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                 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_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 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, current_fsuid(), current_fsgid(), prid,
 186                         XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT,
 187                         &udqp, &gdqp, &pdqp);
 188         if (error)
 189                 return error;
 190
 191         /*
 192          * The symlink will fit into the inode data fork?
 193          * There can't be any attributes so we get the whole variable part.
 194          */
 195         if (pathlen <= XFS_LITINO(mp))
 196                 fs_blocks = 0;
 197         else
 198                 fs_blocks = xfs_symlink_blocks(mp, pathlen);
 199         resblks = XFS_SYMLINK_SPACE_RES(mp, link_name->len, fs_blocks);
 200
 201         error = xfs_trans_alloc_icreate(mp, &M_RES(mp)->tr_symlink, udqp, gdqp,
 202                         pdqp, resblks, &tp);
 203         if (error)
 204                 goto out_release_dquots;
 205
 206         xfs_ilock(dp, XFS_ILOCK_EXCL | XFS_ILOCK_PARENT);
 207         unlock_dp_on_error = true;
 208
 209         /*
 210          * Check whether the directory allows new symlinks or not.
 211          */
 212         if (dp->i_d.di_flags & XFS_DIFLAG_NOSYMLINKS) {
 213                 error = -EPERM;
 214                 goto out_trans_cancel;
 215         }
 216
 217         error = xfs_iext_count_may_overflow(dp, XFS_DATA_FORK,
 218                         XFS_IEXT_DIR_MANIP_CNT(mp));
 219         if (error)
 220                 goto out_trans_cancel;
 221
 222         /*
 223          * Allocate an inode for the symlink.
 224          */
 225         error = xfs_dir_ialloc(mnt_userns, &tp, dp, S_IFLNK | (mode & ~S_IFMT),
 226                                1, 0, prid, &ip);
 227         if (error)
 228                 goto out_trans_cancel;
 229
 230         /*
 231          * Now we join the directory inode to the transaction.  We do not do it
 232          * earlier because xfs_dir_ialloc might commit the previous transaction
 233          * (and release all the locks).  An error from here on will result in
 234          * the transaction cancel unlocking dp so don't do it explicitly in the
 235          * error path.
 236          */
 237         xfs_trans_ijoin(tp, dp, XFS_ILOCK_EXCL);
 238         unlock_dp_on_error = false;
 239
 240         /*
 241          * Also attach the dquot(s) to it, if applicable.
 242          */
 243         xfs_qm_vop_create_dqattach(tp, ip, udqp, gdqp, pdqp);
 244
 245         resblks -= XFS_IALLOC_SPACE_RES(mp);
 246         /*
 247          * If the symlink will fit into the inode, write it inline.
 248          */
 249         if (pathlen <= XFS_IFORK_DSIZE(ip)) {
 250                 xfs_init_local_fork(ip, XFS_DATA_FORK, target_path, pathlen);
 251
 252                 ip->i_d.di_size = pathlen;
 253                 ip->i_df.if_format = XFS_DINODE_FMT_LOCAL;
 254                 xfs_trans_log_inode(tp, ip, XFS_ILOG_DDATA | XFS_ILOG_CORE);
 255         } else {
 256                 int     offset;
 257
 258                 first_fsb = 0;
 259                 nmaps = XFS_SYMLINK_MAPS;
 260
 261                 error = xfs_bmapi_write(tp, ip, first_fsb, fs_blocks,
 262                                   XFS_BMAPI_METADATA, resblks, mval, &nmaps);
 263                 if (error)
 264                         goto out_trans_cancel;
 265
 266                 resblks -= fs_blocks;
 267                 ip->i_d.di_size = pathlen;
 268                 xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 269
 270                 cur_chunk = target_path;
 271                 offset = 0;
 272                 for (n = 0; n < nmaps; n++) {
 273                         char    *buf;
 274
 275                         d = XFS_FSB_TO_DADDR(mp, mval[n].br_startblock);
 276                         byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
 277                         error = xfs_trans_get_buf(tp, mp->m_ddev_targp, d,
 278                                                BTOBB(byte_cnt), 0, &bp);
 279                         if (error)
 280                                 goto out_trans_cancel;
 281                         bp->b_ops = &xfs_symlink_buf_ops;
 282
 283                         byte_cnt = XFS_SYMLINK_BUF_SPACE(mp, byte_cnt);
 284                         byte_cnt = min(byte_cnt, pathlen);
 285
 286                         buf = bp->b_addr;
 287                         buf += xfs_symlink_hdr_set(mp, ip->i_ino, offset,
 288                                                    byte_cnt, bp);
 289
 290                         memcpy(buf, cur_chunk, byte_cnt);
 291
 292                         cur_chunk += byte_cnt;
 293                         pathlen -= byte_cnt;
 294                         offset += byte_cnt;
 295
 296                         xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SYMLINK_BUF);
 297                         xfs_trans_log_buf(tp, bp, 0, (buf + byte_cnt - 1) -
 298                                                         (char *)bp->b_addr);
 299                 }
 300                 ASSERT(pathlen == 0);
 301         }
 302         i_size_write(VFS_I(ip), ip->i_d.di_size);
 303
 304         /*
 305          * Create the directory entry for the symlink.
 306          */
 307         error = xfs_dir_createname(tp, dp, link_name, ip->i_ino, resblks);
 308         if (error)
 309                 goto out_trans_cancel;
 310         xfs_trans_ichgtime(tp, dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
 311         xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);
 312
 313         /*
 314          * If this is a synchronous mount, make sure that the
 315          * symlink transaction goes to disk before returning to
 316          * the user.
 317          */
 318         if (mp->m_flags & (XFS_MOUNT_WSYNC|XFS_MOUNT_DIRSYNC)) {
 319                 xfs_trans_set_sync(tp);
 320         }
 321
 322         error = xfs_trans_commit(tp);
 323         if (error)
 324                 goto out_release_inode;
 325
 326         xfs_qm_dqrele(udqp);
 327         xfs_qm_dqrele(gdqp);
 328         xfs_qm_dqrele(pdqp);
 329
 330         *ipp = ip;
 331         return 0;
 332
 333 out_trans_cancel:
 334         xfs_trans_cancel(tp);
 335 out_release_inode:
 336         /*
 337          * Wait until after the current transaction is aborted to finish the
 338          * setup of the inode and release the inode.  This prevents recursive
 339          * transactions and deadlocks from xfs_inactive.
 340          */
 341         if (ip) {
 342                 xfs_finish_inode_setup(ip);
 343                 xfs_irele(ip);
 344         }
 345 out_release_dquots:
 346         xfs_qm_dqrele(udqp);
 347         xfs_qm_dqrele(gdqp);
 348         xfs_qm_dqrele(pdqp);
 349
 350         if (unlock_dp_on_error)
 351                 xfs_iunlock(dp, XFS_ILOCK_EXCL);
 352         return error;
 353 }
 354
 355 /*
 356  * Free a symlink that has blocks associated with it.
 357  *
 358  * Note: zero length symlinks are not allowed to exist. When we set the size to
 359  * zero, also change it to a regular file so that it does not get written to
 360  * disk as a zero length symlink. The inode is on the unlinked list already, so
 361  * userspace cannot find this inode anymore, so this change is not user visible
 362  * but allows us to catch corrupt zero-length symlinks in the verifiers.
 363  */
 364 STATIC int
 365 xfs_inactive_symlink_rmt(
 366         struct xfs_inode *ip)
 367 {
 368         struct xfs_buf  *bp;
 369         int             done;
 370         int             error;
 371         int             i;
 372         xfs_mount_t     *mp;
 373         xfs_bmbt_irec_t mval[XFS_SYMLINK_MAPS];
 374         int             nmaps;
 375         int             size;
 376         xfs_trans_t     *tp;
 377
 378         mp = ip->i_mount;
 379         ASSERT(ip->i_df.if_flags & XFS_IFEXTENTS);
 380         /*
 381          * We're freeing a symlink that has some
 382          * blocks allocated to it.  Free the
 383          * blocks here.  We know that we've got
 384          * either 1 or 2 extents and that we can
 385          * free them all in one bunmapi call.
 386          */
 387         ASSERT(ip->i_df.if_nextents > 0 && ip->i_df.if_nextents <= 2);
 388
 389         error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp);
 390         if (error)
 391                 return error;
 392
 393         xfs_ilock(ip, XFS_ILOCK_EXCL);
 394         xfs_trans_ijoin(tp, ip, 0);
 395
 396         /*
 397          * Lock the inode, fix the size, turn it into a regular file and join it
 398          * to the transaction.  Hold it so in the normal path, we still have it
 399          * locked for the second transaction.  In the error paths we need it
 400          * held so the cancel won't rele it, see below.
 401          */
 402         size = (int)ip->i_d.di_size;
 403         ip->i_d.di_size = 0;
 404         VFS_I(ip)->i_mode = (VFS_I(ip)->i_mode & ~S_IFMT) | S_IFREG;
 405         xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 406         /*
 407          * Find the block(s) so we can inval and unmap them.
 408          */
 409         done = 0;
 410         nmaps = ARRAY_SIZE(mval);
 411         error = xfs_bmapi_read(ip, 0, xfs_symlink_blocks(mp, size),
 412                                 mval, &nmaps, 0);
 413         if (error)
 414                 goto error_trans_cancel;
 415         /*
 416          * Invalidate the block(s). No validation is done.
 417          */
 418         for (i = 0; i < nmaps; i++) {
 419                 error = xfs_trans_get_buf(tp, mp->m_ddev_targp,
 420                                 XFS_FSB_TO_DADDR(mp, mval[i].br_startblock),
 421                                 XFS_FSB_TO_BB(mp, mval[i].br_blockcount), 0,
 422                                 &bp);
 423                 if (error)
 424                         goto error_trans_cancel;
 425                 xfs_trans_binval(tp, bp);
 426         }
 427         /*
 428          * Unmap the dead block(s) to the dfops.
 429          */
 430         error = xfs_bunmapi(tp, ip, 0, size, 0, nmaps, &done);
 431         if (error)
 432                 goto error_trans_cancel;
 433         ASSERT(done);
 434
 435         /*
 436          * Commit the transaction. This first logs the EFI and the inode, then
 437          * rolls and commits the transaction that frees the extents.
 438          */
 439         xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 440         error = xfs_trans_commit(tp);
 441         if (error) {
 442                 ASSERT(XFS_FORCED_SHUTDOWN(mp));
 443                 goto error_unlock;
 444         }
 445
 446         /*
 447          * Remove the memory for extent descriptions (just bookkeeping).
 448          */
 449         if (ip->i_df.if_bytes)
 450                 xfs_idata_realloc(ip, -ip->i_df.if_bytes, XFS_DATA_FORK);
 451         ASSERT(ip->i_df.if_bytes == 0);
 452
 453         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 454         return 0;
 455
 456 error_trans_cancel:
 457         xfs_trans_cancel(tp);
 458 error_unlock:
 459         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 460         return error;
 461 }
 462
 463 /*
 464  * xfs_inactive_symlink - free a symlink
 465  */
 466 int
 467 xfs_inactive_symlink(
 468         struct xfs_inode        *ip)
 469 {
 470         struct xfs_mount        *mp = ip->i_mount;
 471         int                     pathlen;
 472
 473         trace_xfs_inactive_symlink(ip);
 474
 475         if (XFS_FORCED_SHUTDOWN(mp))
 476                 return -EIO;
 477
 478         xfs_ilock(ip, XFS_ILOCK_EXCL);
 479         pathlen = (int)ip->i_d.di_size;
 480         ASSERT(pathlen);
 481
 482         if (pathlen <= 0 || pathlen > XFS_SYMLINK_MAXLEN) {
 483                 xfs_alert(mp, "%s: inode (0x%llx) bad symlink length (%d)",
 484                          __func__, (unsigned long long)ip->i_ino, pathlen);
 485                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
 486                 ASSERT(0);
 487                 return -EFSCORRUPTED;
 488         }
 489
 490         /*
 491          * Inline fork state gets removed by xfs_difree() so we have nothing to
 492          * do here in that case.
 493          */
 494         if (ip->i_df.if_flags & XFS_IFINLINE) {
 495                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
 496                 return 0;
 497         }
 498
 499         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 500
 501         /* remove the remote symlink */
 502         return xfs_inactive_symlink_rmt(ip);
 503 }