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