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_da_format.h"
  16 #include "xfs_da_btree.h"
  17 #include "xfs_defer.h"
  18 #include "xfs_dir2.h"
  19 #include "xfs_inode.h"
  20 #include "xfs_ialloc.h"
  21 #include "xfs_alloc.h"
  22 #include "xfs_bmap.h"
  23 #include "xfs_bmap_btree.h"
  24 #include "xfs_bmap_util.h"
  25 #include "xfs_error.h"
  26 #include "xfs_quota.h"
  27 #include "xfs_trans_space.h"
  28 #include "xfs_trace.h"
  29 #include "xfs_symlink.h"
  30 #include "xfs_trans.h"
  31 #include "xfs_log.h"
  32
  33 /* ----- Kernel only functions below ----- */
  34 int
  35 xfs_readlink_bmap_ilocked(
  36         struct xfs_inode        *ip,
  37         char                    *link)
  38 {
  39         struct xfs_mount        *mp = ip->i_mount;
  40         struct xfs_bmbt_irec    mval[XFS_SYMLINK_MAPS];
  41         struct xfs_buf          *bp;
  42         xfs_daddr_t             d;
  43         char                    *cur_chunk;
  44         int                     pathlen = ip->i_d.di_size;
  45         int                     nmaps = XFS_SYMLINK_MAPS;
  46         int                     byte_cnt;
  47         int                     n;
  48         int                     error = 0;
  49         int                     fsblocks = 0;
  50         int                     offset;
  51
  52         ASSERT(xfs_isilocked(ip, XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
  53
  54         fsblocks = xfs_symlink_blocks(mp, pathlen);
  55         error = xfs_bmapi_read(ip, 0, fsblocks, mval, &nmaps, 0);
  56         if (error)
  57                 goto out;
  58
  59         offset = 0;
  60         for (n = 0; n < nmaps; n++) {
  61                 d = XFS_FSB_TO_DADDR(mp, mval[n].br_startblock);
  62                 byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
  63
  64                 bp = xfs_buf_read(mp->m_ddev_targp, d, BTOBB(byte_cnt), 0,
  65                                   &xfs_symlink_buf_ops);
  66                 if (!bp)
  67                         return -ENOMEM;
  68                 error = bp->b_error;
  69                 if (error) {
  70                         xfs_buf_ioerror_alert(bp, __func__);
  71                         xfs_buf_relse(bp);
  72
  73                         /* bad CRC means corrupted metadata */
  74                         if (error == -EFSBADCRC)
  75                                 error = -EFSCORRUPTED;
  76                         goto out;
  77                 }
  78                 byte_cnt = XFS_SYMLINK_BUF_SPACE(mp, byte_cnt);
  79                 if (pathlen < byte_cnt)
  80                         byte_cnt = pathlen;
  81
  82                 cur_chunk = bp->b_addr;
  83                 if (xfs_sb_version_hascrc(&mp->m_sb)) {
  84                         if (!xfs_symlink_hdr_ok(ip->i_ino, offset,
  85                                                         byte_cnt, bp)) {
  86                                 error = -EFSCORRUPTED;
  87                                 xfs_alert(mp,
  88 "symlink header does not match required off/len/owner (0x%x/Ox%x,0x%llx)",
  89                                         offset, byte_cnt, ip->i_ino);
  90                                 xfs_buf_relse(bp);
  91                                 goto out;
  92
  93                         }
  94
  95                         cur_chunk += sizeof(struct xfs_dsymlink_hdr);
  96                 }
  97
  98                 memcpy(link + offset, cur_chunk, byte_cnt);
  99
 100                 pathlen -= byte_cnt;
 101                 offset += byte_cnt;
 102
 103                 xfs_buf_relse(bp);
 104         }
 105         ASSERT(pathlen == 0);
 106
 107         link[ip->i_d.di_size] = '\0';
 108         error = 0;
 109
 110  out:
 111         return error;
 112 }
 113
 114 int
 115 xfs_readlink(
 116         struct xfs_inode *ip,
 117         char            *link)
 118 {
 119         struct xfs_mount *mp = ip->i_mount;
 120         xfs_fsize_t     pathlen;
 121         int             error = 0;
 122
 123         trace_xfs_readlink(ip);
 124
 125         ASSERT(!(ip->i_df.if_flags & XFS_IFINLINE));
 126
 127         if (XFS_FORCED_SHUTDOWN(mp))
 128                 return -EIO;
 129
 130         xfs_ilock(ip, XFS_ILOCK_SHARED);
 131
 132         pathlen = ip->i_d.di_size;
 133         if (!pathlen)
 134                 goto out;
 135
 136         if (pathlen < 0 || pathlen > XFS_SYMLINK_MAXLEN) {
 137                 xfs_alert(mp, "%s: inode (%llu) bad symlink length (%lld)",
 138                          __func__, (unsigned long long) ip->i_ino,
 139                          (long long) pathlen);
 140                 ASSERT(0);
 141                 error = -EFSCORRUPTED;
 142                 goto out;
 143         }
 144
 145
 146         error = xfs_readlink_bmap_ilocked(ip, link);
 147
 148  out:
 149         xfs_iunlock(ip, XFS_ILOCK_SHARED);
 150         return error;
 151 }
 152
 153 int
 154 xfs_symlink(
 155         struct xfs_inode        *dp,
 156         struct xfs_name         *link_name,
 157         const char              *target_path,
 158         umode_t                 mode,
 159         struct xfs_inode        **ipp)
 160 {
 161         struct xfs_mount        *mp = dp->i_mount;
 162         struct xfs_trans        *tp = NULL;
 163         struct xfs_inode        *ip = NULL;
 164         int                     error = 0;
 165         int                     pathlen;
 166         bool                    unlock_dp_on_error = false;
 167         xfs_fileoff_t           first_fsb;
 168         xfs_filblks_t           fs_blocks;
 169         int                     nmaps;
 170         struct xfs_bmbt_irec    mval[XFS_SYMLINK_MAPS];
 171         xfs_daddr_t             d;
 172         const char              *cur_chunk;
 173         int                     byte_cnt;
 174         int                     n;
 175         xfs_buf_t               *bp;
 176         prid_t                  prid;
 177         struct xfs_dquot        *udqp = NULL;
 178         struct xfs_dquot        *gdqp = NULL;
 179         struct xfs_dquot        *pdqp = NULL;
 180         uint                    resblks;
 181
 182         *ipp = NULL;
 183
 184         trace_xfs_symlink(dp, link_name);
 185
 186         if (XFS_FORCED_SHUTDOWN(mp))
 187                 return -EIO;
 188
 189         /*
 190          * Check component lengths of the target path name.
 191          */
 192         pathlen = strlen(target_path);
 193         if (pathlen >= XFS_SYMLINK_MAXLEN)      /* total string too long */
 194                 return -ENAMETOOLONG;
 195         ASSERT(pathlen > 0);
 196
 197         udqp = gdqp = NULL;
 198         prid = xfs_get_initial_prid(dp);
 199
 200         /*
 201          * Make sure that we have allocated dquot(s) on disk.
 202          */
 203         error = xfs_qm_vop_dqalloc(dp,
 204                         xfs_kuid_to_uid(current_fsuid()),
 205                         xfs_kgid_to_gid(current_fsgid()), prid,
 206                         XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT,
 207                         &udqp, &gdqp, &pdqp);
 208         if (error)
 209                 return error;
 210
 211         /*
 212          * The symlink will fit into the inode data fork?
 213          * There can't be any attributes so we get the whole variable part.
 214          */
 215         if (pathlen <= XFS_LITINO(mp, dp->i_d.di_version))
 216                 fs_blocks = 0;
 217         else
 218                 fs_blocks = xfs_symlink_blocks(mp, pathlen);
 219         resblks = XFS_SYMLINK_SPACE_RES(mp, link_name->len, fs_blocks);
 220
 221         error = xfs_trans_alloc(mp, &M_RES(mp)->tr_symlink, resblks, 0, 0, &tp);
 222         if (error)
 223                 goto out_release_inode;
 224
 225         xfs_ilock(dp, XFS_ILOCK_EXCL | XFS_ILOCK_PARENT);
 226         unlock_dp_on_error = true;
 227
 228         /*
 229          * Check whether the directory allows new symlinks or not.
 230          */
 231         if (dp->i_d.di_flags & XFS_DIFLAG_NOSYMLINKS) {
 232                 error = -EPERM;
 233                 goto out_trans_cancel;
 234         }
 235
 236         /*
 237          * Reserve disk quota : blocks and inode.
 238          */
 239         error = xfs_trans_reserve_quota(tp, mp, udqp, gdqp,
 240                                                 pdqp, resblks, 1, 0);
 241         if (error)
 242                 goto out_trans_cancel;
 243
 244         /*
 245          * Allocate an inode for the symlink.
 246          */
 247         error = xfs_dir_ialloc(&tp, dp, S_IFLNK | (mode & ~S_IFMT), 1, 0,
 248                                prid, &ip);
 249         if (error)
 250                 goto out_trans_cancel;
 251
 252         /*
 253          * Now we join the directory inode to the transaction.  We do not do it
 254          * earlier because xfs_dir_ialloc might commit the previous transaction
 255          * (and release all the locks).  An error from here on will result in
 256          * the transaction cancel unlocking dp so don't do it explicitly in the
 257          * error path.
 258          */
 259         xfs_trans_ijoin(tp, dp, XFS_ILOCK_EXCL);
 260         unlock_dp_on_error = false;
 261
 262         /*
 263          * Also attach the dquot(s) to it, if applicable.
 264          */
 265         xfs_qm_vop_create_dqattach(tp, ip, udqp, gdqp, pdqp);
 266
 267         if (resblks)
 268                 resblks -= XFS_IALLOC_SPACE_RES(mp);
 269         /*
 270          * If the symlink will fit into the inode, write it inline.
 271          */
 272         if (pathlen <= XFS_IFORK_DSIZE(ip)) {
 273                 xfs_init_local_fork(ip, XFS_DATA_FORK, target_path, pathlen);
 274
 275                 ip->i_d.di_size = pathlen;
 276                 ip->i_d.di_format = XFS_DINODE_FMT_LOCAL;
 277                 xfs_trans_log_inode(tp, ip, XFS_ILOG_DDATA | XFS_ILOG_CORE);
 278         } else {
 279                 int     offset;
 280
 281                 first_fsb = 0;
 282                 nmaps = XFS_SYMLINK_MAPS;
 283
 284                 error = xfs_bmapi_write(tp, ip, first_fsb, fs_blocks,
 285                                   XFS_BMAPI_METADATA, resblks, mval, &nmaps);
 286                 if (error)
 287                         goto out_trans_cancel;
 288
 289                 if (resblks)
 290                         resblks -= fs_blocks;
 291                 ip->i_d.di_size = pathlen;
 292                 xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 293
 294                 cur_chunk = target_path;
 295                 offset = 0;
 296                 for (n = 0; n < nmaps; n++) {
 297                         char    *buf;
 298
 299                         d = XFS_FSB_TO_DADDR(mp, mval[n].br_startblock);
 300                         byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
 301                         bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, d,
 302                                                BTOBB(byte_cnt), 0);
 303                         if (!bp) {
 304                                 error = -ENOMEM;
 305                                 goto out_trans_cancel;
 306                         }
 307                         bp->b_ops = &xfs_symlink_buf_ops;
 308
 309                         byte_cnt = XFS_SYMLINK_BUF_SPACE(mp, byte_cnt);
 310                         byte_cnt = min(byte_cnt, pathlen);
 311
 312                         buf = bp->b_addr;
 313                         buf += xfs_symlink_hdr_set(mp, ip->i_ino, offset,
 314                                                    byte_cnt, bp);
 315
 316                         memcpy(buf, cur_chunk, byte_cnt);
 317
 318                         cur_chunk += byte_cnt;
 319                         pathlen -= byte_cnt;
 320                         offset += byte_cnt;
 321
 322                         xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SYMLINK_BUF);
 323                         xfs_trans_log_buf(tp, bp, 0, (buf + byte_cnt - 1) -
 324                                                         (char *)bp->b_addr);
 325                 }
 326                 ASSERT(pathlen == 0);
 327         }
 328
 329         /*
 330          * Create the directory entry for the symlink.
 331          */
 332         error = xfs_dir_createname(tp, dp, link_name, ip->i_ino, resblks);
 333         if (error)
 334                 goto out_trans_cancel;
 335         xfs_trans_ichgtime(tp, dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
 336         xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);
 337
 338         /*
 339          * If this is a synchronous mount, make sure that the
 340          * symlink transaction goes to disk before returning to
 341          * the user.
 342          */
 343         if (mp->m_flags & (XFS_MOUNT_WSYNC|XFS_MOUNT_DIRSYNC)) {
 344                 xfs_trans_set_sync(tp);
 345         }
 346
 347         error = xfs_trans_commit(tp);
 348         if (error)
 349                 goto out_release_inode;
 350
 351         xfs_qm_dqrele(udqp);
 352         xfs_qm_dqrele(gdqp);
 353         xfs_qm_dqrele(pdqp);
 354
 355         *ipp = ip;
 356         return 0;
 357
 358 out_trans_cancel:
 359         xfs_trans_cancel(tp);
 360 out_release_inode:
 361         /*
 362          * Wait until after the current transaction is aborted to finish the
 363          * setup of the inode and release the inode.  This prevents recursive
 364          * transactions and deadlocks from xfs_inactive.
 365          */
 366         if (ip) {
 367                 xfs_finish_inode_setup(ip);
 368                 xfs_irele(ip);
 369         }
 370
 371         xfs_qm_dqrele(udqp);
 372         xfs_qm_dqrele(gdqp);
 373         xfs_qm_dqrele(pdqp);
 374
 375         if (unlock_dp_on_error)
 376                 xfs_iunlock(dp, XFS_ILOCK_EXCL);
 377         return error;
 378 }
 379
 380 /*
 381  * Free a symlink that has blocks associated with it.
 382  *
 383  * Note: zero length symlinks are not allowed to exist. When we set the size to
 384  * zero, also change it to a regular file so that it does not get written to
 385  * disk as a zero length symlink. The inode is on the unlinked list already, so
 386  * userspace cannot find this inode anymore, so this change is not user visible
 387  * but allows us to catch corrupt zero-length symlinks in the verifiers.
 388  */
 389 STATIC int
 390 xfs_inactive_symlink_rmt(
 391         struct xfs_inode *ip)
 392 {
 393         xfs_buf_t       *bp;
 394         int             done;
 395         int             error;
 396         int             i;
 397         xfs_mount_t     *mp;
 398         xfs_bmbt_irec_t mval[XFS_SYMLINK_MAPS];
 399         int             nmaps;
 400         int             size;
 401         xfs_trans_t     *tp;
 402
 403         mp = ip->i_mount;
 404         ASSERT(ip->i_df.if_flags & XFS_IFEXTENTS);
 405         /*
 406          * We're freeing a symlink that has some
 407          * blocks allocated to it.  Free the
 408          * blocks here.  We know that we've got
 409          * either 1 or 2 extents and that we can
 410          * free them all in one bunmapi call.
 411          */
 412         ASSERT(ip->i_d.di_nextents > 0 && ip->i_d.di_nextents <= 2);
 413
 414         error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp);
 415         if (error)
 416                 return error;
 417
 418         xfs_ilock(ip, XFS_ILOCK_EXCL);
 419         xfs_trans_ijoin(tp, ip, 0);
 420
 421         /*
 422          * Lock the inode, fix the size, turn it into a regular file and join it
 423          * to the transaction.  Hold it so in the normal path, we still have it
 424          * locked for the second transaction.  In the error paths we need it
 425          * held so the cancel won't rele it, see below.
 426          */
 427         size = (int)ip->i_d.di_size;
 428         ip->i_d.di_size = 0;
 429         VFS_I(ip)->i_mode = (VFS_I(ip)->i_mode & ~S_IFMT) | S_IFREG;
 430         xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 431         /*
 432          * Find the block(s) so we can inval and unmap them.
 433          */
 434         done = 0;
 435         nmaps = ARRAY_SIZE(mval);
 436         error = xfs_bmapi_read(ip, 0, xfs_symlink_blocks(mp, size),
 437                                 mval, &nmaps, 0);
 438         if (error)
 439                 goto error_trans_cancel;
 440         /*
 441          * Invalidate the block(s). No validation is done.
 442          */
 443         for (i = 0; i < nmaps; i++) {
 444                 bp = xfs_trans_get_buf(tp, mp->m_ddev_targp,
 445                         XFS_FSB_TO_DADDR(mp, mval[i].br_startblock),
 446                         XFS_FSB_TO_BB(mp, mval[i].br_blockcount), 0);
 447                 if (!bp) {
 448                         error = -ENOMEM;
 449                         goto error_trans_cancel;
 450                 }
 451                 xfs_trans_binval(tp, bp);
 452         }
 453         /*
 454          * Unmap the dead block(s) to the dfops.
 455          */
 456         error = xfs_bunmapi(tp, ip, 0, size, 0, nmaps, &done);
 457         if (error)
 458                 goto error_trans_cancel;
 459         ASSERT(done);
 460
 461         /*
 462          * Commit the transaction. This first logs the EFI and the inode, then
 463          * rolls and commits the transaction that frees the extents.
 464          */
 465         xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 466         error = xfs_trans_commit(tp);
 467         if (error) {
 468                 ASSERT(XFS_FORCED_SHUTDOWN(mp));
 469                 goto error_unlock;
 470         }
 471
 472         /*
 473          * Remove the memory for extent descriptions (just bookkeeping).
 474          */
 475         if (ip->i_df.if_bytes)
 476                 xfs_idata_realloc(ip, -ip->i_df.if_bytes, XFS_DATA_FORK);
 477         ASSERT(ip->i_df.if_bytes == 0);
 478
 479         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 480         return 0;
 481
 482 error_trans_cancel:
 483         xfs_trans_cancel(tp);
 484 error_unlock:
 485         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 486         return error;
 487 }
 488
 489 /*
 490  * xfs_inactive_symlink - free a symlink
 491  */
 492 int
 493 xfs_inactive_symlink(
 494         struct xfs_inode        *ip)
 495 {
 496         struct xfs_mount        *mp = ip->i_mount;
 497         int                     pathlen;
 498
 499         trace_xfs_inactive_symlink(ip);
 500
 501         if (XFS_FORCED_SHUTDOWN(mp))
 502                 return -EIO;
 503
 504         xfs_ilock(ip, XFS_ILOCK_EXCL);
 505         pathlen = (int)ip->i_d.di_size;
 506         ASSERT(pathlen);
 507
 508         if (pathlen <= 0 || pathlen > XFS_SYMLINK_MAXLEN) {
 509                 xfs_alert(mp, "%s: inode (0x%llx) bad symlink length (%d)",
 510                          __func__, (unsigned long long)ip->i_ino, pathlen);
 511                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
 512                 ASSERT(0);
 513                 return -EFSCORRUPTED;
 514         }
 515
 516         /*
 517          * Inline fork state gets removed by xfs_difree() so we have nothing to
 518          * do here in that case.
 519          */
 520         if (ip->i_df.if_flags & XFS_IFINLINE) {
 521                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
 522                 return 0;
 523         }
 524
 525         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 526
 527         /* remove the remote symlink */
 528         return xfs_inactive_symlink_rmt(ip);
 529 }