block_validity.c

   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 = 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
 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