Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759064AbaJaTTd (ORCPT ); Fri, 31 Oct 2014 15:19:33 -0400 Received: from mail-yh0-f74.google.com ([209.85.213.74]:40903 "EHLO mail-yh0-f74.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759034AbaJaTT2 (ORCPT ); Fri, 31 Oct 2014 15:19:28 -0400 From: Aditya Kali To: tj@kernel.org, lizefan@huawei.com, serge.hallyn@ubuntu.com, luto@amacapital.net, ebiederm@xmission.com, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, mingo@redhat.com Cc: containers@lists.linux-foundation.org, jnagal@google.com, Aditya Kali Subject: [PATCHv2 7/7] cgroup: mount cgroupns-root when inside non-init cgroupns Date: Fri, 31 Oct 2014 12:19:01 -0700 Message-Id: <1414783141-6947-8-git-send-email-adityakali@google.com> X-Mailer: git-send-email 2.1.0.rc2.206.gedb03e5 In-Reply-To: <1414783141-6947-1-git-send-email-adityakali@google.com> References: <1414783141-6947-1-git-send-email-adityakali@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. In order to support this, a new kernfs api is added to lookup the dentry for the cgroupns-root. Signed-off-by: Aditya Kali --- fs/kernfs/mount.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/kernfs.h | 2 ++ kernel/cgroup.c | 47 +++++++++++++++++++++++++++++++++++++++++++++-- 3 files changed, 95 insertions(+), 2 deletions(-) diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c index f973ae9..e334f45 100644 --- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -62,6 +62,54 @@ struct kernfs_root *kernfs_root_from_sb(struct super_block *sb) return NULL; } +/** + * kernfs_make_root - create new root dentry for the given kernfs_node. + * @sb: the kernfs super_block + * @kn: kernfs_node for which a dentry is needed + * + * This can used used by callers which want to mount only a part of the kernfs + * as root of the filesystem. + */ +struct dentry *kernfs_obtain_root(struct super_block *sb, + struct kernfs_node *kn) +{ + struct dentry *dentry; + struct inode *inode; + + BUG_ON(sb->s_op != &kernfs_sops); + + /* inode for the given kernfs_node should already exist. */ + inode = ilookup(sb, kn->ino); + if (!inode) { + pr_debug("kernfs: could not get inode for '"); + pr_cont_kernfs_path(kn); + pr_cont("'.\n"); + return ERR_PTR(-EINVAL); + } + + /* instantiate and link root dentry */ + dentry = d_obtain_root(inode); + if (!dentry) { + pr_debug("kernfs: could not get dentry for '"); + pr_cont_kernfs_path(kn); + pr_cont("'.\n"); + return ERR_PTR(-ENOMEM); + } + + /* If this is a new dentry, set it up. We need kernfs_mutex because this + * may be called by callers other than kernfs_fill_super. */ + mutex_lock(&kernfs_mutex); + if (!dentry->d_fsdata) { + kernfs_get(kn); + dentry->d_fsdata = kn; + } else { + WARN_ON(dentry->d_fsdata != kn); + } + mutex_unlock(&kernfs_mutex); + + return dentry; +} + static int kernfs_fill_super(struct super_block *sb, unsigned long magic) { struct kernfs_super_info *info = kernfs_info(sb); diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h index 3c2be75..b9538e0 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -274,6 +274,8 @@ void kernfs_put(struct kernfs_node *kn); struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry); struct kernfs_root *kernfs_root_from_sb(struct super_block *sb); +struct dentry *kernfs_obtain_root(struct super_block *sb, + struct kernfs_node *kn); struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags, void *priv); void kernfs_destroy_root(struct kernfs_root *root); diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 7e5d597..250aaec 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1302,6 +1302,13 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) memset(opts, 0, sizeof(*opts)); + /* Implicitly add CGRP_ROOT_SANE_BEHAVIOR if inside a non-init cgroup + * namespace. + */ + if (current->nsproxy->cgroup_ns != &init_cgroup_ns) { + opts->flags |= CGRP_ROOT_SANE_BEHAVIOR; + } + while ((token = strsep(&o, ",")) != NULL) { nr_opts++; @@ -1391,7 +1398,7 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) { pr_warn("sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n"); - if (nr_opts != 1) { + if (nr_opts > 1) { pr_err("sane_behavior: no other mount options allowed\n"); return -EINVAL; } @@ -1581,6 +1588,15 @@ static void init_cgroup_root(struct cgroup_root *root, set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags); } +struct dentry *cgroupns_get_root(struct super_block *sb, + struct cgroup_namespace *ns) +{ + struct dentry *nsdentry; + + nsdentry = kernfs_obtain_root(sb, ns->root_cgrp->kn); + return nsdentry; +} + static int cgroup_setup_root(struct cgroup_root *root, unsigned int ss_mask) { LIST_HEAD(tmp_links); @@ -1685,6 +1701,14 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, int ret; int i; bool new_sb; + struct cgroup_namespace *ns = + get_cgroup_ns(current->nsproxy->cgroup_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 @@ -1817,11 +1841,28 @@ out_free: kfree(opts.release_agent); kfree(opts.name); - if (ret) + if (ret) { + put_cgroup_ns(ns); return ERR_PTR(ret); + } dentry = kernfs_mount(fs_type, flags, root->kf_root, CGROUP_SUPER_MAGIC, &new_sb); + + if (!IS_ERR(dentry) && (root == &cgrp_dfl_root)) { + /* If this mount is for the default hierarchy in non-init cgroup + * namespace, then instead of root cgroup's dentry, we return + * the dentry corresponding to the cgroupns->root_cgrp. + */ + if (ns != &init_cgroup_ns) { + struct dentry *nsdentry; + + nsdentry = cgroupns_get_root(dentry->d_sb, ns); + dput(dentry); + dentry = nsdentry; + } + } + if (IS_ERR(dentry) || !new_sb) cgroup_put(&root->cgrp); @@ -1834,6 +1875,7 @@ out_free: deactivate_super(pinned_sb); } + put_cgroup_ns(ns); return dentry; } @@ -1862,6 +1904,7 @@ static struct file_system_type cgroup_fs_type = { .name = "cgroup", .mount = cgroup_mount, .kill_sb = cgroup_kill_sb, + .fs_flags = FS_USERNS_MOUNT, }; static struct kobject *cgroup_kobj; -- 2.1.0.rc2.206.gedb03e5 -- 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/