Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754380AbbLIT3w (ORCPT ); Wed, 9 Dec 2015 14:29:52 -0500 Received: from h2.hallyn.com ([78.46.35.8]:38533 "EHLO h2.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754048AbbLIT3J (ORCPT ); Wed, 9 Dec 2015 14:29:09 -0500 From: serge.hallyn@ubuntu.com To: linux-kernel@vger.kernel.org Cc: adityakali@google.com, tj@kernel.org, linux-api@vger.kernel.org, containers@lists.linux-foundation.org, cgroups@vger.kernel.org, lxc-devel@lists.linuxcontainers.org, akpm@linux-foundation.org, ebiederm@xmission.com, gregkh@linuxfoundation.org, lizefan@huawei.com, hannes@cmpxchg.org, Serge Hallyn , Serge Hallyn Subject: [PATCH 6/8] cgroup: mount cgroupns-root when inside non-init cgroupns Date: Wed, 9 Dec 2015 13:28:59 -0600 Message-Id: <1449689341-28742-7-git-send-email-serge.hallyn@ubuntu.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1449689341-28742-1-git-send-email-serge.hallyn@ubuntu.com> References: <1449689341-28742-1-git-send-email-serge.hallyn@ubuntu.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3467 Lines: 116 From: Serge Hallyn This patch enables cgroup mounting inside userns when a process as appropriate privileges. The cgroup filesystem mounted is rooted at the cgroupns-root. Thus, in a container-setup, only the hierarchy under the cgroupns-root is exposed inside the container. This allows container management tools to run inside the containers without depending on any global state. Signed-off-by: Serge Hallyn --- Changelog: 20151116 - Don't allow user namespaces to bind new subsystems 20151118 - postpone the FS_USERNS_MOUNT flag until the last patch, until we can convince ourselves it is safe. 20151207 - Switch to walking up the kernfs path from kn root. - Group initialized variables - Explain the capable(CAP_SYS_ADMIN) check - Style fixes --- kernel/cgroup.c | 40 +++++++++++++++++++++++++++++++++++++++- 1 file changed, 39 insertions(+), 1 deletion(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index f34551a..b92b3fd 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2006,6 +2006,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, { bool is_v2 = fs_type == &cgroup2_fs_type; struct super_block *pinned_sb = NULL; + struct cgroup_namespace *ns = current->nsproxy->cgroup_ns; struct cgroup_subsys *ss; struct cgroup_root *root; struct cgroup_sb_opts opts; @@ -2014,6 +2015,14 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, int i; bool new_sb; + get_cgroup_ns(ns); + + /* Check if the caller has permission to mount. */ + if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) { + put_cgroup_ns(ns); + return ERR_PTR(-EPERM); + } + /* * The first time anyone tries to mount a cgroup, enable the list * linking each css_set to its tasks and fix up all existing tasks. @@ -2129,6 +2138,16 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, goto out_unlock; } + /* + * We know this subsystem has not yet been bound. Users in a non-init + * user namespace may only mount hierarchies with no bound subsystems, + * i.e. 'none,name=user1' + */ + if (!opts.none && !capable(CAP_SYS_ADMIN)) { + ret = -EPERM; + goto out_unlock; + } + root = kzalloc(sizeof(*root), GFP_KERNEL); if (!root) { ret = -ENOMEM; @@ -2147,12 +2166,30 @@ out_free: kfree(opts.release_agent); kfree(opts.name); - if (ret) + if (ret) { + put_cgroup_ns(ns); return ERR_PTR(ret); + } out_mount: dentry = kernfs_mount(fs_type, flags, root->kf_root, is_v2 ? CGROUP2_SUPER_MAGIC : CGROUP_SUPER_MAGIC, &new_sb); + + /* + * In non-init cgroup namespace, instead of root cgroup's + * dentry, we return the dentry corresponding to the + * cgroupns->root_cgrp. + */ + if (!IS_ERR(dentry) && ns != &init_cgroup_ns) { + struct dentry *nsdentry; + struct cgroup *cgrp; + + cgrp = cset_cgroup_from_root(ns->root_cset, root); + nsdentry = kernfs_node_dentry(cgrp->kn, dentry->d_sb); + dput(dentry); + dentry = nsdentry; + } + if (IS_ERR(dentry) || !new_sb) cgroup_put(&root->cgrp); @@ -2165,6 +2202,7 @@ out_mount: deactivate_super(pinned_sb); } + put_cgroup_ns(ns); return dentry; } -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/