From patchwork Tue Feb 11 16:57:30 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 11375939 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E5D161580 for ; Tue, 11 Feb 2020 16:59:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C583A20873 for ; Tue, 11 Feb 2020 16:59:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730946AbgBKQ7h (ORCPT ); Tue, 11 Feb 2020 11:59:37 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:53406 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729829AbgBKQ7f (ORCPT ); Tue, 11 Feb 2020 11:59:35 -0500 Received: from ip5f5bf7ec.dynamic.kabel-deutschland.de ([95.91.247.236] helo=wittgenstein.fritz.box) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1j1YsO-00014T-Fl; Tue, 11 Feb 2020 16:59:08 +0000 From: Christian Brauner To: =?utf-8?q?St=C3=A9phane_Graber?= , "Eric W. Biederman" , Aleksa Sarai , Jann Horn Cc: smbarber@chromium.org, Alexander Viro , Alexey Dobriyan , Serge Hallyn , James Morris , Kees Cook , Jonathan Corbet , 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, Christian Brauner Subject: [PATCH 01/24] user_namespace: introduce fsid mappings infrastructure Date: Tue, 11 Feb 2020 17:57:30 +0100 Message-Id: <20200211165753.356508-2-christian.brauner@ubuntu.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200211165753.356508-1-christian.brauner@ubuntu.com> References: <20200211165753.356508-1-christian.brauner@ubuntu.com> MIME-Version: 1.0 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: This introduces the infrastructure to setup fsid mappings which will be used in later patches. All new code depends on CONFIG_USER_NS_FSID=y. It currently defaults to "N". If CONFIG_USER_NS_FSID is not set, no new code is added. In this patch fsuid_m_show() and fsgid_m_show() are introduced. They are identical to uid_m_show() and gid_m_show() until we introduce from_kfsuid() and from_kfsgid() in a follow-up patch. Signed-off-by: Christian Brauner --- include/linux/user_namespace.h | 10 +++ init/Kconfig | 11 +++ kernel/user.c | 22 ++++++ kernel/user_namespace.c | 122 +++++++++++++++++++++++++++++++++ 4 files changed, 165 insertions(+) diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index fb9f4f799554..ffbd5e7e5ec7 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -55,6 +55,10 @@ enum ucount_type { struct user_namespace { struct uid_gid_map uid_map; struct uid_gid_map gid_map; +#ifdef CONFIG_USER_NS_FSID + struct uid_gid_map fsuid_map; + struct uid_gid_map fsgid_map; +#endif struct uid_gid_map projid_map; atomic_t count; struct user_namespace *parent; @@ -126,6 +130,12 @@ struct seq_operations; extern const struct seq_operations proc_uid_seq_operations; extern const struct seq_operations proc_gid_seq_operations; extern const struct seq_operations proc_projid_seq_operations; +#ifdef CONFIG_USER_NS_FSID +extern const struct seq_operations proc_fsuid_seq_operations; +extern const struct seq_operations proc_fsgid_seq_operations; +extern ssize_t proc_fsuid_map_write(struct file *, const char __user *, size_t, loff_t *); +extern ssize_t proc_fsgid_map_write(struct file *, const char __user *, size_t, loff_t *); +#endif extern ssize_t proc_uid_map_write(struct file *, const char __user *, size_t, loff_t *); extern ssize_t proc_gid_map_write(struct file *, const char __user *, size_t, loff_t *); extern ssize_t proc_projid_map_write(struct file *, const char __user *, size_t, loff_t *); diff --git a/init/Kconfig b/init/Kconfig index a34064a031a5..4da082e4f787 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1102,6 +1102,17 @@ config USER_NS If unsure, say N. +config USER_NS_FSID + bool "User namespace fsid mappings" + depends on USER_NS + default n + help + This allows containers, to alter their filesystem id mappings. + With this containers with different id mappings can still share + the same filesystem. + + If unsure, say N. + config PID_NS bool "PID Namespaces" default y diff --git a/kernel/user.c b/kernel/user.c index 5235d7f49982..2ccaea9b810b 100644 --- a/kernel/user.c +++ b/kernel/user.c @@ -55,6 +55,28 @@ struct user_namespace init_user_ns = { }, }, }, +#ifdef CONFIG_USER_NS_FSID + .fsuid_map = { + .nr_extents = 1, + { + .extent[0] = { + .first = 0, + .lower_first = 0, + .count = 4294967295U, + }, + }, + }, + .fsgid_map = { + .nr_extents = 1, + { + .extent[0] = { + .first = 0, + .lower_first = 0, + .count = 4294967295U, + }, + }, + }, +#endif .count = ATOMIC_INIT(3), .owner = GLOBAL_ROOT_UID, .group = GLOBAL_ROOT_GID, diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 8eadadc478f9..cbdf456f95f0 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -191,6 +191,16 @@ static void free_user_ns(struct work_struct *work) kfree(ns->projid_map.forward); kfree(ns->projid_map.reverse); } +#ifdef CONFIG_USER_NS_FSID + if (ns->fsgid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) { + kfree(ns->fsgid_map.forward); + kfree(ns->fsgid_map.reverse); + } + if (ns->fsuid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) { + kfree(ns->fsuid_map.forward); + kfree(ns->fsuid_map.reverse); + } +#endif retire_userns_sysctls(ns); key_free_user_ns(ns); ns_free_inum(&ns->ns); @@ -637,6 +647,50 @@ static int projid_m_show(struct seq_file *seq, void *v) return 0; } +#ifdef CONFIG_USER_NS_FSID +static int fsuid_m_show(struct seq_file *seq, void *v) +{ + struct user_namespace *ns = seq->private; + struct uid_gid_extent *extent = v; + struct user_namespace *lower_ns; + uid_t lower; + + lower_ns = seq_user_ns(seq); + if ((lower_ns == ns) && lower_ns->parent) + lower_ns = lower_ns->parent; + + lower = from_kuid(lower_ns, KUIDT_INIT(extent->lower_first)); + + seq_printf(seq, "%10u %10u %10u\n", + extent->first, + lower, + extent->count); + + return 0; +} + +static int fsgid_m_show(struct seq_file *seq, void *v) +{ + struct user_namespace *ns = seq->private; + struct uid_gid_extent *extent = v; + struct user_namespace *lower_ns; + gid_t lower; + + lower_ns = seq_user_ns(seq); + if ((lower_ns == ns) && lower_ns->parent) + lower_ns = lower_ns->parent; + + lower = from_kgid(lower_ns, KGIDT_INIT(extent->lower_first)); + + seq_printf(seq, "%10u %10u %10u\n", + extent->first, + lower, + extent->count); + + return 0; +} +#endif + static void *m_start(struct seq_file *seq, loff_t *ppos, struct uid_gid_map *map) { @@ -674,6 +728,22 @@ static void *projid_m_start(struct seq_file *seq, loff_t *ppos) return m_start(seq, ppos, &ns->projid_map); } +#ifdef CONFIG_USER_NS_FSID +static void *fsuid_m_start(struct seq_file *seq, loff_t *ppos) +{ + struct user_namespace *ns = seq->private; + + return m_start(seq, ppos, &ns->fsuid_map); +} + +static void *fsgid_m_start(struct seq_file *seq, loff_t *ppos) +{ + struct user_namespace *ns = seq->private; + + return m_start(seq, ppos, &ns->fsgid_map); +} +#endif + static void *m_next(struct seq_file *seq, void *v, loff_t *pos) { (*pos)++; @@ -706,6 +776,22 @@ const struct seq_operations proc_projid_seq_operations = { .show = projid_m_show, }; +#ifdef CONFIG_USER_NS_FSID +const struct seq_operations proc_fsuid_seq_operations = { + .start = fsuid_m_start, + .stop = m_stop, + .next = m_next, + .show = fsuid_m_show, +}; + +const struct seq_operations proc_fsgid_seq_operations = { + .start = fsgid_m_start, + .stop = m_stop, + .next = m_next, + .show = fsgid_m_show, +}; +#endif + static bool mappings_overlap(struct uid_gid_map *new_map, struct uid_gid_extent *extent) { @@ -1081,6 +1167,42 @@ ssize_t proc_projid_map_write(struct file *file, const char __user *buf, &ns->projid_map, &ns->parent->projid_map); } +#ifdef CONFIG_USER_NS_FSID +ssize_t proc_fsuid_map_write(struct file *file, const char __user *buf, + size_t size, loff_t *ppos) +{ + struct seq_file *seq = file->private_data; + struct user_namespace *ns = seq->private; + struct user_namespace *seq_ns = seq_user_ns(seq); + + if (!ns->parent) + return -EPERM; + + if ((seq_ns != ns) && (seq_ns != ns->parent)) + return -EPERM; + + return map_write(file, buf, size, ppos, CAP_SETUID, &ns->fsuid_map, + &ns->parent->fsuid_map); +} + +ssize_t proc_fsgid_map_write(struct file *file, const char __user *buf, + size_t size, loff_t *ppos) +{ + struct seq_file *seq = file->private_data; + struct user_namespace *ns = seq->private; + struct user_namespace *seq_ns = seq_user_ns(seq); + + if (!ns->parent) + return -EPERM; + + if ((seq_ns != ns) && (seq_ns != ns->parent)) + return -EPERM; + + return map_write(file, buf, size, ppos, CAP_SETGID, &ns->fsgid_map, + &ns->parent->fsgid_map); +} +#endif + static bool new_idmap_permitted(const struct file *file, struct user_namespace *ns, int cap_setid, struct uid_gid_map *new_map)