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/pid_namespace.h>
12 #include <linux/user_namespace.h>
13 #include <linux/nsfs.h>
14 #include <linux/uaccess.h>
15 #include <linux/mnt_namespace.h>
16
17 #include "mount.h"
18 #include "internal.h"
19
20 static struct vfsmount *nsfs_mnt;
21
22 static long ns_ioctl(struct file *filp, unsigned int ioctl,
23 unsigned long arg);
24 static const struct file_operations ns_file_operations = {
25 .unlocked_ioctl = ns_ioctl,
26 .compat_ioctl = compat_ptr_ioctl,
27 };
28
ns_dname(struct dentry * dentry,char * buffer,int buflen)29 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
30 {
31 struct inode *inode = d_inode(dentry);
32 struct ns_common *ns = inode->i_private;
33 const struct proc_ns_operations *ns_ops = ns->ops;
34
35 return dynamic_dname(buffer, buflen, "%s:[%lu]",
36 ns_ops->name, inode->i_ino);
37 }
38
39 const struct dentry_operations ns_dentry_operations = {
40 .d_delete = always_delete_dentry,
41 .d_dname = ns_dname,
42 .d_prune = stashed_dentry_prune,
43 };
44
nsfs_evict(struct inode * inode)45 static void nsfs_evict(struct inode *inode)
46 {
47 struct ns_common *ns = inode->i_private;
48 clear_inode(inode);
49 ns->ops->put(ns);
50 }
51
ns_get_path_cb(struct path * path,ns_get_path_helper_t * ns_get_cb,void * private_data)52 int ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb,
53 void *private_data)
54 {
55 struct ns_common *ns;
56
57 ns = ns_get_cb(private_data);
58 if (!ns)
59 return -ENOENT;
60
61 return path_from_stashed(&ns->stashed, nsfs_mnt, ns, path);
62 }
63
64 struct ns_get_path_task_args {
65 const struct proc_ns_operations *ns_ops;
66 struct task_struct *task;
67 };
68
ns_get_path_task(void * private_data)69 static struct ns_common *ns_get_path_task(void *private_data)
70 {
71 struct ns_get_path_task_args *args = private_data;
72
73 return args->ns_ops->get(args->task);
74 }
75
ns_get_path(struct path * path,struct task_struct * task,const struct proc_ns_operations * ns_ops)76 int ns_get_path(struct path *path, struct task_struct *task,
77 const struct proc_ns_operations *ns_ops)
78 {
79 struct ns_get_path_task_args args = {
80 .ns_ops = ns_ops,
81 .task = task,
82 };
83
84 return ns_get_path_cb(path, ns_get_path_task, &args);
85 }
86
87 /**
88 * open_namespace - open a namespace
89 * @ns: the namespace to open
90 *
91 * This will consume a reference to @ns indendent of success or failure.
92 *
93 * Return: A file descriptor on success or a negative error code on failure.
94 */
open_namespace(struct ns_common * ns)95 int open_namespace(struct ns_common *ns)
96 {
97 struct path path __free(path_put) = {};
98 struct file *f;
99 int err;
100
101 /* call first to consume reference */
102 err = path_from_stashed(&ns->stashed, nsfs_mnt, ns, &path);
103 if (err < 0)
104 return err;
105
106 CLASS(get_unused_fd, fd)(O_CLOEXEC);
107 if (fd < 0)
108 return fd;
109
110 f = dentry_open(&path, O_RDONLY, current_cred());
111 if (IS_ERR(f))
112 return PTR_ERR(f);
113
114 fd_install(fd, f);
115 return take_fd(fd);
116 }
117
open_related_ns(struct ns_common * ns,struct ns_common * (* get_ns)(struct ns_common * ns))118 int open_related_ns(struct ns_common *ns,
119 struct ns_common *(*get_ns)(struct ns_common *ns))
120 {
121 struct ns_common *relative;
122
123 relative = get_ns(ns);
124 if (IS_ERR(relative))
125 return PTR_ERR(relative);
126
127 return open_namespace(relative);
128 }
129 EXPORT_SYMBOL_GPL(open_related_ns);
130
copy_ns_info_to_user(const struct mnt_namespace * mnt_ns,struct mnt_ns_info __user * uinfo,size_t usize,struct mnt_ns_info * kinfo)131 static int copy_ns_info_to_user(const struct mnt_namespace *mnt_ns,
132 struct mnt_ns_info __user *uinfo, size_t usize,
133 struct mnt_ns_info *kinfo)
134 {
135 /*
136 * If userspace and the kernel have the same struct size it can just
137 * be copied. If userspace provides an older struct, only the bits that
138 * userspace knows about will be copied. If userspace provides a new
139 * struct, only the bits that the kernel knows aobut will be copied and
140 * the size value will be set to the size the kernel knows about.
141 */
142 kinfo->size = min(usize, sizeof(*kinfo));
143 kinfo->mnt_ns_id = mnt_ns->seq;
144 kinfo->nr_mounts = READ_ONCE(mnt_ns->nr_mounts);
145 /* Subtract the root mount of the mount namespace. */
146 if (kinfo->nr_mounts)
147 kinfo->nr_mounts--;
148
149 if (copy_to_user(uinfo, kinfo, kinfo->size))
150 return -EFAULT;
151
152 return 0;
153 }
154
ns_ioctl(struct file * filp,unsigned int ioctl,unsigned long arg)155 static long ns_ioctl(struct file *filp, unsigned int ioctl,
156 unsigned long arg)
157 {
158 struct user_namespace *user_ns;
159 struct pid_namespace *pid_ns;
160 struct task_struct *tsk;
161 struct ns_common *ns = get_proc_ns(file_inode(filp));
162 struct mnt_namespace *mnt_ns;
163 bool previous = false;
164 uid_t __user *argp;
165 uid_t uid;
166 int ret;
167
168 switch (ioctl) {
169 case NS_GET_USERNS:
170 return open_related_ns(ns, ns_get_owner);
171 case NS_GET_PARENT:
172 if (!ns->ops->get_parent)
173 return -EINVAL;
174 return open_related_ns(ns, ns->ops->get_parent);
175 case NS_GET_NSTYPE:
176 return ns->ops->type;
177 case NS_GET_OWNER_UID:
178 if (ns->ops->type != CLONE_NEWUSER)
179 return -EINVAL;
180 user_ns = container_of(ns, struct user_namespace, ns);
181 argp = (uid_t __user *) arg;
182 uid = from_kuid_munged(current_user_ns(), user_ns->owner);
183 return put_user(uid, argp);
184 case NS_GET_MNTNS_ID: {
185 __u64 __user *idp;
186 __u64 id;
187
188 if (ns->ops->type != CLONE_NEWNS)
189 return -EINVAL;
190
191 mnt_ns = container_of(ns, struct mnt_namespace, ns);
192 idp = (__u64 __user *)arg;
193 id = mnt_ns->seq;
194 return put_user(id, idp);
195 }
196 case NS_GET_PID_FROM_PIDNS:
197 fallthrough;
198 case NS_GET_TGID_FROM_PIDNS:
199 fallthrough;
200 case NS_GET_PID_IN_PIDNS:
201 fallthrough;
202 case NS_GET_TGID_IN_PIDNS: {
203 if (ns->ops->type != CLONE_NEWPID)
204 return -EINVAL;
205
206 ret = -ESRCH;
207 pid_ns = container_of(ns, struct pid_namespace, ns);
208
209 guard(rcu)();
210
211 if (ioctl == NS_GET_PID_IN_PIDNS ||
212 ioctl == NS_GET_TGID_IN_PIDNS)
213 tsk = find_task_by_vpid(arg);
214 else
215 tsk = find_task_by_pid_ns(arg, pid_ns);
216 if (!tsk)
217 break;
218
219 switch (ioctl) {
220 case NS_GET_PID_FROM_PIDNS:
221 ret = task_pid_vnr(tsk);
222 break;
223 case NS_GET_TGID_FROM_PIDNS:
224 ret = task_tgid_vnr(tsk);
225 break;
226 case NS_GET_PID_IN_PIDNS:
227 ret = task_pid_nr_ns(tsk, pid_ns);
228 break;
229 case NS_GET_TGID_IN_PIDNS:
230 ret = task_tgid_nr_ns(tsk, pid_ns);
231 break;
232 default:
233 ret = 0;
234 break;
235 }
236
237 if (!ret)
238 ret = -ESRCH;
239 return ret;
240 }
241 }
242
243 /* extensible ioctls */
244 switch (_IOC_NR(ioctl)) {
245 case _IOC_NR(NS_MNT_GET_INFO): {
246 struct mnt_ns_info kinfo = {};
247 struct mnt_ns_info __user *uinfo = (struct mnt_ns_info __user *)arg;
248 size_t usize = _IOC_SIZE(ioctl);
249
250 if (ns->ops->type != CLONE_NEWNS)
251 return -EINVAL;
252
253 if (!uinfo)
254 return -EINVAL;
255
256 if (usize < MNT_NS_INFO_SIZE_VER0)
257 return -EINVAL;
258
259 return copy_ns_info_to_user(to_mnt_ns(ns), uinfo, usize, &kinfo);
260 }
261 case _IOC_NR(NS_MNT_GET_PREV):
262 previous = true;
263 fallthrough;
264 case _IOC_NR(NS_MNT_GET_NEXT): {
265 struct mnt_ns_info kinfo = {};
266 struct mnt_ns_info __user *uinfo = (struct mnt_ns_info __user *)arg;
267 struct path path __free(path_put) = {};
268 struct file *f __free(fput) = NULL;
269 size_t usize = _IOC_SIZE(ioctl);
270
271 if (ns->ops->type != CLONE_NEWNS)
272 return -EINVAL;
273
274 if (usize < MNT_NS_INFO_SIZE_VER0)
275 return -EINVAL;
276
277 if (previous)
278 mnt_ns = lookup_prev_mnt_ns(to_mnt_ns(ns));
279 else
280 mnt_ns = lookup_next_mnt_ns(to_mnt_ns(ns));
281 if (IS_ERR(mnt_ns))
282 return PTR_ERR(mnt_ns);
283
284 ns = to_ns_common(mnt_ns);
285 /* Transfer ownership of @mnt_ns reference to @path. */
286 ret = path_from_stashed(&ns->stashed, nsfs_mnt, ns, &path);
287 if (ret)
288 return ret;
289
290 CLASS(get_unused_fd, fd)(O_CLOEXEC);
291 if (fd < 0)
292 return fd;
293
294 f = dentry_open(&path, O_RDONLY, current_cred());
295 if (IS_ERR(f))
296 return PTR_ERR(f);
297
298 if (uinfo) {
299 /*
300 * If @uinfo is passed return all information about the
301 * mount namespace as well.
302 */
303 ret = copy_ns_info_to_user(to_mnt_ns(ns), uinfo, usize, &kinfo);
304 if (ret)
305 return ret;
306 }
307
308 /* Transfer reference of @f to caller's fdtable. */
309 fd_install(fd, no_free_ptr(f));
310 /* File descriptor is live so hand it off to the caller. */
311 return take_fd(fd);
312 }
313 default:
314 ret = -ENOTTY;
315 }
316
317 return ret;
318 }
319
ns_get_name(char * buf,size_t size,struct task_struct * task,const struct proc_ns_operations * ns_ops)320 int ns_get_name(char *buf, size_t size, struct task_struct *task,
321 const struct proc_ns_operations *ns_ops)
322 {
323 struct ns_common *ns;
324 int res = -ENOENT;
325 const char *name;
326 ns = ns_ops->get(task);
327 if (ns) {
328 name = ns_ops->real_ns_name ? : ns_ops->name;
329 res = snprintf(buf, size, "%s:[%u]", name, ns->inum);
330 ns_ops->put(ns);
331 }
332 return res;
333 }
334
proc_ns_file(const struct file * file)335 bool proc_ns_file(const struct file *file)
336 {
337 return file->f_op == &ns_file_operations;
338 }
339
340 /**
341 * ns_match() - Returns true if current namespace matches dev/ino provided.
342 * @ns: current namespace
343 * @dev: dev_t from nsfs that will be matched against current nsfs
344 * @ino: ino_t from nsfs that will be matched against current nsfs
345 *
346 * Return: true if dev and ino matches the current nsfs.
347 */
ns_match(const struct ns_common * ns,dev_t dev,ino_t ino)348 bool ns_match(const struct ns_common *ns, dev_t dev, ino_t ino)
349 {
350 return (ns->inum == ino) && (nsfs_mnt->mnt_sb->s_dev == dev);
351 }
352
353
nsfs_show_path(struct seq_file * seq,struct dentry * dentry)354 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
355 {
356 struct inode *inode = d_inode(dentry);
357 const struct ns_common *ns = inode->i_private;
358 const struct proc_ns_operations *ns_ops = ns->ops;
359
360 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
361 return 0;
362 }
363
364 static const struct super_operations nsfs_ops = {
365 .statfs = simple_statfs,
366 .evict_inode = nsfs_evict,
367 .show_path = nsfs_show_path,
368 };
369
nsfs_init_inode(struct inode * inode,void * data)370 static int nsfs_init_inode(struct inode *inode, void *data)
371 {
372 struct ns_common *ns = data;
373
374 inode->i_private = data;
375 inode->i_mode |= S_IRUGO;
376 inode->i_fop = &ns_file_operations;
377 inode->i_ino = ns->inum;
378 return 0;
379 }
380
nsfs_put_data(void * data)381 static void nsfs_put_data(void *data)
382 {
383 struct ns_common *ns = data;
384 ns->ops->put(ns);
385 }
386
387 static const struct stashed_operations nsfs_stashed_ops = {
388 .init_inode = nsfs_init_inode,
389 .put_data = nsfs_put_data,
390 };
391
nsfs_init_fs_context(struct fs_context * fc)392 static int nsfs_init_fs_context(struct fs_context *fc)
393 {
394 struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC);
395 if (!ctx)
396 return -ENOMEM;
397 ctx->ops = &nsfs_ops;
398 ctx->dops = &ns_dentry_operations;
399 fc->s_fs_info = (void *)&nsfs_stashed_ops;
400 return 0;
401 }
402
403 static struct file_system_type nsfs = {
404 .name = "nsfs",
405 .init_fs_context = nsfs_init_fs_context,
406 .kill_sb = kill_anon_super,
407 };
408
nsfs_init(void)409 void __init nsfs_init(void)
410 {
411 nsfs_mnt = kern_mount(&nsfs);
412 if (IS_ERR(nsfs_mnt))
413 panic("can't set nsfs up\n");
414 nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER;
415 }
416