summaryrefslogtreecommitdiff
path: root/fs/overlayfs/inode.c
blob: a4ff5d0d7db91605880b4eb350ea37aa397c9c9d (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
/*
 *
 * Copyright (C) 2011 Novell Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 */

#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/xattr.h>
#include "overlayfs.h"

static int ovl_copy_up_truncate(struct dentry *dentry)
{
	int err;
	struct dentry *parent;
	struct kstat stat;
	struct path lowerpath;

	parent = dget_parent(dentry);
	err = ovl_copy_up(parent);
	if (err)
		goto out_dput_parent;

	ovl_path_lower(dentry, &lowerpath);
	err = vfs_getattr(&lowerpath, &stat);
	if (err)
		goto out_dput_parent;

	stat.size = 0;
	err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);

out_dput_parent:
	dput(parent);
	return err;
}

int ovl_setattr(struct dentry *dentry, struct iattr *attr)
{
	int err;
	struct dentry *upperdentry;

	/*
	 * Check for permissions before trying to copy-up.  This is redundant
	 * since it will be rechecked later by ->setattr() on upper dentry.  But
	 * without this, copy-up can be triggered by just about anybody.
	 *
	 * We don't initialize inode->size, which just means that
	 * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
	 * check for a swapfile (which this won't be anyway).
	 */
	err = inode_change_ok(dentry->d_inode, attr);
	if (err)
		return err;

	err = ovl_want_write(dentry);
	if (err)
		goto out;

	err = ovl_copy_up(dentry);
	if (!err) {
		upperdentry = ovl_dentry_upper(dentry);

		inode_lock(upperdentry->d_inode);
		err = notify_change(upperdentry, attr, NULL);
		if (!err)
			ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
		inode_unlock(upperdentry->d_inode);
	}
	ovl_drop_write(dentry);
out:
	return err;
}

static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
			 struct kstat *stat)
{
	struct path realpath;

	ovl_path_real(dentry, &realpath);
	return vfs_getattr(&realpath, stat);
}

int ovl_permission(struct inode *inode, int mask)
{
	struct ovl_entry *oe;
	struct dentry *alias = NULL;
	struct inode *realinode;
	struct dentry *realdentry;
	bool is_upper;
	int err;

	if (S_ISDIR(inode->i_mode)) {
		oe = inode->i_private;
	} else if (mask & MAY_NOT_BLOCK) {
		return -ECHILD;
	} else {
		/*
		 * For non-directories find an alias and get the info
		 * from there.
		 */
		alias = d_find_any_alias(inode);
		if (WARN_ON(!alias))
			return -ENOENT;

		oe = alias->d_fsdata;
	}

	realdentry = ovl_entry_real(oe, &is_upper);

	if (ovl_is_default_permissions(inode)) {
		struct kstat stat;
		struct path realpath = { .dentry = realdentry };

		if (mask & MAY_NOT_BLOCK)
			return -ECHILD;

		realpath.mnt = ovl_entry_mnt_real(oe, inode, is_upper);

		err = vfs_getattr(&realpath, &stat);
		if (err)
			return err;

		if ((stat.mode ^ inode->i_mode) & S_IFMT)
			return -ESTALE;

		inode->i_mode = stat.mode;
		inode->i_uid = stat.uid;
		inode->i_gid = stat.gid;

		return generic_permission(inode, mask);
	}

	/* Careful in RCU walk mode */
	realinode = ACCESS_ONCE(realdentry->d_inode);
	if (!realinode) {
		WARN_ON(!(mask & MAY_NOT_BLOCK));
		err = -ENOENT;
		goto out_dput;
	}

	if (mask & MAY_WRITE) {
		umode_t mode = realinode->i_mode;

		/*
		 * Writes will always be redirected to upper layer, so
		 * ignore lower layer being read-only.
		 *
		 * If the overlay itself is read-only then proceed
		 * with the permission check, don't return EROFS.
		 * This will only happen if this is the lower layer of
		 * another overlayfs.
		 *
		 * If upper fs becomes read-only after the overlay was
		 * constructed return EROFS to prevent modification of
		 * upper layer.
		 */
		err = -EROFS;
		if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
			goto out_dput;
	}

	err = __inode_permission(realinode, mask);
out_dput:
	dput(alias);
	return err;
}

static const char *ovl_get_link(struct dentry *dentry,
				struct inode *inode,
				struct delayed_call *done)
{
	struct dentry *realdentry;
	struct inode *realinode;

	if (!dentry)
		return ERR_PTR(-ECHILD);

	realdentry = ovl_dentry_real(dentry);
	realinode = realdentry->d_inode;

	if (WARN_ON(!realinode->i_op->get_link))
		return ERR_PTR(-EPERM);

	return realinode->i_op->get_link(realdentry, realinode, done);
}

static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
{
	struct path realpath;
	struct inode *realinode;

	ovl_path_real(dentry, &realpath);
	realinode = realpath.dentry->d_inode;

	if (!realinode->i_op->readlink)
		return -EINVAL;

	touch_atime(&realpath);

	return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
}


static bool ovl_is_private_xattr(const char *name)
{
	return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0;
}

int ovl_setxattr(struct dentry *dentry, const char *name,
		 const void *value, size_t size, int flags)
{
	int err;
	struct dentry *upperdentry;

	err = ovl_want_write(dentry);
	if (err)
		goto out;

	err = -EPERM;
	if (ovl_is_private_xattr(name))
		goto out_drop_write;

	err = ovl_copy_up(dentry);
	if (err)
		goto out_drop_write;

	upperdentry = ovl_dentry_upper(dentry);
	err = vfs_setxattr(upperdentry, name, value, size, flags);

out_drop_write:
	ovl_drop_write(dentry);
out:
	return err;
}

static bool ovl_need_xattr_filter(struct dentry *dentry,
				  enum ovl_path_type type)
{
	if ((type & (__OVL_PATH_PURE | __OVL_PATH_UPPER)) == __OVL_PATH_UPPER)
		return S_ISDIR(dentry->d_inode->i_mode);
	else
		return false;
}

ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
		     void *value, size_t size)
{
	struct path realpath;
	enum ovl_path_type type = ovl_path_real(dentry, &realpath);

	if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))
		return -ENODATA;

	return vfs_getxattr(realpath.dentry, name, value, size);
}

ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
{
	struct path realpath;
	enum ovl_path_type type = ovl_path_real(dentry, &realpath);
	ssize_t res;
	int off;

	res = vfs_listxattr(realpath.dentry, list, size);
	if (res <= 0 || size == 0)
		return res;

	if (!ovl_need_xattr_filter(dentry, type))
		return res;

	/* filter out private xattrs */
	for (off = 0; off < res;) {
		char *s = list + off;
		size_t slen = strlen(s) + 1;

		BUG_ON(off + slen > res);

		if (ovl_is_private_xattr(s)) {
			res -= slen;
			memmove(s, s + slen, res - off);
		} else {
			off += slen;
		}
	}

	return res;
}

int ovl_removexattr(struct dentry *dentry, const char *name)
{
	int err;
	struct path realpath;
	enum ovl_path_type type = ovl_path_real(dentry, &realpath);

	err = ovl_want_write(dentry);
	if (err)
		goto out;

	err = -ENODATA;
	if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))
		goto out_drop_write;

	if (!OVL_TYPE_UPPER(type)) {
		err = vfs_getxattr(realpath.dentry, name, NULL, 0);
		if (err < 0)
			goto out_drop_write;

		err = ovl_copy_up(dentry);
		if (err)
			goto out_drop_write;

		ovl_path_upper(dentry, &realpath);
	}

	err = vfs_removexattr(realpath.dentry, name);
out_drop_write:
	ovl_drop_write(dentry);
out:
	return err;
}

static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
				  struct dentry *realdentry)
{
	if (OVL_TYPE_UPPER(type))
		return false;

	if (special_file(realdentry->d_inode->i_mode))
		return false;

	if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
		return false;

	return true;
}

struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags)
{
	int err;
	struct path realpath;
	enum ovl_path_type type;

	if (d_is_dir(dentry))
		return d_backing_inode(dentry);

	type = ovl_path_real(dentry, &realpath);
	if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
		err = ovl_want_write(dentry);
		if (err)
			return ERR_PTR(err);

		if (file_flags & O_TRUNC)
			err = ovl_copy_up_truncate(dentry);
		else
			err = ovl_copy_up(dentry);
		ovl_drop_write(dentry);
		if (err)
			return ERR_PTR(err);

		ovl_path_upper(dentry, &realpath);
	}

	if (realpath.dentry->d_flags & DCACHE_OP_SELECT_INODE)
		return realpath.dentry->d_op->d_select_inode(realpath.dentry, file_flags);

	return d_backing_inode(realpath.dentry);
}

static const struct inode_operations ovl_file_inode_operations = {
	.setattr	= ovl_setattr,
	.permission	= ovl_permission,
	.getattr	= ovl_getattr,
	.setxattr	= ovl_setxattr,
	.getxattr	= ovl_getxattr,
	.listxattr	= ovl_listxattr,
	.removexattr	= ovl_removexattr,
};

static const struct inode_operations ovl_symlink_inode_operations = {
	.setattr	= ovl_setattr,
	.get_link	= ovl_get_link,
	.readlink	= ovl_readlink,
	.getattr	= ovl_getattr,
	.setxattr	= ovl_setxattr,
	.getxattr	= ovl_getxattr,
	.listxattr	= ovl_listxattr,
	.removexattr	= ovl_removexattr,
};

struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
			    struct ovl_entry *oe)
{
	struct inode *inode;

	inode = new_inode(sb);
	if (!inode)
		return NULL;

	mode &= S_IFMT;

	inode->i_ino = get_next_ino();
	inode->i_mode = mode;
	inode->i_flags |= S_NOATIME | S_NOCMTIME;

	switch (mode) {
	case S_IFDIR:
		inode->i_private = oe;
		inode->i_op = &ovl_dir_inode_operations;
		inode->i_fop = &ovl_dir_operations;
		break;

	case S_IFLNK:
		inode->i_op = &ovl_symlink_inode_operations;
		break;

	case S_IFREG:
	case S_IFSOCK:
	case S_IFBLK:
	case S_IFCHR:
	case S_IFIFO:
		inode->i_op = &ovl_file_inode_operations;
		break;

	default:
		WARN(1, "illegal file type: %i\n", mode);
		iput(inode);
		inode = NULL;
	}

	return inode;
}