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=-6.6 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 09A4DC43441 for ; Sun, 11 Nov 2018 23:45:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C612D20818 for ; Sun, 11 Nov 2018 23:45:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="pH67PZhH" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C612D20818 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387663AbeKLJgQ (ORCPT ); Mon, 12 Nov 2018 04:36:16 -0500 Received: from mail.kernel.org ([198.145.29.99]:39838 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387398AbeKLITF (ORCPT ); Mon, 12 Nov 2018 03:19:05 -0500 Received: from localhost (unknown [206.108.79.134]) (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 D961B21707; Sun, 11 Nov 2018 22:29:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1541975349; bh=mlaQI9CFS8NN7nIDYVHfW2nqwPLVZWfN7f6GrLztkHE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pH67PZhHiK801jjGCm+3IsQiviwnAeUDum8d3GDKNcHGu5s0UKuQKTPE07LiADa4o gerLif/LXReuMVJ1G2GztUuQgb/1Yx1H+7gwLHULl5cf61jFXL2ptAZ7CnDVGunYmn UykexVRw6T02HrUoB3Ezadvb3PE3IQiZq8DOB+R0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jann Horn , "Eric W. Biederman" Subject: [PATCH 4.19 359/361] userns: also map extents in the reverse map to kernel IDs Date: Sun, 11 Nov 2018 14:21:46 -0800 Message-Id: <20181111221702.182204786@linuxfoundation.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20181111221619.915519183@linuxfoundation.org> References: <20181111221619.915519183@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review 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 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jann Horn commit d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd upstream. The current logic first clones the extent array and sorts both copies, then maps the lower IDs of the forward mapping into the lower namespace, but doesn't map the lower IDs of the reverse mapping. This means that code in a nested user namespace with >5 extents will see incorrect IDs. It also breaks some access checks, like inode_owner_or_capable() and privileged_wrt_inode_uidgid(), so a process can incorrectly appear to be capable relative to an inode. To fix it, we have to make sure that the "lower_first" members of extents in both arrays are translated; and we have to make sure that the reverse map is sorted *after* the translation (since otherwise the translation can break the sorting). This is CVE-2018-18955. Fixes: 6397fac4915a ("userns: bump idmap limits to 340") Cc: stable@vger.kernel.org Signed-off-by: Jann Horn Tested-by: Eric W. Biederman Reviewed-by: Eric W. Biederman Signed-off-by: Eric W. Biederman Signed-off-by: Greg Kroah-Hartman --- kernel/user_namespace.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -974,10 +974,6 @@ static ssize_t map_write(struct file *fi if (!new_idmap_permitted(file, ns, cap_setid, &new_map)) goto out; - ret = sort_idmaps(&new_map); - if (ret < 0) - goto out; - ret = -EPERM; /* Map the lower ids from the parent user namespace to the * kernel global id space. @@ -1004,6 +1000,14 @@ static ssize_t map_write(struct file *fi e->lower_first = lower_first; } + /* + * If we want to use binary search for lookup, this clones the extent + * array and sorts both copies. + */ + ret = sort_idmaps(&new_map); + if (ret < 0) + goto out; + /* Install the map */ if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) { memcpy(map->extent, new_map.extent,