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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 AD008C282C5 for ; Thu, 24 Jan 2019 19:26:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6A020218FE for ; Thu, 24 Jan 2019 19:26:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548357961; bh=jVn0Q5RodvRQmDLJgakOPbwwNp4Rl4FFNWLh6z/3LQ0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=FEmCzyS5xi6CZm5a0AAujub3Ggw0JwhMvmQZR4BvC5+ugJpwB8/sibheO6m93Jsgq k0S7sewamG1V+UxeM1p3tk87fW6pidk5zfW8R5F3IM8dDTONQK1HytOhqfLzGMCpE7 mg+8iSM6/a/J6XrKkP+D39Bgc1QCxaH0hlx2DPhA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730488AbfAXT0A (ORCPT ); Thu, 24 Jan 2019 14:26:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:51744 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729680AbfAXTZ4 (ORCPT ); Thu, 24 Jan 2019 14:25:56 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 706FF217D7; Thu, 24 Jan 2019 19:25:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548357955; bh=jVn0Q5RodvRQmDLJgakOPbwwNp4Rl4FFNWLh6z/3LQ0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=I8li1EO8OO/QdEgXXkMmK7E2ksJN4BTbdy5eRM5zxNnkzNXU9ZEtBbu0MUKaovza8 rahpngH//J0IpuAWqwY8tFf5Shag7JXUQdl/etYg4Bb8QP6LwW0TuLDQ2Kilh1apzL lT/4kH6IJMeohuc7AZVgb0DVypN+OjP1lt3LuNqQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+a9ac39bf55329e206219@syzkaller.appspotmail.com, Oleg Nesterov , Kees Cook , James Morris Subject: [PATCH 4.4 049/104] Yama: Check for pid death before checking ancestry Date: Thu, 24 Jan 2019 20:19:38 +0100 Message-Id: <20190124190201.140687919@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190124190154.968308875@linuxfoundation.org> References: <20190124190154.968308875@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable 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") Cc: stable@vger.kernel.org Suggested-by: Oleg Nesterov Signed-off-by: Kees Cook Signed-off-by: James Morris Signed-off-by: Greg Kroah-Hartman --- 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 @@ -288,7 +288,9 @@ static int yama_ptrace_access_check(stru 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;