1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/mount.h>
3 #include <linux/pseudo_fs.h>
4 #include <linux/file.h>
6 #include <linux/proc_fs.h>
7 #include <linux/proc_ns.h>
8 #include <linux/magic.h>
9 #include <linux/ktime.h>
10 #include <linux/seq_file.h>
11 #include <linux/user_namespace.h>
12 #include <linux/nsfs.h>
13 #include <linux/uaccess.h>
17 static struct vfsmount *nsfs_mnt;
19 static long ns_ioctl(struct file *filp, unsigned int ioctl,
21 static const struct file_operations ns_file_operations = {
23 .unlocked_ioctl = ns_ioctl,
26 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
28 struct inode *inode = d_inode(dentry);
29 const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
31 return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
32 ns_ops->name, inode->i_ino);
35 static void ns_prune_dentry(struct dentry *dentry)
37 struct inode *inode = d_inode(dentry);
39 struct ns_common *ns = inode->i_private;
40 atomic_long_set(&ns->stashed, 0);
44 const struct dentry_operations ns_dentry_operations =
46 .d_prune = ns_prune_dentry,
47 .d_delete = always_delete_dentry,
51 static void nsfs_evict(struct inode *inode)
53 struct ns_common *ns = inode->i_private;
58 static void *__ns_get_path(struct path *path, struct ns_common *ns)
60 struct vfsmount *mnt = nsfs_mnt;
61 struct dentry *dentry;
66 d = atomic_long_read(&ns->stashed);
69 dentry = (struct dentry *)d;
70 if (!lockref_get_not_dead(&dentry->d_lockref))
75 path->mnt = mntget(mnt);
76 path->dentry = dentry;
80 inode = new_inode_pseudo(mnt->mnt_sb);
83 return ERR_PTR(-ENOMEM);
85 inode->i_ino = ns->inum;
86 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
87 inode->i_flags |= S_IMMUTABLE;
88 inode->i_mode = S_IFREG | S_IRUGO;
89 inode->i_fop = &ns_file_operations;
90 inode->i_private = ns;
92 dentry = d_alloc_anon(mnt->mnt_sb);
95 return ERR_PTR(-ENOMEM);
97 d_instantiate(dentry, inode);
98 dentry->d_fsdata = (void *)ns->ops;
99 d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
101 d_delete(dentry); /* make sure ->d_prune() does nothing */
104 return ERR_PTR(-EAGAIN);
109 void *ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb,
115 struct ns_common *ns = ns_get_cb(private_data);
117 return ERR_PTR(-ENOENT);
119 ret = __ns_get_path(path, ns);
120 } while (ret == ERR_PTR(-EAGAIN));
125 struct ns_get_path_task_args {
126 const struct proc_ns_operations *ns_ops;
127 struct task_struct *task;
130 static struct ns_common *ns_get_path_task(void *private_data)
132 struct ns_get_path_task_args *args = private_data;
134 return args->ns_ops->get(args->task);
137 void *ns_get_path(struct path *path, struct task_struct *task,
138 const struct proc_ns_operations *ns_ops)
140 struct ns_get_path_task_args args = {
145 return ns_get_path_cb(path, ns_get_path_task, &args);
148 int open_related_ns(struct ns_common *ns,
149 struct ns_common *(*get_ns)(struct ns_common *ns))
151 struct path path = {};
156 fd = get_unused_fd_flags(O_CLOEXEC);
161 struct ns_common *relative;
163 relative = get_ns(ns);
164 if (IS_ERR(relative)) {
166 return PTR_ERR(relative);
169 err = __ns_get_path(&path, relative);
170 } while (err == ERR_PTR(-EAGAIN));
177 f = dentry_open(&path, O_RDONLY, current_cred());
187 EXPORT_SYMBOL_GPL(open_related_ns);
189 static long ns_ioctl(struct file *filp, unsigned int ioctl,
192 struct user_namespace *user_ns;
193 struct ns_common *ns = get_proc_ns(file_inode(filp));
199 return open_related_ns(ns, ns_get_owner);
201 if (!ns->ops->get_parent)
203 return open_related_ns(ns, ns->ops->get_parent);
205 return ns->ops->type;
206 case NS_GET_OWNER_UID:
207 if (ns->ops->type != CLONE_NEWUSER)
209 user_ns = container_of(ns, struct user_namespace, ns);
210 argp = (uid_t __user *) arg;
211 uid = from_kuid_munged(current_user_ns(), user_ns->owner);
212 return put_user(uid, argp);
218 int ns_get_name(char *buf, size_t size, struct task_struct *task,
219 const struct proc_ns_operations *ns_ops)
221 struct ns_common *ns;
224 ns = ns_ops->get(task);
226 name = ns_ops->real_ns_name ? : ns_ops->name;
227 res = snprintf(buf, size, "%s:[%u]", name, ns->inum);
233 struct file *proc_ns_fget(int fd)
239 return ERR_PTR(-EBADF);
241 if (file->f_op != &ns_file_operations)
248 return ERR_PTR(-EINVAL);
251 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
253 struct inode *inode = d_inode(dentry);
254 const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
256 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
260 static const struct super_operations nsfs_ops = {
261 .statfs = simple_statfs,
262 .evict_inode = nsfs_evict,
263 .show_path = nsfs_show_path,
266 static int nsfs_init_fs_context(struct fs_context *fc)
268 struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC);
271 ctx->ops = &nsfs_ops;
272 ctx->dops = &ns_dentry_operations;
276 static struct file_system_type nsfs = {
278 .init_fs_context = nsfs_init_fs_context,
279 .kill_sb = kill_anon_super,
282 void __init nsfs_init(void)
284 nsfs_mnt = kern_mount(&nsfs);
285 if (IS_ERR(nsfs_mnt))
286 panic("can't set nsfs up\n");
287 nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER;