// SPDX-License-Identifier: GPL-2.0/* *  linux/fs/ext4/block_validity.c * * Copyright (C) 2009 * Theodore Ts'o (tytso@mit.edu) * * 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_obj(*system_blks);	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;	journal_t *journal = EXT4_SB(inode->i_sb)->s_journal; 	if (journal && inode == journal->j_inode)		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;}