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 }; 28 29 static struct kmem_cache *ext4_system_zone_cachep; 30 31 int __init ext4_init_system_zone(void) 32 { 33 ext4_system_zone_cachep = KMEM_CACHE(ext4_system_zone, 0); 34 if (ext4_system_zone_cachep == NULL) 35 return -ENOMEM; 36 return 0; 37 } 38 39 void ext4_exit_system_zone(void) 40 { 41 rcu_barrier(); 42 kmem_cache_destroy(ext4_system_zone_cachep); 43 } 44 45 static inline int can_merge(struct ext4_system_zone *entry1, 46 struct ext4_system_zone *entry2) 47 { 48 if ((entry1->start_blk + entry1->count) == entry2->start_blk) 49 return 1; 50 return 0; 51 } 52 53 static void release_system_zone(struct ext4_system_blocks *system_blks) 54 { 55 struct ext4_system_zone *entry, *n; 56 57 rbtree_postorder_for_each_entry_safe(entry, n, 58 &system_blks->root, node) 59 kmem_cache_free(ext4_system_zone_cachep, entry); 60 } 61 62 /* 63 * Mark a range of blocks as belonging to the "system zone" --- that 64 * is, filesystem metadata blocks which should never be used by 65 * inodes. 66 */ 67 static int add_system_zone(struct ext4_system_blocks *system_blks, 68 ext4_fsblk_t start_blk, 69 unsigned int count) 70 { 71 struct ext4_system_zone *new_entry = NULL, *entry; 72 struct rb_node **n = &system_blks->root.rb_node, *node; 73 struct rb_node *parent = NULL, *new_node = NULL; 74 75 while (*n) { 76 parent = *n; 77 entry = rb_entry(parent, struct ext4_system_zone, node); 78 if (start_blk < entry->start_blk) 79 n = &(*n)->rb_left; 80 else if (start_blk >= (entry->start_blk + entry->count)) 81 n = &(*n)->rb_right; 82 else { 83 if (start_blk + count > (entry->start_blk + 84 entry->count)) 85 entry->count = (start_blk + count - 86 entry->start_blk); 87 new_node = *n; 88 new_entry = rb_entry(new_node, struct ext4_system_zone, 89 node); 90 break; 91 } 92 } 93 94 if (!new_entry) { 95 new_entry = kmem_cache_alloc(ext4_system_zone_cachep, 96 GFP_KERNEL); 97 if (!new_entry) 98 return -ENOMEM; 99 new_entry->start_blk = start_blk; 100 new_entry->count = count; 101 new_node = &new_entry->node; 102 103 rb_link_node(new_node, parent, n); 104 rb_insert_color(new_node, &system_blks->root); 105 } 106 107 /* Can we merge to the left? */ 108 node = rb_prev(new_node); 109 if (node) { 110 entry = rb_entry(node, struct ext4_system_zone, node); 111 if (can_merge(entry, new_entry)) { 112 new_entry->start_blk = entry->start_blk; 113 new_entry->count += entry->count; 114 rb_erase(node, &system_blks->root); 115 kmem_cache_free(ext4_system_zone_cachep, entry); 116 } 117 } 118 119 /* Can we merge to the right? */ 120 node = rb_next(new_node); 121 if (node) { 122 entry = rb_entry(node, struct ext4_system_zone, node); 123 if (can_merge(new_entry, entry)) { 124 new_entry->count += entry->count; 125 rb_erase(node, &system_blks->root); 126 kmem_cache_free(ext4_system_zone_cachep, entry); 127 } 128 } 129 return 0; 130 } 131 132 static void debug_print_tree(struct ext4_sb_info *sbi) 133 { 134 struct rb_node *node; 135 struct ext4_system_zone *entry; 136 struct ext4_system_blocks *system_blks; 137 int first = 1; 138 139 printk(KERN_INFO "System zones: "); 140 rcu_read_lock(); 141 system_blks = rcu_dereference(sbi->system_blks); 142 node = rb_first(&system_blks->root); 143 while (node) { 144 entry = rb_entry(node, struct ext4_system_zone, node); 145 printk(KERN_CONT "%s%llu-%llu", first ? "" : ", ", 146 entry->start_blk, entry->start_blk + entry->count - 1); 147 first = 0; 148 node = rb_next(node); 149 } 150 rcu_read_unlock(); 151 printk(KERN_CONT "\n"); 152 } 153 154 /* 155 * Returns 1 if the passed-in block region (start_blk, 156 * start_blk+count) is valid; 0 if some part of the block region 157 * overlaps with filesystem metadata blocks. 158 */ 159 static int ext4_data_block_valid_rcu(struct ext4_sb_info *sbi, 160 struct ext4_system_blocks *system_blks, 161 ext4_fsblk_t start_blk, 162 unsigned int count) 163 { 164 struct ext4_system_zone *entry; 165 struct rb_node *n; 166 167 if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) || 168 (start_blk + count < start_blk) || 169 (start_blk + count > ext4_blocks_count(sbi->s_es))) { 170 sbi->s_es->s_last_error_block = cpu_to_le64(start_blk); 171 return 0; 172 } 173 174 if (system_blks == NULL) 175 return 1; 176 177 n = system_blks->root.rb_node; 178 while (n) { 179 entry = rb_entry(n, struct ext4_system_zone, node); 180 if (start_blk + count - 1 < entry->start_blk) 181 n = n->rb_left; 182 else if (start_blk >= (entry->start_blk + entry->count)) 183 n = n->rb_right; 184 else { 185 sbi->s_es->s_last_error_block = cpu_to_le64(start_blk); 186 return 0; 187 } 188 } 189 return 1; 190 } 191 192 static int ext4_protect_reserved_inode(struct super_block *sb, 193 struct ext4_system_blocks *system_blks, 194 u32 ino) 195 { 196 struct inode *inode; 197 struct ext4_sb_info *sbi = EXT4_SB(sb); 198 struct ext4_map_blocks map; 199 u32 i = 0, num; 200 int err = 0, n; 201 202 if ((ino < EXT4_ROOT_INO) || 203 (ino > le32_to_cpu(sbi->s_es->s_inodes_count))) 204 return -EINVAL; 205 inode = ext4_iget(sb, ino, EXT4_IGET_SPECIAL); 206 if (IS_ERR(inode)) 207 return PTR_ERR(inode); 208 num = (inode->i_size + sb->s_blocksize - 1) >> sb->s_blocksize_bits; 209 while (i < num) { 210 cond_resched(); 211 map.m_lblk = i; 212 map.m_len = num - i; 213 n = ext4_map_blocks(NULL, inode, &map, 0); 214 if (n < 0) { 215 err = n; 216 break; 217 } 218 if (n == 0) { 219 i++; 220 } else { 221 if (!ext4_data_block_valid_rcu(sbi, system_blks, 222 map.m_pblk, n)) { 223 ext4_error(sb, "blocks %llu-%llu from inode %u " 224 "overlap system zone", map.m_pblk, 225 map.m_pblk + map.m_len - 1, ino); 226 err = -EFSCORRUPTED; 227 break; 228 } 229 err = add_system_zone(system_blks, map.m_pblk, n); 230 if (err < 0) 231 break; 232 i += n; 233 } 234 } 235 iput(inode); 236 return err; 237 } 238 239 static void ext4_destroy_system_zone(struct rcu_head *rcu) 240 { 241 struct ext4_system_blocks *system_blks; 242 243 system_blks = container_of(rcu, struct ext4_system_blocks, rcu); 244 release_system_zone(system_blks); 245 kfree(system_blks); 246 } 247 248 /* 249 * Build system zone rbtree which is used for block validity checking. 250 * 251 * The update of system_blks pointer in this function is protected by 252 * sb->s_umount semaphore. However we have to be careful as we can be 253 * racing with ext4_data_block_valid() calls reading system_blks rbtree 254 * protected only by RCU. That's why we first build the rbtree and then 255 * swap it in place. 256 */ 257 int ext4_setup_system_zone(struct super_block *sb) 258 { 259 ext4_group_t ngroups = ext4_get_groups_count(sb); 260 struct ext4_sb_info *sbi = EXT4_SB(sb); 261 struct ext4_system_blocks *system_blks; 262 struct ext4_group_desc *gdp; 263 ext4_group_t i; 264 int flex_size = ext4_flex_bg_size(sbi); 265 int ret; 266 267 if (!test_opt(sb, BLOCK_VALIDITY)) { 268 if (sbi->system_blks) 269 ext4_release_system_zone(sb); 270 return 0; 271 } 272 if (sbi->system_blks) 273 return 0; 274 275 system_blks = kzalloc(sizeof(*system_blks), GFP_KERNEL); 276 if (!system_blks) 277 return -ENOMEM; 278 279 for (i=0; i < ngroups; i++) { 280 cond_resched(); 281 if (ext4_bg_has_super(sb, i) && 282 ((i < 5) || ((i % flex_size) == 0))) 283 add_system_zone(system_blks, 284 ext4_group_first_block_no(sb, i), 285 ext4_bg_num_gdb(sb, i) + 1); 286 gdp = ext4_get_group_desc(sb, i, NULL); 287 ret = add_system_zone(system_blks, 288 ext4_block_bitmap(sb, gdp), 1); 289 if (ret) 290 goto err; 291 ret = add_system_zone(system_blks, 292 ext4_inode_bitmap(sb, gdp), 1); 293 if (ret) 294 goto err; 295 ret = add_system_zone(system_blks, 296 ext4_inode_table(sb, gdp), 297 sbi->s_itb_per_group); 298 if (ret) 299 goto err; 300 } 301 if (ext4_has_feature_journal(sb) && sbi->s_es->s_journal_inum) { 302 ret = ext4_protect_reserved_inode(sb, system_blks, 303 le32_to_cpu(sbi->s_es->s_journal_inum)); 304 if (ret) 305 goto err; 306 } 307 308 /* 309 * System blks rbtree complete, announce it once to prevent racing 310 * with ext4_data_block_valid() accessing the rbtree at the same 311 * time. 312 */ 313 rcu_assign_pointer(sbi->system_blks, system_blks); 314 315 if (test_opt(sb, DEBUG)) 316 debug_print_tree(sbi); 317 return 0; 318 err: 319 release_system_zone(system_blks); 320 kfree(system_blks); 321 return ret; 322 } 323 324 /* 325 * Called when the filesystem is unmounted or when remounting it with 326 * noblock_validity specified. 327 * 328 * The update of system_blks pointer in this function is protected by 329 * sb->s_umount semaphore. However we have to be careful as we can be 330 * racing with ext4_data_block_valid() calls reading system_blks rbtree 331 * protected only by RCU. So we first clear the system_blks pointer and 332 * then free the rbtree only after RCU grace period expires. 333 */ 334 void ext4_release_system_zone(struct super_block *sb) 335 { 336 struct ext4_system_blocks *system_blks; 337 338 system_blks = rcu_dereference_protected(EXT4_SB(sb)->system_blks, 339 lockdep_is_held(&sb->s_umount)); 340 rcu_assign_pointer(EXT4_SB(sb)->system_blks, NULL); 341 342 if (system_blks) 343 call_rcu(&system_blks->rcu, ext4_destroy_system_zone); 344 } 345 346 int ext4_data_block_valid(struct ext4_sb_info *sbi, ext4_fsblk_t start_blk, 347 unsigned int count) 348 { 349 struct ext4_system_blocks *system_blks; 350 int ret; 351 352 /* 353 * Lock the system zone to prevent it being released concurrently 354 * when doing a remount which inverse current "[no]block_validity" 355 * mount option. 356 */ 357 rcu_read_lock(); 358 system_blks = rcu_dereference(sbi->system_blks); 359 ret = ext4_data_block_valid_rcu(sbi, system_blks, start_blk, 360 count); 361 rcu_read_unlock(); 362 return ret; 363 } 364 365 int ext4_check_blockref(const char *function, unsigned int line, 366 struct inode *inode, __le32 *p, unsigned int max) 367 { 368 struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es; 369 __le32 *bref = p; 370 unsigned int blk; 371 372 if (ext4_has_feature_journal(inode->i_sb) && 373 (inode->i_ino == 374 le32_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_journal_inum))) 375 return 0; 376 377 while (bref < p+max) { 378 blk = le32_to_cpu(*bref++); 379 if (blk && 380 unlikely(!ext4_data_block_valid(EXT4_SB(inode->i_sb), 381 blk, 1))) { 382 es->s_last_error_block = cpu_to_le64(blk); 383 ext4_error_inode(inode, function, line, blk, 384 "invalid block"); 385 return -EFSCORRUPTED; 386 } 387 } 388 return 0; 389 } 390 391