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
  25 /* ----- Kernel only functions below ----- */
  26 int
  27 xfs_readlink_bmap_ilocked(
  28         struct xfs_inode        *ip,
  29         char                    *link)
  30 {
  31         struct xfs_mount        *mp = ip->i_mount;
  32         struct xfs_bmbt_irec    mval[XFS_SYMLINK_MAPS];
  33         struct xfs_buf          *bp;
  34         xfs_daddr_t             d;
  35         char                    *cur_chunk;
  36         int                     pathlen = ip->i_d.di_size;
  37         int                     nmaps = XFS_SYMLINK_MAPS;
  38         int                     byte_cnt;
  39         int                     n;
  40         int                     error = 0;
  41         int                     fsblocks = 0;
  42         int                     offset;
  43
  44         ASSERT(xfs_isilocked(ip, XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
  45
  46         fsblocks = xfs_symlink_blocks(mp, pathlen);
  47         error = xfs_bmapi_read(ip, 0, fsblocks, mval, &nmaps, 0);
  48         if (error)
  49                 goto out;
  50
  51         offset = 0;
  52         for (n = 0; n < nmaps; n++) {
  53                 d = XFS_FSB_TO_DADDR(mp, mval[n].br_startblock);
  54                 byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
  55
  56                 bp = xfs_buf_read(mp->m_ddev_targp, d, BTOBB(byte_cnt), 0,
  57                                   &xfs_symlink_buf_ops);
  58                 if (!bp)
  59                         return -ENOMEM;
  60                 error = bp->b_error;
  61                 if (error) {
  62                         xfs_buf_ioerror_alert(bp, __func__);
  63                         xfs_buf_relse(bp);
  64
  65                         /* bad CRC means corrupted metadata */
  66                         if (error == -EFSBADCRC)
  67                                 error = -EFSCORRUPTED;
  68                         goto out;
  69                 }
  70                 byte_cnt = XFS_SYMLINK_BUF_SPACE(mp, byte_cnt);
  71                 if (pathlen < byte_cnt)
  72                         byte_cnt = pathlen;
  73
  74                 cur_chunk = bp->b_addr;
  75                 if (xfs_sb_version_hascrc(&mp->m_sb)) {
  76                         if (!xfs_symlink_hdr_ok(ip->i_ino, offset,
  77                                                         byte_cnt, bp)) {
  78                                 error = -EFSCORRUPTED;
  79                                 xfs_alert(mp,
  80 "symlink header does not match required off/len/owner (0x%x/Ox%x,0x%llx)",
  81                                         offset, byte_cnt, ip->i_ino);
  82                                 xfs_buf_relse(bp);
  83                                 goto out;
  84
  85                         }
  86
  87                         cur_chunk += sizeof(struct xfs_dsymlink_hdr);
  88                 }
  89
  90                 memcpy(link + offset, cur_chunk, byte_cnt);
  91
  92                 pathlen -= byte_cnt;
  93                 offset += byte_cnt;
  94
  95                 xfs_buf_relse(bp);
  96         }
  97         ASSERT(pathlen == 0);
  98
  99         link[ip->i_d.di_size] = '\0';
 100         error = 0;
 101
 102  out:
 103         return error;
 104 }
 105
 106 int
 107 xfs_readlink(
 108         struct xfs_inode *ip,
 109         char            *link)
 110 {
 111         struct xfs_mount *mp = ip->i_mount;
 112         xfs_fsize_t     pathlen;
 113         int             error = 0;
 114
 115         trace_xfs_readlink(ip);
 116
 117         ASSERT(!(ip->i_df.if_flags & XFS_IFINLINE));
 118
 119         if (XFS_FORCED_SHUTDOWN(mp))
 120                 return -EIO;
 121
 122         xfs_ilock(ip, XFS_ILOCK_SHARED);
 123
 124         pathlen = ip->i_d.di_size;
 125         if (!pathlen)
 126                 goto out;
 127
 128         if (pathlen < 0 || pathlen > XFS_SYMLINK_MAXLEN) {
 129                 xfs_alert(mp, "%s: inode (%llu) bad symlink length (%lld)",
 130                          __func__, (unsigned long long) ip->i_ino,
 131                          (long long) pathlen);
 132                 ASSERT(0);
 133                 error = -EFSCORRUPTED;
 134                 goto out;
 135         }
 136
 137
 138         error = xfs_readlink_bmap_ilocked(ip, link);
 139
 140  out:
 141         xfs_iunlock(ip, XFS_ILOCK_SHARED);
 142         return error;
 143 }
 144
 145 int
 146 xfs_symlink(
 147         struct xfs_inode        *dp,
 148         struct xfs_name         *link_name,
 149         const char              *target_path,
 150         umode_t                 mode,
 151         struct xfs_inode        **ipp)
 152 {
 153         struct xfs_mount        *mp = dp->i_mount;
 154         struct xfs_trans        *tp = NULL;
 155         struct xfs_inode        *ip = NULL;
 156         int                     error = 0;
 157         int                     pathlen;
 158         bool                    unlock_dp_on_error = false;
 159         xfs_fileoff_t           first_fsb;
 160         xfs_filblks_t           fs_blocks;
 161         int                     nmaps;
 162         struct xfs_bmbt_irec    mval[XFS_SYMLINK_MAPS];
 163         xfs_daddr_t             d;
 164         const char              *cur_chunk;
 165         int                     byte_cnt;
 166         int                     n;
 167         xfs_buf_t               *bp;
 168         prid_t                  prid;
 169         struct xfs_dquot        *udqp = NULL;
 170         struct xfs_dquot        *gdqp = NULL;
 171         struct xfs_dquot        *pdqp = NULL;
 172         uint                    resblks;
 173
 174         *ipp = NULL;
 175
 176         trace_xfs_symlink(dp, link_name);
 177
 178         if (XFS_FORCED_SHUTDOWN(mp))
 179                 return -EIO;
 180
 181         /*
 182          * Check component lengths of the target path name.
 183          */
 184         pathlen = strlen(target_path);
 185         if (pathlen >= XFS_SYMLINK_MAXLEN)      /* total string too long */
 186                 return -ENAMETOOLONG;
 187         ASSERT(pathlen > 0);
 188
 189         udqp = gdqp = NULL;
 190         prid = xfs_get_initial_prid(dp);
 191
 192         /*
 193          * Make sure that we have allocated dquot(s) on disk.
 194          */
 195         error = xfs_qm_vop_dqalloc(dp,
 196                         xfs_kuid_to_uid(current_fsuid()),
 197                         xfs_kgid_to_gid(current_fsgid()), 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, dp->i_d.di_version))
 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(mp, &M_RES(mp)->tr_symlink, resblks, 0, 0, &tp);
 214         if (error)
 215                 goto out_release_inode;
 216
 217         xfs_ilock(dp, XFS_ILOCK_EXCL | XFS_ILOCK_PARENT);
 218         unlock_dp_on_error = true;
 219
 220         /*
 221          * Check whether the directory allows new symlinks or not.
 222          */
 223         if (dp->i_d.di_flags & XFS_DIFLAG_NOSYMLINKS) {
 224                 error = -EPERM;
 225                 goto out_trans_cancel;
 226         }
 227
 228         /*
 229          * Reserve disk quota : blocks and inode.
 230          */
 231         error = xfs_trans_reserve_quota(tp, mp, udqp, gdqp,
 232                                                 pdqp, resblks, 1, 0);
 233         if (error)
 234                 goto out_trans_cancel;
 235
 236         /*
 237          * Allocate an inode for the symlink.
 238          */
 239         error = xfs_dir_ialloc(&tp, dp, S_IFLNK | (mode & ~S_IFMT), 1, 0,
 240                                prid, &ip);
 241         if (error)
 242                 goto out_trans_cancel;
 243
 244         /*
 245          * Now we join the directory inode to the transaction.  We do not do it
 246          * earlier because xfs_dir_ialloc might commit the previous transaction
 247          * (and release all the locks).  An error from here on will result in
 248          * the transaction cancel unlocking dp so don't do it explicitly in the
 249          * error path.
 250          */
 251         xfs_trans_ijoin(tp, dp, XFS_ILOCK_EXCL);
 252         unlock_dp_on_error = false;
 253
 254         /*
 255          * Also attach the dquot(s) to it, if applicable.
 256          */
 257         xfs_qm_vop_create_dqattach(tp, ip, udqp, gdqp, pdqp);
 258
 259         if (resblks)
 260                 resblks -= XFS_IALLOC_SPACE_RES(mp);
 261         /*
 262          * If the symlink will fit into the inode, write it inline.
 263          */
 264         if (pathlen <= XFS_IFORK_DSIZE(ip)) {
 265                 xfs_init_local_fork(ip, XFS_DATA_FORK, target_path, pathlen);
 266
 267                 ip->i_d.di_size = pathlen;
 268                 ip->i_d.di_format = XFS_DINODE_FMT_LOCAL;
 269                 xfs_trans_log_inode(tp, ip, XFS_ILOG_DDATA | XFS_ILOG_CORE);
 270         } else {
 271                 int     offset;
 272
 273                 first_fsb = 0;
 274                 nmaps = XFS_SYMLINK_MAPS;
 275
 276                 error = xfs_bmapi_write(tp, ip, first_fsb, fs_blocks,
 277                                   XFS_BMAPI_METADATA, resblks, mval, &nmaps);
 278                 if (error)
 279                         goto out_trans_cancel;
 280
 281                 if (resblks)
 282                         resblks -= fs_blocks;
 283                 ip->i_d.di_size = pathlen;
 284                 xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 285
 286                 cur_chunk = target_path;
 287                 offset = 0;
 288                 for (n = 0; n < nmaps; n++) {
 289                         char    *buf;
 290
 291                         d = XFS_FSB_TO_DADDR(mp, mval[n].br_startblock);
 292                         byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
 293                         bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, d,
 294                                                BTOBB(byte_cnt), 0);
 295                         if (!bp) {
 296                                 error = -ENOMEM;
 297                                 goto out_trans_cancel;
 298                         }
 299                         bp->b_ops = &xfs_symlink_buf_ops;
 300
 301                         byte_cnt = XFS_SYMLINK_BUF_SPACE(mp, byte_cnt);
 302                         byte_cnt = min(byte_cnt, pathlen);
 303
 304                         buf = bp->b_addr;
 305                         buf += xfs_symlink_hdr_set(mp, ip->i_ino, offset,
 306                                                    byte_cnt, bp);
 307
 308                         memcpy(buf, cur_chunk, byte_cnt);
 309
 310                         cur_chunk += byte_cnt;
 311                         pathlen -= byte_cnt;
 312                         offset += byte_cnt;
 313
 314                         xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SYMLINK_BUF);
 315                         xfs_trans_log_buf(tp, bp, 0, (buf + byte_cnt - 1) -
 316                                                         (char *)bp->b_addr);
 317                 }
 318                 ASSERT(pathlen == 0);
 319         }
 320
 321         /*
 322          * Create the directory entry for the symlink.
 323          */
 324         error = xfs_dir_createname(tp, dp, link_name, ip->i_ino, resblks);
 325         if (error)
 326                 goto out_trans_cancel;
 327         xfs_trans_ichgtime(tp, dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
 328         xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);
 329
 330         /*
 331          * If this is a synchronous mount, make sure that the
 332          * symlink transaction goes to disk before returning to
 333          * the user.
 334          */
 335         if (mp->m_flags & (XFS_MOUNT_WSYNC|XFS_MOUNT_DIRSYNC)) {
 336                 xfs_trans_set_sync(tp);
 337         }
 338
 339         error = xfs_trans_commit(tp);
 340         if (error)
 341                 goto out_release_inode;
 342
 343         xfs_qm_dqrele(udqp);
 344         xfs_qm_dqrele(gdqp);
 345         xfs_qm_dqrele(pdqp);
 346
 347         *ipp = ip;
 348         return 0;
 349
 350 out_trans_cancel:
 351         xfs_trans_cancel(tp);
 352 out_release_inode:
 353         /*
 354          * Wait until after the current transaction is aborted to finish the
 355          * setup of the inode and release the inode.  This prevents recursive
 356          * transactions and deadlocks from xfs_inactive.
 357          */
 358         if (ip) {
 359                 xfs_finish_inode_setup(ip);
 360                 xfs_irele(ip);
 361         }
 362
 363         xfs_qm_dqrele(udqp);
 364         xfs_qm_dqrele(gdqp);
 365         xfs_qm_dqrele(pdqp);
 366
 367         if (unlock_dp_on_error)
 368                 xfs_iunlock(dp, XFS_ILOCK_EXCL);
 369         return error;
 370 }
 371
 372 /*
 373  * Free a symlink that has blocks associated with it.
 374  *
 375  * Note: zero length symlinks are not allowed to exist. When we set the size to
 376  * zero, also change it to a regular file so that it does not get written to
 377  * disk as a zero length symlink. The inode is on the unlinked list already, so
 378  * userspace cannot find this inode anymore, so this change is not user visible
 379  * but allows us to catch corrupt zero-length symlinks in the verifiers.
 380  */
 381 STATIC int
 382 xfs_inactive_symlink_rmt(
 383         struct xfs_inode *ip)
 384 {
 385         xfs_buf_t       *bp;
 386         int             done;
 387         int             error;
 388         int             i;
 389         xfs_mount_t     *mp;
 390         xfs_bmbt_irec_t mval[XFS_SYMLINK_MAPS];
 391         int             nmaps;
 392         int             size;
 393         xfs_trans_t     *tp;
 394
 395         mp = ip->i_mount;
 396         ASSERT(ip->i_df.if_flags & XFS_IFEXTENTS);
 397         /*
 398          * We're freeing a symlink that has some
 399          * blocks allocated to it.  Free the
 400          * blocks here.  We know that we've got
 401          * either 1 or 2 extents and that we can
 402          * free them all in one bunmapi call.
 403          */
 404         ASSERT(ip->i_d.di_nextents > 0 && ip->i_d.di_nextents <= 2);
 405
 406         error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp);
 407         if (error)
 408                 return error;
 409
 410         xfs_ilock(ip, XFS_ILOCK_EXCL);
 411         xfs_trans_ijoin(tp, ip, 0);
 412
 413         /*
 414          * Lock the inode, fix the size, turn it into a regular file and join it
 415          * to the transaction.  Hold it so in the normal path, we still have it
 416          * locked for the second transaction.  In the error paths we need it
 417          * held so the cancel won't rele it, see below.
 418          */
 419         size = (int)ip->i_d.di_size;
 420         ip->i_d.di_size = 0;
 421         VFS_I(ip)->i_mode = (VFS_I(ip)->i_mode & ~S_IFMT) | S_IFREG;
 422         xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 423         /*
 424          * Find the block(s) so we can inval and unmap them.
 425          */
 426         done = 0;
 427         nmaps = ARRAY_SIZE(mval);
 428         error = xfs_bmapi_read(ip, 0, xfs_symlink_blocks(mp, size),
 429                                 mval, &nmaps, 0);
 430         if (error)
 431                 goto error_trans_cancel;
 432         /*
 433          * Invalidate the block(s). No validation is done.
 434          */
 435         for (i = 0; i < nmaps; i++) {
 436                 bp = xfs_trans_get_buf(tp, mp->m_ddev_targp,
 437                         XFS_FSB_TO_DADDR(mp, mval[i].br_startblock),
 438                         XFS_FSB_TO_BB(mp, mval[i].br_blockcount), 0);
 439                 if (!bp) {
 440                         error = -ENOMEM;
 441                         goto error_trans_cancel;
 442                 }
 443                 xfs_trans_binval(tp, bp);
 444         }
 445         /*
 446          * Unmap the dead block(s) to the dfops.
 447          */
 448         error = xfs_bunmapi(tp, ip, 0, size, 0, nmaps, &done);
 449         if (error)
 450                 goto error_trans_cancel;
 451         ASSERT(done);
 452
 453         /*
 454          * Commit the transaction. This first logs the EFI and the inode, then
 455          * rolls and commits the transaction that frees the extents.
 456          */
 457         xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 458         error = xfs_trans_commit(tp);
 459         if (error) {
 460                 ASSERT(XFS_FORCED_SHUTDOWN(mp));
 461                 goto error_unlock;
 462         }
 463
 464         /*
 465          * Remove the memory for extent descriptions (just bookkeeping).
 466          */
 467         if (ip->i_df.if_bytes)
 468                 xfs_idata_realloc(ip, -ip->i_df.if_bytes, XFS_DATA_FORK);
 469         ASSERT(ip->i_df.if_bytes == 0);
 470
 471         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 472         return 0;
 473
 474 error_trans_cancel:
 475         xfs_trans_cancel(tp);
 476 error_unlock:
 477         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 478         return error;
 479 }
 480
 481 /*
 482  * xfs_inactive_symlink - free a symlink
 483  */
 484 int
 485 xfs_inactive_symlink(
 486         struct xfs_inode        *ip)
 487 {
 488         struct xfs_mount        *mp = ip->i_mount;
 489         int                     pathlen;
 490
 491         trace_xfs_inactive_symlink(ip);
 492
 493         if (XFS_FORCED_SHUTDOWN(mp))
 494                 return -EIO;
 495
 496         xfs_ilock(ip, XFS_ILOCK_EXCL);
 497         pathlen = (int)ip->i_d.di_size;
 498         ASSERT(pathlen);
 499
 500         if (pathlen <= 0 || pathlen > XFS_SYMLINK_MAXLEN) {
 501                 xfs_alert(mp, "%s: inode (0x%llx) bad symlink length (%d)",
 502                          __func__, (unsigned long long)ip->i_ino, pathlen);
 503                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
 504                 ASSERT(0);
 505                 return -EFSCORRUPTED;
 506         }
 507
 508         /*
 509          * Inline fork state gets removed by xfs_difree() so we have nothing to
 510          * do here in that case.
 511          */
 512         if (ip->i_df.if_flags & XFS_IFINLINE) {
 513                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
 514                 return 0;
 515         }
 516
 517         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 518
 519         /* remove the remote symlink */
 520         return xfs_inactive_symlink_rmt(ip);
 521 }