// SPDX-License-Identifier: GPL-2.0
/*
* linux/fs/ext4/block_validity.c
*
* Copyright (C) 2009
* Theodore Ts'o ([email protected])
*
* Track which blocks in the filesystem are metadata blocks that
* should never be used as data blocks by files or directories.
*/
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/quotaops.h>
#include <linux/buffer_head.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/blkdev.h>
#include <linux/slab.h>
#include "ext4.h"
struct ext4_system_zone {
struct rb_node node;
ext4_fsblk_t start_blk;
unsigned int count;
u32 ino;
};
static struct kmem_cache *ext4_system_zone_cachep;
int __init ext4_init_system_zone(void)
{
ext4_system_zone_cachep = KMEM_CACHE(ext4_system_zone, 0);
if (ext4_system_zone_cachep == NULL)
return -ENOMEM;
return 0;
}
void ext4_exit_system_zone(void)
{
rcu_barrier();
kmem_cache_destroy(ext4_system_zone_cachep);
}
static inline int can_merge(struct ext4_system_zone *entry1,
struct ext4_system_zone *entry2)
{
if ((entry1->start_blk + entry1->count) == entry2->start_blk &&
entry1->ino == entry2->ino)
return 1;
return 0;
}
static void release_system_zone(struct ext4_system_blocks *system_blks)
{
struct ext4_system_zone *entry, *n;
rbtree_postorder_for_each_entry_safe(entry, n,
&system_blks->root, node)
kmem_cache_free(ext4_system_zone_cachep, entry);
}
/*
* Mark a range of blocks as belonging to the "system zone" --- that
* is, filesystem metadata blocks which should never be used by
* inodes.
*/
static int add_system_zone(struct ext4_system_blocks *system_blks,
ext4_fsblk_t start_blk,
unsigned int count, u32 ino)
{
struct ext4_system_zone *new_entry, *entry;
struct rb_node **n = &system_blks->root.rb_node, *node;
struct rb_node *parent = NULL, *new_node;
while (*n) {
parent = *n;
entry = rb_entry(parent, struct ext4_system_zone, node);
if (start_blk < entry->start_blk)
n = &(*n)->rb_left;
else if (start_blk >= (entry->start_blk + entry->count))
n = &(*n)->rb_right;
else /* Unexpected overlap of system zones. */
return -EFSCORRUPTED;
}
new_entry = kmem_cache_alloc(ext4_system_zone_cachep,
GFP_KERNEL);
if (!new_entry)
return -ENOMEM;
new_entry->start_blk = start_blk;
new_entry->count = count;
new_entry->ino = ino;
new_node = &new_entry->node;
rb_link_node(new_node, parent, n);
rb_insert_color(new_node, &system_blks->root);
/* Can we merge to the left? */
node = rb_prev(new_node);
if (node) {
entry = rb_entry(node, struct ext4_system_zone, node);
if (can_merge(entry, new_entry)) {
new_entry->start_blk = entry->start_blk;
new_entry->count += entry->count;
rb_erase(node, &system_blks->root);
kmem_cache_free(ext4_system_zone_cachep, entry);
}
}
/* Can we merge to the right? */
node = rb_next(new_node);
if (node) {
entry = rb_entry(node, struct ext4_system_zone, node);
if (can_merge(new_entry, entry)) {
new_entry->count += entry->count;
rb_erase(node, &system_blks->root);
kmem_cache_free(ext4_system_zone_cachep, entry);
}
}
return 0;
}
static void debug_print_tree(struct ext4_sb_info *sbi)
{
struct rb_node *node;
struct ext4_system_zone *entry;
struct ext4_system_blocks *system_blks;
int first = 1;
printk(KERN_INFO "System zones: ");
rcu_read_lock();
system_blks = rcu_dereference(sbi->s_system_blks);
node = rb_first(&system_blks->root);
while (node) {
entry = rb_entry(node, struct ext4_system_zone, node);
printk(KERN_CONT "%s%llu-%llu", first ? "" : ", ",
entry->start_blk, entry->start_blk + entry->count - 1);
first = 0;
node = rb_next(node);
}
rcu_read_unlock();
printk(KERN_CONT "\n");
}
static int ext4_protect_reserved_inode(struct super_block *sb,
struct ext4_system_blocks *system_blks,
u32 ino)
{
struct inode *inode;
struct ext4_sb_info *sbi = EXT4_SB(sb);
struct ext4_map_blocks map;
u32 i = 0, num;
int err = 0, n;
if ((ino < EXT4_ROOT_INO) ||
(ino > le32_to_cpu(sbi->s_es->s_inodes_count)))
return -EINVAL;
inode = ext4_iget(sb, ino, EXT4_IGET_SPECIAL);
if (IS_ERR(inode))
return PTR_ERR(inode);
num = (inode->i_size + sb->s_blocksize - 1) >> sb->s_blocksize_bits;
while (i < num) {
cond_resched();
map.m_lblk = i;
map.m_len = num - i;
n = ext4_map_blocks(NULL, inode, &map, 0);
if (n < 0) {
err = n;
break;
}
if (n == 0) {
i++;
} else {
err = add_system_zone(system_blks, map.m_pblk, n, ino);
if (err < 0) {
if (err == -EFSCORRUPTED) {
EXT4_ERROR_INODE_ERR(inode, -err,
"blocks %llu-%llu from inode overlap system zone",
map.m_pblk,
map.m_pblk + map.m_len - 1);
}
break;
}
i += n;
}
}
iput(inode);
return err;
}
static void ext4_destroy_system_zone(struct rcu_head *rcu)
{
struct ext4_system_blocks *system_blks;
system_blks = container_of(rcu, struct ext4_system_blocks, rcu);
release_system_zone(system_blks);
kfree(system_blks);
}
/*
* Build system zone rbtree which is used for block validity checking.
*
* The update of system_blks pointer in this function is protected by
* sb->s_umount semaphore. However we have to be careful as we can be
* racing with ext4_inode_block_valid() calls reading system_blks rbtree
* protected only by RCU. That's why we first build the rbtree and then
* swap it in place.
*/
int ext4_setup_system_zone(struct super_block *sb)
{
ext4_group_t ngroups = ext4_get_groups_count(sb);
struct ext4_sb_info *sbi = EXT4_SB(sb);
struct ext4_system_blocks *system_blks;
struct ext4_group_desc *gdp;
ext4_group_t i;
int ret;
system_blks = kzalloc(sizeof(*system_blks), GFP_KERNEL);
if (!system_blks)
return -ENOMEM;
for (i=0; i < ngroups; i++) {
unsigned int meta_blks = ext4_num_base_meta_blocks(sb, i);
cond_resched();
if (meta_blks != 0) {
ret = add_system_zone(system_blks,
ext4_group_first_block_no(sb, i),
meta_blks, 0);
if (ret)
goto err;
}
gdp = ext4_get_group_desc(sb, i, NULL);
ret = add_system_zone(system_blks,
ext4_block_bitmap(sb, gdp), 1, 0);
if (ret)
goto err;
ret = add_system_zone(system_blks,
ext4_inode_bitmap(sb, gdp), 1, 0);
if (ret)
goto err;
ret = add_system_zone(system_blks,
ext4_inode_table(sb, gdp),
sbi->s_itb_per_group, 0);
if (ret)
goto err;
}
if (ext4_has_feature_journal(sb) && sbi->s_es->s_journal_inum) {
ret = ext4_protect_reserved_inode(sb, system_blks,
le32_to_cpu(sbi->s_es->s_journal_inum));
if (ret)
goto err;
}
/*
* System blks rbtree complete, announce it once to prevent racing
* with ext4_inode_block_valid() accessing the rbtree at the same
* time.
*/
rcu_assign_pointer(sbi->s_system_blks, system_blks);
if (test_opt(sb, DEBUG))
debug_print_tree(sbi);
return 0;
err:
release_system_zone(system_blks);
kfree(system_blks);
return ret;
}
/*
* Called when the filesystem is unmounted or when remounting it with
* noblock_validity specified.
*
* The update of system_blks pointer in this function is protected by
* sb->s_umount semaphore. However we have to be careful as we can be
* racing with ext4_inode_block_valid() calls reading system_blks rbtree
* protected only by RCU. So we first clear the system_blks pointer and
* then free the rbtree only after RCU grace period expires.
*/
void ext4_release_system_zone(struct super_block *sb)
{
struct ext4_system_blocks *system_blks;
system_blks = rcu_dereference_protected(EXT4_SB(sb)->s_system_blks,
lockdep_is_held(&sb->s_umount));
rcu_assign_pointer(EXT4_SB(sb)->s_system_blks, NULL);
if (system_blks)
call_rcu(&system_blks->rcu, ext4_destroy_system_zone);
}
int ext4_sb_block_valid(struct super_block *sb, struct inode *inode,
ext4_fsblk_t start_blk, unsigned int count)
{
struct ext4_sb_info *sbi = EXT4_SB(sb);
struct ext4_system_blocks *system_blks;
struct ext4_system_zone *entry;
struct rb_node *n;
int ret = 1;
if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
(start_blk + count < start_blk) ||
(start_blk + count > ext4_blocks_count(sbi->s_es)))
return 0;
/*
* Lock the system zone to prevent it being released concurrently
* when doing a remount which inverse current "[no]block_validity"
* mount option.
*/
rcu_read_lock();
system_blks = rcu_dereference(sbi->s_system_blks);
if (system_blks == NULL)
goto out_rcu;
n = system_blks->root.rb_node;
while (n) {
entry = rb_entry(n, struct ext4_system_zone, node);
if (start_blk + count - 1 < entry->start_blk)
n = n->rb_left;
else if (start_blk >= (entry->start_blk + entry->count))
n = n->rb_right;
else {
ret = 0;
if (inode)
ret = (entry->ino == inode->i_ino);
break;
}
}
out_rcu:
rcu_read_unlock();
return ret;
}
/*
* Returns 1 if the passed-in block region (start_blk,
* start_blk+count) is valid; 0 if some part of the block region
* overlaps with some other filesystem metadata blocks.
*/
int ext4_inode_block_valid(struct inode *inode, ext4_fsblk_t start_blk,
unsigned int count)
{
return ext4_sb_block_valid(inode->i_sb, inode, start_blk, count);
}
int ext4_check_blockref(const char *function, unsigned int line,
struct inode *inode, __le32 *p, unsigned int max)
{
__le32 *bref = p;
unsigned int blk;
if (ext4_has_feature_journal(inode->i_sb) &&
(inode->i_ino ==
le32_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_journal_inum)))
return 0;
while (bref < p+max) {
blk = le32_to_cpu(*bref++);
if (blk &&
unlikely(!ext4_inode_block_valid(inode, blk, 1))) {
ext4_error_inode(inode, function, line, blk,
"invalid block");
return -EFSCORRUPTED;
}
}
return 0;
}
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