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
23struct ext4_system_zone {
24	struct rb_node	node;
25	ext4_fsblk_t	start_blk;
26	unsigned int	count;
27	u32		ino;
28};
29
30static struct kmem_cache *ext4_system_zone_cachep;
31
32int __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
40void ext4_exit_system_zone(void)
41{
42	rcu_barrier();
43	kmem_cache_destroy(ext4_system_zone_cachep);
44}
45
46static 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
55static 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 */
69static 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 = NULL;
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
125static 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
147static 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
193static 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 */
211int 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;
267err:
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 */
283void 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
295int 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	}
333out_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 */
343int 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
349int 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