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