xref: /linux/fs/nsfs.c (revision 3d85d6c8539950dfcf4339f9ea865fb5d8f7ce03)
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_dname	= ns_dname,
41 	.d_prune	= stashed_dentry_prune,
42 };
43 
nsfs_evict(struct inode * inode)44 static void nsfs_evict(struct inode *inode)
45 {
46 	struct ns_common *ns = inode->i_private;
47 	clear_inode(inode);
48 	ns->ops->put(ns);
49 }
50 
ns_get_path_cb(struct path * path,ns_get_path_helper_t * ns_get_cb,void * private_data)51 int ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb,
52 		     void *private_data)
53 {
54 	struct ns_common *ns;
55 
56 	ns = ns_get_cb(private_data);
57 	if (!ns)
58 		return -ENOENT;
59 
60 	return path_from_stashed(&ns->stashed, nsfs_mnt, ns, path);
61 }
62 
63 struct ns_get_path_task_args {
64 	const struct proc_ns_operations *ns_ops;
65 	struct task_struct *task;
66 };
67 
ns_get_path_task(void * private_data)68 static struct ns_common *ns_get_path_task(void *private_data)
69 {
70 	struct ns_get_path_task_args *args = private_data;
71 
72 	return args->ns_ops->get(args->task);
73 }
74 
ns_get_path(struct path * path,struct task_struct * task,const struct proc_ns_operations * ns_ops)75 int ns_get_path(struct path *path, struct task_struct *task,
76 		  const struct proc_ns_operations *ns_ops)
77 {
78 	struct ns_get_path_task_args args = {
79 		.ns_ops	= ns_ops,
80 		.task	= task,
81 	};
82 
83 	return ns_get_path_cb(path, ns_get_path_task, &args);
84 }
85 
86 /**
87  * open_namespace - open a namespace
88  * @ns: the namespace to open
89  *
90  * This will consume a reference to @ns indendent of success or failure.
91  *
92  * Return: A file descriptor on success or a negative error code on failure.
93  */
open_namespace(struct ns_common * ns)94 int open_namespace(struct ns_common *ns)
95 {
96 	struct path path __free(path_put) = {};
97 	struct file *f;
98 	int err;
99 
100 	/* call first to consume reference */
101 	err = path_from_stashed(&ns->stashed, nsfs_mnt, ns, &path);
102 	if (err < 0)
103 		return err;
104 
105 	CLASS(get_unused_fd, fd)(O_CLOEXEC);
106 	if (fd < 0)
107 		return fd;
108 
109 	f = dentry_open(&path, O_RDONLY, current_cred());
110 	if (IS_ERR(f))
111 		return PTR_ERR(f);
112 
113 	fd_install(fd, f);
114 	return take_fd(fd);
115 }
116 
open_related_ns(struct ns_common * ns,struct ns_common * (* get_ns)(struct ns_common * ns))117 int open_related_ns(struct ns_common *ns,
118 		   struct ns_common *(*get_ns)(struct ns_common *ns))
119 {
120 	struct ns_common *relative;
121 
122 	relative = get_ns(ns);
123 	if (IS_ERR(relative))
124 		return PTR_ERR(relative);
125 
126 	return open_namespace(relative);
127 }
128 EXPORT_SYMBOL_GPL(open_related_ns);
129 
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)130 static int copy_ns_info_to_user(const struct mnt_namespace *mnt_ns,
131 				struct mnt_ns_info __user *uinfo, size_t usize,
132 				struct mnt_ns_info *kinfo)
133 {
134 	/*
135 	 * If userspace and the kernel have the same struct size it can just
136 	 * be copied. If userspace provides an older struct, only the bits that
137 	 * userspace knows about will be copied. If userspace provides a new
138 	 * struct, only the bits that the kernel knows aobut will be copied and
139 	 * the size value will be set to the size the kernel knows about.
140 	 */
141 	kinfo->size		= min(usize, sizeof(*kinfo));
142 	kinfo->mnt_ns_id	= mnt_ns->seq;
143 	kinfo->nr_mounts	= READ_ONCE(mnt_ns->nr_mounts);
144 	/* Subtract the root mount of the mount namespace. */
145 	if (kinfo->nr_mounts)
146 		kinfo->nr_mounts--;
147 
148 	if (copy_to_user(uinfo, kinfo, kinfo->size))
149 		return -EFAULT;
150 
151 	return 0;
152 }
153 
ns_ioctl(struct file * filp,unsigned int ioctl,unsigned long arg)154 static long ns_ioctl(struct file *filp, unsigned int ioctl,
155 			unsigned long arg)
156 {
157 	struct user_namespace *user_ns;
158 	struct pid_namespace *pid_ns;
159 	struct task_struct *tsk;
160 	struct ns_common *ns = get_proc_ns(file_inode(filp));
161 	struct mnt_namespace *mnt_ns;
162 	bool previous = false;
163 	uid_t __user *argp;
164 	uid_t uid;
165 	int ret;
166 
167 	switch (ioctl) {
168 	case NS_GET_USERNS:
169 		return open_related_ns(ns, ns_get_owner);
170 	case NS_GET_PARENT:
171 		if (!ns->ops->get_parent)
172 			return -EINVAL;
173 		return open_related_ns(ns, ns->ops->get_parent);
174 	case NS_GET_NSTYPE:
175 		return ns->ops->type;
176 	case NS_GET_OWNER_UID:
177 		if (ns->ops->type != CLONE_NEWUSER)
178 			return -EINVAL;
179 		user_ns = container_of(ns, struct user_namespace, ns);
180 		argp = (uid_t __user *) arg;
181 		uid = from_kuid_munged(current_user_ns(), user_ns->owner);
182 		return put_user(uid, argp);
183 	case NS_GET_MNTNS_ID: {
184 		__u64 __user *idp;
185 		__u64 id;
186 
187 		if (ns->ops->type != CLONE_NEWNS)
188 			return -EINVAL;
189 
190 		mnt_ns = container_of(ns, struct mnt_namespace, ns);
191 		idp = (__u64 __user *)arg;
192 		id = mnt_ns->seq;
193 		return put_user(id, idp);
194 	}
195 	case NS_GET_PID_FROM_PIDNS:
196 		fallthrough;
197 	case NS_GET_TGID_FROM_PIDNS:
198 		fallthrough;
199 	case NS_GET_PID_IN_PIDNS:
200 		fallthrough;
201 	case NS_GET_TGID_IN_PIDNS: {
202 		if (ns->ops->type != CLONE_NEWPID)
203 			return -EINVAL;
204 
205 		ret = -ESRCH;
206 		pid_ns = container_of(ns, struct pid_namespace, ns);
207 
208 		guard(rcu)();
209 
210 		if (ioctl == NS_GET_PID_IN_PIDNS ||
211 		    ioctl == NS_GET_TGID_IN_PIDNS)
212 			tsk = find_task_by_vpid(arg);
213 		else
214 			tsk = find_task_by_pid_ns(arg, pid_ns);
215 		if (!tsk)
216 			break;
217 
218 		switch (ioctl) {
219 		case NS_GET_PID_FROM_PIDNS:
220 			ret = task_pid_vnr(tsk);
221 			break;
222 		case NS_GET_TGID_FROM_PIDNS:
223 			ret = task_tgid_vnr(tsk);
224 			break;
225 		case NS_GET_PID_IN_PIDNS:
226 			ret = task_pid_nr_ns(tsk, pid_ns);
227 			break;
228 		case NS_GET_TGID_IN_PIDNS:
229 			ret = task_tgid_nr_ns(tsk, pid_ns);
230 			break;
231 		default:
232 			ret = 0;
233 			break;
234 		}
235 
236 		if (!ret)
237 			ret = -ESRCH;
238 		return ret;
239 	}
240 	}
241 
242 	/* extensible ioctls */
243 	switch (_IOC_NR(ioctl)) {
244 	case _IOC_NR(NS_MNT_GET_INFO): {
245 		struct mnt_ns_info kinfo = {};
246 		struct mnt_ns_info __user *uinfo = (struct mnt_ns_info __user *)arg;
247 		size_t usize = _IOC_SIZE(ioctl);
248 
249 		if (ns->ops->type != CLONE_NEWNS)
250 			return -EINVAL;
251 
252 		if (!uinfo)
253 			return -EINVAL;
254 
255 		if (usize < MNT_NS_INFO_SIZE_VER0)
256 			return -EINVAL;
257 
258 		return copy_ns_info_to_user(to_mnt_ns(ns), uinfo, usize, &kinfo);
259 	}
260 	case _IOC_NR(NS_MNT_GET_PREV):
261 		previous = true;
262 		fallthrough;
263 	case _IOC_NR(NS_MNT_GET_NEXT): {
264 		struct mnt_ns_info kinfo = {};
265 		struct mnt_ns_info __user *uinfo = (struct mnt_ns_info __user *)arg;
266 		struct path path __free(path_put) = {};
267 		struct file *f __free(fput) = NULL;
268 		size_t usize = _IOC_SIZE(ioctl);
269 
270 		if (ns->ops->type != CLONE_NEWNS)
271 			return -EINVAL;
272 
273 		if (usize < MNT_NS_INFO_SIZE_VER0)
274 			return -EINVAL;
275 
276 		mnt_ns = get_sequential_mnt_ns(to_mnt_ns(ns), previous);
277 		if (IS_ERR(mnt_ns))
278 			return PTR_ERR(mnt_ns);
279 
280 		ns = to_ns_common(mnt_ns);
281 		/* Transfer ownership of @mnt_ns reference to @path. */
282 		ret = path_from_stashed(&ns->stashed, nsfs_mnt, ns, &path);
283 		if (ret)
284 			return ret;
285 
286 		CLASS(get_unused_fd, fd)(O_CLOEXEC);
287 		if (fd < 0)
288 			return fd;
289 
290 		f = dentry_open(&path, O_RDONLY, current_cred());
291 		if (IS_ERR(f))
292 			return PTR_ERR(f);
293 
294 		if (uinfo) {
295 			/*
296 			 * If @uinfo is passed return all information about the
297 			 * mount namespace as well.
298 			 */
299 			ret = copy_ns_info_to_user(to_mnt_ns(ns), uinfo, usize, &kinfo);
300 			if (ret)
301 				return ret;
302 		}
303 
304 		/* Transfer reference of @f to caller's fdtable. */
305 		fd_install(fd, no_free_ptr(f));
306 		/* File descriptor is live so hand it off to the caller. */
307 		return take_fd(fd);
308 	}
309 	default:
310 		ret = -ENOTTY;
311 	}
312 
313 	return ret;
314 }
315 
ns_get_name(char * buf,size_t size,struct task_struct * task,const struct proc_ns_operations * ns_ops)316 int ns_get_name(char *buf, size_t size, struct task_struct *task,
317 			const struct proc_ns_operations *ns_ops)
318 {
319 	struct ns_common *ns;
320 	int res = -ENOENT;
321 	const char *name;
322 	ns = ns_ops->get(task);
323 	if (ns) {
324 		name = ns_ops->real_ns_name ? : ns_ops->name;
325 		res = snprintf(buf, size, "%s:[%u]", name, ns->inum);
326 		ns_ops->put(ns);
327 	}
328 	return res;
329 }
330 
proc_ns_file(const struct file * file)331 bool proc_ns_file(const struct file *file)
332 {
333 	return file->f_op == &ns_file_operations;
334 }
335 
336 /**
337  * ns_match() - Returns true if current namespace matches dev/ino provided.
338  * @ns: current namespace
339  * @dev: dev_t from nsfs that will be matched against current nsfs
340  * @ino: ino_t from nsfs that will be matched against current nsfs
341  *
342  * Return: true if dev and ino matches the current nsfs.
343  */
ns_match(const struct ns_common * ns,dev_t dev,ino_t ino)344 bool ns_match(const struct ns_common *ns, dev_t dev, ino_t ino)
345 {
346 	return (ns->inum == ino) && (nsfs_mnt->mnt_sb->s_dev == dev);
347 }
348 
349 
nsfs_show_path(struct seq_file * seq,struct dentry * dentry)350 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
351 {
352 	struct inode *inode = d_inode(dentry);
353 	const struct ns_common *ns = inode->i_private;
354 	const struct proc_ns_operations *ns_ops = ns->ops;
355 
356 	seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
357 	return 0;
358 }
359 
360 static const struct super_operations nsfs_ops = {
361 	.statfs = simple_statfs,
362 	.evict_inode = nsfs_evict,
363 	.show_path = nsfs_show_path,
364 };
365 
nsfs_init_inode(struct inode * inode,void * data)366 static int nsfs_init_inode(struct inode *inode, void *data)
367 {
368 	struct ns_common *ns = data;
369 
370 	inode->i_private = data;
371 	inode->i_mode |= S_IRUGO;
372 	inode->i_fop = &ns_file_operations;
373 	inode->i_ino = ns->inum;
374 	return 0;
375 }
376 
nsfs_put_data(void * data)377 static void nsfs_put_data(void *data)
378 {
379 	struct ns_common *ns = data;
380 	ns->ops->put(ns);
381 }
382 
383 static const struct stashed_operations nsfs_stashed_ops = {
384 	.init_inode = nsfs_init_inode,
385 	.put_data = nsfs_put_data,
386 };
387 
nsfs_init_fs_context(struct fs_context * fc)388 static int nsfs_init_fs_context(struct fs_context *fc)
389 {
390 	struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC);
391 	if (!ctx)
392 		return -ENOMEM;
393 	ctx->ops = &nsfs_ops;
394 	ctx->dops = &ns_dentry_operations;
395 	fc->s_fs_info = (void *)&nsfs_stashed_ops;
396 	return 0;
397 }
398 
399 static struct file_system_type nsfs = {
400 	.name = "nsfs",
401 	.init_fs_context = nsfs_init_fs_context,
402 	.kill_sb = kill_anon_super,
403 };
404 
nsfs_init(void)405 void __init nsfs_init(void)
406 {
407 	nsfs_mnt = kern_mount(&nsfs);
408 	if (IS_ERR(nsfs_mnt))
409 		panic("can't set nsfs up\n");
410 	nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER;
411 }
412