summaryrefslogtreecommitdiff
path: root/fs/fsopen.c
blob: ce03f6521c8870fb31127dc85be0cdeff370074b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
// SPDX-License-Identifier: GPL-2.0-or-later
/* Filesystem access-by-fd.
 *
 * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/fs_context.h>
#include <linux/fs_parser.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/syscalls.h>
#include <linux/security.h>
#include <linux/anon_inodes.h>
#include <linux/namei.h>
#include <linux/file.h>
#include <uapi/linux/mount.h>
#include "internal.h"
#include "mount.h"

/*
 * Allow the user to read back any error, warning or informational messages.
 */
static ssize_t fscontext_read(struct file *file,
			      char __user *_buf, size_t len, loff_t *pos)
{
	struct fs_context *fc = file->private_data;
	struct fc_log *log = fc->log.log;
	unsigned int logsize = ARRAY_SIZE(log->buffer);
	ssize_t ret;
	char *p;
	bool need_free;
	int index, n;

	ret = mutex_lock_interruptible(&fc->uapi_mutex);
	if (ret < 0)
		return ret;

	if (log->head == log->tail) {
		mutex_unlock(&fc->uapi_mutex);
		return -ENODATA;
	}

	index = log->tail & (logsize - 1);
	p = log->buffer[index];
	need_free = log->need_free & (1 << index);
	log->buffer[index] = NULL;
	log->need_free &= ~(1 << index);
	log->tail++;
	mutex_unlock(&fc->uapi_mutex);

	ret = -EMSGSIZE;
	n = strlen(p);
	if (n > len)
		goto err_free;
	ret = -EFAULT;
	if (copy_to_user(_buf, p, n) != 0)
		goto err_free;
	ret = n;

err_free:
	if (need_free)
		kfree(p);
	return ret;
}

static int fscontext_release(struct inode *inode, struct file *file)
{
	struct fs_context *fc = file->private_data;

	if (fc) {
		file->private_data = NULL;
		put_fs_context(fc);
	}
	return 0;
}

const struct file_operations fscontext_fops = {
	.read		= fscontext_read,
	.release	= fscontext_release,
	.llseek		= no_llseek,
};

/*
 * Attach a filesystem context to a file and an fd.
 */
static int fscontext_create_fd(struct fs_context *fc, unsigned int o_flags)
{
	int fd;

	fd = anon_inode_getfd("[fscontext]", &fscontext_fops, fc,
			      O_RDWR | o_flags);
	if (fd < 0)
		put_fs_context(fc);
	return fd;
}

static int fscontext_alloc_log(struct fs_context *fc)
{
	fc->log.log = kzalloc(sizeof(*fc->log.log), GFP_KERNEL);
	if (!fc->log.log)
		return -ENOMEM;
	refcount_set(&fc->log.log->usage, 1);
	fc->log.log->owner = fc->fs_type->owner;
	return 0;
}

/*
 * Open a filesystem by name so that it can be configured for mounting.
 *
 * We are allowed to specify a container in which the filesystem will be
 * opened, thereby indicating which namespaces will be used (notably, which
 * network namespace will be used for network filesystems).
 */
SYSCALL_DEFINE2(fsopen, const char __user *, _fs_name, unsigned int, flags)
{
	struct file_system_type *fs_type;
	struct fs_context *fc;
	const char *fs_name;
	int ret;

	if (!may_mount())
		return -EPERM;

	if (flags & ~FSOPEN_CLOEXEC)
		return -EINVAL;

	fs_name = strndup_user(_fs_name, PAGE_SIZE);
	if (IS_ERR(fs_name))
		return PTR_ERR(fs_name);

	fs_type = get_fs_type(fs_name);
	kfree(fs_name);
	if (!fs_type)
		return -ENODEV;

	fc = fs_context_for_mount(fs_type, 0);
	put_filesystem(fs_type);
	if (IS_ERR(fc))
		return PTR_ERR(fc);

	fc->phase = FS_CONTEXT_CREATE_PARAMS;

	ret = fscontext_alloc_log(fc);
	if (ret < 0)
		goto err_fc;

	return fscontext_create_fd(fc, flags & FSOPEN_CLOEXEC ? O_CLOEXEC : 0);

err_fc:
	put_fs_context(fc);
	return ret;
}

/*
 * Pick a superblock into a context for reconfiguration.
 */
SYSCALL_DEFINE3(fspick, int, dfd, const char __user *, path, unsigned int, flags)
{
	struct fs_context *fc;
	struct path target;
	unsigned int lookup_flags;
	int ret;

	if (!may_mount())
		return -EPERM;

	if ((flags & ~(FSPICK_CLOEXEC |
		       FSPICK_SYMLINK_NOFOLLOW |
		       FSPICK_NO_AUTOMOUNT |
		       FSPICK_EMPTY_PATH)) != 0)
		return -EINVAL;

	lookup_flags = LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT;
	if (flags & FSPICK_SYMLINK_NOFOLLOW)
		lookup_flags &= ~LOOKUP_FOLLOW;
	if (flags & FSPICK_NO_AUTOMOUNT)
		lookup_flags &= ~LOOKUP_AUTOMOUNT;
	if (flags & FSPICK_EMPTY_PATH)
		lookup_flags |= LOOKUP_EMPTY;
	ret = user_path_at(dfd, path, lookup_flags, &target);
	if (ret < 0)
		goto err;

	ret = -EINVAL;
	if (target.mnt->mnt_root != target.dentry)
		goto err_path;

	fc = fs_context_for_reconfigure(target.dentry, 0, 0);
	if (IS_ERR(fc)) {
		ret = PTR_ERR(fc);
		goto err_path;
	}

	fc->phase = FS_CONTEXT_RECONF_PARAMS;

	ret = fscontext_alloc_log(fc);
	if (ret < 0)
		goto err_fc;

	path_put(&target);
	return fscontext_create_fd(fc, flags & FSPICK_CLOEXEC ? O_CLOEXEC : 0);

err_fc:
	put_fs_context(fc);
err_path:
	path_put(&target);
err:
	return ret;
}

static int vfs_cmd_create(struct fs_context *fc, bool exclusive)
{
	struct super_block *sb;
	int ret;

	if (fc->phase != FS_CONTEXT_CREATE_PARAMS)
		return -EBUSY;

	if (!mount_capable(fc))
		return -EPERM;

	/* require the new mount api */
	if (exclusive && fc->ops == &legacy_fs_context_ops)
		return -EOPNOTSUPP;

	fc->phase = FS_CONTEXT_CREATING;
	fc->exclusive = exclusive;

	ret = vfs_get_tree(fc);
	if (ret) {
		fc->phase = FS_CONTEXT_FAILED;
		return ret;
	}

	sb = fc->root->d_sb;
	ret = security_sb_kern_mount(sb);
	if (unlikely(ret)) {
		fc_drop_locked(fc);
		fc->phase = FS_CONTEXT_FAILED;
		return ret;
	}

	/* vfs_get_tree() callchains will have grabbed @s_umount */
	up_write(&sb->s_umount);
	fc->phase = FS_CONTEXT_AWAITING_MOUNT;
	return 0;
}

static int vfs_cmd_reconfigure(struct fs_context *fc)
{
	struct super_block *sb;
	int ret;

	if (fc->phase != FS_CONTEXT_RECONF_PARAMS)
		return -EBUSY;

	fc->phase = FS_CONTEXT_RECONFIGURING;

	sb = fc->root->d_sb;
	if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) {
		fc->phase = FS_CONTEXT_FAILED;
		return -EPERM;
	}

	down_write(&sb->s_umount);
	ret = reconfigure_super(fc);
	up_write(&sb->s_umount);
	if (ret) {
		fc->phase = FS_CONTEXT_FAILED;
		return ret;
	}

	vfs_clean_context(fc);
	return 0;
}

/*
 * Check the state and apply the configuration.  Note that this function is
 * allowed to 'steal' the value by setting param->xxx to NULL before returning.
 */
static int vfs_fsconfig_locked(struct fs_context *fc, int cmd,
			       struct fs_parameter *param)
{
	int ret;

	ret = finish_clean_context(fc);
	if (ret)
		return ret;
	switch (cmd) {
	case FSCONFIG_CMD_CREATE:
		return vfs_cmd_create(fc, false);
	case FSCONFIG_CMD_CREATE_EXCL:
		return vfs_cmd_create(fc, true);
	case FSCONFIG_CMD_RECONFIGURE:
		return vfs_cmd_reconfigure(fc);
	default:
		if (fc->phase != FS_CONTEXT_CREATE_PARAMS &&
		    fc->phase != FS_CONTEXT_RECONF_PARAMS)
			return -EBUSY;

		return vfs_parse_fs_param(fc, param);
	}
}

/**
 * sys_fsconfig - Set parameters and trigger actions on a context
 * @fd: The filesystem context to act upon
 * @cmd: The action to take
 * @_key: Where appropriate, the parameter key to set
 * @_value: Where appropriate, the parameter value to set
 * @aux: Additional information for the value
 *
 * This system call is used to set parameters on a context, including
 * superblock settings, data source and security labelling.
 *
 * Actions include triggering the creation of a superblock and the
 * reconfiguration of the superblock attached to the specified context.
 *
 * When setting a parameter, @cmd indicates the type of value being proposed
 * and @_key indicates the parameter to be altered.
 *
 * @_value and @aux are used to specify the value, should a value be required:
 *
 * (*) fsconfig_set_flag: No value is specified.  The parameter must be boolean
 *     in nature.  The key may be prefixed with "no" to invert the
 *     setting. @_value must be NULL and @aux must be 0.
 *
 * (*) fsconfig_set_string: A string value is specified.  The parameter can be
 *     expecting boolean, integer, string or take a path.  A conversion to an
 *     appropriate type will be attempted (which may include looking up as a
 *     path).  @_value points to a NUL-terminated string and @aux must be 0.
 *
 * (*) fsconfig_set_binary: A binary blob is specified.  @_value points to the
 *     blob and @aux indicates its size.  The parameter must be expecting a
 *     blob.
 *
 * (*) fsconfig_set_path: A non-empty path is specified.  The parameter must be
 *     expecting a path object.  @_value points to a NUL-terminated string that
 *     is the path and @aux is a file descriptor at which to start a relative
 *     lookup or AT_FDCWD.
 *
 * (*) fsconfig_set_path_empty: As fsconfig_set_path, but with AT_EMPTY_PATH
 *     implied.
 *
 * (*) fsconfig_set_fd: An open file descriptor is specified.  @_value must be
 *     NULL and @aux indicates the file descriptor.
 */
SYSCALL_DEFINE5(fsconfig,
		int, fd,
		unsigned int, cmd,
		const char __user *, _key,
		const void __user *, _value,
		int, aux)
{
	struct fs_context *fc;
	struct fd f;
	int ret;
	int lookup_flags = 0;

	struct fs_parameter param = {
		.type	= fs_value_is_undefined,
	};

	if (fd < 0)
		return -EINVAL;

	switch (cmd) {
	case FSCONFIG_SET_FLAG:
		if (!_key || _value || aux)
			return -EINVAL;
		break;
	case FSCONFIG_SET_STRING:
		if (!_key || !_value || aux)
			return -EINVAL;
		break;
	case FSCONFIG_SET_BINARY:
		if (!_key || !_value || aux <= 0 || aux > 1024 * 1024)
			return -EINVAL;
		break;
	case FSCONFIG_SET_PATH:
	case FSCONFIG_SET_PATH_EMPTY:
		if (!_key || !_value || (aux != AT_FDCWD && aux < 0))
			return -EINVAL;
		break;
	case FSCONFIG_SET_FD:
		if (!_key || _value || aux < 0)
			return -EINVAL;
		break;
	case FSCONFIG_CMD_CREATE:
	case FSCONFIG_CMD_CREATE_EXCL:
	case FSCONFIG_CMD_RECONFIGURE:
		if (_key || _value || aux)
			return -EINVAL;
		break;
	default:
		return -EOPNOTSUPP;
	}

	f = fdget(fd);
	if (!f.file)
		return -EBADF;
	ret = -EINVAL;
	if (f.file->f_op != &fscontext_fops)
		goto out_f;

	fc = f.file->private_data;
	if (fc->ops == &legacy_fs_context_ops) {
		switch (cmd) {
		case FSCONFIG_SET_BINARY:
		case FSCONFIG_SET_PATH:
		case FSCONFIG_SET_PATH_EMPTY:
		case FSCONFIG_SET_FD:
			ret = -EOPNOTSUPP;
			goto out_f;
		}
	}

	if (_key) {
		param.key = strndup_user(_key, 256);
		if (IS_ERR(param.key)) {
			ret = PTR_ERR(param.key);
			goto out_f;
		}
	}

	switch (cmd) {
	case FSCONFIG_SET_FLAG:
		param.type = fs_value_is_flag;
		break;
	case FSCONFIG_SET_STRING:
		param.type = fs_value_is_string;
		param.string = strndup_user(_value, 256);
		if (IS_ERR(param.string)) {
			ret = PTR_ERR(param.string);
			goto out_key;
		}
		param.size = strlen(param.string);
		break;
	case FSCONFIG_SET_BINARY:
		param.type = fs_value_is_blob;
		param.size = aux;
		param.blob = memdup_user_nul(_value, aux);
		if (IS_ERR(param.blob)) {
			ret = PTR_ERR(param.blob);
			goto out_key;
		}
		break;
	case FSCONFIG_SET_PATH_EMPTY:
		lookup_flags = LOOKUP_EMPTY;
		fallthrough;
	case FSCONFIG_SET_PATH:
		param.type = fs_value_is_filename;
		param.name = getname_flags(_value, lookup_flags, NULL);
		if (IS_ERR(param.name)) {
			ret = PTR_ERR(param.name);
			goto out_key;
		}
		param.dirfd = aux;
		param.size = strlen(param.name->name);
		break;
	case FSCONFIG_SET_FD:
		param.type = fs_value_is_file;
		ret = -EBADF;
		param.file = fget(aux);
		if (!param.file)
			goto out_key;
		break;
	default:
		break;
	}

	ret = mutex_lock_interruptible(&fc->uapi_mutex);
	if (ret == 0) {
		ret = vfs_fsconfig_locked(fc, cmd, &param);
		mutex_unlock(&fc->uapi_mutex);
	}

	/* Clean up the our record of any value that we obtained from
	 * userspace.  Note that the value may have been stolen by the LSM or
	 * filesystem, in which case the value pointer will have been cleared.
	 */
	switch (cmd) {
	case FSCONFIG_SET_STRING:
	case FSCONFIG_SET_BINARY:
		kfree(param.string);
		break;
	case FSCONFIG_SET_PATH:
	case FSCONFIG_SET_PATH_EMPTY:
		if (param.name)
			putname(param.name);
		break;
	case FSCONFIG_SET_FD:
		if (param.file)
			fput(param.file);
		break;
	default:
		break;
	}
out_key:
	kfree(param.key);
out_f:
	fdput(f);
	return ret;
}