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 X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3C2D1C43218 for ; Sat, 27 Apr 2019 15:25:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0B1CC208CA for ; Sat, 27 Apr 2019 15:25:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728301AbfD0PZr (ORCPT ); Sat, 27 Apr 2019 11:25:47 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:34782 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727408AbfD0PZp (ORCPT ); Sat, 27 Apr 2019 11:25:45 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hKP3B-0000zP-IT; Sat, 27 Apr 2019 16:15:37 +0100 Received: from ben by deadeye with local (Exim 4.92) (envelope-from ) id 1hKP2i-0004RL-Dc; Sat, 27 Apr 2019 16:15:08 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Oleg Nesterov" , "James Morris" , syzbot+a9ac39bf55329e206219@syzkaller.appspotmail.com, "Kees Cook" Date: Sat, 27 Apr 2019 16:13:09 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 047/202] Yama: Check for pid death before checking ancestry In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.66-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Kees Cook commit 9474f4e7cd71a633fa1ef93b7daefd44bbdfd482 upstream. It's possible that a pid has died before we take the rcu lock, in which case we can't walk the ancestry list as it may be detached. Instead, check for death first before doing the walk. Reported-by: syzbot+a9ac39bf55329e206219@syzkaller.appspotmail.com Fixes: 2d514487faf1 ("security: Yama LSM") Suggested-by: Oleg Nesterov Signed-off-by: Kees Cook Signed-off-by: James Morris Signed-off-by: Ben Hutchings --- security/yama/yama_lsm.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/security/yama/yama_lsm.c +++ b/security/yama/yama_lsm.c @@ -299,7 +299,9 @@ int yama_ptrace_access_check(struct task break; case YAMA_SCOPE_RELATIONAL: rcu_read_lock(); - if (!task_is_descendant(current, child) && + if (!pid_alive(child)) + rc = -EPERM; + if (!rc && !task_is_descendant(current, child) && !ptracer_exception_found(current, child) && !ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE)) rc = -EPERM;