From patchwork Mon Mar 28 17:50:31 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 12794037 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 EBCA7C4321E for ; Mon, 28 Mar 2022 17:55:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244980AbiC1R5i (ORCPT ); Mon, 28 Mar 2022 13:57:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45298 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245074AbiC1R4v (ORCPT ); Mon, 28 Mar 2022 13:56:51 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CA96621E1F; Mon, 28 Mar 2022 10:55:04 -0700 (PDT) Received: from fraeml714-chm.china.huawei.com (unknown [172.18.147.226]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4KS0dr4kkWz67Q5R; Tue, 29 Mar 2022 01:52:32 +0800 (CST) Received: from roberto-ThinkStation-P620.huawei.com (10.204.63.22) by fraeml714-chm.china.huawei.com (10.206.15.33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 28 Mar 2022 19:55:01 +0200 From: Roberto Sassu To: , , , , , , , , , CC: , , , , , , , , , , Roberto Sassu Subject: [PATCH 16/18] bpf-preload: Do kernel mount to ensure that pinned objects don't disappear Date: Mon, 28 Mar 2022 19:50:31 +0200 Message-ID: <20220328175033.2437312-17-roberto.sassu@huawei.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220328175033.2437312-1-roberto.sassu@huawei.com> References: <20220328175033.2437312-1-roberto.sassu@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.204.63.22] X-ClientProxiedBy: lhreml754-chm.china.huawei.com (10.201.108.204) To fraeml714-chm.china.huawei.com (10.206.15.33) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org One of the differences between traditional LSMs in the security subsystem and LSMs implemented as eBPF programs is that for the latter category it cannot be guaranteed that they cannot be stopped. If a pinned program is unpinned, its execution will be stopped and will not enforce anymore its policy. For traditional LSMs this problem does not arise as, once they are invoked by the kernel, only the LSMs themselves decide whether or not they could be stopped. Solve this problem by mounting the bpf filesystem from the kernel, so that an object cannot be unpinned (a kernel mount is not accessible to user space). This will ensure that the LSM will run until the very end of the kernel lifecycle. Delay the kernel mount until the security subsystem (e.g. IMA) is fully initialized (e.g. keys loaded), so that the security subsystem can evaluate kernel modules loaded by populate_bpffs(). Signed-off-by: Roberto Sassu Reported-by: kernel test robot Reported-by: kernel test robot --- fs/namespace.c | 1 + include/linux/bpf.h | 5 +++++ init/main.c | 2 ++ kernel/bpf/inode.c | 9 +++++++++ 4 files changed, 17 insertions(+) diff --git a/fs/namespace.c b/fs/namespace.c index 6e9844b8c6fb..3b69f96dc641 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -31,6 +31,7 @@ #include #include #include +#include #include #include "pnode.h" diff --git a/include/linux/bpf.h b/include/linux/bpf.h index bdb5298735ce..5f624310fda2 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1103,6 +1103,8 @@ static inline void bpf_module_put(const void *data, struct module *owner) module_put(owner); } +void __init mount_bpffs(void); + #ifdef CONFIG_NET /* Define it here to avoid the use of forward declaration */ struct bpf_dummy_ops_state { @@ -1141,6 +1143,9 @@ static inline int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map, { return -EINVAL; } +static inline void __init mount_bpffs(void) +{ +} #endif struct bpf_array { diff --git a/init/main.c b/init/main.c index 0c064c2c79fd..30dcd0dd9faa 100644 --- a/init/main.c +++ b/init/main.c @@ -99,6 +99,7 @@ #include #include #include +#include #include #include @@ -1638,4 +1639,5 @@ static noinline void __init kernel_init_freeable(void) */ integrity_load_keys(); + mount_bpffs(); } diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c index c1941c65ce95..e8361d7679d0 100644 --- a/kernel/bpf/inode.c +++ b/kernel/bpf/inode.c @@ -1020,3 +1020,12 @@ static int __init bpf_init(void) return ret; } fs_initcall(bpf_init); + +static struct vfsmount *bpffs_mount __read_mostly; + +void __init mount_bpffs(void) +{ + bpffs_mount = kern_mount(&bpf_fs_type); + if (IS_ERR(bpffs_mount)) + pr_err("bpffs: could not mount!\n"); +}