From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EC1D3C433FE for ; Fri, 11 Feb 2022 02:14:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347212AbiBKCOH (ORCPT ); Thu, 10 Feb 2022 21:14:07 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:34774 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347204AbiBKCOD (ORCPT ); Thu, 10 Feb 2022 21:14:03 -0500 Received: from out01.mta.xmission.com (out01.mta.xmission.com [166.70.13.231]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 862B55FB4; Thu, 10 Feb 2022 18:14:03 -0800 (PST) Received: from in01.mta.xmission.com ([166.70.13.51]:56868) by out01.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1nILRi-000fQN-LA; Thu, 10 Feb 2022 19:14:02 -0700 Received: from ip68-227-174-4.om.om.cox.net ([68.227.174.4]:52650 helo=localhost.localdomain) by in01.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1nILRg-00FMXV-2b; Thu, 10 Feb 2022 19:14:01 -0700 From: "Eric W. Biederman" To: linux-kernel@vger.kernel.org Cc: Alexey Gladkov , Kees Cook , Shuah Khan , Christian Brauner , Solar Designer , Ran Xiaokai , containers@lists.linux-foundation.org, =?UTF-8?q?Michal=20Koutn=C3=BD?= , "Eric W. Biederman" , stable@vger.kernel.org Date: Thu, 10 Feb 2022 20:13:18 -0600 Message-Id: <20220211021324.4116773-2-ebiederm@xmission.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <87o83e2mbu.fsf@email.froward.int.ebiederm.org> References: <87o83e2mbu.fsf@email.froward.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-XM-SPF: eid=1nILRg-00FMXV-2b;;;mid=<20220211021324.4116773-2-ebiederm@xmission.com>;;;hst=in01.mta.xmission.com;;;ip=68.227.174.4;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX180vY7xLxiQ5Z1bAjs0XvdVF8ggxZUA/u4= X-SA-Exim-Connect-IP: 68.227.174.4 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH 2/8] ucounts: Fix set_cred_ucounts X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Michal Koutný wrote: > Tasks are associated to multiple users at once. Historically and as per > setrlimit(2) RLIMIT_NPROC is enforce based on real user ID. > > The commit 21d1c5e386bc ("Reimplement RLIMIT_NPROC on top of ucounts") > made the accounting structure "indexed" by euid and hence potentially > account tasks differently. > > The effective user ID may be different e.g. for setuid programs but > those are exec'd into already existing task (i.e. below limit), so > different accounting is moot. > > Some special setresuid(2) users may notice the difference, justifying > this fix. I looked at the cred->ucount is only used for rlimit operations that were previously stored in cred->user. Making the fact cred->ucount can refer to a different user from cred->user a bug working will all rlimits not just RLIMIT_NPROC. So fix set_cred_ucounts to always use the real uid not the effective uid. Further simplify set_cred_ucounts by noticing that set_cred_ucounts somehow retained a draft version of the check to see if alloc_ucounts was needed that checks the new->user and new->user_ns against the current_real_cred(), when nothing matters for setting the ucounts field of a struct cred except the other fields in that same struct cred. So delete the confusing and wrong check against the current_real_cred(), and all of it's intermediate variables. Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20220207121800.5079-4-mkoutny@suse.com Reported-by: Michal Koutný Fixes: 21d1c5e386bc ("Reimplement RLIMIT_NPROC on top of ucounts") Signed-off-by: "Eric W. Biederman" --- kernel/cred.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/kernel/cred.c b/kernel/cred.c index 473d17c431f3..933155c96922 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -665,21 +665,16 @@ EXPORT_SYMBOL(cred_fscmp); int set_cred_ucounts(struct cred *new) { - struct task_struct *task = current; - const struct cred *old = task->real_cred; struct ucounts *new_ucounts, *old_ucounts = new->ucounts; - if (new->user == old->user && new->user_ns == old->user_ns) - return 0; - /* * This optimization is needed because alloc_ucounts() uses locks * for table lookups. */ - if (old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->euid)) + if (old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->uid)) return 0; - if (!(new_ucounts = alloc_ucounts(new->user_ns, new->euid))) + if (!(new_ucounts = alloc_ucounts(new->user_ns, new->uid))) return -EAGAIN; new->ucounts = new_ucounts; -- 2.29.2