From patchwork Thu May 28 15:49:44 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eric W. Biederman" X-Patchwork-Id: 11576247 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id CE50B1391 for ; Thu, 28 May 2020 15:53:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF470207D3 for ; Thu, 28 May 2020 15:53:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404691AbgE1Pxj (ORCPT ); Thu, 28 May 2020 11:53:39 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:33472 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404511AbgE1Pxh (ORCPT ); Thu, 28 May 2020 11:53:37 -0400 Received: from in01.mta.xmission.com ([166.70.13.51]) by out01.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jeKqe-0001Zi-I4; Thu, 28 May 2020 09:53:36 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1jeKqd-00085a-M7; Thu, 28 May 2020 09:53:36 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Cc: Linus Torvalds , Oleg Nesterov , Jann Horn , Kees Cook , Greg Ungerer , Rob Landley , Bernd Edlinger , , Al Viro , Alexey Dobriyan , Andrew Morton , Casey Schaufler , linux-security-module@vger.kernel.org, James Morris , "Serge E. Hallyn" , Andy Lutomirski References: <87h7wujhmz.fsf@x220.int.ebiederm.org> <87sgga6ze4.fsf@x220.int.ebiederm.org> <87v9l4zyla.fsf_-_@x220.int.ebiederm.org> <877dx822er.fsf_-_@x220.int.ebiederm.org> <87k10wysqz.fsf_-_@x220.int.ebiederm.org> Date: Thu, 28 May 2020 10:49:44 -0500 In-Reply-To: <87k10wysqz.fsf_-_@x220.int.ebiederm.org> (Eric W. Biederman's message of "Thu, 28 May 2020 10:38:28 -0500") Message-ID: <87y2pcvz3b.fsf_-_@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 X-XM-SPF: eid=1jeKqd-00085a-M7;;;mid=<87y2pcvz3b.fsf_-_@x220.int.ebiederm.org>;;;hst=in01.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1+Uao3hKNmbCnTKyFSqtDONOkhIC5W+4JQ= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on sa06.xmission.com X-Spam-Level: **** X-Spam-Status: No, score=4.3 required=8.0 tests=ALL_TRUSTED,BAYES_50, DCC_CHECK_NEGATIVE,T_TooManySym_01,XMNoVowels,XMSubLong, XMSubMetaSxObfu_03,XMSubMetaSx_00 autolearn=disabled version=3.4.2 X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.5000] * 1.5 XMNoVowels Alpha-numberic number with no vowels * 0.7 XMSubLong Long Subject * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa06 0; Body=1 Fuz1=1 Fuz2=1] * 1.0 XMSubMetaSx_00 1+ Sexy Words * 0.0 T_TooManySym_01 4+ unique symbols in subject * 1.2 XMSubMetaSxObfu_03 Obfuscated Sexy Noun-People X-Spam-DCC: ; sa06 0; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ****; X-Spam-Relay-Country: X-Spam-Timing: total 385 ms - load_scoreonly_sql: 0.04 (0.0%), signal_user_changed: 10 (2.6%), b_tie_ro: 9 (2.3%), parse: 1.04 (0.3%), extract_message_metadata: 11 (2.8%), get_uri_detail_list: 1.44 (0.4%), tests_pri_-1000: 13 (3.4%), tests_pri_-950: 1.24 (0.3%), tests_pri_-900: 1.00 (0.3%), tests_pri_-90: 84 (21.9%), check_bayes: 83 (21.5%), b_tokenize: 8 (2.1%), b_tok_get_all: 8 (2.1%), b_comp_prob: 2.7 (0.7%), b_tok_touch_all: 60 (15.6%), b_finish: 0.94 (0.2%), tests_pri_0: 246 (64.0%), check_dkim_signature: 0.55 (0.1%), check_dkim_adsp: 2.5 (0.6%), poll_dns_idle: 0.48 (0.1%), tests_pri_10: 2.3 (0.6%), tests_pri_500: 12 (3.0%), rewrite_mail: 0.00 (0.0%) Subject: [PATCH 09/11] exec: In bprm_fill_uid only set per_clear when honoring suid or sgid X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org It makes no sense to set active_per_clear when the kernel decides not to honor the executables setuid or or setgid bits. Instead set active_per_clear when the kernel actually decides to honor the suid or sgid permission bits of an executable. As far as I can tell this was the intended behavior but with the ptrace logic hiding out in security/commcap.c:cap_bprm_apply_creds I believe it was just overlooked that the setuid or setgid operation could be cancelled. History Tree: git://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Fixes: 1bb0fa189c6a ("[PATCH] NX: clean up legacy binary support") Signed-off-by: "Eric W. Biederman" --- fs/exec.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index af108ecf9632..347dade4bc54 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1634,15 +1634,16 @@ static void bprm_fill_uid(struct linux_binprm *bprm) need_cap = bprm->unsafe & LSM_UNSAFE_SHARE || !ptracer_capable(current, new->user_ns); - if (mode & S_ISUID) { + if ((mode & S_ISUID) && + (!need_cap || ns_capable(new->user_ns, CAP_SETUID))) { bprm->per_clear = 1; - if (!need_cap || ns_capable(new->user_ns, CAP_SETUID)) - new->suid = new->fsuid = new->euid = uid; + new->suid = new->fsuid = new->euid = uid; } - if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { + + if (((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) && + (!need_cap || ns_capable(new->user_ns, CAP_SETGID))) { bprm->per_clear = 1; - if (!need_cap || ns_capable(new->user_ns, CAP_SETGID)) - new->sgid = new->fsgid = new->egid = gid; + new->sgid = new->fsgid = new->egid = gid; } after_setid: