1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Squashfs - a compressed read only filesystem for Linux
4 *
5 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
6 * Phillip Lougher <phillip@squashfs.org.uk>
7 *
8 * super.c
9 */
10
11 /*
12 * This file implements code to read the superblock, read and initialise
13 * in-memory structures at mount time, and all the VFS glue code to register
14 * the filesystem.
15 */
16
17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18
19 #include <linux/fs.h>
20 #include <linux/fs_context.h>
21 #include <linux/vfs.h>
22 #include <linux/slab.h>
23 #include <linux/mutex.h>
24 #include <linux/pagemap.h>
25 #include <linux/init.h>
26 #include <linux/module.h>
27 #include <linux/magic.h>
28 #include <linux/xattr.h>
29 #include <linux/backing-dev.h>
30
31 #include "squashfs_fs.h"
32 #include "squashfs_fs_sb.h"
33 #include "squashfs_fs_i.h"
34 #include "squashfs.h"
35 #include "decompressor.h"
36 #include "xattr.h"
37
38 static struct file_system_type squashfs_fs_type;
39 static const struct super_operations squashfs_super_ops;
40
supported_squashfs_filesystem(struct fs_context * fc,short major,short minor,short id)41 static const struct squashfs_decompressor *supported_squashfs_filesystem(
42 struct fs_context *fc,
43 short major, short minor, short id)
44 {
45 const struct squashfs_decompressor *decompressor;
46
47 if (major < SQUASHFS_MAJOR) {
48 errorf(fc, "Major/Minor mismatch, older Squashfs %d.%d "
49 "filesystems are unsupported", major, minor);
50 return NULL;
51 } else if (major > SQUASHFS_MAJOR || minor > SQUASHFS_MINOR) {
52 errorf(fc, "Major/Minor mismatch, trying to mount newer "
53 "%d.%d filesystem", major, minor);
54 errorf(fc, "Please update your kernel");
55 return NULL;
56 }
57
58 decompressor = squashfs_lookup_decompressor(id);
59 if (!decompressor->supported) {
60 errorf(fc, "Filesystem uses \"%s\" compression. This is not supported",
61 decompressor->name);
62 return NULL;
63 }
64
65 return decompressor;
66 }
67
squashfs_bdi_init(struct super_block * sb)68 static int squashfs_bdi_init(struct super_block *sb)
69 {
70 int err;
71 unsigned int major = MAJOR(sb->s_dev);
72 unsigned int minor = MINOR(sb->s_dev);
73
74 bdi_put(sb->s_bdi);
75 sb->s_bdi = &noop_backing_dev_info;
76
77 err = super_setup_bdi_name(sb, "squashfs_%u_%u", major, minor);
78 if (err)
79 return err;
80
81 sb->s_bdi->ra_pages = 0;
82 sb->s_bdi->io_pages = 0;
83
84 return 0;
85 }
86
squashfs_fill_super(struct super_block * sb,struct fs_context * fc)87 static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
88 {
89 struct squashfs_sb_info *msblk;
90 struct squashfs_super_block *sblk = NULL;
91 struct inode *root;
92 long long root_inode;
93 unsigned short flags;
94 unsigned int fragments;
95 u64 lookup_table_start, xattr_id_table_start, next_table;
96 int err;
97
98 TRACE("Entered squashfs_fill_superblock\n");
99
100 /*
101 * squashfs provides 'backing_dev_info' in order to disable read-ahead. For
102 * squashfs, I/O is not deferred, it is done immediately in readpage,
103 * which means the user would have to wait not just for their own I/O
104 * but the read-ahead I/O as well i.e. completely pointless.squashfs_bdi_init
105 * will set sb->s_bdi->ra_pages and sb->s_bdi->io_pages to 0.
106 */
107 err = squashfs_bdi_init(sb);
108 if (err) {
109 errorf(fc, "squashfs init bdi failed");
110 return err;
111 }
112
113 sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
114 if (sb->s_fs_info == NULL) {
115 ERROR("Failed to allocate squashfs_sb_info\n");
116 return -ENOMEM;
117 }
118 msblk = sb->s_fs_info;
119
120 msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
121 if (!msblk->devblksize) {
122 errorf(fc, "squashfs: unable to set blocksize\n");
123 return -EINVAL;
124 }
125
126 msblk->devblksize_log2 = ffz(~msblk->devblksize);
127
128 mutex_init(&msblk->meta_index_mutex);
129
130 /*
131 * msblk->bytes_used is checked in squashfs_read_table to ensure reads
132 * are not beyond filesystem end. But as we're using
133 * squashfs_read_table here to read the superblock (including the value
134 * of bytes_used) we need to set it to an initial sensible dummy value
135 */
136 msblk->bytes_used = sizeof(*sblk);
137 sblk = squashfs_read_table(sb, SQUASHFS_START, sizeof(*sblk));
138
139 if (IS_ERR(sblk)) {
140 errorf(fc, "unable to read squashfs_super_block");
141 err = PTR_ERR(sblk);
142 sblk = NULL;
143 goto failed_mount;
144 }
145
146 err = -EINVAL;
147
148 /* Check it is a SQUASHFS superblock */
149 sb->s_magic = le32_to_cpu(sblk->s_magic);
150 if (sb->s_magic != SQUASHFS_MAGIC) {
151 if (!(fc->sb_flags & SB_SILENT))
152 errorf(fc, "Can't find a SQUASHFS superblock on %pg",
153 sb->s_bdev);
154 goto failed_mount;
155 }
156
157 /* Check the MAJOR & MINOR versions and lookup compression type */
158 msblk->decompressor = supported_squashfs_filesystem(
159 fc,
160 le16_to_cpu(sblk->s_major),
161 le16_to_cpu(sblk->s_minor),
162 le16_to_cpu(sblk->compression));
163 if (msblk->decompressor == NULL)
164 goto failed_mount;
165
166 /* Check the filesystem does not extend beyond the end of the
167 block device */
168 msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
169 if (msblk->bytes_used < 0 || msblk->bytes_used >
170 i_size_read(sb->s_bdev->bd_inode))
171 goto failed_mount;
172
173 /* Check block size for sanity */
174 msblk->block_size = le32_to_cpu(sblk->block_size);
175 if (msblk->block_size > SQUASHFS_FILE_MAX_SIZE)
176 goto insanity;
177
178 /*
179 * Check the system page size is not larger than the filesystem
180 * block size (by default 128K). This is currently not supported.
181 */
182 if (PAGE_SIZE > msblk->block_size) {
183 errorf(fc, "Page size > filesystem block size (%d). This is "
184 "currently not supported!", msblk->block_size);
185 goto failed_mount;
186 }
187
188 /* Check block log for sanity */
189 msblk->block_log = le16_to_cpu(sblk->block_log);
190 if (msblk->block_log > SQUASHFS_FILE_MAX_LOG)
191 goto failed_mount;
192
193 /* Check that block_size and block_log match */
194 if (msblk->block_size != (1 << msblk->block_log))
195 goto insanity;
196
197 /* Check the root inode for sanity */
198 root_inode = le64_to_cpu(sblk->root_inode);
199 if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)
200 goto insanity;
201
202 msblk->inode_table = le64_to_cpu(sblk->inode_table_start);
203 msblk->directory_table = le64_to_cpu(sblk->directory_table_start);
204 msblk->inodes = le32_to_cpu(sblk->inodes);
205 msblk->fragments = le32_to_cpu(sblk->fragments);
206 msblk->ids = le16_to_cpu(sblk->no_ids);
207 flags = le16_to_cpu(sblk->flags);
208
209 TRACE("Found valid superblock on %pg\n", sb->s_bdev);
210 TRACE("Inodes are %scompressed\n", SQUASHFS_UNCOMPRESSED_INODES(flags)
211 ? "un" : "");
212 TRACE("Data is %scompressed\n", SQUASHFS_UNCOMPRESSED_DATA(flags)
213 ? "un" : "");
214 TRACE("Filesystem size %lld bytes\n", msblk->bytes_used);
215 TRACE("Block size %d\n", msblk->block_size);
216 TRACE("Number of inodes %d\n", msblk->inodes);
217 TRACE("Number of fragments %d\n", msblk->fragments);
218 TRACE("Number of ids %d\n", msblk->ids);
219 TRACE("sblk->inode_table_start %llx\n", msblk->inode_table);
220 TRACE("sblk->directory_table_start %llx\n", msblk->directory_table);
221 TRACE("sblk->fragment_table_start %llx\n",
222 (u64) le64_to_cpu(sblk->fragment_table_start));
223 TRACE("sblk->id_table_start %llx\n",
224 (u64) le64_to_cpu(sblk->id_table_start));
225
226 sb->s_maxbytes = MAX_LFS_FILESIZE;
227 sb->s_time_min = 0;
228 sb->s_time_max = U32_MAX;
229 sb->s_flags |= SB_RDONLY;
230 sb->s_op = &squashfs_super_ops;
231
232 err = -ENOMEM;
233
234 msblk->block_cache = squashfs_cache_init("metadata",
235 SQUASHFS_CACHED_BLKS, SQUASHFS_METADATA_SIZE);
236 if (msblk->block_cache == NULL)
237 goto failed_mount;
238
239 /* Allocate read_page block */
240 msblk->read_page = squashfs_cache_init("data",
241 squashfs_max_decompressors(), msblk->block_size);
242 if (msblk->read_page == NULL) {
243 errorf(fc, "Failed to allocate read_page block");
244 goto failed_mount;
245 }
246
247 msblk->stream = squashfs_decompressor_setup(sb, flags);
248 if (IS_ERR(msblk->stream)) {
249 err = PTR_ERR(msblk->stream);
250 msblk->stream = NULL;
251 goto insanity;
252 }
253
254 /* Handle xattrs */
255 sb->s_xattr = squashfs_xattr_handlers;
256 xattr_id_table_start = le64_to_cpu(sblk->xattr_id_table_start);
257 if (xattr_id_table_start == SQUASHFS_INVALID_BLK) {
258 next_table = msblk->bytes_used;
259 goto allocate_id_index_table;
260 }
261
262 /* Allocate and read xattr id lookup table */
263 msblk->xattr_id_table = squashfs_read_xattr_id_table(sb,
264 xattr_id_table_start, &msblk->xattr_table, &msblk->xattr_ids);
265 if (IS_ERR(msblk->xattr_id_table)) {
266 errorf(fc, "unable to read xattr id index table");
267 err = PTR_ERR(msblk->xattr_id_table);
268 msblk->xattr_id_table = NULL;
269 if (err != -ENOTSUPP)
270 goto failed_mount;
271 }
272 next_table = msblk->xattr_table;
273
274 allocate_id_index_table:
275 /* Allocate and read id index table */
276 msblk->id_table = squashfs_read_id_index_table(sb,
277 le64_to_cpu(sblk->id_table_start), next_table, msblk->ids);
278 if (IS_ERR(msblk->id_table)) {
279 errorf(fc, "unable to read id index table");
280 err = PTR_ERR(msblk->id_table);
281 msblk->id_table = NULL;
282 goto failed_mount;
283 }
284 next_table = le64_to_cpu(msblk->id_table[0]);
285
286 /* Handle inode lookup table */
287 lookup_table_start = le64_to_cpu(sblk->lookup_table_start);
288 if (lookup_table_start == SQUASHFS_INVALID_BLK)
289 goto handle_fragments;
290
291 /* Allocate and read inode lookup table */
292 msblk->inode_lookup_table = squashfs_read_inode_lookup_table(sb,
293 lookup_table_start, next_table, msblk->inodes);
294 if (IS_ERR(msblk->inode_lookup_table)) {
295 errorf(fc, "unable to read inode lookup table");
296 err = PTR_ERR(msblk->inode_lookup_table);
297 msblk->inode_lookup_table = NULL;
298 goto failed_mount;
299 }
300 next_table = le64_to_cpu(msblk->inode_lookup_table[0]);
301
302 sb->s_export_op = &squashfs_export_ops;
303
304 handle_fragments:
305 fragments = msblk->fragments;
306 if (fragments == 0)
307 goto check_directory_table;
308
309 msblk->fragment_cache = squashfs_cache_init("fragment",
310 SQUASHFS_CACHED_FRAGMENTS, msblk->block_size);
311 if (msblk->fragment_cache == NULL) {
312 err = -ENOMEM;
313 goto failed_mount;
314 }
315
316 /* Allocate and read fragment index table */
317 msblk->fragment_index = squashfs_read_fragment_index_table(sb,
318 le64_to_cpu(sblk->fragment_table_start), next_table, fragments);
319 if (IS_ERR(msblk->fragment_index)) {
320 errorf(fc, "unable to read fragment index table");
321 err = PTR_ERR(msblk->fragment_index);
322 msblk->fragment_index = NULL;
323 goto failed_mount;
324 }
325 next_table = le64_to_cpu(msblk->fragment_index[0]);
326
327 check_directory_table:
328 /* Sanity check directory_table */
329 if (msblk->directory_table > next_table) {
330 err = -EINVAL;
331 goto insanity;
332 }
333
334 /* Sanity check inode_table */
335 if (msblk->inode_table >= msblk->directory_table) {
336 err = -EINVAL;
337 goto insanity;
338 }
339
340 /* allocate root */
341 root = new_inode(sb);
342 if (!root) {
343 err = -ENOMEM;
344 goto failed_mount;
345 }
346
347 err = squashfs_read_inode(root, root_inode);
348 if (err) {
349 make_bad_inode(root);
350 iput(root);
351 goto failed_mount;
352 }
353 insert_inode_hash(root);
354
355 sb->s_root = d_make_root(root);
356 if (sb->s_root == NULL) {
357 ERROR("Root inode create failed\n");
358 err = -ENOMEM;
359 goto failed_mount;
360 }
361
362 TRACE("Leaving squashfs_fill_super\n");
363 kfree(sblk);
364 return 0;
365
366 insanity:
367 errorf(fc, "squashfs image failed sanity check");
368 failed_mount:
369 squashfs_cache_delete(msblk->block_cache);
370 squashfs_cache_delete(msblk->fragment_cache);
371 squashfs_cache_delete(msblk->read_page);
372 squashfs_decompressor_destroy(msblk);
373 kfree(msblk->inode_lookup_table);
374 kfree(msblk->fragment_index);
375 kfree(msblk->id_table);
376 kfree(msblk->xattr_id_table);
377 kfree(sb->s_fs_info);
378 sb->s_fs_info = NULL;
379 kfree(sblk);
380 return err;
381 }
382
squashfs_get_tree(struct fs_context * fc)383 static int squashfs_get_tree(struct fs_context *fc)
384 {
385 return get_tree_bdev(fc, squashfs_fill_super);
386 }
387
squashfs_reconfigure(struct fs_context * fc)388 static int squashfs_reconfigure(struct fs_context *fc)
389 {
390 sync_filesystem(fc->root->d_sb);
391 fc->sb_flags |= SB_RDONLY;
392 return 0;
393 }
394
395 static const struct fs_context_operations squashfs_context_ops = {
396 .get_tree = squashfs_get_tree,
397 .reconfigure = squashfs_reconfigure,
398 };
399
squashfs_init_fs_context(struct fs_context * fc)400 static int squashfs_init_fs_context(struct fs_context *fc)
401 {
402 fc->ops = &squashfs_context_ops;
403 return 0;
404 }
405
squashfs_statfs(struct dentry * dentry,struct kstatfs * buf)406 static int squashfs_statfs(struct dentry *dentry, struct kstatfs *buf)
407 {
408 struct squashfs_sb_info *msblk = dentry->d_sb->s_fs_info;
409 u64 id = huge_encode_dev(dentry->d_sb->s_bdev->bd_dev);
410
411 TRACE("Entered squashfs_statfs\n");
412
413 buf->f_type = SQUASHFS_MAGIC;
414 buf->f_bsize = msblk->block_size;
415 buf->f_blocks = ((msblk->bytes_used - 1) >> msblk->block_log) + 1;
416 buf->f_bfree = buf->f_bavail = 0;
417 buf->f_files = msblk->inodes;
418 buf->f_ffree = 0;
419 buf->f_namelen = SQUASHFS_NAME_LEN;
420 buf->f_fsid = u64_to_fsid(id);
421
422 return 0;
423 }
424
425
squashfs_put_super(struct super_block * sb)426 static void squashfs_put_super(struct super_block *sb)
427 {
428 if (sb->s_fs_info) {
429 struct squashfs_sb_info *sbi = sb->s_fs_info;
430 squashfs_cache_delete(sbi->block_cache);
431 squashfs_cache_delete(sbi->fragment_cache);
432 squashfs_cache_delete(sbi->read_page);
433 squashfs_decompressor_destroy(sbi);
434 kfree(sbi->id_table);
435 kfree(sbi->fragment_index);
436 kfree(sbi->meta_index);
437 kfree(sbi->inode_lookup_table);
438 kfree(sbi->xattr_id_table);
439 kfree(sb->s_fs_info);
440 sb->s_fs_info = NULL;
441 }
442 }
443
444 static struct kmem_cache *squashfs_inode_cachep;
445
446
init_once(void * foo)447 static void init_once(void *foo)
448 {
449 struct squashfs_inode_info *ei = foo;
450
451 inode_init_once(&ei->vfs_inode);
452 }
453
454
init_inodecache(void)455 static int __init init_inodecache(void)
456 {
457 squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
458 sizeof(struct squashfs_inode_info), 0,
459 SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|SLAB_ACCOUNT,
460 init_once);
461
462 return squashfs_inode_cachep ? 0 : -ENOMEM;
463 }
464
465
destroy_inodecache(void)466 static void destroy_inodecache(void)
467 {
468 /*
469 * Make sure all delayed rcu free inodes are flushed before we
470 * destroy cache.
471 */
472 rcu_barrier();
473 kmem_cache_destroy(squashfs_inode_cachep);
474 }
475
476
init_squashfs_fs(void)477 static int __init init_squashfs_fs(void)
478 {
479 int err = init_inodecache();
480
481 if (err)
482 return err;
483
484 err = register_filesystem(&squashfs_fs_type);
485 if (err) {
486 destroy_inodecache();
487 return err;
488 }
489
490 pr_info("version 4.0 (2009/01/31) Phillip Lougher\n");
491
492 return 0;
493 }
494
495
exit_squashfs_fs(void)496 static void __exit exit_squashfs_fs(void)
497 {
498 unregister_filesystem(&squashfs_fs_type);
499 destroy_inodecache();
500 }
501
502
squashfs_alloc_inode(struct super_block * sb)503 static struct inode *squashfs_alloc_inode(struct super_block *sb)
504 {
505 struct squashfs_inode_info *ei =
506 kmem_cache_alloc(squashfs_inode_cachep, GFP_KERNEL);
507
508 return ei ? &ei->vfs_inode : NULL;
509 }
510
511
squashfs_free_inode(struct inode * inode)512 static void squashfs_free_inode(struct inode *inode)
513 {
514 kmem_cache_free(squashfs_inode_cachep, squashfs_i(inode));
515 }
516
517 static struct file_system_type squashfs_fs_type = {
518 .owner = THIS_MODULE,
519 .name = "squashfs",
520 .init_fs_context = squashfs_init_fs_context,
521 .kill_sb = kill_block_super,
522 .fs_flags = FS_REQUIRES_DEV
523 };
524 MODULE_ALIAS_FS("squashfs");
525
526 static const struct super_operations squashfs_super_ops = {
527 .alloc_inode = squashfs_alloc_inode,
528 .free_inode = squashfs_free_inode,
529 .statfs = squashfs_statfs,
530 .put_super = squashfs_put_super,
531 };
532
533 module_init(init_squashfs_fs);
534 module_exit(exit_squashfs_fs);
535 MODULE_DESCRIPTION("squashfs 4.0, a compressed read-only filesystem");
536 MODULE_AUTHOR("Phillip Lougher <phillip@squashfs.org.uk>");
537 MODULE_LICENSE("GPL");
538