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 64142C169C4 for ; Sun, 3 Feb 2019 14:32:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3EDB22073D for ; Sun, 3 Feb 2019 14:32:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731065AbfBCOcc (ORCPT ); Sun, 3 Feb 2019 09:32:32 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:55168 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728597AbfBCOTu (ORCPT ); Sun, 3 Feb 2019 09:19:50 -0500 Received: from cable-78.29.236.164.coditel.net ([78.29.236.164] helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1gqIcf-00062o-Ee; Sun, 03 Feb 2019 14:19:49 +0000 Received: from ben by deadeye with local (Exim 4.92-RC4) (envelope-from ) id 1gqI9Y-0006y9-DW; Sun, 03 Feb 2019 14:49:44 +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 , "Mike Snitzer" , "Wenwen Wang" Date: Sun, 03 Feb 2019 14:45:08 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 102/305] dm ioctl: harden copy_params()'s copy_from_user() from malicious users In-Reply-To: X-SA-Exim-Connect-IP: 78.29.236.164 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 3.16.63-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Wenwen Wang commit 800a7340ab7dd667edf95e74d8e4f23a17e87076 upstream. In copy_params(), the struct 'dm_ioctl' is first copied from the user space buffer 'user' to 'param_kernel' and the field 'data_size' is checked against 'minimum_data_size' (size of 'struct dm_ioctl' payload up to its 'data' member). If the check fails, an error code EINVAL will be returned. Otherwise, param_kernel->data_size is used to do a second copy, which copies from the same user-space buffer to 'dmi'. After the second copy, only 'dmi->data_size' is checked against 'param_kernel->data_size'. Given that the buffer 'user' resides in the user space, a malicious user-space process can race to change the content in the buffer between the two copies. This way, the attacker can inject inconsistent data into 'dmi' (versus previously validated 'param_kernel'). Fix redundant copying of 'minimum_data_size' from user-space buffer by using the first copy stored in 'param_kernel'. Also remove the 'data_size' check after the second copy because it is now unnecessary. Signed-off-by: Wenwen Wang Signed-off-by: Mike Snitzer Signed-off-by: Ben Hutchings --- drivers/md/dm-ioctl.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -1681,8 +1681,7 @@ static void free_params(struct dm_ioctl } static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kernel, - int ioctl_flags, - struct dm_ioctl **param, int *param_flags) + int ioctl_flags, struct dm_ioctl **param, int *param_flags) { struct dm_ioctl *dmi; int secure_data; @@ -1730,18 +1729,13 @@ static int copy_params(struct dm_ioctl _ return -ENOMEM; } - if (copy_from_user(dmi, user, param_kernel->data_size)) - goto bad; + /* Copy from param_kernel (which was already copied from user) */ + memcpy(dmi, param_kernel, minimum_data_size); -data_copied: - /* - * Abort if something changed the ioctl data while it was being copied. - */ - if (dmi->data_size != param_kernel->data_size) { - DMERR("rejecting ioctl: data size modified while processing parameters"); + if (copy_from_user(&dmi->data, (char __user *)user + minimum_data_size, + param_kernel->data_size - minimum_data_size)) goto bad; - } - +data_copied: /* Wipe the user buffer so we do not return it to userspace */ if (secure_data && clear_user(user, param_kernel->data_size)) goto bad;