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 void *__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 NULL;
78slow:
79 rcu_read_unlock();
80 inode = new_inode_pseudo(mnt->mnt_sb);
81 if (!inode) {
82 ns->ops->put(ns);
83 return ERR_PTR(-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 ERR_PTR(-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 ERR_PTR(-EAGAIN);
105 }
106 goto got_it;
107}
108
109void *ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb,
110 void *private_data)
111{
112 void *ret;
113
114 do {
115 struct ns_common *ns = ns_get_cb(private_data);
116 if (!ns)
117 return ERR_PTR(-ENOENT);
118
119 ret = __ns_get_path(path, ns);
120 } while (ret == ERR_PTR(-EAGAIN));
121
122 return ret;
123}
124
125struct ns_get_path_task_args {
126 const struct proc_ns_operations *ns_ops;
127 struct task_struct *task;
128};
129
130static struct ns_common *ns_get_path_task(void *private_data)
131{
132 struct ns_get_path_task_args *args = private_data;
133
134 return args->ns_ops->get(args->task);
135}
136
137void *ns_get_path(struct path *path, struct task_struct *task,
138 const struct proc_ns_operations *ns_ops)
139{
140 struct ns_get_path_task_args args = {
141 .ns_ops = ns_ops,
142 .task = task,
143 };
144
145 return ns_get_path_cb(path, ns_get_path_task, &args);
146}
147
148int open_related_ns(struct ns_common *ns,
149 struct ns_common *(*get_ns)(struct ns_common *ns))
150{
151 struct path path = {};
152 struct file *f;
153 void *err;
154 int fd;
155
156 fd = get_unused_fd_flags(O_CLOEXEC);
157 if (fd < 0)
158 return fd;
159
160 do {
161 struct ns_common *relative;
162
163 relative = get_ns(ns);
164 if (IS_ERR(relative)) {
165 put_unused_fd(fd);
166 return PTR_ERR(relative);
167 }
168
169 err = __ns_get_path(&path, relative);
170 } while (err == ERR_PTR(-EAGAIN));
171
172 if (IS_ERR(err)) {
173 put_unused_fd(fd);
174 return PTR_ERR(err);
175 }
176
177 f = dentry_open(&path, O_RDONLY, current_cred());
178 path_put(&path);
179 if (IS_ERR(f)) {
180 put_unused_fd(fd);
181 fd = PTR_ERR(f);
182 } else
183 fd_install(fd, f);
184
185 return fd;
186}
187EXPORT_SYMBOL_GPL(open_related_ns);
188
189static long ns_ioctl(struct file *filp, unsigned int ioctl,
190 unsigned long arg)
191{
192 struct user_namespace *user_ns;
193 struct ns_common *ns = get_proc_ns(file_inode(filp));
194 uid_t __user *argp;
195 uid_t uid;
196
197 switch (ioctl) {
198 case NS_GET_USERNS:
199 return open_related_ns(ns, ns_get_owner);
200 case NS_GET_PARENT:
201 if (!ns->ops->get_parent)
202 return -EINVAL;
203 return open_related_ns(ns, ns->ops->get_parent);
204 case NS_GET_NSTYPE:
205 return ns->ops->type;
206 case NS_GET_OWNER_UID:
207 if (ns->ops->type != CLONE_NEWUSER)
208 return -EINVAL;
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);
213 default:
214 return -ENOTTY;
215 }
216}
217
218int ns_get_name(char *buf, size_t size, struct task_struct *task,
219 const struct proc_ns_operations *ns_ops)
220{
221 struct ns_common *ns;
222 int res = -ENOENT;
223 const char *name;
224 ns = ns_ops->get(task);
225 if (ns) {
226 name = ns_ops->real_ns_name ? : ns_ops->name;
227 res = snprintf(buf, size, "%s:[%u]", name, ns->inum);
228 ns_ops->put(ns);
229 }
230 return res;
231}
232
233struct file *proc_ns_fget(int fd)
234{
235 struct file *file;
236
237 file = fget(fd);
238 if (!file)
239 return ERR_PTR(-EBADF);
240
241 if (file->f_op != &ns_file_operations)
242 goto out_invalid;
243
244 return file;
245
246out_invalid:
247 fput(file);
248 return ERR_PTR(-EINVAL);
249}
250
251static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
252{
253 struct inode *inode = d_inode(dentry);
254 const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
255
256 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
257 return 0;
258}
259
260static const struct super_operations nsfs_ops = {
261 .statfs = simple_statfs,
262 .evict_inode = nsfs_evict,
263 .show_path = nsfs_show_path,
264};
265
266static int nsfs_init_fs_context(struct fs_context *fc)
267{
268 struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC);
269 if (!ctx)
270 return -ENOMEM;
271 ctx->ops = &nsfs_ops;
272 ctx->dops = &ns_dentry_operations;
273 return 0;
274}
275
276static struct file_system_type nsfs = {
277 .name = "nsfs",
278 .init_fs_context = nsfs_init_fs_context,
279 .kill_sb = kill_anon_super,
280};
281
282void __init nsfs_init(void)
283{
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;
288}
289
