ static int check_kill_permission(int sig, struct siginfo *info, >> >> > cred = current_cred(); >> >> > tcred = __task_cred(t); >> >> Nit pick you don't need to compute cred and tcred here now. >> > >> > Just to make sure I understand right: you mean wait until after the >> > same_thread_group() check to save calculation in that case, right? >> >> I mean cred and tcred are only use in kill_ok_by_cred. >> So we can eliminate those two variables from check_kill_permission. > > Thanks for the review. Here is an updated version. This one looks good. Reviewed-by: "Eric W. Biederman" > > Subject: [PATCH 4/5] allow killing tasks in your own or child userns > > Changelog: > Dec 8: Fixed bug in my check_kill_permission pointed out by > Eric Biederman. > Dec 13: Apply Eric's suggestion to pass target task into kill_ok_by_cred() > for clarity > Dec 31: address comment by Eric Biederman: > don't need cred/tcred in check_kill_permission. > > Signed-off-by: Serge E. Hallyn > --- > kernel/signal.c | 36 ++++++++++++++++++++++++++++-------- > 1 files changed, 28 insertions(+), 8 deletions(-) > > diff --git a/kernel/signal.c b/kernel/signal.c > index 4e3cff1..d890c99 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -636,13 +636,39 @@ static inline bool si_fromuser(const struct siginfo *info) > } > > /* > + * called with RCU read lock from check_kill_permission() > + */ > +static inline int kill_ok_by_cred(struct task_struct *t) > +{ > + struct cred *cred = current_cred(); > + struct cred *tcred = __task_cred(t); > + > + 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 > */ > static int check_kill_permission(int sig, struct siginfo *info, > struct task_struct *t) > { > - const struct cred *cred, *tcred; > struct pid *sid; > int error; > > @@ -656,14 +682,8 @@ static int check_kill_permission(int sig, struct siginfo *info, > if (error) > return error; > > - 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(t)) { > switch (sig) { > case SIGCONT: > sid = task_session(t);