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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 A7A25C34031 for ; Wed, 19 Feb 2020 02:35:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 88F7322B48 for ; Wed, 19 Feb 2020 02:35:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728156AbgBSCfz (ORCPT ); Tue, 18 Feb 2020 21:35:55 -0500 Received: from mail.hallyn.com ([178.63.66.53]:49488 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728087AbgBSCfy (ORCPT ); Tue, 18 Feb 2020 21:35:54 -0500 Received: by mail.hallyn.com (Postfix, from userid 1001) id 4AFEEFF9; Tue, 18 Feb 2020 20:35:52 -0600 (CST) Date: Tue, 18 Feb 2020 20:35:52 -0600 From: "Serge E. Hallyn" To: Christian Brauner Cc: =?iso-8859-1?Q?St=E9phane?= Graber , "Eric W. Biederman" , Aleksa Sarai , Jann Horn , smbarber@chromium.org, Seth Forshee , Alexander Viro , Alexey Dobriyan , Serge Hallyn , James Morris , Kees Cook , Jonathan Corbet , Phil Estes , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, containers@lists.linux-foundation.org, linux-security-module@vger.kernel.org, linux-api@vger.kernel.org Subject: Re: [PATCH v3 05/25] user_namespace: refactor map_write() Message-ID: <20200219023552.GD19144@mail.hallyn.com> References: <20200218143411.2389182-1-christian.brauner@ubuntu.com> <20200218143411.2389182-6-christian.brauner@ubuntu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200218143411.2389182-6-christian.brauner@ubuntu.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 18, 2020 at 03:33:51PM +0100, Christian Brauner wrote: > Refactor map_write() to prepare for adding fsid mappings support. This mainly > factors out various open-coded parts into helpers that can be reused in the > follow up patch. > > Cc: Jann Horn > Signed-off-by: Christian Brauner Acked-by: Serge Hallyn > --- > /* v2 */ > patch not present > > /* v3 */ > patch added > - Jann Horn : > - Split changes to map_write() to implement fsid mappings into three separate > patches: basic fsid helpers, preparatory changes to map_write(), actual > fsid mapping support in map_write(). > --- > kernel/user_namespace.c | 117 +++++++++++++++++++++++++--------------- > 1 file changed, 74 insertions(+), 43 deletions(-) > > diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c > index 2cfd1e519cc4..e91141262bcc 100644 > --- a/kernel/user_namespace.c > +++ b/kernel/user_namespace.c > @@ -1038,10 +1038,10 @@ static int cmp_extents_reverse(const void *a, const void *b) > } > > /** > - * sort_idmaps - Sorts an array of idmap entries. > + * sort_map - Sorts an array of idmap entries. > * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS. > */ > -static int sort_idmaps(struct uid_gid_map *map) > +static int sort_map(struct uid_gid_map *map) > { > if (map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) > return 0; > @@ -1064,6 +1064,71 @@ static int sort_idmaps(struct uid_gid_map *map) > return 0; > } > > +static int sort_idmaps(struct uid_gid_map *map) > +{ > + return sort_map(map); > +} > + > +static int map_from_parent(struct uid_gid_map *new_map, > + struct uid_gid_map *parent_map) > +{ > + unsigned idx; > + > + /* Map the lower ids from the parent user namespace to the > + * kernel global id space. > + */ > + for (idx = 0; idx < new_map->nr_extents; idx++) { > + struct uid_gid_extent *e; > + u32 lower_first; > + > + if (new_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) > + e = &new_map->extent[idx]; > + else > + e = &new_map->forward[idx]; > + > + lower_first = map_id_range_down(parent_map, e->lower_first, e->count); > + > + /* Fail if we can not map the specified extent to > + * the kernel global id space. > + */ > + if (lower_first == (u32)-1) > + return -EPERM; > + > + e->lower_first = lower_first; > + } > + > + return 0; > +} > + > +static int map_into_kids(struct uid_gid_map *id_map, > + struct uid_gid_map *parent_id_map) > +{ > + return map_from_parent(id_map, parent_id_map); > +} > + > +static void install_idmaps(struct uid_gid_map *id_map, > + struct uid_gid_map *new_id_map) > +{ > + if (new_id_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) { > + memcpy(id_map->extent, new_id_map->extent, > + new_id_map->nr_extents * sizeof(new_id_map->extent[0])); > + } else { > + id_map->forward = new_id_map->forward; > + id_map->reverse = new_id_map->reverse; > + } > +} > + > +static void free_idmaps(struct uid_gid_map *new_id_map) > +{ > + if (new_id_map->nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) { > + kfree(new_id_map->forward); > + kfree(new_id_map->reverse); > + new_id_map->forward = NULL; > + new_id_map->reverse = NULL; > + new_id_map->nr_extents = 0; > + } > +} > + > static ssize_t map_write(struct file *file, const char __user *buf, > size_t count, loff_t *ppos, > int cap_setid, > @@ -1073,7 +1138,6 @@ static ssize_t map_write(struct file *file, const char __user *buf, > struct seq_file *seq = file->private_data; > struct user_namespace *ns = seq->private; > struct uid_gid_map new_map; > - unsigned idx; > struct uid_gid_extent extent; > char *kbuf = NULL, *pos, *next_line; > ssize_t ret; > @@ -1191,61 +1255,28 @@ static ssize_t map_write(struct file *file, const char __user *buf, > if (!new_idmap_permitted(file, ns, cap_setid, &new_map)) > goto out; > > - ret = -EPERM; > - /* Map the lower ids from the parent user namespace to the > - * kernel global id space. > - */ > - for (idx = 0; idx < new_map.nr_extents; idx++) { > - struct uid_gid_extent *e; > - u32 lower_first; > - > - if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) > - e = &new_map.extent[idx]; > - else > - e = &new_map.forward[idx]; > - > - lower_first = map_id_range_down(parent_map, > - e->lower_first, > - e->count); > - > - /* Fail if we can not map the specified extent to > - * the kernel global id space. > - */ > - if (lower_first == (u32) -1) > - goto out; > - > - e->lower_first = lower_first; > - } > + ret = map_into_kids(&new_map, parent_map); > + if (ret) > + goto out; > > /* > * 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) > + if (ret) > goto out; > > /* Install the map */ > - if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) { > - memcpy(map->extent, new_map.extent, > - new_map.nr_extents * sizeof(new_map.extent[0])); > - } else { > - map->forward = new_map.forward; > - map->reverse = new_map.reverse; > - } > + install_idmaps(map, &new_map); > smp_wmb(); > map->nr_extents = new_map.nr_extents; > > *ppos = count; > ret = count; > out: > - if (ret < 0 && new_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) { > - kfree(new_map.forward); > - kfree(new_map.reverse); > - map->forward = NULL; > - map->reverse = NULL; > - map->nr_extents = 0; > - } > + if (ret < 0) > + free_idmaps(&new_map); > > mutex_unlock(&userns_state_mutex); > kfree(kbuf); > -- > 2.25.0