Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752220AbaJQMUB (ORCPT ); Fri, 17 Oct 2014 08:20:01 -0400 Received: from static.92.5.9.176.clients.your-server.de ([176.9.5.92]:39369 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750911AbaJQMT7 (ORCPT ); Fri, 17 Oct 2014 08:19:59 -0400 Date: Fri, 17 Oct 2014 14:19:57 +0200 From: "Serge E. Hallyn" To: Aditya Kali Cc: tj@kernel.org, lizefan@huawei.com, serge.hallyn@ubuntu.com, luto@amacapital.net, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, mingo@redhat.com, containers@lists.linux-foundation.org, jnagal@google.com Subject: Re: [PATCHv1 8/8] cgroup: mount cgroupns-root when inside non-init cgroupns Message-ID: <20141017121957.GA10235@mail.hallyn.com> References: <1413235430-22944-1-git-send-email-adityakali@google.com> <1413235430-22944-9-git-send-email-adityakali@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1413235430-22944-9-git-send-email-adityakali@google.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Aditya Kali (adityakali@google.com): > 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 Acked-by: Serge Hallyn > --- > 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 2fc0dfa..ef27dc4 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); > @@ -1684,6 +1700,14 @@ 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 > @@ -1816,11 +1840,28 @@ 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)) { > + /* If this mount is for a non-init cgroup namespace, then > + * Instead of root's dentry, we return the dentry specific 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); > > @@ -1833,6 +1874,7 @@ out_free: > deactivate_super(pinned_sb); > } > > + put_cgroup_ns(ns); > return dentry; > } > > @@ -1861,6 +1903,7 @@ 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/ -- 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/