From patchwork Fri May 8 18:45:25 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: 11537443 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 B3A2E14B4 for ; Fri, 8 May 2020 18:48:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A5957207DD for ; Fri, 8 May 2020 18:48:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727798AbgEHSsy (ORCPT ); Fri, 8 May 2020 14:48:54 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:54612 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726864AbgEHSsx (ORCPT ); Fri, 8 May 2020 14:48:53 -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 1jX83I-0005SA-Sr; Fri, 08 May 2020 12:48:52 -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 1jX83I-0002xa-4g; Fri, 08 May 2020 12:48:52 -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 References: <87h7wujhmz.fsf@x220.int.ebiederm.org> <87sgga6ze4.fsf@x220.int.ebiederm.org> Date: Fri, 08 May 2020 13:45:25 -0500 In-Reply-To: <87sgga6ze4.fsf@x220.int.ebiederm.org> (Eric W. Biederman's message of "Fri, 08 May 2020 13:43:31 -0500") Message-ID: <87blmy6zay.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=1jX83I-0002xa-4g;;;mid=<87blmy6zay.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/M8xbipLE7+kJXgkEYUSylu3e6cNqDnCs= 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 sa02.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-Virus: No 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] * 0.7 XMSubLong Long Subject * 1.5 XMNoVowels Alpha-numberic number with no vowels * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa02 0; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject X-Spam-DCC: ; sa02 0; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: **; X-Spam-Relay-Country: X-Spam-Timing: total 299 ms - load_scoreonly_sql: 0.03 (0.0%), signal_user_changed: 3.7 (1.2%), b_tie_ro: 2.5 (0.9%), parse: 0.74 (0.2%), extract_message_metadata: 9 (2.9%), get_uri_detail_list: 0.86 (0.3%), tests_pri_-1000: 11 (3.5%), tests_pri_-950: 1.01 (0.3%), tests_pri_-900: 0.81 (0.3%), tests_pri_-90: 62 (20.7%), check_bayes: 61 (20.3%), b_tokenize: 5 (1.8%), b_tok_get_all: 5 (1.7%), b_comp_prob: 1.55 (0.5%), b_tok_touch_all: 46 (15.5%), b_finish: 0.63 (0.2%), tests_pri_0: 202 (67.6%), check_dkim_signature: 0.38 (0.1%), check_dkim_adsp: 2.3 (0.8%), poll_dns_idle: 0.92 (0.3%), tests_pri_10: 1.77 (0.6%), tests_pri_500: 5 (1.8%), rewrite_mail: 0.00 (0.0%) Subject: [PATCH 3/6] exec: Stop open coding mutex_lock_killable of cred_guard_mutex 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 Oleg modified the code that did "mutex_lock_interruptible(¤t->cred_guard_mutex)" to return -ERESTARTNOINTR instead of -EINTR, so that userspace will never see a failure to grab the mutex. Slightly earlier Liam R. Howlett defined mutex_lock_killable for exactly the same situation but it does it a little more cleanly. Switch the code to mutex_lock_killable so that it is clearer what the code is doing. Ref: ad776537cc6b ("Add mutex_lock_killable") Ref: 793285fcafce ("cred_guard_mutex: do not return -EINTR to user-space") Signed-off-by: "Eric W. Biederman" Reviewed-by: Kees Cook --- fs/exec.c | 5 +++-- kernel/ptrace.c | 4 ++-- 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 82106241ed53..11a5c073aa35 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1493,8 +1493,9 @@ EXPORT_SYMBOL(finalize_exec); */ static int prepare_bprm_creds(struct linux_binprm *bprm) { - if (mutex_lock_interruptible(¤t->signal->cred_guard_mutex)) - return -ERESTARTNOINTR; + int retval = mutex_lock_killable(¤t->signal->cred_guard_mutex); + if (retval) + return retval; bprm->cred = prepare_exec_creds(); if (likely(bprm->cred)) diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 43d6179508d6..1876b3392488 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -391,8 +391,8 @@ static int ptrace_attach(struct task_struct *task, long request, * SUID, SGID and LSM creds get determined differently * under ptrace. */ - retval = -ERESTARTNOINTR; - if (mutex_lock_interruptible(&task->signal->cred_guard_mutex)) + retval = mutex_lock_killable(&task->signal->cred_guard_mutex); + if (retval) goto out; task_lock(task);