1
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};
25
26static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
27{
28 struct inode *inode = d_inode(dentry);
29 const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
30
31 return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
32 ns_ops->name, inode->i_ino);
33}
34
35static void ns_prune_dentry(struct dentry *dentry)
36{
37 struct inode *inode = d_inode(dentry);
38 if (inode) {
39 struct ns_common *ns = inode->i_private;
40 atomic_long_set(&ns->stashed, 0);
41 }
42}
43
44const struct dentry_operations ns_dentry_operations =
45{
46 .d_prune = ns_prune_dentry,
47 .d_delete = always_delete_dentry,
48 .d_dname = ns_dname,
49};
50
51static void nsfs_evict(struct inode *inode)
52{
53 struct ns_common *ns = inode->i_private;
54 clear_inode(inode);
55 ns->ops->put(ns);
56}
57
58static int __ns_get_path(struct path *path, struct ns_common *ns)
59{
60 struct vfsmount *mnt = nsfs_mnt;
61 struct dentry *dentry;
62 struct inode *inode;
63 unsigned long d;
64
65 rcu_read_lock();
66 d = atomic_long_read(&ns->stashed);
67 if (!d)
68 goto slow;
69 dentry = (struct dentry *)d;
70 if (!lockref_get_not_dead(&dentry->d_lockref))
71 goto slow;
72 rcu_read_unlock();
73 ns->ops->put(ns);
74got_it:
75 path->mnt = mntget(mnt);
76 path->dentry = dentry;
77 return 0;
78slow:
79 rcu_read_unlock();
80 inode = new_inode_pseudo(mnt->mnt_sb);
81 if (!inode) {
82 ns->ops->put(ns);
83 return -ENOMEM;
84 }
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;
91
92 dentry = d_alloc_anon(mnt->mnt_sb);
93 if (!dentry) {
94 iput(inode);
95 return -ENOMEM;
96 }
97 d_instantiate(dentry, inode);
98 dentry->d_fsdata = (void *)ns->ops;
99 d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
100 if (d) {
101 d_delete(dentry);
102 dput(dentry);
103 cpu_relax();
104 return -EAGAIN;
105 }
106 goto got_it;
107}
108
109int ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb,
110 void *private_data)
111{
112 int ret;
113
114 do {
115 struct ns_common *ns = ns_get_cb(private_data);
116 if (!ns)
117 return -ENOENT;
118 ret = __ns_get_path(path, ns);
119 } while (ret == -EAGAIN);
120
121 return ret;
122}
123
124struct ns_get_path_task_args {
125 const struct proc_ns_operations *ns_ops;
126 struct task_struct *task;
127};
128
129static struct ns_common *ns_get_path_task(void *private_data)
130{
131 struct ns_get_path_task_args *args = private_data;
132
133 return args->ns_ops->get(args->task);
134}
135
136int ns_get_path(struct path *path, struct task_struct *task,
137 const struct proc_ns_operations *ns_ops)
138{
139 struct ns_get_path_task_args args = {
140 .ns_ops = ns_ops,
141 .task = task,
142 };
143
144 return ns_get_path_cb(path, ns_get_path_task, &args);
145}
146
147int open_related_ns(struct ns_common *ns,
148 struct ns_common *(*get_ns)(struct ns_common *ns))
149{
150 struct path path = {};
151 struct file *f;
152 int err;
153 int fd;
154
155 fd = get_unused_fd_flags(O_CLOEXEC);
156 if (fd < 0)
157 return fd;
158
159 do {
160 struct ns_common *relative;
161
162 relative = get_ns(ns);
163 if (IS_ERR(relative)) {
164 put_unused_fd(fd);
165 return PTR_ERR(relative);
166 }
167
168 err = __ns_get_path(&path, relative);
169 } while (err == -EAGAIN);
170
171 if (err) {
172 put_unused_fd(fd);
173 return err;
174 }
175
176 f = dentry_open(&path, O_RDONLY, current_cred());
177 path_put(&path);
178 if (IS_ERR(f)) {
179 put_unused_fd(fd);
180 fd = PTR_ERR(f);
181 } else
182 fd_install(fd, f);
183
184 return fd;
185}
186EXPORT_SYMBOL_GPL(open_related_ns);
187
188static long ns_ioctl(struct file *filp, unsigned int ioctl,
189 unsigned long arg)
190{
191 struct user_namespace *user_ns;
192 struct ns_common *ns = get_proc_ns(file_inode(filp));
193 uid_t __user *argp;
194 uid_t uid;
195
196 switch (ioctl) {
197 case NS_GET_USERNS:
198 return open_related_ns(ns, ns_get_owner);
199 case NS_GET_PARENT:
200 if (!ns->ops->get_parent)
201 return -EINVAL;
202 return open_related_ns(ns, ns->ops->get_parent);
203 case NS_GET_NSTYPE:
204 return ns->ops->type;
205 case NS_GET_OWNER_UID:
206 if (ns->ops->type != CLONE_NEWUSER)
207 return -EINVAL;
208 user_ns = container_of(ns, struct user_namespace, ns);
209 argp = (uid_t __user *) arg;
210 uid = from_kuid_munged(current_user_ns(), user_ns->owner);
211 return put_user(uid, argp);
212 default:
213 return -ENOTTY;
214 }
215}
216
217int ns_get_name(char *buf, size_t size, struct task_struct *task,
218 const struct proc_ns_operations *ns_ops)
219{
220 struct ns_common *ns;
221 int res = -ENOENT;
222 const char *name;
223 ns = ns_ops->get(task);
224 if (ns) {
225 name = ns_ops->real_ns_name ? : ns_ops->name;
226 res = snprintf(buf, size, "%s:[%u]", name, ns->inum);
227 ns_ops->put(ns);
228 }
229 return res;
230}
231
232bool proc_ns_file(const struct file *file)
233{
234 return file->f_op == &ns_file_operations;
235}
236
237struct file *proc_ns_fget(int fd)
238{
239 struct file *file;
240
241 file = fget(fd);
242 if (!file)
243 return ERR_PTR(-EBADF);
244
245 if (file->f_op != &ns_file_operations)
246 goto out_invalid;
247
248 return file;
249
250out_invalid:
251 fput(file);
252 return ERR_PTR(-EINVAL);
253}
254
255
256
257
258
259
260
261
262
263bool ns_match(const struct ns_common *ns, dev_t dev, ino_t ino)
264{
265 return (ns->inum == ino) && (nsfs_mnt->mnt_sb->s_dev == dev);
266}
267
268
269static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
270{
271 struct inode *inode = d_inode(dentry);
272 const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
273
274 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
275 return 0;
276}
277
278static const struct super_operations nsfs_ops = {
279 .statfs = simple_statfs,
280 .evict_inode = nsfs_evict,
281 .show_path = nsfs_show_path,
282};
283
284static int nsfs_init_fs_context(struct fs_context *fc)
285{
286 struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC);
287 if (!ctx)
288 return -ENOMEM;
289 ctx->ops = &nsfs_ops;
290 ctx->dops = &ns_dentry_operations;
291 return 0;
292}
293
294static struct file_system_type nsfs = {
295 .name = "nsfs",
296 .init_fs_context = nsfs_init_fs_context,
297 .kill_sb = kill_anon_super,
298};
299
300void __init nsfs_init(void)
301{
302 nsfs_mnt = kern_mount(&nsfs);
303 if (IS_ERR(nsfs_mnt))
304 panic("can't set nsfs up\n");
305 nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER;
306}
307
