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