Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5909EC433FE for ; Thu, 16 Dec 2021 14:08:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237600AbhLPOIT (ORCPT ); Thu, 16 Dec 2021 09:08:19 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:49704 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237531AbhLPOIT (ORCPT ); Thu, 16 Dec 2021 09:08:19 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id A3044B8241A; Thu, 16 Dec 2021 14:08:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 88048C36AE4; Thu, 16 Dec 2021 14:08:10 +0000 (UTC) Date: Thu, 16 Dec 2021 15:08:06 +0100 From: Christian Brauner To: Stefan Berger Cc: linux-integrity@vger.kernel.org, zohar@linux.ibm.com, serge@hallyn.com, containers@lists.linux.dev, dmitry.kasatkin@gmail.com, ebiederm@xmission.com, krzysztof.struczynski@huawei.com, roberto.sassu@huawei.com, mpeters@redhat.com, lhinds@redhat.com, lsturman@redhat.com, puiterwi@redhat.com, jejb@linux.ibm.com, jamjoom@us.ibm.com, linux-kernel@vger.kernel.org, paul@paul-moore.com, rgb@redhat.com, linux-security-module@vger.kernel.org, jmorris@namei.org, Stefan Berger , James Bottomley Subject: Re: [PATCH v7 01/14] ima: Add IMA namespace support Message-ID: <20211216140806.hi4jxw54yvbu5cox@wittgenstein> References: <20211216054323.1707384-1-stefanb@linux.vnet.ibm.com> <20211216054323.1707384-2-stefanb@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20211216054323.1707384-2-stefanb@linux.vnet.ibm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 16, 2021 at 12:43:10AM -0500, Stefan Berger wrote: > From: Stefan Berger > > Implement an IMA namespace data structure that gets created alongside a > user namespace with CLONE_NEWUSER. This lays down the foundation for > namespacing the different aspects of IMA (eg. IMA-audit, IMA-measurement, > IMA-appraisal). > > Signed-off-by: Stefan Berger > Suggested-by: James Bottomley > --- > include/linux/ima.h | 33 ++++++++++++ > include/linux/user_namespace.h | 4 ++ > init/Kconfig | 10 ++++ > kernel/user.c | 7 +++ > kernel/user_namespace.c | 8 +++ > security/integrity/ima/Makefile | 3 +- > security/integrity/ima/ima.h | 8 +++ > security/integrity/ima/ima_init.c | 4 ++ > security/integrity/ima/ima_init_ima_ns.c | 28 ++++++++++ > security/integrity/ima/ima_ns.c | 65 ++++++++++++++++++++++++ > 10 files changed, 169 insertions(+), 1 deletion(-) > create mode 100644 security/integrity/ima/ima_init_ima_ns.c > create mode 100644 security/integrity/ima/ima_ns.c > > diff --git a/include/linux/ima.h b/include/linux/ima.h > index b6ab66a546ae..61461ee5b208 100644 > --- a/include/linux/ima.h > +++ b/include/linux/ima.h > @@ -11,6 +11,7 @@ > #include > #include > #include > +#include > #include > struct linux_binprm; > > @@ -210,6 +211,38 @@ static inline int ima_inode_removexattr(struct dentry *dentry, > } > #endif /* CONFIG_IMA_APPRAISE */ > > +extern struct ima_namespace init_ima_ns; > + > +#ifdef CONFIG_IMA_NS > + > +void free_ima_ns(struct user_namespace *ns); > +int create_ima_ns(struct user_namespace *user_ns); > + > +static inline struct ima_namespace *get_current_ns(void) > +{ > + return current_user_ns()->ima_ns; > +} > + > +#else > + > +static inline void free_ima_ns(struct user_namespace *user_ns) > +{ > +} > + > +static inline int create_ima_ns(struct user_namespace *user_ns) > +{ > +#ifdef CONFIG_IMA > + user_ns->ima_ns = &init_ima_ns; > +#endif > + return 0; > +} > + > +static inline struct ima_namespace *get_current_ns(void) > +{ > + return &init_ima_ns; > +} > +#endif /* CONFIG_IMA_NS */ > + > #if defined(CONFIG_IMA_APPRAISE) && defined(CONFIG_INTEGRITY_TRUSTED_KEYRING) > extern bool ima_appraise_signature(enum kernel_read_file_id func); > #else > diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h > index 33a4240e6a6f..5249db04d62b 100644 > --- a/include/linux/user_namespace.h > +++ b/include/linux/user_namespace.h > @@ -36,6 +36,7 @@ struct uid_gid_map { /* 64 bytes -- 1 cache line */ > #define USERNS_INIT_FLAGS USERNS_SETGROUPS_ALLOWED > > struct ucounts; > +struct ima_namespace; > > enum ucount_type { > UCOUNT_USER_NAMESPACES, > @@ -99,6 +100,9 @@ struct user_namespace { > #endif > struct ucounts *ucounts; > long ucount_max[UCOUNT_COUNTS]; > +#ifdef CONFIG_IMA > + struct ima_namespace *ima_ns; > +#endif > } __randomize_layout; > > struct ucounts { > diff --git a/init/Kconfig b/init/Kconfig > index 11f8a845f259..27890607e8cb 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -1242,6 +1242,16 @@ config NET_NS > Allow user space to create what appear to be multiple instances > of the network stack. > > +config IMA_NS > + bool "IMA namespace" > + depends on USER_NS > + depends on IMA > + default y > + help > + Allow the creation of IMA namespaces for each user namespace. > + Namespaced IMA enables having IMA features work separately > + in each IMA namespace. > + > endif # NAMESPACES > > config CHECKPOINT_RESTORE > diff --git a/kernel/user.c b/kernel/user.c > index e2cf8c22b539..287751d89b44 100644 > --- a/kernel/user.c > +++ b/kernel/user.c > @@ -20,6 +20,10 @@ > #include > #include > > +#ifdef CONFIG_IMA > +extern struct ima_namespace init_ima_ns; > +#endif > + > /* > * userns count is 1 for root user, 1 for init_uts_ns, > * and 1 for... ? > @@ -67,6 +71,9 @@ struct user_namespace init_user_ns = { > .keyring_name_list = LIST_HEAD_INIT(init_user_ns.keyring_name_list), > .keyring_sem = __RWSEM_INITIALIZER(init_user_ns.keyring_sem), > #endif > +#ifdef CONFIG_IMA > + .ima_ns = &init_ima_ns, > +#endif > }; > EXPORT_SYMBOL_GPL(init_user_ns); > > diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c > index 6b2e3ca7ee99..6fa01323aac9 100644 > --- a/kernel/user_namespace.c > +++ b/kernel/user_namespace.c > @@ -20,6 +20,7 @@ > #include > #include > #include > +#include > > static struct kmem_cache *user_ns_cachep __read_mostly; > static DEFINE_MUTEX(userns_state_mutex); > @@ -141,8 +142,14 @@ int create_user_ns(struct cred *new) > if (!setup_userns_sysctls(ns)) > goto fail_keyring; > > + ret = create_ima_ns(ns); Instead of greedily allocating a new ima namespace for each new user namespace creation and wasting memory that is likely wasted since most containers won't use ima (for a long time at least) have you considered lazily allocating it like I suggested in one of my first reviews? So under the assumption that the only way for a container to get its own ima policy it needs to have mounted a new securityfs instance you can move the ima namespace allocation into fill_super/ima_fs_ns_init(): From 46fd4f19e1360bee167fccb11e793a3a3331ccc2 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 16 Dec 2021 14:57:30 +0100 Subject: [PATCH] !!!! HERE BE DRAGONS - COMPLETELY UNTESTED !!!! Lazily initialize ima_ns. This avoids pointlessly wasting memory that is never needed or used which I think will be the case for most containers. --- include/linux/ima.h | 2 +- kernel/user_namespace.c | 6 ------ security/integrity/ima/ima_fs.c | 20 ++++++++++++++++++-- security/integrity/ima/ima_main.c | 5 ++++- security/integrity/ima/ima_ns.c | 7 ++++++- 5 files changed, 29 insertions(+), 11 deletions(-) diff --git a/include/linux/ima.h b/include/linux/ima.h index a2705aa5242a..cb1b94df11a1 100644 --- a/include/linux/ima.h +++ b/include/linux/ima.h @@ -230,7 +230,7 @@ int create_ima_ns(struct user_namespace *user_ns); static inline struct ima_namespace *get_current_ns(void) { - return current_user_ns()->ima_ns; + return smp_load_acquire(¤t_user_ns()->ima_ns); } static inline int ima_securityfs_init(struct user_namespace *user_ns, diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 6fa01323aac9..653f8fa83b69 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -142,14 +142,8 @@ int create_user_ns(struct cred *new) if (!setup_userns_sysctls(ns)) goto fail_keyring; - ret = create_ima_ns(ns); - if (ret) - goto fail_sysctls; - set_cred_user_ns(new, ns); return 0; -fail_sysctls: - retire_userns_sysctls(ns); fail_keyring: #ifdef CONFIG_PERSISTENT_KEYRINGS key_put(ns->persistent_keyring_register); diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c index 3b8001ba62e3..971620a22dab 100644 --- a/security/integrity/ima/ima_fs.c +++ b/security/integrity/ima/ima_fs.c @@ -378,7 +378,7 @@ static const struct seq_operations ima_policy_seqops = { static int ima_open_policy(struct inode *inode, struct file *filp) { struct user_namespace *user_ns = ima_user_ns_from_file(filp); - struct ima_namespace *ns = user_ns->ima_ns; + struct ima_namespace *ns = user_ns->ima_ns; /* no need to use acquire semantics it's guaranteed to be initialized */ if (!(filp->f_flags & O_WRONLY)) { #ifndef CONFIG_IMA_READ_POLICY @@ -450,7 +450,8 @@ static const struct file_operations ima_measure_policy_ops = { int ima_fs_ns_init(struct user_namespace *user_ns, struct dentry *root) { - struct ima_namespace *ns = user_ns->ima_ns; + int ret; + struct ima_namespace *ns = user_ns->ima_ns; /* no need to use acquire semantics it's guaranteed to be initialized */ struct dentry *int_dir; struct dentry *ima_dir = NULL; struct dentry *ima_symlink = NULL; @@ -459,6 +460,21 @@ int ima_fs_ns_init(struct user_namespace *user_ns, struct dentry *root) struct dentry *runtime_measurements_count = NULL; struct dentry *violations = NULL; + /* + * While multiple superblocks can exist they are keyed by userns in + * s_fs_info for securityfs. The first time a userns mounts a + * securityfs instance we lazily allocate the ima_namespace for the + * userns since that's the only way a userns can meaningfully use ima. + * The vfs ensure we're the only one to call fill_super() and hence + * ima_fs_ns_init() so we don't need any memory barriers here, i.e. + * user_ns->ima_ns can't change while we're in here. + */ + if (!ns) { + ret = create_ima_ns(user_ns); + if (ret) + return ret; + } + /* FIXME: update when evm and integrity are namespaced */ if (user_ns != &init_user_ns) { int_dir = diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 4c85a8df3c86..a0e71416561d 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -414,7 +414,10 @@ static int process_measurement(struct ima_namespace *ns, int ret = 0; while (user_ns) { - ns = user_ns->ima_ns; + /* the container has not loaded a separate policy (yet) */ + ns = smp_load_acquire(&user_ns->ima_ns); + if (!ns) + continue; ret = __process_measurement(ns, file, cred, secid, buf, size, mask, func); diff --git a/security/integrity/ima/ima_ns.c b/security/integrity/ima/ima_ns.c index d192a80c927f..5c7177b07344 100644 --- a/security/integrity/ima/ima_ns.c +++ b/security/integrity/ima/ima_ns.c @@ -31,7 +31,8 @@ int create_ima_ns(struct user_namespace *user_ns) if (err) goto fail_free; - user_ns->ima_ns = ns; + /* Pairs with smp_load_acquire() in get_current_ns() and process_measurement(). */ + smp_store_release(&user_ns->ima_ns, ns); return 0; @@ -52,6 +53,10 @@ static void destroy_ima_ns(struct ima_namespace *ns) void free_ima_ns(struct user_namespace *user_ns) { + /* No need to use acquire semantics as the userns can't be reached + * anymore from userspace so either ima_ns has been initialized or it + * never has. + */ struct ima_namespace *ns = user_ns->ima_ns; if (WARN_ON(ns == &init_ima_ns)) -- 2.30.2