fs/xfs/xfs_symlink.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (c) 2000-2006 Silicon Graphics, Inc.
   4  * Copyright (c) 2012-2013 Red Hat, Inc.
   5  * All rights reserved.
   6  */
   7 #include "xfs.h"
   8 #include "xfs_shared.h"
   9 #include "xfs_fs.h"
  10 #include "xfs_format.h"
  11 #include "xfs_log_format.h"
  12 #include "xfs_trans_resv.h"
  13 #include "xfs_bit.h"
  14 #include "xfs_mount.h"
  15 #include "xfs_dir2.h"
  16 #include "xfs_inode.h"
  17 #include "xfs_bmap.h"
  18 #include "xfs_bmap_btree.h"
  19 #include "xfs_quota.h"
  20 #include "xfs_symlink.h"
  21 #include "xfs_trans_space.h"
  22 #include "xfs_trace.h"
  23 #include "xfs_trans.h"
  24 #include "xfs_ialloc.h"
  25 #include "xfs_error.h"
  26
  27 /* ----- Kernel only functions below ----- */
  28 int
  29 xfs_readlink_bmap_ilocked(
  30         struct xfs_inode        *ip,
  31         char                    *link)
  32 {
  33         struct xfs_mount        *mp = ip->i_mount;
  34         struct xfs_bmbt_irec    mval[XFS_SYMLINK_MAPS];
  35         struct xfs_buf          *bp;
  36         xfs_daddr_t             d;
  37         char                    *cur_chunk;
  38         int                     pathlen = ip->i_disk_size;
  39         int                     nmaps = XFS_SYMLINK_MAPS;
  40         int                     byte_cnt;
  41         int                     n;
  42         int                     error = 0;
  43         int                     fsblocks = 0;
  44         int                     offset;
  45
  46         ASSERT(xfs_isilocked(ip, XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
  47
  48         fsblocks = xfs_symlink_blocks(mp, pathlen);
  49         error = xfs_bmapi_read(ip, 0, fsblocks, mval, &nmaps, 0);
  50         if (error)
  51                 goto out;
  52
  53         offset = 0;
  54         for (n = 0; n < nmaps; n++) {
  55                 d = XFS_FSB_TO_DADDR(mp, mval[n].br_startblock);
  56                 byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
  57
  58                 error = xfs_buf_read(mp->m_ddev_targp, d, BTOBB(byte_cnt), 0,
  59                                 &bp, &xfs_symlink_buf_ops);
  60                 if (error)
  61                         return error;
  62                 byte_cnt = XFS_SYMLINK_BUF_SPACE(mp, byte_cnt);
  63                 if (pathlen < byte_cnt)
  64                         byte_cnt = pathlen;
  65
  66                 cur_chunk = bp->b_addr;
  67                 if (xfs_has_crc(mp)) {
  68                         if (!xfs_symlink_hdr_ok(ip->i_ino, offset,
  69                                                         byte_cnt, bp)) {
  70                                 error = -EFSCORRUPTED;
  71                                 xfs_alert(mp,
  72 "symlink header does not match required off/len/owner (0x%x/Ox%x,0x%llx)",
  73                                         offset, byte_cnt, ip->i_ino);
  74                                 xfs_buf_relse(bp);
  75                                 goto out;
  76
  77                         }
  78
  79                         cur_chunk += sizeof(struct xfs_dsymlink_hdr);
  80                 }
  81
  82                 memcpy(link + offset, cur_chunk, byte_cnt);
  83
  84                 pathlen -= byte_cnt;
  85                 offset += byte_cnt;
  86
  87                 xfs_buf_relse(bp);
  88         }
  89         ASSERT(pathlen == 0);
  90
  91         link[ip->i_disk_size] = '\0';
  92         error = 0;
  93
  94  out:
  95         return error;
  96 }
  97
  98 int
  99 xfs_readlink(
 100         struct xfs_inode        *ip,
 101         char                    *link)
 102 {
 103         struct xfs_mount        *mp = ip->i_mount;
 104         xfs_fsize_t             pathlen;
 105         int                     error = -EFSCORRUPTED;
 106
 107         trace_xfs_readlink(ip);
 108
 109         if (xfs_is_shutdown(mp))
 110                 return -EIO;
 111
 112         xfs_ilock(ip, XFS_ILOCK_SHARED);
 113
 114         pathlen = ip->i_disk_size;
 115         if (!pathlen)
 116                 goto out;
 117
 118         if (pathlen < 0 || pathlen > XFS_SYMLINK_MAXLEN) {
 119                 xfs_alert(mp, "%s: inode (%llu) bad symlink length (%lld)",
 120                          __func__, (unsigned long long) ip->i_ino,
 121                          (long long) pathlen);
 122                 ASSERT(0);
 123                 goto out;
 124         }
 125
 126         if (ip->i_df.if_format == XFS_DINODE_FMT_LOCAL) {
 127                 /*
 128                  * The VFS crashes on a NULL pointer, so return -EFSCORRUPTED
 129                  * if if_data is junk.
 130                  */
 131                 if (XFS_IS_CORRUPT(ip->i_mount, !ip->i_df.if_u1.if_data))
 132                         goto out;
 133
 134                 memcpy(link, ip->i_df.if_u1.if_data, pathlen + 1);
 135                 error = 0;
 136         } else {
 137                 error = xfs_readlink_bmap_ilocked(ip, link);
 138         }
 139
 140  out:
 141         xfs_iunlock(ip, XFS_ILOCK_SHARED);
 142         return error;
 143 }
 144
 145 int
 146 xfs_symlink(
 147         struct user_namespace   *mnt_userns,
 148         struct xfs_inode        *dp,
 149         struct xfs_name         *link_name,
 150         const char              *target_path,
 151         umode_t                 mode,
 152         struct xfs_inode        **ipp)
 153 {
 154         struct xfs_mount        *mp = dp->i_mount;
 155         struct xfs_trans        *tp = NULL;
 156         struct xfs_inode        *ip = NULL;
 157         int                     error = 0;
 158         int                     pathlen;
 159         bool                    unlock_dp_on_error = false;
 160         xfs_fileoff_t           first_fsb;
 161         xfs_filblks_t           fs_blocks;
 162         int                     nmaps;
 163         struct xfs_bmbt_irec    mval[XFS_SYMLINK_MAPS];
 164         xfs_daddr_t             d;
 165         const char              *cur_chunk;
 166         int                     byte_cnt;
 167         int                     n;
 168         struct xfs_buf          *bp;
 169         prid_t                  prid;
 170         struct xfs_dquot        *udqp = NULL;
 171         struct xfs_dquot        *gdqp = NULL;
 172         struct xfs_dquot        *pdqp = NULL;
 173         uint                    resblks;
 174         xfs_ino_t               ino;
 175
 176         *ipp = NULL;
 177
 178         trace_xfs_symlink(dp, link_name);
 179
 180         if (xfs_is_shutdown(mp))
 181                 return -EIO;
 182
 183         /*
 184          * Check component lengths of the target path name.
 185          */
 186         pathlen = strlen(target_path);
 187         if (pathlen >= XFS_SYMLINK_MAXLEN)      /* total string too long */
 188                 return -ENAMETOOLONG;
 189         ASSERT(pathlen > 0);
 190
 191         prid = xfs_get_initial_prid(dp);
 192
 193         /*
 194          * Make sure that we have allocated dquot(s) on disk.
 195          */
 196         error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(mnt_userns, &init_user_ns),
 197                         mapped_fsgid(mnt_userns, &init_user_ns), prid,
 198                         XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT,
 199                         &udqp, &gdqp, &pdqp);
 200         if (error)
 201                 return error;
 202
 203         /*
 204          * The symlink will fit into the inode data fork?
 205          * There can't be any attributes so we get the whole variable part.
 206          */
 207         if (pathlen <= XFS_LITINO(mp))
 208                 fs_blocks = 0;
 209         else
 210                 fs_blocks = xfs_symlink_blocks(mp, pathlen);
 211         resblks = XFS_SYMLINK_SPACE_RES(mp, link_name->len, fs_blocks);
 212
 213         error = xfs_trans_alloc_icreate(mp, &M_RES(mp)->tr_symlink, udqp, gdqp,
 214                         pdqp, resblks, &tp);
 215         if (error)
 216                 goto out_release_dquots;
 217
 218         xfs_ilock(dp, XFS_ILOCK_EXCL | XFS_ILOCK_PARENT);
 219         unlock_dp_on_error = true;
 220
 221         /*
 222          * Check whether the directory allows new symlinks or not.
 223          */
 224         if (dp->i_diflags & XFS_DIFLAG_NOSYMLINKS) {
 225                 error = -EPERM;
 226                 goto out_trans_cancel;
 227         }
 228
 229         /*
 230          * Allocate an inode for the symlink.
 231          */
 232         error = xfs_dialloc(&tp, dp->i_ino, S_IFLNK, &ino);
 233         if (!error)
 234                 error = xfs_init_new_inode(mnt_userns, tp, dp, ino,
 235                                 S_IFLNK | (mode & ~S_IFMT), 1, 0, prid,
 236                                 false, &ip);
 237         if (error)
 238                 goto out_trans_cancel;
 239
 240         /*
 241          * Now we join the directory inode to the transaction.  We do not do it
 242          * earlier because xfs_dir_ialloc might commit the previous transaction
 243          * (and release all the locks).  An error from here on will result in
 244          * the transaction cancel unlocking dp so don't do it explicitly in the
 245          * error path.
 246          */
 247         xfs_trans_ijoin(tp, dp, XFS_ILOCK_EXCL);
 248         unlock_dp_on_error = false;
 249
 250         /*
 251          * Also attach the dquot(s) to it, if applicable.
 252          */
 253         xfs_qm_vop_create_dqattach(tp, ip, udqp, gdqp, pdqp);
 254
 255         resblks -= XFS_IALLOC_SPACE_RES(mp);
 256         /*
 257          * If the symlink will fit into the inode, write it inline.
 258          */
 259         if (pathlen <= XFS_IFORK_DSIZE(ip)) {
 260                 xfs_init_local_fork(ip, XFS_DATA_FORK, target_path, pathlen);
 261
 262                 ip->i_disk_size = pathlen;
 263                 ip->i_df.if_format = XFS_DINODE_FMT_LOCAL;
 264                 xfs_trans_log_inode(tp, ip, XFS_ILOG_DDATA | XFS_ILOG_CORE);
 265         } else {
 266                 int     offset;
 267
 268                 first_fsb = 0;
 269                 nmaps = XFS_SYMLINK_MAPS;
 270
 271                 error = xfs_bmapi_write(tp, ip, first_fsb, fs_blocks,
 272                                   XFS_BMAPI_METADATA, resblks, mval, &nmaps);
 273                 if (error)
 274                         goto out_trans_cancel;
 275
 276                 resblks -= fs_blocks;
 277                 ip->i_disk_size = pathlen;
 278                 xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 279
 280                 cur_chunk = target_path;
 281                 offset = 0;
 282                 for (n = 0; n < nmaps; n++) {
 283                         char    *buf;
 284
 285                         d = XFS_FSB_TO_DADDR(mp, mval[n].br_startblock);
 286                         byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
 287                         error = xfs_trans_get_buf(tp, mp->m_ddev_targp, d,
 288                                                BTOBB(byte_cnt), 0, &bp);
 289                         if (error)
 290                                 goto out_trans_cancel;
 291                         bp->b_ops = &xfs_symlink_buf_ops;
 292
 293                         byte_cnt = XFS_SYMLINK_BUF_SPACE(mp, byte_cnt);
 294                         byte_cnt = min(byte_cnt, pathlen);
 295
 296                         buf = bp->b_addr;
 297                         buf += xfs_symlink_hdr_set(mp, ip->i_ino, offset,
 298                                                    byte_cnt, bp);
 299
 300                         memcpy(buf, cur_chunk, byte_cnt);
 301
 302                         cur_chunk += byte_cnt;
 303                         pathlen -= byte_cnt;
 304                         offset += byte_cnt;
 305
 306                         xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SYMLINK_BUF);
 307                         xfs_trans_log_buf(tp, bp, 0, (buf + byte_cnt - 1) -
 308                                                         (char *)bp->b_addr);
 309                 }
 310                 ASSERT(pathlen == 0);
 311         }
 312         i_size_write(VFS_I(ip), ip->i_disk_size);
 313
 314         /*
 315          * Create the directory entry for the symlink.
 316          */
 317         error = xfs_dir_createname(tp, dp, link_name, ip->i_ino, resblks);
 318         if (error)
 319                 goto out_trans_cancel;
 320         xfs_trans_ichgtime(tp, dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
 321         xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);
 322
 323         /*
 324          * If this is a synchronous mount, make sure that the
 325          * symlink transaction goes to disk before returning to
 326          * the user.
 327          */
 328         if (xfs_has_wsync(mp) || xfs_has_dirsync(mp))
 329                 xfs_trans_set_sync(tp);
 330
 331         error = xfs_trans_commit(tp);
 332         if (error)
 333                 goto out_release_inode;
 334
 335         xfs_qm_dqrele(udqp);
 336         xfs_qm_dqrele(gdqp);
 337         xfs_qm_dqrele(pdqp);
 338
 339         *ipp = ip;
 340         return 0;
 341
 342 out_trans_cancel:
 343         xfs_trans_cancel(tp);
 344 out_release_inode:
 345         /*
 346          * Wait until after the current transaction is aborted to finish the
 347          * setup of the inode and release the inode.  This prevents recursive
 348          * transactions and deadlocks from xfs_inactive.
 349          */
 350         if (ip) {
 351                 xfs_finish_inode_setup(ip);
 352                 xfs_irele(ip);
 353         }
 354 out_release_dquots:
 355         xfs_qm_dqrele(udqp);
 356         xfs_qm_dqrele(gdqp);
 357         xfs_qm_dqrele(pdqp);
 358
 359         if (unlock_dp_on_error)
 360                 xfs_iunlock(dp, XFS_ILOCK_EXCL);
 361         return error;
 362 }
 363
 364 /*
 365  * Free a symlink that has blocks associated with it.
 366  *
 367  * Note: zero length symlinks are not allowed to exist. When we set the size to
 368  * zero, also change it to a regular file so that it does not get written to
 369  * disk as a zero length symlink. The inode is on the unlinked list already, so
 370  * userspace cannot find this inode anymore, so this change is not user visible
 371  * but allows us to catch corrupt zero-length symlinks in the verifiers.
 372  */
 373 STATIC int
 374 xfs_inactive_symlink_rmt(
 375         struct xfs_inode *ip)
 376 {
 377         struct xfs_buf  *bp;
 378         int             done;
 379         int             error;
 380         int             i;
 381         xfs_mount_t     *mp;
 382         xfs_bmbt_irec_t mval[XFS_SYMLINK_MAPS];
 383         int             nmaps;
 384         int             size;
 385         xfs_trans_t     *tp;
 386
 387         mp = ip->i_mount;
 388         ASSERT(!xfs_need_iread_extents(&ip->i_df));
 389         /*
 390          * We're freeing a symlink that has some
 391          * blocks allocated to it.  Free the
 392          * blocks here.  We know that we've got
 393          * either 1 or 2 extents and that we can
 394          * free them all in one bunmapi call.
 395          */
 396         ASSERT(ip->i_df.if_nextents > 0 && ip->i_df.if_nextents <= 2);
 397
 398         error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp);
 399         if (error)
 400                 return error;
 401
 402         xfs_ilock(ip, XFS_ILOCK_EXCL);
 403         xfs_trans_ijoin(tp, ip, 0);
 404
 405         /*
 406          * Lock the inode, fix the size, turn it into a regular file and join it
 407          * to the transaction.  Hold it so in the normal path, we still have it
 408          * locked for the second transaction.  In the error paths we need it
 409          * held so the cancel won't rele it, see below.
 410          */
 411         size = (int)ip->i_disk_size;
 412         ip->i_disk_size = 0;
 413         VFS_I(ip)->i_mode = (VFS_I(ip)->i_mode & ~S_IFMT) | S_IFREG;
 414         xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 415         /*
 416          * Find the block(s) so we can inval and unmap them.
 417          */
 418         done = 0;
 419         nmaps = ARRAY_SIZE(mval);
 420         error = xfs_bmapi_read(ip, 0, xfs_symlink_blocks(mp, size),
 421                                 mval, &nmaps, 0);
 422         if (error)
 423                 goto error_trans_cancel;
 424         /*
 425          * Invalidate the block(s). No validation is done.
 426          */
 427         for (i = 0; i < nmaps; i++) {
 428                 error = xfs_trans_get_buf(tp, mp->m_ddev_targp,
 429                                 XFS_FSB_TO_DADDR(mp, mval[i].br_startblock),
 430                                 XFS_FSB_TO_BB(mp, mval[i].br_blockcount), 0,
 431                                 &bp);
 432                 if (error)
 433                         goto error_trans_cancel;
 434                 xfs_trans_binval(tp, bp);
 435         }
 436         /*
 437          * Unmap the dead block(s) to the dfops.
 438          */
 439         error = xfs_bunmapi(tp, ip, 0, size, 0, nmaps, &done);
 440         if (error)
 441                 goto error_trans_cancel;
 442         ASSERT(done);
 443
 444         /*
 445          * Commit the transaction. This first logs the EFI and the inode, then
 446          * rolls and commits the transaction that frees the extents.
 447          */
 448         xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 449         error = xfs_trans_commit(tp);
 450         if (error) {
 451                 ASSERT(xfs_is_shutdown(mp));
 452                 goto error_unlock;
 453         }
 454
 455         /*
 456          * Remove the memory for extent descriptions (just bookkeeping).
 457          */
 458         if (ip->i_df.if_bytes)
 459                 xfs_idata_realloc(ip, -ip->i_df.if_bytes, XFS_DATA_FORK);
 460         ASSERT(ip->i_df.if_bytes == 0);
 461
 462         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 463         return 0;
 464
 465 error_trans_cancel:
 466         xfs_trans_cancel(tp);
 467 error_unlock:
 468         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 469         return error;
 470 }
 471
 472 /*
 473  * xfs_inactive_symlink - free a symlink
 474  */
 475 int
 476 xfs_inactive_symlink(
 477         struct xfs_inode        *ip)
 478 {
 479         struct xfs_mount        *mp = ip->i_mount;
 480         int                     pathlen;
 481
 482         trace_xfs_inactive_symlink(ip);
 483
 484         if (xfs_is_shutdown(mp))
 485                 return -EIO;
 486
 487         xfs_ilock(ip, XFS_ILOCK_EXCL);
 488         pathlen = (int)ip->i_disk_size;
 489         ASSERT(pathlen);
 490
 491         if (pathlen <= 0 || pathlen > XFS_SYMLINK_MAXLEN) {
 492                 xfs_alert(mp, "%s: inode (0x%llx) bad symlink length (%d)",
 493                          __func__, (unsigned long long)ip->i_ino, pathlen);
 494                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
 495                 ASSERT(0);
 496                 return -EFSCORRUPTED;
 497         }
 498
 499         /*
 500          * Inline fork state gets removed by xfs_difree() so we have nothing to
 501          * do here in that case.
 502          */
 503         if (ip->i_df.if_format == XFS_DINODE_FMT_LOCAL) {
 504                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
 505                 return 0;
 506         }
 507
 508         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 509
 510         /* remove the remote symlink */
 511         return xfs_inactive_symlink_rmt(ip);
 512 }