xref: /openbmc/linux/fs/squashfs/super.c (revision 3381df09)
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  
30  #include "squashfs_fs.h"
31  #include "squashfs_fs_sb.h"
32  #include "squashfs_fs_i.h"
33  #include "squashfs.h"
34  #include "decompressor.h"
35  #include "xattr.h"
36  
37  static struct file_system_type squashfs_fs_type;
38  static const struct super_operations squashfs_super_ops;
39  
40  static const struct squashfs_decompressor *supported_squashfs_filesystem(
41  	struct fs_context *fc,
42  	short major, short minor, short id)
43  {
44  	const struct squashfs_decompressor *decompressor;
45  
46  	if (major < SQUASHFS_MAJOR) {
47  		errorf(fc, "Major/Minor mismatch, older Squashfs %d.%d "
48  		       "filesystems are unsupported", major, minor);
49  		return NULL;
50  	} else if (major > SQUASHFS_MAJOR || minor > SQUASHFS_MINOR) {
51  		errorf(fc, "Major/Minor mismatch, trying to mount newer "
52  		       "%d.%d filesystem", major, minor);
53  		errorf(fc, "Please update your kernel");
54  		return NULL;
55  	}
56  
57  	decompressor = squashfs_lookup_decompressor(id);
58  	if (!decompressor->supported) {
59  		errorf(fc, "Filesystem uses \"%s\" compression. This is not supported",
60  		       decompressor->name);
61  		return NULL;
62  	}
63  
64  	return decompressor;
65  }
66  
67  
68  static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
69  {
70  	struct squashfs_sb_info *msblk;
71  	struct squashfs_super_block *sblk = NULL;
72  	struct inode *root;
73  	long long root_inode;
74  	unsigned short flags;
75  	unsigned int fragments;
76  	u64 lookup_table_start, xattr_id_table_start, next_table;
77  	int err;
78  
79  	TRACE("Entered squashfs_fill_superblock\n");
80  
81  	sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
82  	if (sb->s_fs_info == NULL) {
83  		ERROR("Failed to allocate squashfs_sb_info\n");
84  		return -ENOMEM;
85  	}
86  	msblk = sb->s_fs_info;
87  
88  	msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
89  	msblk->devblksize_log2 = ffz(~msblk->devblksize);
90  
91  	mutex_init(&msblk->meta_index_mutex);
92  
93  	/*
94  	 * msblk->bytes_used is checked in squashfs_read_table to ensure reads
95  	 * are not beyond filesystem end.  But as we're using
96  	 * squashfs_read_table here to read the superblock (including the value
97  	 * of bytes_used) we need to set it to an initial sensible dummy value
98  	 */
99  	msblk->bytes_used = sizeof(*sblk);
100  	sblk = squashfs_read_table(sb, SQUASHFS_START, sizeof(*sblk));
101  
102  	if (IS_ERR(sblk)) {
103  		errorf(fc, "unable to read squashfs_super_block");
104  		err = PTR_ERR(sblk);
105  		sblk = NULL;
106  		goto failed_mount;
107  	}
108  
109  	err = -EINVAL;
110  
111  	/* Check it is a SQUASHFS superblock */
112  	sb->s_magic = le32_to_cpu(sblk->s_magic);
113  	if (sb->s_magic != SQUASHFS_MAGIC) {
114  		if (!(fc->sb_flags & SB_SILENT))
115  			errorf(fc, "Can't find a SQUASHFS superblock on %pg",
116  			       sb->s_bdev);
117  		goto failed_mount;
118  	}
119  
120  	/* Check the MAJOR & MINOR versions and lookup compression type */
121  	msblk->decompressor = supported_squashfs_filesystem(
122  			fc,
123  			le16_to_cpu(sblk->s_major),
124  			le16_to_cpu(sblk->s_minor),
125  			le16_to_cpu(sblk->compression));
126  	if (msblk->decompressor == NULL)
127  		goto failed_mount;
128  
129  	/* Check the filesystem does not extend beyond the end of the
130  	   block device */
131  	msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
132  	if (msblk->bytes_used < 0 || msblk->bytes_used >
133  			i_size_read(sb->s_bdev->bd_inode))
134  		goto failed_mount;
135  
136  	/* Check block size for sanity */
137  	msblk->block_size = le32_to_cpu(sblk->block_size);
138  	if (msblk->block_size > SQUASHFS_FILE_MAX_SIZE)
139  		goto insanity;
140  
141  	/*
142  	 * Check the system page size is not larger than the filesystem
143  	 * block size (by default 128K).  This is currently not supported.
144  	 */
145  	if (PAGE_SIZE > msblk->block_size) {
146  		errorf(fc, "Page size > filesystem block size (%d).  This is "
147  		       "currently not supported!", msblk->block_size);
148  		goto failed_mount;
149  	}
150  
151  	/* Check block log for sanity */
152  	msblk->block_log = le16_to_cpu(sblk->block_log);
153  	if (msblk->block_log > SQUASHFS_FILE_MAX_LOG)
154  		goto failed_mount;
155  
156  	/* Check that block_size and block_log match */
157  	if (msblk->block_size != (1 << msblk->block_log))
158  		goto insanity;
159  
160  	/* Check the root inode for sanity */
161  	root_inode = le64_to_cpu(sblk->root_inode);
162  	if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)
163  		goto insanity;
164  
165  	msblk->inode_table = le64_to_cpu(sblk->inode_table_start);
166  	msblk->directory_table = le64_to_cpu(sblk->directory_table_start);
167  	msblk->inodes = le32_to_cpu(sblk->inodes);
168  	msblk->fragments = le32_to_cpu(sblk->fragments);
169  	flags = le16_to_cpu(sblk->flags);
170  
171  	TRACE("Found valid superblock on %pg\n", sb->s_bdev);
172  	TRACE("Inodes are %scompressed\n", SQUASHFS_UNCOMPRESSED_INODES(flags)
173  				? "un" : "");
174  	TRACE("Data is %scompressed\n", SQUASHFS_UNCOMPRESSED_DATA(flags)
175  				? "un" : "");
176  	TRACE("Filesystem size %lld bytes\n", msblk->bytes_used);
177  	TRACE("Block size %d\n", msblk->block_size);
178  	TRACE("Number of inodes %d\n", msblk->inodes);
179  	TRACE("Number of fragments %d\n", msblk->fragments);
180  	TRACE("Number of ids %d\n", le16_to_cpu(sblk->no_ids));
181  	TRACE("sblk->inode_table_start %llx\n", msblk->inode_table);
182  	TRACE("sblk->directory_table_start %llx\n", msblk->directory_table);
183  	TRACE("sblk->fragment_table_start %llx\n",
184  		(u64) le64_to_cpu(sblk->fragment_table_start));
185  	TRACE("sblk->id_table_start %llx\n",
186  		(u64) le64_to_cpu(sblk->id_table_start));
187  
188  	sb->s_maxbytes = MAX_LFS_FILESIZE;
189  	sb->s_time_min = 0;
190  	sb->s_time_max = U32_MAX;
191  	sb->s_flags |= SB_RDONLY;
192  	sb->s_op = &squashfs_super_ops;
193  
194  	err = -ENOMEM;
195  
196  	msblk->block_cache = squashfs_cache_init("metadata",
197  			SQUASHFS_CACHED_BLKS, SQUASHFS_METADATA_SIZE);
198  	if (msblk->block_cache == NULL)
199  		goto failed_mount;
200  
201  	/* Allocate read_page block */
202  	msblk->read_page = squashfs_cache_init("data",
203  		squashfs_max_decompressors(), msblk->block_size);
204  	if (msblk->read_page == NULL) {
205  		errorf(fc, "Failed to allocate read_page block");
206  		goto failed_mount;
207  	}
208  
209  	msblk->stream = squashfs_decompressor_setup(sb, flags);
210  	if (IS_ERR(msblk->stream)) {
211  		err = PTR_ERR(msblk->stream);
212  		msblk->stream = NULL;
213  		goto insanity;
214  	}
215  
216  	/* Handle xattrs */
217  	sb->s_xattr = squashfs_xattr_handlers;
218  	xattr_id_table_start = le64_to_cpu(sblk->xattr_id_table_start);
219  	if (xattr_id_table_start == SQUASHFS_INVALID_BLK) {
220  		next_table = msblk->bytes_used;
221  		goto allocate_id_index_table;
222  	}
223  
224  	/* Allocate and read xattr id lookup table */
225  	msblk->xattr_id_table = squashfs_read_xattr_id_table(sb,
226  		xattr_id_table_start, &msblk->xattr_table, &msblk->xattr_ids);
227  	if (IS_ERR(msblk->xattr_id_table)) {
228  		errorf(fc, "unable to read xattr id index table");
229  		err = PTR_ERR(msblk->xattr_id_table);
230  		msblk->xattr_id_table = NULL;
231  		if (err != -ENOTSUPP)
232  			goto failed_mount;
233  	}
234  	next_table = msblk->xattr_table;
235  
236  allocate_id_index_table:
237  	/* Allocate and read id index table */
238  	msblk->id_table = squashfs_read_id_index_table(sb,
239  		le64_to_cpu(sblk->id_table_start), next_table,
240  		le16_to_cpu(sblk->no_ids));
241  	if (IS_ERR(msblk->id_table)) {
242  		errorf(fc, "unable to read id index table");
243  		err = PTR_ERR(msblk->id_table);
244  		msblk->id_table = NULL;
245  		goto failed_mount;
246  	}
247  	next_table = le64_to_cpu(msblk->id_table[0]);
248  
249  	/* Handle inode lookup table */
250  	lookup_table_start = le64_to_cpu(sblk->lookup_table_start);
251  	if (lookup_table_start == SQUASHFS_INVALID_BLK)
252  		goto handle_fragments;
253  
254  	/* Allocate and read inode lookup table */
255  	msblk->inode_lookup_table = squashfs_read_inode_lookup_table(sb,
256  		lookup_table_start, next_table, msblk->inodes);
257  	if (IS_ERR(msblk->inode_lookup_table)) {
258  		errorf(fc, "unable to read inode lookup table");
259  		err = PTR_ERR(msblk->inode_lookup_table);
260  		msblk->inode_lookup_table = NULL;
261  		goto failed_mount;
262  	}
263  	next_table = le64_to_cpu(msblk->inode_lookup_table[0]);
264  
265  	sb->s_export_op = &squashfs_export_ops;
266  
267  handle_fragments:
268  	fragments = msblk->fragments;
269  	if (fragments == 0)
270  		goto check_directory_table;
271  
272  	msblk->fragment_cache = squashfs_cache_init("fragment",
273  		SQUASHFS_CACHED_FRAGMENTS, msblk->block_size);
274  	if (msblk->fragment_cache == NULL) {
275  		err = -ENOMEM;
276  		goto failed_mount;
277  	}
278  
279  	/* Allocate and read fragment index table */
280  	msblk->fragment_index = squashfs_read_fragment_index_table(sb,
281  		le64_to_cpu(sblk->fragment_table_start), next_table, fragments);
282  	if (IS_ERR(msblk->fragment_index)) {
283  		errorf(fc, "unable to read fragment index table");
284  		err = PTR_ERR(msblk->fragment_index);
285  		msblk->fragment_index = NULL;
286  		goto failed_mount;
287  	}
288  	next_table = le64_to_cpu(msblk->fragment_index[0]);
289  
290  check_directory_table:
291  	/* Sanity check directory_table */
292  	if (msblk->directory_table > next_table) {
293  		err = -EINVAL;
294  		goto insanity;
295  	}
296  
297  	/* Sanity check inode_table */
298  	if (msblk->inode_table >= msblk->directory_table) {
299  		err = -EINVAL;
300  		goto insanity;
301  	}
302  
303  	/* allocate root */
304  	root = new_inode(sb);
305  	if (!root) {
306  		err = -ENOMEM;
307  		goto failed_mount;
308  	}
309  
310  	err = squashfs_read_inode(root, root_inode);
311  	if (err) {
312  		make_bad_inode(root);
313  		iput(root);
314  		goto failed_mount;
315  	}
316  	insert_inode_hash(root);
317  
318  	sb->s_root = d_make_root(root);
319  	if (sb->s_root == NULL) {
320  		ERROR("Root inode create failed\n");
321  		err = -ENOMEM;
322  		goto failed_mount;
323  	}
324  
325  	TRACE("Leaving squashfs_fill_super\n");
326  	kfree(sblk);
327  	return 0;
328  
329  insanity:
330  	errorf(fc, "squashfs image failed sanity check");
331  failed_mount:
332  	squashfs_cache_delete(msblk->block_cache);
333  	squashfs_cache_delete(msblk->fragment_cache);
334  	squashfs_cache_delete(msblk->read_page);
335  	squashfs_decompressor_destroy(msblk);
336  	kfree(msblk->inode_lookup_table);
337  	kfree(msblk->fragment_index);
338  	kfree(msblk->id_table);
339  	kfree(msblk->xattr_id_table);
340  	kfree(sb->s_fs_info);
341  	sb->s_fs_info = NULL;
342  	kfree(sblk);
343  	return err;
344  }
345  
346  static int squashfs_get_tree(struct fs_context *fc)
347  {
348  	return get_tree_bdev(fc, squashfs_fill_super);
349  }
350  
351  static int squashfs_reconfigure(struct fs_context *fc)
352  {
353  	sync_filesystem(fc->root->d_sb);
354  	fc->sb_flags |= SB_RDONLY;
355  	return 0;
356  }
357  
358  static const struct fs_context_operations squashfs_context_ops = {
359  	.get_tree	= squashfs_get_tree,
360  	.reconfigure	= squashfs_reconfigure,
361  };
362  
363  static int squashfs_init_fs_context(struct fs_context *fc)
364  {
365  	fc->ops = &squashfs_context_ops;
366  	return 0;
367  }
368  
369  static int squashfs_statfs(struct dentry *dentry, struct kstatfs *buf)
370  {
371  	struct squashfs_sb_info *msblk = dentry->d_sb->s_fs_info;
372  	u64 id = huge_encode_dev(dentry->d_sb->s_bdev->bd_dev);
373  
374  	TRACE("Entered squashfs_statfs\n");
375  
376  	buf->f_type = SQUASHFS_MAGIC;
377  	buf->f_bsize = msblk->block_size;
378  	buf->f_blocks = ((msblk->bytes_used - 1) >> msblk->block_log) + 1;
379  	buf->f_bfree = buf->f_bavail = 0;
380  	buf->f_files = msblk->inodes;
381  	buf->f_ffree = 0;
382  	buf->f_namelen = SQUASHFS_NAME_LEN;
383  	buf->f_fsid.val[0] = (u32)id;
384  	buf->f_fsid.val[1] = (u32)(id >> 32);
385  
386  	return 0;
387  }
388  
389  
390  static void squashfs_put_super(struct super_block *sb)
391  {
392  	if (sb->s_fs_info) {
393  		struct squashfs_sb_info *sbi = sb->s_fs_info;
394  		squashfs_cache_delete(sbi->block_cache);
395  		squashfs_cache_delete(sbi->fragment_cache);
396  		squashfs_cache_delete(sbi->read_page);
397  		squashfs_decompressor_destroy(sbi);
398  		kfree(sbi->id_table);
399  		kfree(sbi->fragment_index);
400  		kfree(sbi->meta_index);
401  		kfree(sbi->inode_lookup_table);
402  		kfree(sbi->xattr_id_table);
403  		kfree(sb->s_fs_info);
404  		sb->s_fs_info = NULL;
405  	}
406  }
407  
408  static struct kmem_cache *squashfs_inode_cachep;
409  
410  
411  static void init_once(void *foo)
412  {
413  	struct squashfs_inode_info *ei = foo;
414  
415  	inode_init_once(&ei->vfs_inode);
416  }
417  
418  
419  static int __init init_inodecache(void)
420  {
421  	squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
422  		sizeof(struct squashfs_inode_info), 0,
423  		SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|SLAB_ACCOUNT,
424  		init_once);
425  
426  	return squashfs_inode_cachep ? 0 : -ENOMEM;
427  }
428  
429  
430  static void destroy_inodecache(void)
431  {
432  	/*
433  	 * Make sure all delayed rcu free inodes are flushed before we
434  	 * destroy cache.
435  	 */
436  	rcu_barrier();
437  	kmem_cache_destroy(squashfs_inode_cachep);
438  }
439  
440  
441  static int __init init_squashfs_fs(void)
442  {
443  	int err = init_inodecache();
444  
445  	if (err)
446  		return err;
447  
448  	err = register_filesystem(&squashfs_fs_type);
449  	if (err) {
450  		destroy_inodecache();
451  		return err;
452  	}
453  
454  	pr_info("version 4.0 (2009/01/31) Phillip Lougher\n");
455  
456  	return 0;
457  }
458  
459  
460  static void __exit exit_squashfs_fs(void)
461  {
462  	unregister_filesystem(&squashfs_fs_type);
463  	destroy_inodecache();
464  }
465  
466  
467  static struct inode *squashfs_alloc_inode(struct super_block *sb)
468  {
469  	struct squashfs_inode_info *ei =
470  		kmem_cache_alloc(squashfs_inode_cachep, GFP_KERNEL);
471  
472  	return ei ? &ei->vfs_inode : NULL;
473  }
474  
475  
476  static void squashfs_free_inode(struct inode *inode)
477  {
478  	kmem_cache_free(squashfs_inode_cachep, squashfs_i(inode));
479  }
480  
481  static struct file_system_type squashfs_fs_type = {
482  	.owner = THIS_MODULE,
483  	.name = "squashfs",
484  	.init_fs_context = squashfs_init_fs_context,
485  	.kill_sb = kill_block_super,
486  	.fs_flags = FS_REQUIRES_DEV
487  };
488  MODULE_ALIAS_FS("squashfs");
489  
490  static const struct super_operations squashfs_super_ops = {
491  	.alloc_inode = squashfs_alloc_inode,
492  	.free_inode = squashfs_free_inode,
493  	.statfs = squashfs_statfs,
494  	.put_super = squashfs_put_super,
495  };
496  
497  module_init(init_squashfs_fs);
498  module_exit(exit_squashfs_fs);
499  MODULE_DESCRIPTION("squashfs 4.0, a compressed read-only filesystem");
500  MODULE_AUTHOR("Phillip Lougher <phillip@squashfs.org.uk>");
501  MODULE_LICENSE("GPL");
502