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![David Howells](/assets/img/avatar_default.png)
Provide an empty name (ie. "") qstr for general use. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
258 lines
5.6 KiB
C
258 lines
5.6 KiB
C
#include <linux/mount.h>
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#include <linux/file.h>
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#include <linux/fs.h>
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#include <linux/proc_ns.h>
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#include <linux/magic.h>
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#include <linux/ktime.h>
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#include <linux/seq_file.h>
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#include <linux/user_namespace.h>
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#include <linux/nsfs.h>
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#include <linux/uaccess.h>
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static struct vfsmount *nsfs_mnt;
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static long ns_ioctl(struct file *filp, unsigned int ioctl,
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unsigned long arg);
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static const struct file_operations ns_file_operations = {
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.llseek = no_llseek,
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.unlocked_ioctl = ns_ioctl,
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};
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static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
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{
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struct inode *inode = d_inode(dentry);
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const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
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return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
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ns_ops->name, inode->i_ino);
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}
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static void ns_prune_dentry(struct dentry *dentry)
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{
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struct inode *inode = d_inode(dentry);
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if (inode) {
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struct ns_common *ns = inode->i_private;
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atomic_long_set(&ns->stashed, 0);
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}
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}
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const struct dentry_operations ns_dentry_operations =
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{
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.d_prune = ns_prune_dentry,
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.d_delete = always_delete_dentry,
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.d_dname = ns_dname,
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};
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static void nsfs_evict(struct inode *inode)
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{
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struct ns_common *ns = inode->i_private;
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clear_inode(inode);
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ns->ops->put(ns);
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}
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static void *__ns_get_path(struct path *path, struct ns_common *ns)
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{
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struct vfsmount *mnt = nsfs_mnt;
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struct dentry *dentry;
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struct inode *inode;
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unsigned long d;
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rcu_read_lock();
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d = atomic_long_read(&ns->stashed);
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if (!d)
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goto slow;
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dentry = (struct dentry *)d;
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if (!lockref_get_not_dead(&dentry->d_lockref))
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goto slow;
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rcu_read_unlock();
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ns->ops->put(ns);
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got_it:
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path->mnt = mntget(mnt);
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path->dentry = dentry;
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return NULL;
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slow:
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rcu_read_unlock();
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inode = new_inode_pseudo(mnt->mnt_sb);
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if (!inode) {
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ns->ops->put(ns);
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return ERR_PTR(-ENOMEM);
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}
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inode->i_ino = ns->inum;
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inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
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inode->i_flags |= S_IMMUTABLE;
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inode->i_mode = S_IFREG | S_IRUGO;
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inode->i_fop = &ns_file_operations;
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inode->i_private = ns;
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dentry = d_alloc_pseudo(mnt->mnt_sb, &empty_name);
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if (!dentry) {
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iput(inode);
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return ERR_PTR(-ENOMEM);
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}
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d_instantiate(dentry, inode);
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dentry->d_flags |= DCACHE_RCUACCESS;
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dentry->d_fsdata = (void *)ns->ops;
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d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
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if (d) {
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d_delete(dentry); /* make sure ->d_prune() does nothing */
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dput(dentry);
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cpu_relax();
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return ERR_PTR(-EAGAIN);
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}
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goto got_it;
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}
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void *ns_get_path(struct path *path, struct task_struct *task,
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const struct proc_ns_operations *ns_ops)
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{
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struct ns_common *ns;
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void *ret;
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again:
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ns = ns_ops->get(task);
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if (!ns)
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return ERR_PTR(-ENOENT);
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ret = __ns_get_path(path, ns);
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if (IS_ERR(ret) && PTR_ERR(ret) == -EAGAIN)
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goto again;
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return ret;
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}
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int open_related_ns(struct ns_common *ns,
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struct ns_common *(*get_ns)(struct ns_common *ns))
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{
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struct path path = {};
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struct file *f;
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void *err;
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int fd;
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fd = get_unused_fd_flags(O_CLOEXEC);
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if (fd < 0)
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return fd;
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while (1) {
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struct ns_common *relative;
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relative = get_ns(ns);
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if (IS_ERR(relative)) {
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put_unused_fd(fd);
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return PTR_ERR(relative);
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}
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err = __ns_get_path(&path, relative);
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if (IS_ERR(err) && PTR_ERR(err) == -EAGAIN)
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continue;
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break;
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}
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if (IS_ERR(err)) {
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put_unused_fd(fd);
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return PTR_ERR(err);
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}
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f = dentry_open(&path, O_RDONLY, current_cred());
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path_put(&path);
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if (IS_ERR(f)) {
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put_unused_fd(fd);
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fd = PTR_ERR(f);
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} else
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fd_install(fd, f);
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return fd;
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}
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static long ns_ioctl(struct file *filp, unsigned int ioctl,
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unsigned long arg)
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{
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struct user_namespace *user_ns;
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struct ns_common *ns = get_proc_ns(file_inode(filp));
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uid_t __user *argp;
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uid_t uid;
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switch (ioctl) {
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case NS_GET_USERNS:
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return open_related_ns(ns, ns_get_owner);
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case NS_GET_PARENT:
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if (!ns->ops->get_parent)
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return -EINVAL;
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return open_related_ns(ns, ns->ops->get_parent);
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case NS_GET_NSTYPE:
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return ns->ops->type;
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case NS_GET_OWNER_UID:
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if (ns->ops->type != CLONE_NEWUSER)
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return -EINVAL;
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user_ns = container_of(ns, struct user_namespace, ns);
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argp = (uid_t __user *) arg;
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uid = from_kuid_munged(current_user_ns(), user_ns->owner);
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return put_user(uid, argp);
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default:
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return -ENOTTY;
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}
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}
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int ns_get_name(char *buf, size_t size, struct task_struct *task,
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const struct proc_ns_operations *ns_ops)
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{
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struct ns_common *ns;
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int res = -ENOENT;
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const char *name;
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ns = ns_ops->get(task);
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if (ns) {
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name = ns_ops->real_ns_name ? : ns_ops->name;
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res = snprintf(buf, size, "%s:[%u]", name, ns->inum);
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ns_ops->put(ns);
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}
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return res;
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}
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struct file *proc_ns_fget(int fd)
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{
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struct file *file;
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file = fget(fd);
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if (!file)
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return ERR_PTR(-EBADF);
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if (file->f_op != &ns_file_operations)
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goto out_invalid;
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return file;
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out_invalid:
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fput(file);
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return ERR_PTR(-EINVAL);
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}
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static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
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{
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struct inode *inode = d_inode(dentry);
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const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
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seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
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return 0;
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}
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static const struct super_operations nsfs_ops = {
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.statfs = simple_statfs,
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.evict_inode = nsfs_evict,
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.show_path = nsfs_show_path,
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};
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static struct dentry *nsfs_mount(struct file_system_type *fs_type,
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int flags, const char *dev_name, void *data)
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{
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return mount_pseudo(fs_type, "nsfs:", &nsfs_ops,
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&ns_dentry_operations, NSFS_MAGIC);
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}
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static struct file_system_type nsfs = {
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.name = "nsfs",
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.mount = nsfs_mount,
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.kill_sb = kill_anon_super,
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};
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void __init nsfs_init(void)
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{
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nsfs_mnt = kern_mount(&nsfs);
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if (IS_ERR(nsfs_mnt))
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panic("can't set nsfs up\n");
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nsfs_mnt->mnt_sb->s_flags &= ~MS_NOUSER;
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}
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