1// SPDX-License-Identifier: GPL-2.0
2#include <linux/mount.h>
3#include <linux/pseudo_fs.h>
4#include <linux/file.h>
5#include <linux/fs.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>
14
15#include "internal.h"
16
17static struct vfsmount *nsfs_mnt;
18
19static long ns_ioctl(struct file *filp, unsigned int ioctl,
20 unsigned long arg);
21static const struct file_operations ns_file_operations = {
22 .llseek = no_llseek,
23 .unlocked_ioctl = ns_ioctl,
24 .compat_ioctl = compat_ptr_ioctl,
25};
26
27static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
28{
29 struct inode *inode = d_inode(dentry);
30 struct ns_common *ns = inode->i_private;
31 const struct proc_ns_operations *ns_ops = ns->ops;
32
33 return dynamic_dname(buffer, buflen, "%s:[%lu]",
34 ns_ops->name, inode->i_ino);
35}
36
37const struct dentry_operations ns_dentry_operations = {
38 .d_delete = always_delete_dentry,
39 .d_dname = ns_dname,
40 .d_prune = stashed_dentry_prune,
41};
42
43static void nsfs_evict(struct inode *inode)
44{
45 struct ns_common *ns = inode->i_private;
46 clear_inode(inode);
47 ns->ops->put(ns);
48}
49
50int ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb,
51 void *private_data)
52{
53 struct ns_common *ns;
54
55 ns = ns_get_cb(private_data);
56 if (!ns)
57 return -ENOENT;
58
59 return path_from_stashed(stashed: &ns->stashed, mnt: nsfs_mnt, data: ns, path);
60}
61
62struct ns_get_path_task_args {
63 const struct proc_ns_operations *ns_ops;
64 struct task_struct *task;
65};
66
67static struct ns_common *ns_get_path_task(void *private_data)
68{
69 struct ns_get_path_task_args *args = private_data;
70
71 return args->ns_ops->get(args->task);
72}
73
74int ns_get_path(struct path *path, struct task_struct *task,
75 const struct proc_ns_operations *ns_ops)
76{
77 struct ns_get_path_task_args args = {
78 .ns_ops = ns_ops,
79 .task = task,
80 };
81
82 return ns_get_path_cb(path, ns_get_cb: ns_get_path_task, private_data: &args);
83}
84
85int open_related_ns(struct ns_common *ns,
86 struct ns_common *(*get_ns)(struct ns_common *ns))
87{
88 struct path path = {};
89 struct ns_common *relative;
90 struct file *f;
91 int err;
92 int fd;
93
94 fd = get_unused_fd_flags(O_CLOEXEC);
95 if (fd < 0)
96 return fd;
97
98 relative = get_ns(ns);
99 if (IS_ERR(ptr: relative)) {
100 put_unused_fd(fd);
101 return PTR_ERR(ptr: relative);
102 }
103
104 err = path_from_stashed(stashed: &relative->stashed, mnt: nsfs_mnt, data: relative, path: &path);
105 if (err < 0) {
106 put_unused_fd(fd);
107 return err;
108 }
109
110 f = dentry_open(path: &path, O_RDONLY, current_cred());
111 path_put(&path);
112 if (IS_ERR(ptr: f)) {
113 put_unused_fd(fd);
114 fd = PTR_ERR(ptr: f);
115 } else
116 fd_install(fd, file: f);
117
118 return fd;
119}
120EXPORT_SYMBOL_GPL(open_related_ns);
121
122static long ns_ioctl(struct file *filp, unsigned int ioctl,
123 unsigned long arg)
124{
125 struct user_namespace *user_ns;
126 struct ns_common *ns = get_proc_ns(file_inode(filp));
127 uid_t __user *argp;
128 uid_t uid;
129
130 switch (ioctl) {
131 case NS_GET_USERNS:
132 return open_related_ns(ns, ns_get_owner);
133 case NS_GET_PARENT:
134 if (!ns->ops->get_parent)
135 return -EINVAL;
136 return open_related_ns(ns, ns->ops->get_parent);
137 case NS_GET_NSTYPE:
138 return ns->ops->type;
139 case NS_GET_OWNER_UID:
140 if (ns->ops->type != CLONE_NEWUSER)
141 return -EINVAL;
142 user_ns = container_of(ns, struct user_namespace, ns);
143 argp = (uid_t __user *) arg;
144 uid = from_kuid_munged(current_user_ns(), uid: user_ns->owner);
145 return put_user(uid, argp);
146 default:
147 return -ENOTTY;
148 }
149}
150
151int ns_get_name(char *buf, size_t size, struct task_struct *task,
152 const struct proc_ns_operations *ns_ops)
153{
154 struct ns_common *ns;
155 int res = -ENOENT;
156 const char *name;
157 ns = ns_ops->get(task);
158 if (ns) {
159 name = ns_ops->real_ns_name ? : ns_ops->name;
160 res = snprintf(buf, size, fmt: "%s:[%u]", name, ns->inum);
161 ns_ops->put(ns);
162 }
163 return res;
164}
165
166bool proc_ns_file(const struct file *file)
167{
168 return file->f_op == &ns_file_operations;
169}
170
171/**
172 * ns_match() - Returns true if current namespace matches dev/ino provided.
173 * @ns: current namespace
174 * @dev: dev_t from nsfs that will be matched against current nsfs
175 * @ino: ino_t from nsfs that will be matched against current nsfs
176 *
177 * Return: true if dev and ino matches the current nsfs.
178 */
179bool ns_match(const struct ns_common *ns, dev_t dev, ino_t ino)
180{
181 return (ns->inum == ino) && (nsfs_mnt->mnt_sb->s_dev == dev);
182}
183
184
185static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
186{
187 struct inode *inode = d_inode(dentry);
188 const struct ns_common *ns = inode->i_private;
189 const struct proc_ns_operations *ns_ops = ns->ops;
190
191 seq_printf(m: seq, fmt: "%s:[%lu]", ns_ops->name, inode->i_ino);
192 return 0;
193}
194
195static const struct super_operations nsfs_ops = {
196 .statfs = simple_statfs,
197 .evict_inode = nsfs_evict,
198 .show_path = nsfs_show_path,
199};
200
201static int nsfs_init_inode(struct inode *inode, void *data)
202{
203 struct ns_common *ns = data;
204
205 inode->i_private = data;
206 inode->i_mode |= S_IRUGO;
207 inode->i_fop = &ns_file_operations;
208 inode->i_ino = ns->inum;
209 return 0;
210}
211
212static void nsfs_put_data(void *data)
213{
214 struct ns_common *ns = data;
215 ns->ops->put(ns);
216}
217
218static const struct stashed_operations nsfs_stashed_ops = {
219 .init_inode = nsfs_init_inode,
220 .put_data = nsfs_put_data,
221};
222
223static int nsfs_init_fs_context(struct fs_context *fc)
224{
225 struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC);
226 if (!ctx)
227 return -ENOMEM;
228 ctx->ops = &nsfs_ops;
229 ctx->dops = &ns_dentry_operations;
230 fc->s_fs_info = (void *)&nsfs_stashed_ops;
231 return 0;
232}
233
234static struct file_system_type nsfs = {
235 .name = "nsfs",
236 .init_fs_context = nsfs_init_fs_context,
237 .kill_sb = kill_anon_super,
238};
239
240void __init nsfs_init(void)
241{
242 nsfs_mnt = kern_mount(&nsfs);
243 if (IS_ERR(ptr: nsfs_mnt))
244 panic(fmt: "can't set nsfs up\n");
245 nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER;
246}
247

source code of linux/fs/nsfs.c