From patchwork Sat May 9 19:42:23 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: 11538513 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 C9B01139A for ; Sat, 9 May 2020 19:45:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B7BD4214D8 for ; Sat, 9 May 2020 19:45:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728617AbgEITpz (ORCPT ); Sat, 9 May 2020 15:45:55 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:42758 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728098AbgEITpz (ORCPT ); Sat, 9 May 2020 15:45:55 -0400 Received: from in01.mta.xmission.com ([166.70.13.51]) by out02.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jXVQ1-0003mG-1E; Sat, 09 May 2020 13:45:53 -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 1jXVPz-0006mp-VW; Sat, 09 May 2020 13:45:52 -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> Date: Sat, 09 May 2020 14:42:23 -0500 In-Reply-To: <87v9l4zyla.fsf_-_@x220.int.ebiederm.org> (Eric W. Biederman's message of "Sat, 09 May 2020 14:40:17 -0500") Message-ID: <878si0zyhs.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=1jXVPz-0006mp-VW;;;mid=<878si0zyhs.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+WaFjsADm08u5UbPlcu3GHSSNgJl9oWdE= 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 sa04.xmission.com X-Spam-Level: ** X-Spam-Status: No, score=2.0 required=8.0 tests=ALL_TRUSTED,BAYES_50, DCC_CHECK_NEGATIVE,T_TM2_M_HEADER_IN_MSG,T_TooManySym_01,XMNoVowels, XMSubLong 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 T_TM2_M_HEADER_IN_MSG BODY: No description available. * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa04 0; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject X-Spam-DCC: ; sa04 0; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: **; X-Spam-Relay-Country: X-Spam-Timing: total 529 ms - load_scoreonly_sql: 0.11 (0.0%), signal_user_changed: 14 (2.7%), b_tie_ro: 12 (2.3%), parse: 1.80 (0.3%), extract_message_metadata: 20 (3.7%), get_uri_detail_list: 2.8 (0.5%), tests_pri_-1000: 23 (4.3%), tests_pri_-950: 2.3 (0.4%), tests_pri_-900: 1.96 (0.4%), tests_pri_-90: 101 (19.1%), check_bayes: 98 (18.6%), b_tokenize: 13 (2.4%), b_tok_get_all: 8 (1.6%), b_comp_prob: 3.2 (0.6%), b_tok_touch_all: 69 (13.1%), b_finish: 1.42 (0.3%), tests_pri_0: 350 (66.2%), check_dkim_signature: 1.06 (0.2%), check_dkim_adsp: 3.2 (0.6%), poll_dns_idle: 0.44 (0.1%), tests_pri_10: 2.3 (0.4%), tests_pri_500: 7 (1.3%), rewrite_mail: 0.00 (0.0%) Subject: [PATCH 4/5] exec: Allow load_misc_binary to call prepare_binfmt unconditionally 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 Add a flag preserve_creds that binfmt_misc can set to prevent credentials from being updated. This allows binfmrt_misc to always call prepare_binfmt. Allowing the credential computation logic to be consolidated. Ref: c407c033de84 ("[PATCH] binfmt_misc: improve calculation of interpreter's credentials") Signed-off-by: "Eric W. Biederman" --- fs/binfmt_misc.c | 15 +++------------ fs/exec.c | 14 +++++++++----- include/linux/binfmts.h | 2 ++ 3 files changed, 14 insertions(+), 17 deletions(-) diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c index 127fae9c21ab..16bfafd2671d 100644 --- a/fs/binfmt_misc.c +++ b/fs/binfmt_misc.c @@ -218,19 +218,10 @@ static int load_misc_binary(struct linux_binprm *bprm) goto error; bprm->file = interp_file; - if (fmt->flags & MISC_FMT_CREDENTIALS) { - loff_t pos = 0; - - /* - * No need to call prepare_binprm(), it's already been - * done. bprm->buf is stale, update from interp_file. - */ - memset(bprm->buf, 0, BINPRM_BUF_SIZE); - retval = kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, - &pos); - } else - retval = prepare_binprm(bprm); + if (fmt->flags & MISC_FMT_CREDENTIALS) + bprm->preserve_creds = 1; + retval = prepare_binprm(bprm); if (retval < 0) goto error; diff --git a/fs/exec.c b/fs/exec.c index 8bbf5fa785a6..01dbeb025c46 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1630,14 +1630,18 @@ static void bprm_fill_uid(struct linux_binprm *bprm) */ int prepare_binprm(struct linux_binprm *bprm) { - int retval; loff_t pos = 0; - bprm_fill_uid(bprm); + if (!bprm->preserve_creds) { + int retval; - retval = cap_bprm_set_creds(bprm); - if (retval) - return retval; + bprm_fill_uid(bprm); + + retval = cap_bprm_set_creds(bprm); + if (retval) + return retval; + } + bprm->preserve_creds = 0; memset(bprm->buf, 0, BINPRM_BUF_SIZE); return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos); diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index 89f1135dcb75..cb016f001e7a 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -26,6 +26,8 @@ struct linux_binprm { unsigned long p; /* current top of mem */ unsigned long argmin; /* rlimit marker for copy_strings() */ unsigned int + /* Don't update the creds for an interpreter (see binfmt_misc) */ + preserve_creds:1, /* * True if most recent call to the commoncaps bprm_set_creds * hook (due to multiple prepare_binprm() calls from the