1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * Copyright (C) 2017 Oracle. All Rights Reserved. 4 * Author: Darrick J. Wong <darrick.wong@oracle.com> 5 */ 6 #include "xfs.h" 7 #include "xfs_fs.h" 8 #include "xfs_shared.h" 9 #include "xfs_format.h" 10 #include "xfs_trans_resv.h" 11 #include "xfs_mount.h" 12 #include "xfs_log_format.h" 13 #include "xfs_inode.h" 14 #include "xfs_icache.h" 15 #include "xfs_dir2.h" 16 #include "xfs_dir2_priv.h" 17 #include "scrub/scrub.h" 18 #include "scrub/common.h" 19 20 /* Set us up to scrub parents. */ 21 int 22 xchk_setup_parent( 23 struct xfs_scrub *sc) 24 { 25 return xchk_setup_inode_contents(sc, 0); 26 } 27 28 /* Parent pointers */ 29 30 /* Look for an entry in a parent pointing to this inode. */ 31 32 struct xchk_parent_ctx { 33 struct dir_context dc; 34 struct xfs_scrub *sc; 35 xfs_ino_t ino; 36 xfs_nlink_t nlink; 37 bool cancelled; 38 }; 39 40 /* Look for a single entry in a directory pointing to an inode. */ 41 STATIC int 42 xchk_parent_actor( 43 struct dir_context *dc, 44 const char *name, 45 int namelen, 46 loff_t pos, 47 u64 ino, 48 unsigned type) 49 { 50 struct xchk_parent_ctx *spc; 51 int error = 0; 52 53 spc = container_of(dc, struct xchk_parent_ctx, dc); 54 if (spc->ino == ino) 55 spc->nlink++; 56 57 /* 58 * If we're facing a fatal signal, bail out. Store the cancellation 59 * status separately because the VFS readdir code squashes error codes 60 * into short directory reads. 61 */ 62 if (xchk_should_terminate(spc->sc, &error)) 63 spc->cancelled = true; 64 65 return error; 66 } 67 68 /* Count the number of dentries in the parent dir that point to this inode. */ 69 STATIC int 70 xchk_parent_count_parent_dentries( 71 struct xfs_scrub *sc, 72 struct xfs_inode *parent, 73 xfs_nlink_t *nlink) 74 { 75 struct xchk_parent_ctx spc = { 76 .dc.actor = xchk_parent_actor, 77 .ino = sc->ip->i_ino, 78 .sc = sc, 79 }; 80 size_t bufsize; 81 loff_t oldpos; 82 uint lock_mode; 83 int error = 0; 84 85 /* 86 * If there are any blocks, read-ahead block 0 as we're almost 87 * certain to have the next operation be a read there. This is 88 * how we guarantee that the parent's extent map has been loaded, 89 * if there is one. 90 */ 91 lock_mode = xfs_ilock_data_map_shared(parent); 92 if (parent->i_df.if_nextents > 0) 93 error = xfs_dir3_data_readahead(parent, 0, 0); 94 xfs_iunlock(parent, lock_mode); 95 if (error) 96 return error; 97 98 /* 99 * Iterate the parent dir to confirm that there is 100 * exactly one entry pointing back to the inode being 101 * scanned. 102 */ 103 bufsize = (size_t)min_t(loff_t, XFS_READDIR_BUFSIZE, 104 parent->i_disk_size); 105 oldpos = 0; 106 while (true) { 107 error = xfs_readdir(sc->tp, parent, &spc.dc, bufsize); 108 if (error) 109 goto out; 110 if (spc.cancelled) { 111 error = -EAGAIN; 112 goto out; 113 } 114 if (oldpos == spc.dc.pos) 115 break; 116 oldpos = spc.dc.pos; 117 } 118 *nlink = spc.nlink; 119 out: 120 return error; 121 } 122 123 /* 124 * Given the inode number of the alleged parent of the inode being 125 * scrubbed, try to validate that the parent has exactly one directory 126 * entry pointing back to the inode being scrubbed. 127 */ 128 STATIC int 129 xchk_parent_validate( 130 struct xfs_scrub *sc, 131 xfs_ino_t dnum, 132 bool *try_again) 133 { 134 struct xfs_mount *mp = sc->mp; 135 struct xfs_inode *dp = NULL; 136 xfs_nlink_t expected_nlink; 137 xfs_nlink_t nlink; 138 int error = 0; 139 140 *try_again = false; 141 142 if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT) 143 goto out; 144 145 /* '..' must not point to ourselves. */ 146 if (sc->ip->i_ino == dnum) { 147 xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); 148 goto out; 149 } 150 151 /* 152 * If we're an unlinked directory, the parent /won't/ have a link 153 * to us. Otherwise, it should have one link. 154 */ 155 expected_nlink = VFS_I(sc->ip)->i_nlink == 0 ? 0 : 1; 156 157 /* 158 * Grab this parent inode. We release the inode before we 159 * cancel the scrub transaction. Since we're don't know a 160 * priori that releasing the inode won't trigger eofblocks 161 * cleanup (which allocates what would be a nested transaction) 162 * if the parent pointer erroneously points to a file, we 163 * can't use DONTCACHE here because DONTCACHE inodes can trigger 164 * immediate inactive cleanup of the inode. 165 * 166 * If _iget returns -EINVAL or -ENOENT then the parent inode number is 167 * garbage and the directory is corrupt. If the _iget returns 168 * -EFSCORRUPTED or -EFSBADCRC then the parent is corrupt which is a 169 * cross referencing error. Any other error is an operational error. 170 */ 171 error = xfs_iget(mp, sc->tp, dnum, XFS_IGET_UNTRUSTED, 0, &dp); 172 if (error == -EINVAL || error == -ENOENT) { 173 error = -EFSCORRUPTED; 174 xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error); 175 goto out; 176 } 177 if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0, &error)) 178 goto out; 179 if (dp == sc->ip || !S_ISDIR(VFS_I(dp)->i_mode)) { 180 xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); 181 goto out_rele; 182 } 183 184 /* 185 * We prefer to keep the inode locked while we lock and search 186 * its alleged parent for a forward reference. If we can grab 187 * the iolock, validate the pointers and we're done. We must 188 * use nowait here to avoid an ABBA deadlock on the parent and 189 * the child inodes. 190 */ 191 if (xfs_ilock_nowait(dp, XFS_IOLOCK_SHARED)) { 192 error = xchk_parent_count_parent_dentries(sc, dp, &nlink); 193 if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0, 194 &error)) 195 goto out_unlock; 196 if (nlink != expected_nlink) 197 xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); 198 goto out_unlock; 199 } 200 201 /* 202 * The game changes if we get here. We failed to lock the parent, 203 * so we're going to try to verify both pointers while only holding 204 * one lock so as to avoid deadlocking with something that's actually 205 * trying to traverse down the directory tree. 206 */ 207 xfs_iunlock(sc->ip, sc->ilock_flags); 208 sc->ilock_flags = 0; 209 error = xchk_ilock_inverted(dp, XFS_IOLOCK_SHARED); 210 if (error) 211 goto out_rele; 212 213 /* Go looking for our dentry. */ 214 error = xchk_parent_count_parent_dentries(sc, dp, &nlink); 215 if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, 0, &error)) 216 goto out_unlock; 217 218 /* Drop the parent lock, relock this inode. */ 219 xfs_iunlock(dp, XFS_IOLOCK_SHARED); 220 error = xchk_ilock_inverted(sc->ip, XFS_IOLOCK_EXCL); 221 if (error) 222 goto out_rele; 223 sc->ilock_flags = XFS_IOLOCK_EXCL; 224 225 /* 226 * If we're an unlinked directory, the parent /won't/ have a link 227 * to us. Otherwise, it should have one link. We have to re-set 228 * it here because we dropped the lock on sc->ip. 229 */ 230 expected_nlink = VFS_I(sc->ip)->i_nlink == 0 ? 0 : 1; 231 232 /* Look up '..' to see if the inode changed. */ 233 error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL); 234 if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error)) 235 goto out_rele; 236 237 /* Drat, parent changed. Try again! */ 238 if (dnum != dp->i_ino) { 239 xfs_irele(dp); 240 *try_again = true; 241 return 0; 242 } 243 xfs_irele(dp); 244 245 /* 246 * '..' didn't change, so check that there was only one entry 247 * for us in the parent. 248 */ 249 if (nlink != expected_nlink) 250 xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); 251 return error; 252 253 out_unlock: 254 xfs_iunlock(dp, XFS_IOLOCK_SHARED); 255 out_rele: 256 xfs_irele(dp); 257 out: 258 return error; 259 } 260 261 /* Scrub a parent pointer. */ 262 int 263 xchk_parent( 264 struct xfs_scrub *sc) 265 { 266 struct xfs_mount *mp = sc->mp; 267 xfs_ino_t dnum; 268 bool try_again; 269 int tries = 0; 270 int error = 0; 271 272 /* 273 * If we're a directory, check that the '..' link points up to 274 * a directory that has one entry pointing to us. 275 */ 276 if (!S_ISDIR(VFS_I(sc->ip)->i_mode)) 277 return -ENOENT; 278 279 /* We're not a special inode, are we? */ 280 if (!xfs_verify_dir_ino(mp, sc->ip->i_ino)) { 281 xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); 282 goto out; 283 } 284 285 /* 286 * The VFS grabs a read or write lock via i_rwsem before it reads 287 * or writes to a directory. If we've gotten this far we've 288 * already obtained IOLOCK_EXCL, which (since 4.10) is the same as 289 * getting a write lock on i_rwsem. Therefore, it is safe for us 290 * to drop the ILOCK here in order to do directory lookups. 291 */ 292 sc->ilock_flags &= ~(XFS_ILOCK_EXCL | XFS_MMAPLOCK_EXCL); 293 xfs_iunlock(sc->ip, XFS_ILOCK_EXCL | XFS_MMAPLOCK_EXCL); 294 295 /* Look up '..' */ 296 error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL); 297 if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error)) 298 goto out; 299 if (!xfs_verify_dir_ino(mp, dnum)) { 300 xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); 301 goto out; 302 } 303 304 /* Is this the root dir? Then '..' must point to itself. */ 305 if (sc->ip == mp->m_rootip) { 306 if (sc->ip->i_ino != mp->m_sb.sb_rootino || 307 sc->ip->i_ino != dnum) 308 xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, 0); 309 goto out; 310 } 311 312 do { 313 error = xchk_parent_validate(sc, dnum, &try_again); 314 if (error) 315 goto out; 316 } while (try_again && ++tries < 20); 317 318 /* 319 * We gave it our best shot but failed, so mark this scrub 320 * incomplete. Userspace can decide if it wants to try again. 321 */ 322 if (try_again && tries == 20) 323 xchk_set_incomplete(sc); 324 out: 325 /* 326 * If we failed to lock the parent inode even after a retry, just mark 327 * this scrub incomplete and return. 328 */ 329 if ((sc->flags & XCHK_TRY_HARDER) && error == -EDEADLOCK) { 330 error = 0; 331 xchk_set_incomplete(sc); 332 } 333 return error; 334 } 335