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Merge tag 'kconfig-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy...
[thirdparty/linux.git] / fs / nsfs.c
1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/mount.h>
3 #include <linux/file.h>
4 #include <linux/fs.h>
5 #include <linux/proc_ns.h>
6 #include <linux/magic.h>
7 #include <linux/ktime.h>
8 #include <linux/seq_file.h>
9 #include <linux/user_namespace.h>
10 #include <linux/nsfs.h>
11 #include <linux/uaccess.h>
12
13 static struct vfsmount *nsfs_mnt;
14
15 static long ns_ioctl(struct file *filp, unsigned int ioctl,
16 unsigned long arg);
17 static const struct file_operations ns_file_operations = {
18 .llseek = no_llseek,
19 .unlocked_ioctl = ns_ioctl,
20 };
21
22 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
23 {
24 struct inode *inode = d_inode(dentry);
25 const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
26
27 return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
28 ns_ops->name, inode->i_ino);
29 }
30
31 static void ns_prune_dentry(struct dentry *dentry)
32 {
33 struct inode *inode = d_inode(dentry);
34 if (inode) {
35 struct ns_common *ns = inode->i_private;
36 atomic_long_set(&ns->stashed, 0);
37 }
38 }
39
40 const struct dentry_operations ns_dentry_operations =
41 {
42 .d_prune = ns_prune_dentry,
43 .d_delete = always_delete_dentry,
44 .d_dname = ns_dname,
45 };
46
47 static void nsfs_evict(struct inode *inode)
48 {
49 struct ns_common *ns = inode->i_private;
50 clear_inode(inode);
51 ns->ops->put(ns);
52 }
53
54 static void *__ns_get_path(struct path *path, struct ns_common *ns)
55 {
56 struct vfsmount *mnt = nsfs_mnt;
57 struct dentry *dentry;
58 struct inode *inode;
59 unsigned long d;
60
61 rcu_read_lock();
62 d = atomic_long_read(&ns->stashed);
63 if (!d)
64 goto slow;
65 dentry = (struct dentry *)d;
66 if (!lockref_get_not_dead(&dentry->d_lockref))
67 goto slow;
68 rcu_read_unlock();
69 ns->ops->put(ns);
70 got_it:
71 path->mnt = mntget(mnt);
72 path->dentry = dentry;
73 return NULL;
74 slow:
75 rcu_read_unlock();
76 inode = new_inode_pseudo(mnt->mnt_sb);
77 if (!inode) {
78 ns->ops->put(ns);
79 return ERR_PTR(-ENOMEM);
80 }
81 inode->i_ino = ns->inum;
82 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
83 inode->i_flags |= S_IMMUTABLE;
84 inode->i_mode = S_IFREG | S_IRUGO;
85 inode->i_fop = &ns_file_operations;
86 inode->i_private = ns;
87
88 dentry = d_alloc_anon(mnt->mnt_sb);
89 if (!dentry) {
90 iput(inode);
91 return ERR_PTR(-ENOMEM);
92 }
93 d_instantiate(dentry, inode);
94 dentry->d_fsdata = (void *)ns->ops;
95 d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
96 if (d) {
97 d_delete(dentry); /* make sure ->d_prune() does nothing */
98 dput(dentry);
99 cpu_relax();
100 return ERR_PTR(-EAGAIN);
101 }
102 goto got_it;
103 }
104
105 void *ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb,
106 void *private_data)
107 {
108 void *ret;
109
110 do {
111 struct ns_common *ns = ns_get_cb(private_data);
112 if (!ns)
113 return ERR_PTR(-ENOENT);
114
115 ret = __ns_get_path(path, ns);
116 } while (ret == ERR_PTR(-EAGAIN));
117
118 return ret;
119 }
120
121 struct ns_get_path_task_args {
122 const struct proc_ns_operations *ns_ops;
123 struct task_struct *task;
124 };
125
126 static struct ns_common *ns_get_path_task(void *private_data)
127 {
128 struct ns_get_path_task_args *args = private_data;
129
130 return args->ns_ops->get(args->task);
131 }
132
133 void *ns_get_path(struct path *path, struct task_struct *task,
134 const struct proc_ns_operations *ns_ops)
135 {
136 struct ns_get_path_task_args args = {
137 .ns_ops = ns_ops,
138 .task = task,
139 };
140
141 return ns_get_path_cb(path, ns_get_path_task, &args);
142 }
143
144 int open_related_ns(struct ns_common *ns,
145 struct ns_common *(*get_ns)(struct ns_common *ns))
146 {
147 struct path path = {};
148 struct file *f;
149 void *err;
150 int fd;
151
152 fd = get_unused_fd_flags(O_CLOEXEC);
153 if (fd < 0)
154 return fd;
155
156 do {
157 struct ns_common *relative;
158
159 relative = get_ns(ns);
160 if (IS_ERR(relative)) {
161 put_unused_fd(fd);
162 return PTR_ERR(relative);
163 }
164
165 err = __ns_get_path(&path, relative);
166 } while (err == ERR_PTR(-EAGAIN));
167
168 if (IS_ERR(err)) {
169 put_unused_fd(fd);
170 return PTR_ERR(err);
171 }
172
173 f = dentry_open(&path, O_RDONLY, current_cred());
174 path_put(&path);
175 if (IS_ERR(f)) {
176 put_unused_fd(fd);
177 fd = PTR_ERR(f);
178 } else
179 fd_install(fd, f);
180
181 return fd;
182 }
183 EXPORT_SYMBOL_GPL(open_related_ns);
184
185 static long ns_ioctl(struct file *filp, unsigned int ioctl,
186 unsigned long arg)
187 {
188 struct user_namespace *user_ns;
189 struct ns_common *ns = get_proc_ns(file_inode(filp));
190 uid_t __user *argp;
191 uid_t uid;
192
193 switch (ioctl) {
194 case NS_GET_USERNS:
195 return open_related_ns(ns, ns_get_owner);
196 case NS_GET_PARENT:
197 if (!ns->ops->get_parent)
198 return -EINVAL;
199 return open_related_ns(ns, ns->ops->get_parent);
200 case NS_GET_NSTYPE:
201 return ns->ops->type;
202 case NS_GET_OWNER_UID:
203 if (ns->ops->type != CLONE_NEWUSER)
204 return -EINVAL;
205 user_ns = container_of(ns, struct user_namespace, ns);
206 argp = (uid_t __user *) arg;
207 uid = from_kuid_munged(current_user_ns(), user_ns->owner);
208 return put_user(uid, argp);
209 default:
210 return -ENOTTY;
211 }
212 }
213
214 int ns_get_name(char *buf, size_t size, struct task_struct *task,
215 const struct proc_ns_operations *ns_ops)
216 {
217 struct ns_common *ns;
218 int res = -ENOENT;
219 const char *name;
220 ns = ns_ops->get(task);
221 if (ns) {
222 name = ns_ops->real_ns_name ? : ns_ops->name;
223 res = snprintf(buf, size, "%s:[%u]", name, ns->inum);
224 ns_ops->put(ns);
225 }
226 return res;
227 }
228
229 struct file *proc_ns_fget(int fd)
230 {
231 struct file *file;
232
233 file = fget(fd);
234 if (!file)
235 return ERR_PTR(-EBADF);
236
237 if (file->f_op != &ns_file_operations)
238 goto out_invalid;
239
240 return file;
241
242 out_invalid:
243 fput(file);
244 return ERR_PTR(-EINVAL);
245 }
246
247 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
248 {
249 struct inode *inode = d_inode(dentry);
250 const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
251
252 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
253 return 0;
254 }
255
256 static const struct super_operations nsfs_ops = {
257 .statfs = simple_statfs,
258 .evict_inode = nsfs_evict,
259 .show_path = nsfs_show_path,
260 };
261 static struct dentry *nsfs_mount(struct file_system_type *fs_type,
262 int flags, const char *dev_name, void *data)
263 {
264 return mount_pseudo(fs_type, "nsfs:", &nsfs_ops,
265 &ns_dentry_operations, NSFS_MAGIC);
266 }
267 static struct file_system_type nsfs = {
268 .name = "nsfs",
269 .mount = nsfs_mount,
270 .kill_sb = kill_anon_super,
271 };
272
273 void __init nsfs_init(void)
274 {
275 nsfs_mnt = kern_mount(&nsfs);
276 if (IS_ERR(nsfs_mnt))
277 panic("can't set nsfs up\n");
278 nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER;
279 }