1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/fs/ext4/block_validity.c
4 *
5 * Copyright (C) 2009
6 * Theodore Ts'o (tytso@mit.edu)
7 *
8 * Track which blocks in the filesystem are metadata blocks that
9 * should never be used as data blocks by files or directories.
10 */
11
12 #include <linux/time.h>
13 #include <linux/fs.h>
14 #include <linux/namei.h>
15 #include <linux/quotaops.h>
16 #include <linux/buffer_head.h>
17 #include <linux/swap.h>
18 #include <linux/pagemap.h>
19 #include <linux/blkdev.h>
20 #include <linux/slab.h>
21 #include "ext4.h"
22
23 struct ext4_system_zone {
24 struct rb_node node;
25 ext4_fsblk_t start_blk;
26 unsigned int count;
27 u32 ino;
28 };
29
30 static struct kmem_cache *ext4_system_zone_cachep;
31
32 int __init ext4_init_system_zone(void)
33 {
34 ext4_system_zone_cachep = KMEM_CACHE(ext4_system_zone, 0);
35 if (ext4_system_zone_cachep == NULL)
36 return -ENOMEM;
37 return 0;
38 }
39
40 void ext4_exit_system_zone(void)
41 {
42 rcu_barrier();
43 kmem_cache_destroy(ext4_system_zone_cachep);
44 }
45
46 static inline int can_merge(struct ext4_system_zone *entry1,
47 struct ext4_system_zone *entry2)
48 {
49 if ((entry1->start_blk + entry1->count) == entry2->start_blk &&
50 entry1->ino == entry2->ino)
51 return 1;
52 return 0;
53 }
54
55 static void release_system_zone(struct ext4_system_blocks *system_blks)
56 {
57 struct ext4_system_zone *entry, *n;
58
59 rbtree_postorder_for_each_entry_safe(entry, n,
60 &system_blks->root, node)
61 kmem_cache_free(ext4_system_zone_cachep, entry);
62 }
63
64 /*
65 * Mark a range of blocks as belonging to the "system zone" --- that
66 * is, filesystem metadata blocks which should never be used by
67 * inodes.
68 */
69 static int add_system_zone(struct ext4_system_blocks *system_blks,
70 ext4_fsblk_t start_blk,
71 unsigned int count, u32 ino)
72 {
73 struct ext4_system_zone *new_entry, *entry;
74 struct rb_node **n = &system_blks->root.rb_node, *node;
75 struct rb_node *parent = NULL, *new_node;
76
77 while (*n) {
78 parent = *n;
79 entry = rb_entry(parent, struct ext4_system_zone, node);
80 if (start_blk < entry->start_blk)
81 n = &(*n)->rb_left;
82 else if (start_blk >= (entry->start_blk + entry->count))
83 n = &(*n)->rb_right;
84 else /* Unexpected overlap of system zones. */
85 return -EFSCORRUPTED;
86 }
87
88 new_entry = kmem_cache_alloc(ext4_system_zone_cachep,
89 GFP_KERNEL);
90 if (!new_entry)
91 return -ENOMEM;
92 new_entry->start_blk = start_blk;
93 new_entry->count = count;
94 new_entry->ino = ino;
95 new_node = &new_entry->node;
96
97 rb_link_node(new_node, parent, n);
98 rb_insert_color(new_node, &system_blks->root);
99
100 /* Can we merge to the left? */
101 node = rb_prev(new_node);
102 if (node) {
103 entry = rb_entry(node, struct ext4_system_zone, node);
104 if (can_merge(entry, new_entry)) {
105 new_entry->start_blk = entry->start_blk;
106 new_entry->count += entry->count;
107 rb_erase(node, &system_blks->root);
108 kmem_cache_free(ext4_system_zone_cachep, entry);
109 }
110 }
111
112 /* Can we merge to the right? */
113 node = rb_next(new_node);
114 if (node) {
115 entry = rb_entry(node, struct ext4_system_zone, node);
116 if (can_merge(new_entry, entry)) {
117 new_entry->count += entry->count;
118 rb_erase(node, &system_blks->root);
119 kmem_cache_free(ext4_system_zone_cachep, entry);
120 }
121 }
122 return 0;
123 }
124
125 static void debug_print_tree(struct ext4_sb_info *sbi)
126 {
127 struct rb_node *node;
128 struct ext4_system_zone *entry;
129 struct ext4_system_blocks *system_blks;
130 int first = 1;
131
132 printk(KERN_INFO "System zones: ");
133 rcu_read_lock();
134 system_blks = rcu_dereference(sbi->s_system_blks);
135 node = rb_first(&system_blks->root);
136 while (node) {
137 entry = rb_entry(node, struct ext4_system_zone, node);
138 printk(KERN_CONT "%s%llu-%llu", first ? "" : ", ",
139 entry->start_blk, entry->start_blk + entry->count - 1);
140 first = 0;
141 node = rb_next(node);
142 }
143 rcu_read_unlock();
144 printk(KERN_CONT "\n");
145 }
146
147 static int ext4_protect_reserved_inode(struct super_block *sb,
148 struct ext4_system_blocks *system_blks,
149 u32 ino)
150 {
151 struct inode *inode;
152 struct ext4_sb_info *sbi = EXT4_SB(sb);
153 struct ext4_map_blocks map;
154 u32 i = 0, num;
155 int err = 0, n;
156
157 if ((ino < EXT4_ROOT_INO) ||
158 (ino > le32_to_cpu(sbi->s_es->s_inodes_count)))
159 return -EINVAL;
160 inode = ext4_iget(sb, ino, EXT4_IGET_SPECIAL);
161 if (IS_ERR(inode))
162 return PTR_ERR(inode);
163 num = (inode->i_size + sb->s_blocksize - 1) >> sb->s_blocksize_bits;
164 while (i < num) {
165 cond_resched();
166 map.m_lblk = i;
167 map.m_len = num - i;
168 n = ext4_map_blocks(NULL, inode, &map, 0);
169 if (n < 0) {
170 err = n;
171 break;
172 }
173 if (n == 0) {
174 i++;
175 } else {
176 err = add_system_zone(system_blks, map.m_pblk, n, ino);
177 if (err < 0) {
178 if (err == -EFSCORRUPTED) {
179 EXT4_ERROR_INODE_ERR(inode, -err,
180 "blocks %llu-%llu from inode overlap system zone",
181 map.m_pblk,
182 map.m_pblk + map.m_len - 1);
183 }
184 break;
185 }
186 i += n;
187 }
188 }
189 iput(inode);
190 return err;
191 }
192
193 static void ext4_destroy_system_zone(struct rcu_head *rcu)
194 {
195 struct ext4_system_blocks *system_blks;
196
197 system_blks = container_of(rcu, struct ext4_system_blocks, rcu);
198 release_system_zone(system_blks);
199 kfree(system_blks);
200 }
201
202 /*
203 * Build system zone rbtree which is used for block validity checking.
204 *
205 * The update of system_blks pointer in this function is protected by
206 * sb->s_umount semaphore. However we have to be careful as we can be
207 * racing with ext4_inode_block_valid() calls reading system_blks rbtree
208 * protected only by RCU. That's why we first build the rbtree and then
209 * swap it in place.
210 */
211 int ext4_setup_system_zone(struct super_block *sb)
212 {
213 ext4_group_t ngroups = ext4_get_groups_count(sb);
214 struct ext4_sb_info *sbi = EXT4_SB(sb);
215 struct ext4_system_blocks *system_blks;
216 struct ext4_group_desc *gdp;
217 ext4_group_t i;
218 int ret;
219
220 system_blks = kzalloc(sizeof(*system_blks), GFP_KERNEL);
221 if (!system_blks)
222 return -ENOMEM;
223
224 for (i=0; i < ngroups; i++) {
225 unsigned int meta_blks = ext4_num_base_meta_blocks(sb, i);
226
227 cond_resched();
228 if (meta_blks != 0) {
229 ret = add_system_zone(system_blks,
230 ext4_group_first_block_no(sb, i),
231 meta_blks, 0);
232 if (ret)
233 goto err;
234 }
235 gdp = ext4_get_group_desc(sb, i, NULL);
236 ret = add_system_zone(system_blks,
237 ext4_block_bitmap(sb, gdp), 1, 0);
238 if (ret)
239 goto err;
240 ret = add_system_zone(system_blks,
241 ext4_inode_bitmap(sb, gdp), 1, 0);
242 if (ret)
243 goto err;
244 ret = add_system_zone(system_blks,
245 ext4_inode_table(sb, gdp),
246 sbi->s_itb_per_group, 0);
247 if (ret)
248 goto err;
249 }
250 if (ext4_has_feature_journal(sb) && sbi->s_es->s_journal_inum) {
251 ret = ext4_protect_reserved_inode(sb, system_blks,
252 le32_to_cpu(sbi->s_es->s_journal_inum));
253 if (ret)
254 goto err;
255 }
256
257 /*
258 * System blks rbtree complete, announce it once to prevent racing
259 * with ext4_inode_block_valid() accessing the rbtree at the same
260 * time.
261 */
262 rcu_assign_pointer(sbi->s_system_blks, system_blks);
263
264 if (test_opt(sb, DEBUG))
265 debug_print_tree(sbi);
266 return 0;
267 err:
268 release_system_zone(system_blks);
269 kfree(system_blks);
270 return ret;
271 }
272
273 /*
274 * Called when the filesystem is unmounted or when remounting it with
275 * noblock_validity specified.
276 *
277 * The update of system_blks pointer in this function is protected by
278 * sb->s_umount semaphore. However we have to be careful as we can be
279 * racing with ext4_inode_block_valid() calls reading system_blks rbtree
280 * protected only by RCU. So we first clear the system_blks pointer and
281 * then free the rbtree only after RCU grace period expires.
282 */
283 void ext4_release_system_zone(struct super_block *sb)
284 {
285 struct ext4_system_blocks *system_blks;
286
287 system_blks = rcu_dereference_protected(EXT4_SB(sb)->s_system_blks,
288 lockdep_is_held(&sb->s_umount));
289 rcu_assign_pointer(EXT4_SB(sb)->s_system_blks, NULL);
290
291 if (system_blks)
292 call_rcu(&system_blks->rcu, ext4_destroy_system_zone);
293 }
294
295 int ext4_sb_block_valid(struct super_block *sb, struct inode *inode,
296 ext4_fsblk_t start_blk, unsigned int count)
297 {
298 struct ext4_sb_info *sbi = EXT4_SB(sb);
299 struct ext4_system_blocks *system_blks;
300 struct ext4_system_zone *entry;
301 struct rb_node *n;
302 int ret = 1;
303
304 if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
305 (start_blk + count < start_blk) ||
306 (start_blk + count > ext4_blocks_count(sbi->s_es)))
307 return 0;
308
309 /*
310 * Lock the system zone to prevent it being released concurrently
311 * when doing a remount which inverse current "[no]block_validity"
312 * mount option.
313 */
314 rcu_read_lock();
315 system_blks = rcu_dereference(sbi->s_system_blks);
316 if (system_blks == NULL)
317 goto out_rcu;
318
319 n = system_blks->root.rb_node;
320 while (n) {
321 entry = rb_entry(n, struct ext4_system_zone, node);
322 if (start_blk + count - 1 < entry->start_blk)
323 n = n->rb_left;
324 else if (start_blk >= (entry->start_blk + entry->count))
325 n = n->rb_right;
326 else {
327 ret = 0;
328 if (inode)
329 ret = (entry->ino == inode->i_ino);
330 break;
331 }
332 }
333 out_rcu:
334 rcu_read_unlock();
335 return ret;
336 }
337
338 /*
339 * Returns 1 if the passed-in block region (start_blk,
340 * start_blk+count) is valid; 0 if some part of the block region
341 * overlaps with some other filesystem metadata blocks.
342 */
343 int ext4_inode_block_valid(struct inode *inode, ext4_fsblk_t start_blk,
344 unsigned int count)
345 {
346 return ext4_sb_block_valid(inode->i_sb, inode, start_blk, count);
347 }
348
349 int ext4_check_blockref(const char *function, unsigned int line,
350 struct inode *inode, __le32 *p, unsigned int max)
351 {
352 __le32 *bref = p;
353 unsigned int blk;
354
355 if (ext4_has_feature_journal(inode->i_sb) &&
356 (inode->i_ino ==
357 le32_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_journal_inum)))
358 return 0;
359
360 while (bref < p+max) {
361 blk = le32_to_cpu(*bref++);
362 if (blk &&
363 unlikely(!ext4_inode_block_valid(inode, blk, 1))) {
364 ext4_error_inode(inode, function, line, blk,
365 "invalid block");
366 return -EFSCORRUPTED;
367 }
368 }
369 return 0;
370 }
371
372
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