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