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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 34ED8C47082 for ; Mon, 31 May 2021 13:16:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 118306108D for ; Mon, 31 May 2021 13:16:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231649AbhEaNS0 (ORCPT ); Mon, 31 May 2021 09:18:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:53110 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231569AbhEaNSH (ORCPT ); Mon, 31 May 2021 09:18:07 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8E11C6135F; Mon, 31 May 2021 13:16:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1622466985; bh=FQ0bWZloYuzpTbO8HPdEnp4GtKAMDHCFua/32F3fh5w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JM1JqOXln+6J/xQWrdHXfvVcpgFwdQyTo24lPcRNqyx4mWMDJPK7zPgW2S94TVwcL S72xIjb1a+JatpyW/JjY4mjbEG3Cb3UZeYEkIU7qx9QMbr0z+v3omAUDCuN1iGOxrg XyO51pLISSy9jiG2eIrjt96ubS4l6R3ncNpZbFwo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kees Cook , Linus Torvalds Subject: [PATCH 4.4 04/54] proc: Check /proc/$pid/attr/ writes against file opener Date: Mon, 31 May 2021 15:13:30 +0200 Message-Id: <20210531130635.213072129@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210531130635.070310929@linuxfoundation.org> References: <20210531130635.070310929@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kees Cook commit bfb819ea20ce8bbeeba17e1a6418bf8bda91fc28 upstream. Fix another "confused deputy" weakness[1]. Writes to /proc/$pid/attr/ files need to check the opener credentials, since these fds do not transition state across execve(). Without this, it is possible to trick another process (which may have different credentials) to write to its own /proc/$pid/attr/ files, leading to unexpected and possibly exploitable behaviors. [1] https://www.kernel.org/doc/html/latest/security/credentials.html?highlight=confused#open-file-credentials Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Kees Cook Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/proc/base.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2413,6 +2413,10 @@ static ssize_t proc_pid_attr_write(struc ssize_t length; struct task_struct *task = get_proc_task(inode); + /* A task may only write when it was the opener. */ + if (file->f_cred != current_real_cred()) + return -EPERM; + length = -ESRCH; if (!task) goto out_no_task;