fs/namei.c

   1 /*
   2  *  linux/fs/namei.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  * Some corrections by tytso.
   9  */
  10
  11 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
  12  * lookup logic.
  13  */
  14 /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
  15  */
  16
  17 #include <linux/init.h>
  18 #include <linux/module.h>
  19 #include <linux/slab.h>
  20 #include <linux/fs.h>
  21 #include <linux/namei.h>
  22 #include <linux/quotaops.h>
  23 #include <linux/pagemap.h>
  24 #include <linux/dnotify.h>
  25 #include <linux/smp_lock.h>
  26 #include <linux/personality.h>
  27 #include <linux/security.h>
  28 #include <linux/syscalls.h>
  29 #include <linux/mount.h>
  30 #include <linux/audit.h>
  31 #include <asm/namei.h>
  32 #include <asm/uaccess.h>
  33
  34 #define ACC_MODE(x) ("\000\004\002\006"[(x)&O_ACCMODE])
  35
  36 /* [Feb-1997 T. Schoebel-Theuer]
  37  * Fundamental changes in the pathname lookup mechanisms (namei)
  38  * were necessary because of omirr.  The reason is that omirr needs
  39  * to know the _real_ pathname, not the user-supplied one, in case
  40  * of symlinks (and also when transname replacements occur).
  41  *
  42  * The new code replaces the old recursive symlink resolution with
  43  * an iterative one (in case of non-nested symlink chains).  It does
  44  * this with calls to <fs>_follow_link().
  45  * As a side effect, dir_namei(), _namei() and follow_link() are now
  46  * replaced with a single function lookup_dentry() that can handle all
  47  * the special cases of the former code.
  48  *
  49  * With the new dcache, the pathname is stored at each inode, at least as
  50  * long as the refcount of the inode is positive.  As a side effect, the
  51  * size of the dcache depends on the inode cache and thus is dynamic.
  52  *
  53  * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
  54  * resolution to correspond with current state of the code.
  55  *
  56  * Note that the symlink resolution is not *completely* iterative.
  57  * There is still a significant amount of tail- and mid- recursion in
  58  * the algorithm.  Also, note that <fs>_readlink() is not used in
  59  * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
  60  * may return different results than <fs>_follow_link().  Many virtual
  61  * filesystems (including /proc) exhibit this behavior.
  62  */
  63
  64 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
  65  * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
  66  * and the name already exists in form of a symlink, try to create the new
  67  * name indicated by the symlink. The old code always complained that the
  68  * name already exists, due to not following the symlink even if its target
  69  * is nonexistent.  The new semantics affects also mknod() and link() when
  70  * the name is a symlink pointing to a non-existant name.
  71  *
  72  * I don't know which semantics is the right one, since I have no access
  73  * to standards. But I found by trial that HP-UX 9.0 has the full "new"
  74  * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
  75  * "old" one. Personally, I think the new semantics is much more logical.
  76  * Note that "ln old new" where "new" is a symlink pointing to a non-existing
  77  * file does succeed in both HP-UX and SunOs, but not in Solaris
  78  * and in the old Linux semantics.
  79  */
  80
  81 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
  82  * semantics.  See the comments in "open_namei" and "do_link" below.
  83  *
  84  * [10-Sep-98 Alan Modra] Another symlink change.
  85  */
  86
  87 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
  88  *      inside the path - always follow.
  89  *      in the last component in creation/removal/renaming - never follow.
  90  *      if LOOKUP_FOLLOW passed - follow.
  91  *      if the pathname has trailing slashes - follow.
  92  *      otherwise - don't follow.
  93  * (applied in that order).
  94  *
  95  * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
  96  * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
  97  * During the 2.4 we need to fix the userland stuff depending on it -
  98  * hopefully we will be able to get rid of that wart in 2.5. So far only
  99  * XEmacs seems to be relying on it...
 100  */
 101 /*
 102  * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
 103  * implemented.  Let's see if raised priority of ->s_vfs_rename_sem gives
 104  * any extra contention...
 105  */
 106
 107 /* In order to reduce some races, while at the same time doing additional
 108  * checking and hopefully speeding things up, we copy filenames to the
 109  * kernel data space before using them..
 110  *
 111  * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
 112  * PATH_MAX includes the nul terminator --RR.
 113  */
 114 static inline int do_getname(const char __user *filename, char *page)
 115 {
 116         int retval;
 117         unsigned long len = PATH_MAX;
 118
 119         if (!segment_eq(get_fs(), KERNEL_DS)) {
 120                 if ((unsigned long) filename >= TASK_SIZE)
 121                         return -EFAULT;
 122                 if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
 123                         len = TASK_SIZE - (unsigned long) filename;
 124         }
 125
 126         retval = strncpy_from_user(page, filename, len);
 127         if (retval > 0) {
 128                 if (retval < len)
 129                         return 0;
 130                 return -ENAMETOOLONG;
 131         } else if (!retval)
 132                 retval = -ENOENT;
 133         return retval;
 134 }
 135
 136 char * getname(const char __user * filename)
 137 {
 138         char *tmp, *result;
 139
 140         result = ERR_PTR(-ENOMEM);
 141         tmp = __getname();
 142         if (tmp)  {
 143                 int retval = do_getname(filename, tmp);
 144
 145                 result = tmp;
 146                 if (retval < 0) {
 147                         __putname(tmp);
 148                         result = ERR_PTR(retval);
 149                 }
 150         }
 151         audit_getname(result);
 152         return result;
 153 }
 154
 155 #ifdef CONFIG_AUDITSYSCALL
 156 void putname(const char *name)
 157 {
 158         if (unlikely(current->audit_context))
 159                 audit_putname(name);
 160         else
 161                 __putname(name);
 162 }
 163 EXPORT_SYMBOL(putname);
 164 #endif
 165
 166
 167 /**
 168  * generic_permission  -  check for access rights on a Posix-like filesystem
 169  * @inode:      inode to check access rights for
 170  * @mask:       right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
 171  * @check_acl:  optional callback to check for Posix ACLs
 172  *
 173  * Used to check for read/write/execute permissions on a file.
 174  * We use "fsuid" for this, letting us set arbitrary permissions
 175  * for filesystem access without changing the "normal" uids which
 176  * are used for other things..
 177  */
 178 int generic_permission(struct inode *inode, int mask,
 179                 int (*check_acl)(struct inode *inode, int mask))
 180 {
 181         umode_t                 mode = inode->i_mode;
 182
 183         if (current->fsuid == inode->i_uid)
 184                 mode >>= 6;
 185         else {
 186                 if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
 187                         int error = check_acl(inode, mask);
 188                         if (error == -EACCES)
 189                                 goto check_capabilities;
 190                         else if (error != -EAGAIN)
 191                                 return error;
 192                 }
 193
 194                 if (in_group_p(inode->i_gid))
 195                         mode >>= 3;
 196         }
 197
 198         /*
 199          * If the DACs are ok we don't need any capability check.
 200          */
 201         if (((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask))
 202                 return 0;
 203
 204  check_capabilities:
 205         /*
 206          * Read/write DACs are always overridable.
 207          * Executable DACs are overridable if at least one exec bit is set.
 208          */
 209         if (!(mask & MAY_EXEC) ||
 210             (inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode))
 211                 if (capable(CAP_DAC_OVERRIDE))
 212                         return 0;
 213
 214         /*
 215          * Searching includes executable on directories, else just read.
 216          */
 217         if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
 218                 if (capable(CAP_DAC_READ_SEARCH))
 219                         return 0;
 220
 221         return -EACCES;
 222 }
 223
 224 int permission(struct inode *inode, int mask, struct nameidata *nd)
 225 {
 226         int retval, submask;
 227
 228         if (mask & MAY_WRITE) {
 229                 umode_t mode = inode->i_mode;
 230
 231                 /*
 232                  * Nobody gets write access to a read-only fs.
 233                  */
 234                 if (IS_RDONLY(inode) &&
 235                     (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
 236                         return -EROFS;
 237
 238                 /*
 239                  * Nobody gets write access to an immutable file.
 240                  */
 241                 if (IS_IMMUTABLE(inode))
 242                         return -EACCES;
 243         }
 244
 245
 246         /* Ordinary permission routines do not understand MAY_APPEND. */
 247         submask = mask & ~MAY_APPEND;
 248         if (inode->i_op && inode->i_op->permission)
 249                 retval = inode->i_op->permission(inode, submask, nd);
 250         else
 251                 retval = generic_permission(inode, submask, NULL);
 252         if (retval)
 253                 return retval;
 254
 255         return security_inode_permission(inode, mask, nd);
 256 }
 257
 258 /*
 259  * get_write_access() gets write permission for a file.
 260  * put_write_access() releases this write permission.
 261  * This is used for regular files.
 262  * We cannot support write (and maybe mmap read-write shared) accesses and
 263  * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
 264  * can have the following values:
 265  * 0: no writers, no VM_DENYWRITE mappings
 266  * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
 267  * > 0: (i_writecount) users are writing to the file.
 268  *
 269  * Normally we operate on that counter with atomic_{inc,dec} and it's safe
 270  * except for the cases where we don't hold i_writecount yet. Then we need to
 271  * use {get,deny}_write_access() - these functions check the sign and refuse
 272  * to do the change if sign is wrong. Exclusion between them is provided by
 273  * the inode->i_lock spinlock.
 274  */
 275
 276 int get_write_access(struct inode * inode)
 277 {
 278         spin_lock(&inode->i_lock);
 279         if (atomic_read(&inode->i_writecount) < 0) {
 280                 spin_unlock(&inode->i_lock);
 281                 return -ETXTBSY;
 282         }
 283         atomic_inc(&inode->i_writecount);
 284         spin_unlock(&inode->i_lock);
 285
 286         return 0;
 287 }
 288
 289 int deny_write_access(struct file * file)
 290 {
 291         struct inode *inode = file->f_dentry->d_inode;
 292
 293         spin_lock(&inode->i_lock);
 294         if (atomic_read(&inode->i_writecount) > 0) {
 295                 spin_unlock(&inode->i_lock);
 296                 return -ETXTBSY;
 297         }
 298         atomic_dec(&inode->i_writecount);
 299         spin_unlock(&inode->i_lock);
 300
 301         return 0;
 302 }
 303
 304 void path_release(struct nameidata *nd)
 305 {
 306         dput(nd->dentry);
 307         mntput(nd->mnt);
 308 }
 309
 310 /*
 311  * umount() mustn't call path_release()/mntput() as that would clear
 312  * mnt_expiry_mark
 313  */
 314 void path_release_on_umount(struct nameidata *nd)
 315 {
 316         dput(nd->dentry);
 317         _mntput(nd->mnt);
 318 }
 319
 320 /*
 321  * Internal lookup() using the new generic dcache.
 322  * SMP-safe
 323  */
 324 static struct dentry * cached_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
 325 {
 326         struct dentry * dentry = __d_lookup(parent, name);
 327
 328         /* lockess __d_lookup may fail due to concurrent d_move()
 329          * in some unrelated directory, so try with d_lookup
 330          */
 331         if (!dentry)
 332                 dentry = d_lookup(parent, name);
 333
 334         if (dentry && dentry->d_op && dentry->d_op->d_revalidate) {
 335                 if (!dentry->d_op->d_revalidate(dentry, nd) && !d_invalidate(dentry)) {
 336                         dput(dentry);
 337                         dentry = NULL;
 338                 }
 339         }
 340         return dentry;
 341 }
 342
 343 /*
 344  * Short-cut version of permission(), for calling by
 345  * path_walk(), when dcache lock is held.  Combines parts
 346  * of permission() and generic_permission(), and tests ONLY for
 347  * MAY_EXEC permission.
 348  *
 349  * If appropriate, check DAC only.  If not appropriate, or
 350  * short-cut DAC fails, then call permission() to do more
 351  * complete permission check.
 352  */
 353 static inline int exec_permission_lite(struct inode *inode,
 354                                        struct nameidata *nd)
 355 {
 356         umode_t mode = inode->i_mode;
 357
 358         if (inode->i_op && inode->i_op->permission)
 359                 return -EAGAIN;
 360
 361         if (current->fsuid == inode->i_uid)
 362                 mode >>= 6;
 363         else if (in_group_p(inode->i_gid))
 364                 mode >>= 3;
 365
 366         if (mode & MAY_EXEC)
 367                 goto ok;
 368
 369         if ((inode->i_mode & S_IXUGO) && capable(CAP_DAC_OVERRIDE))
 370                 goto ok;
 371
 372         if (S_ISDIR(inode->i_mode) && capable(CAP_DAC_OVERRIDE))
 373                 goto ok;
 374
 375         if (S_ISDIR(inode->i_mode) && capable(CAP_DAC_READ_SEARCH))
 376                 goto ok;
 377
 378         return -EACCES;
 379 ok:
 380         return security_inode_permission(inode, MAY_EXEC, nd);
 381 }
 382
 383 /*
 384  * This is called when everything else fails, and we actually have
 385  * to go to the low-level filesystem to find out what we should do..
 386  *
 387  * We get the directory semaphore, and after getting that we also
 388  * make sure that nobody added the entry to the dcache in the meantime..
 389  * SMP-safe
 390  */
 391 static struct dentry * real_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
 392 {
 393         struct dentry * result;
 394         struct inode *dir = parent->d_inode;
 395
 396         down(&dir->i_sem);
 397         /*
 398          * First re-do the cached lookup just in case it was created
 399          * while we waited for the directory semaphore..
 400          *
 401          * FIXME! This could use version numbering or similar to
 402          * avoid unnecessary cache lookups.
 403          *
 404          * The "dcache_lock" is purely to protect the RCU list walker
 405          * from concurrent renames at this point (we mustn't get false
 406          * negatives from the RCU list walk here, unlike the optimistic
 407          * fast walk).
 408          *
 409          * so doing d_lookup() (with seqlock), instead of lockfree __d_lookup
 410          */
 411         result = d_lookup(parent, name);
 412         if (!result) {
 413                 struct dentry * dentry = d_alloc(parent, name);
 414                 result = ERR_PTR(-ENOMEM);
 415                 if (dentry) {
 416                         result = dir->i_op->lookup(dir, dentry, nd);
 417                         if (result)
 418                                 dput(dentry);
 419                         else
 420                                 result = dentry;
 421                 }
 422                 up(&dir->i_sem);
 423                 return result;
 424         }
 425
 426         /*
 427          * Uhhuh! Nasty case: the cache was re-populated while
 428          * we waited on the semaphore. Need to revalidate.
 429          */
 430         up(&dir->i_sem);
 431         if (result->d_op && result->d_op->d_revalidate) {
 432                 if (!result->d_op->d_revalidate(result, nd) && !d_invalidate(result)) {
 433                         dput(result);
 434                         result = ERR_PTR(-ENOENT);
 435                 }
 436         }
 437         return result;
 438 }
 439
 440 static int __emul_lookup_dentry(const char *, struct nameidata *);
 441
 442 /* SMP-safe */
 443 static inline int
 444 walk_init_root(const char *name, struct nameidata *nd)
 445 {
 446         read_lock(&current->fs->lock);
 447         if (current->fs->altroot && !(nd->flags & LOOKUP_NOALT)) {
 448                 nd->mnt = mntget(current->fs->altrootmnt);
 449                 nd->dentry = dget(current->fs->altroot);
 450                 read_unlock(&current->fs->lock);
 451                 if (__emul_lookup_dentry(name,nd))
 452                         return 0;
 453                 read_lock(&current->fs->lock);
 454         }
 455         nd->mnt = mntget(current->fs->rootmnt);
 456         nd->dentry = dget(current->fs->root);
 457         read_unlock(&current->fs->lock);
 458         return 1;
 459 }
 460
 461 static inline int __vfs_follow_link(struct nameidata *nd, const char *link)
 462 {
 463         int res = 0;
 464         char *name;
 465         if (IS_ERR(link))
 466                 goto fail;
 467
 468         if (*link == '/') {
 469                 path_release(nd);
 470                 if (!walk_init_root(link, nd))
 471                         /* weird __emul_prefix() stuff did it */
 472                         goto out;
 473         }
 474         res = link_path_walk(link, nd);
 475 out:
 476         if (nd->depth || res || nd->last_type!=LAST_NORM)
 477                 return res;
 478         /*
 479          * If it is an iterative symlinks resolution in open_namei() we
 480          * have to copy the last component. And all that crap because of
 481          * bloody create() on broken symlinks. Furrfu...
 482          */
 483         name = __getname();
 484         if (unlikely(!name)) {
 485                 path_release(nd);
 486                 return -ENOMEM;
 487         }
 488         strcpy(name, nd->last.name);
 489         nd->last.name = name;
 490         return 0;
 491 fail:
 492         path_release(nd);
 493         return PTR_ERR(link);
 494 }
 495
 496 static inline int __do_follow_link(struct dentry *dentry, struct nameidata *nd)
 497 {
 498         int error;
 499
 500         touch_atime(nd->mnt, dentry);
 501         nd_set_link(nd, NULL);
 502         error = dentry->d_inode->i_op->follow_link(dentry, nd);
 503         if (!error) {
 504                 char *s = nd_get_link(nd);
 505                 if (s)
 506                         error = __vfs_follow_link(nd, s);
 507                 if (dentry->d_inode->i_op->put_link)
 508                         dentry->d_inode->i_op->put_link(dentry, nd);
 509         }
 510
 511         return error;
 512 }
 513
 514 /*
 515  * This limits recursive symlink follows to 8, while
 516  * limiting consecutive symlinks to 40.
 517  *
 518  * Without that kind of total limit, nasty chains of consecutive
 519  * symlinks can cause almost arbitrarily long lookups.
 520  */
 521 static inline int do_follow_link(struct dentry *dentry, struct nameidata *nd)
 522 {
 523         int err = -ELOOP;
 524         if (current->link_count >= MAX_NESTED_LINKS)
 525                 goto loop;
 526         if (current->total_link_count >= 40)
 527                 goto loop;
 528         BUG_ON(nd->depth >= MAX_NESTED_LINKS);
 529         cond_resched();
 530         err = security_inode_follow_link(dentry, nd);
 531         if (err)
 532                 goto loop;
 533         current->link_count++;
 534         current->total_link_count++;
 535         nd->depth++;
 536         err = __do_follow_link(dentry, nd);
 537         current->link_count--;
 538         nd->depth--;
 539         return err;
 540 loop:
 541         path_release(nd);
 542         return err;
 543 }
 544
 545 int follow_up(struct vfsmount **mnt, struct dentry **dentry)
 546 {
 547         struct vfsmount *parent;
 548         struct dentry *mountpoint;
 549         spin_lock(&vfsmount_lock);
 550         parent=(*mnt)->mnt_parent;
 551         if (parent == *mnt) {
 552                 spin_unlock(&vfsmount_lock);
 553                 return 0;
 554         }
 555         mntget(parent);
 556         mountpoint=dget((*mnt)->mnt_mountpoint);
 557         spin_unlock(&vfsmount_lock);
 558         dput(*dentry);
 559         *dentry = mountpoint;
 560         mntput(*mnt);
 561         *mnt = parent;
 562         return 1;
 563 }
 564
 565 /* no need for dcache_lock, as serialization is taken care in
 566  * namespace.c
 567  */
 568 static int follow_mount(struct vfsmount **mnt, struct dentry **dentry)
 569 {
 570         int res = 0;
 571         while (d_mountpoint(*dentry)) {
 572                 struct vfsmount *mounted = lookup_mnt(*mnt, *dentry);
 573                 if (!mounted)
 574                         break;
 575                 mntput(*mnt);
 576                 *mnt = mounted;
 577                 dput(*dentry);
 578                 *dentry = dget(mounted->mnt_root);
 579                 res = 1;
 580         }
 581         return res;
 582 }
 583
 584 /* no need for dcache_lock, as serialization is taken care in
 585  * namespace.c
 586  */
 587 static inline int __follow_down(struct vfsmount **mnt, struct dentry **dentry)
 588 {
 589         struct vfsmount *mounted;
 590
 591         mounted = lookup_mnt(*mnt, *dentry);
 592         if (mounted) {
 593                 mntput(*mnt);
 594                 *mnt = mounted;
 595                 dput(*dentry);
 596                 *dentry = dget(mounted->mnt_root);
 597                 return 1;
 598         }
 599         return 0;
 600 }
 601
 602 int follow_down(struct vfsmount **mnt, struct dentry **dentry)
 603 {
 604         return __follow_down(mnt,dentry);
 605 }
 606
 607 static inline void follow_dotdot(struct vfsmount **mnt, struct dentry **dentry)
 608 {
 609         while(1) {
 610                 struct vfsmount *parent;
 611                 struct dentry *old = *dentry;
 612
 613                 read_lock(&current->fs->lock);
 614                 if (*dentry == current->fs->root &&
 615                     *mnt == current->fs->rootmnt) {
 616                         read_unlock(&current->fs->lock);
 617                         break;
 618                 }
 619                 read_unlock(&current->fs->lock);
 620                 spin_lock(&dcache_lock);
 621                 if (*dentry != (*mnt)->mnt_root) {
 622                         *dentry = dget((*dentry)->d_parent);
 623                         spin_unlock(&dcache_lock);
 624                         dput(old);
 625                         break;
 626                 }
 627                 spin_unlock(&dcache_lock);
 628                 spin_lock(&vfsmount_lock);
 629                 parent = (*mnt)->mnt_parent;
 630                 if (parent == *mnt) {
 631                         spin_unlock(&vfsmount_lock);
 632                         break;
 633                 }
 634                 mntget(parent);
 635                 *dentry = dget((*mnt)->mnt_mountpoint);
 636                 spin_unlock(&vfsmount_lock);
 637                 dput(old);
 638                 mntput(*mnt);
 639                 *mnt = parent;
 640         }
 641         follow_mount(mnt, dentry);
 642 }
 643
 644 struct path {
 645         struct vfsmount *mnt;
 646         struct dentry *dentry;
 647 };
 648
 649 /*
 650  *  It's more convoluted than I'd like it to be, but... it's still fairly
 651  *  small and for now I'd prefer to have fast path as straight as possible.
 652  *  It _is_ time-critical.
 653  */
 654 static int do_lookup(struct nameidata *nd, struct qstr *name,
 655                      struct path *path)
 656 {
 657         struct vfsmount *mnt = nd->mnt;
 658         struct dentry *dentry = __d_lookup(nd->dentry, name);
 659
 660         if (!dentry)
 661                 goto need_lookup;
 662         if (dentry->d_op && dentry->d_op->d_revalidate)
 663                 goto need_revalidate;
 664 done:
 665         path->mnt = mnt;
 666         path->dentry = dentry;
 667         return 0;
 668
 669 need_lookup:
 670         dentry = real_lookup(nd->dentry, name, nd);
 671         if (IS_ERR(dentry))
 672                 goto fail;
 673         goto done;
 674
 675 need_revalidate:
 676         if (dentry->d_op->d_revalidate(dentry, nd))
 677                 goto done;
 678         if (d_invalidate(dentry))
 679                 goto done;
 680         dput(dentry);
 681         goto need_lookup;
 682
 683 fail:
 684         return PTR_ERR(dentry);
 685 }
 686
 687 /*
 688  * Name resolution.
 689  *
 690  * This is the basic name resolution function, turning a pathname
 691  * into the final dentry.
 692  *
 693  * We expect 'base' to be positive and a directory.
 694  */
 695 static fastcall int __link_path_walk(const char * name, struct nameidata *nd)
 696 {
 697         struct path next;
 698         struct inode *inode;
 699         int err;
 700         unsigned int lookup_flags = nd->flags;
 701
 702         while (*name=='/')
 703                 name++;
 704         if (!*name)
 705                 goto return_reval;
 706
 707         inode = nd->dentry->d_inode;
 708         if (nd->depth)
 709                 lookup_flags = LOOKUP_FOLLOW;
 710
 711         /* At this point we know we have a real path component. */
 712         for(;;) {
 713                 unsigned long hash;
 714                 struct qstr this;
 715                 unsigned int c;
 716
 717                 err = exec_permission_lite(inode, nd);
 718                 if (err == -EAGAIN) {
 719                         err = permission(inode, MAY_EXEC, nd);
 720                 }
 721                 if (err)
 722                         break;
 723
 724                 this.name = name;
 725                 c = *(const unsigned char *)name;
 726
 727                 hash = init_name_hash();
 728                 do {
 729                         name++;
 730                         hash = partial_name_hash(c, hash);
 731                         c = *(const unsigned char *)name;
 732                 } while (c && (c != '/'));
 733                 this.len = name - (const char *) this.name;
 734                 this.hash = end_name_hash(hash);
 735
 736                 /* remove trailing slashes? */
 737                 if (!c)
 738                         goto last_component;
 739                 while (*++name == '/');
 740                 if (!*name)
 741                         goto last_with_slashes;
 742
 743                 /*
 744                  * "." and ".." are special - ".." especially so because it has
 745                  * to be able to know about the current root directory and
 746                  * parent relationships.
 747                  */
 748                 if (this.name[0] == '.') switch (this.len) {
 749                         default:
 750                                 break;
 751                         case 2:
 752                                 if (this.name[1] != '.')
 753                                         break;
 754                                 follow_dotdot(&nd->mnt, &nd->dentry);
 755                                 inode = nd->dentry->d_inode;
 756                                 /* fallthrough */
 757                         case 1:
 758                                 continue;
 759                 }
 760                 /*
 761                  * See if the low-level filesystem might want
 762                  * to use its own hash..
 763                  */
 764                 if (nd->dentry->d_op && nd->dentry->d_op->d_hash) {
 765                         err = nd->dentry->d_op->d_hash(nd->dentry, &this);
 766                         if (err < 0)
 767                                 break;
 768                 }
 769                 nd->flags |= LOOKUP_CONTINUE;
 770                 /* This does the actual lookups.. */
 771                 err = do_lookup(nd, &this, &next);
 772                 if (err)
 773                         break;
 774                 /* Check mountpoints.. */
 775                 follow_mount(&next.mnt, &next.dentry);
 776
 777                 err = -ENOENT;
 778                 inode = next.dentry->d_inode;
 779                 if (!inode)
 780                         goto out_dput;
 781                 err = -ENOTDIR;
 782                 if (!inode->i_op)
 783                         goto out_dput;
 784
 785                 if (inode->i_op->follow_link) {
 786                         mntget(next.mnt);
 787                         err = do_follow_link(next.dentry, nd);
 788                         dput(next.dentry);
 789                         mntput(next.mnt);
 790                         if (err)
 791                                 goto return_err;
 792                         err = -ENOENT;
 793                         inode = nd->dentry->d_inode;
 794                         if (!inode)
 795                                 break;
 796                         err = -ENOTDIR;
 797                         if (!inode->i_op)
 798                                 break;
 799                 } else {
 800                         dput(nd->dentry);
 801                         nd->mnt = next.mnt;
 802                         nd->dentry = next.dentry;
 803                 }
 804                 err = -ENOTDIR;
 805                 if (!inode->i_op->lookup)
 806                         break;
 807                 continue;
 808                 /* here ends the main loop */
 809
 810 last_with_slashes:
 811                 lookup_flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 812 last_component:
 813                 nd->flags &= ~LOOKUP_CONTINUE;
 814                 if (lookup_flags & LOOKUP_PARENT)
 815                         goto lookup_parent;
 816                 if (this.name[0] == '.') switch (this.len) {
 817                         default:
 818                                 break;
 819                         case 2:
 820                                 if (this.name[1] != '.')
 821                                         break;
 822                                 follow_dotdot(&nd->mnt, &nd->dentry);
 823                                 inode = nd->dentry->d_inode;
 824                                 /* fallthrough */
 825                         case 1:
 826                                 goto return_reval;
 827                 }
 828                 if (nd->dentry->d_op && nd->dentry->d_op->d_hash) {
 829                         err = nd->dentry->d_op->d_hash(nd->dentry, &this);
 830                         if (err < 0)
 831                                 break;
 832                 }
 833                 err = do_lookup(nd, &this, &next);
 834                 if (err)
 835                         break;
 836                 follow_mount(&next.mnt, &next.dentry);
 837                 inode = next.dentry->d_inode;
 838                 if ((lookup_flags & LOOKUP_FOLLOW)
 839                     && inode && inode->i_op && inode->i_op->follow_link) {
 840                         mntget(next.mnt);
 841                         err = do_follow_link(next.dentry, nd);
 842                         dput(next.dentry);
 843                         mntput(next.mnt);
 844                         if (err)
 845                                 goto return_err;
 846                         inode = nd->dentry->d_inode;
 847                 } else {
 848                         dput(nd->dentry);
 849                         nd->mnt = next.mnt;
 850                         nd->dentry = next.dentry;
 851                 }
 852                 err = -ENOENT;
 853                 if (!inode)
 854                         break;
 855                 if (lookup_flags & LOOKUP_DIRECTORY) {
 856                         err = -ENOTDIR;
 857                         if (!inode->i_op || !inode->i_op->lookup)
 858                                 break;
 859                 }
 860                 goto return_base;
 861 lookup_parent:
 862                 nd->last = this;
 863                 nd->last_type = LAST_NORM;
 864                 if (this.name[0] != '.')
 865                         goto return_base;
 866                 if (this.len == 1)
 867                         nd->last_type = LAST_DOT;
 868                 else if (this.len == 2 && this.name[1] == '.')
 869                         nd->last_type = LAST_DOTDOT;
 870                 else
 871                         goto return_base;
 872 return_reval:
 873                 /*
 874                  * We bypassed the ordinary revalidation routines.
 875                  * We may need to check the cached dentry for staleness.
 876                  */
 877                 if (nd->dentry && nd->dentry->d_sb &&
 878                     (nd->dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)) {
 879                         err = -ESTALE;
 880                         /* Note: we do not d_invalidate() */
 881                         if (!nd->dentry->d_op->d_revalidate(nd->dentry, nd))
 882                                 break;
 883                 }
 884 return_base:
 885                 return 0;
 886 out_dput:
 887                 dput(next.dentry);
 888                 break;
 889         }
 890         path_release(nd);
 891 return_err:
 892         return err;
 893 }
 894
 895 /*
 896  * Wrapper to retry pathname resolution whenever the underlying
 897  * file system returns an ESTALE.
 898  *
 899  * Retry the whole path once, forcing real lookup requests
 900  * instead of relying on the dcache.
 901  */
 902 int fastcall link_path_walk(const char *name, struct nameidata *nd)
 903 {
 904         struct nameidata save = *nd;
 905         int result;
 906
 907         /* make sure the stuff we saved doesn't go away */
 908         dget(save.dentry);
 909         mntget(save.mnt);
 910
 911         result = __link_path_walk(name, nd);
 912         if (result == -ESTALE) {
 913                 *nd = save;
 914                 dget(nd->dentry);
 915                 mntget(nd->mnt);
 916                 nd->flags |= LOOKUP_REVAL;
 917                 result = __link_path_walk(name, nd);
 918         }
 919
 920         dput(save.dentry);
 921         mntput(save.mnt);
 922
 923         return result;
 924 }
 925
 926 int fastcall path_walk(const char * name, struct nameidata *nd)
 927 {
 928         current->total_link_count = 0;
 929         return link_path_walk(name, nd);
 930 }
 931
 932 /* SMP-safe */
 933 /* returns 1 if everything is done */
 934 static int __emul_lookup_dentry(const char *name, struct nameidata *nd)
 935 {
 936         if (path_walk(name, nd))
 937                 return 0;               /* something went wrong... */
 938
 939         if (!nd->dentry->d_inode || S_ISDIR(nd->dentry->d_inode->i_mode)) {
 940                 struct dentry *old_dentry = nd->dentry;
 941                 struct vfsmount *old_mnt = nd->mnt;
 942                 struct qstr last = nd->last;
 943                 int last_type = nd->last_type;
 944                 /*
 945                  * NAME was not found in alternate root or it's a directory.  Try to find
 946                  * it in the normal root:
 947                  */
 948                 nd->last_type = LAST_ROOT;
 949                 read_lock(&current->fs->lock);
 950                 nd->mnt = mntget(current->fs->rootmnt);
 951                 nd->dentry = dget(current->fs->root);
 952                 read_unlock(&current->fs->lock);
 953                 if (path_walk(name, nd) == 0) {
 954                         if (nd->dentry->d_inode) {
 955                                 dput(old_dentry);
 956                                 mntput(old_mnt);
 957                                 return 1;
 958                         }
 959                         path_release(nd);
 960                 }
 961                 nd->dentry = old_dentry;
 962                 nd->mnt = old_mnt;
 963                 nd->last = last;
 964                 nd->last_type = last_type;
 965         }
 966         return 1;
 967 }
 968
 969 void set_fs_altroot(void)
 970 {
 971         char *emul = __emul_prefix();
 972         struct nameidata nd;
 973         struct vfsmount *mnt = NULL, *oldmnt;
 974         struct dentry *dentry = NULL, *olddentry;
 975         int err;
 976
 977         if (!emul)
 978                 goto set_it;
 979         err = path_lookup(emul, LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_NOALT, &nd);
 980         if (!err) {
 981                 mnt = nd.mnt;
 982                 dentry = nd.dentry;
 983         }
 984 set_it:
 985         write_lock(&current->fs->lock);
 986         oldmnt = current->fs->altrootmnt;
 987         olddentry = current->fs->altroot;
 988         current->fs->altrootmnt = mnt;
 989         current->fs->altroot = dentry;
 990         write_unlock(&current->fs->lock);
 991         if (olddentry) {
 992                 dput(olddentry);
 993                 mntput(oldmnt);
 994         }
 995 }
 996
 997 int fastcall path_lookup(const char *name, unsigned int flags, struct nameidata *nd)
 998 {
 999         int retval;
1000
1001         nd->last_type = LAST_ROOT; /* if there are only slashes... */
1002         nd->flags = flags;
1003         nd->depth = 0;
1004
1005         read_lock(&current->fs->lock);
1006         if (*name=='/') {
1007                 if (current->fs->altroot && !(nd->flags & LOOKUP_NOALT)) {
1008                         nd->mnt = mntget(current->fs->altrootmnt);
1009                         nd->dentry = dget(current->fs->altroot);
1010                         read_unlock(&current->fs->lock);
1011                         if (__emul_lookup_dentry(name,nd))
1012                                 return 0;
1013                         read_lock(&current->fs->lock);
1014                 }
1015                 nd->mnt = mntget(current->fs->rootmnt);
1016                 nd->dentry = dget(current->fs->root);
1017         } else {
1018                 nd->mnt = mntget(current->fs->pwdmnt);
1019                 nd->dentry = dget(current->fs->pwd);
1020         }
1021         read_unlock(&current->fs->lock);
1022         current->total_link_count = 0;
1023         retval = link_path_walk(name, nd);
1024         if (unlikely(current->audit_context
1025                      && nd && nd->dentry && nd->dentry->d_inode))
1026                 audit_inode(name, nd->dentry->d_inode);
1027         return retval;
1028 }
1029
1030 /*
1031  * Restricted form of lookup. Doesn't follow links, single-component only,
1032  * needs parent already locked. Doesn't follow mounts.
1033  * SMP-safe.
1034  */
1035 static struct dentry * __lookup_hash(struct qstr *name, struct dentry * base, struct nameidata *nd)
1036 {
1037         struct dentry * dentry;
1038         struct inode *inode;
1039         int err;
1040
1041         inode = base->d_inode;
1042         err = permission(inode, MAY_EXEC, nd);
1043         dentry = ERR_PTR(err);
1044         if (err)
1045                 goto out;
1046
1047         /*
1048          * See if the low-level filesystem might want
1049          * to use its own hash..
1050          */
1051         if (base->d_op && base->d_op->d_hash) {
1052                 err = base->d_op->d_hash(base, name);
1053                 dentry = ERR_PTR(err);
1054                 if (err < 0)
1055                         goto out;
1056         }
1057
1058         dentry = cached_lookup(base, name, nd);
1059         if (!dentry) {
1060                 struct dentry *new = d_alloc(base, name);
1061                 dentry = ERR_PTR(-ENOMEM);
1062                 if (!new)
1063                         goto out;
1064                 dentry = inode->i_op->lookup(inode, new, nd);
1065                 if (!dentry)
1066                         dentry = new;
1067                 else
1068                         dput(new);
1069         }
1070 out:
1071         return dentry;
1072 }
1073
1074 struct dentry * lookup_hash(struct qstr *name, struct dentry * base)
1075 {
1076         return __lookup_hash(name, base, NULL);
1077 }
1078
1079 /* SMP-safe */
1080 struct dentry * lookup_one_len(const char * name, struct dentry * base, int len)
1081 {
1082         unsigned long hash;
1083         struct qstr this;
1084         unsigned int c;
1085
1086         this.name = name;
1087         this.len = len;
1088         if (!len)
1089                 goto access;
1090
1091         hash = init_name_hash();
1092         while (len--) {
1093                 c = *(const unsigned char *)name++;
1094                 if (c == '/' || c == '\0')
1095                         goto access;
1096                 hash = partial_name_hash(c, hash);
1097         }
1098         this.hash = end_name_hash(hash);
1099
1100         return lookup_hash(&this, base);
1101 access:
1102         return ERR_PTR(-EACCES);
1103 }
1104
1105 /*
1106  *      namei()
1107  *
1108  * is used by most simple commands to get the inode of a specified name.
1109  * Open, link etc use their own routines, but this is enough for things
1110  * like 'chmod' etc.
1111  *
1112  * namei exists in two versions: namei/lnamei. The only difference is
1113  * that namei follows links, while lnamei does not.
1114  * SMP-safe
1115  */
1116 int fastcall __user_walk(const char __user *name, unsigned flags, struct nameidata *nd)
1117 {
1118         char *tmp = getname(name);
1119         int err = PTR_ERR(tmp);
1120
1121         if (!IS_ERR(tmp)) {
1122                 err = path_lookup(tmp, flags, nd);
1123                 putname(tmp);
1124         }
1125         return err;
1126 }
1127
1128 /*
1129  * It's inline, so penalty for filesystems that don't use sticky bit is
1130  * minimal.
1131  */
1132 static inline int check_sticky(struct inode *dir, struct inode *inode)
1133 {
1134         if (!(dir->i_mode & S_ISVTX))
1135                 return 0;
1136         if (inode->i_uid == current->fsuid)
1137                 return 0;
1138         if (dir->i_uid == current->fsuid)
1139                 return 0;
1140         return !capable(CAP_FOWNER);
1141 }
1142
1143 /*
1144  *      Check whether we can remove a link victim from directory dir, check
1145  *  whether the type of victim is right.
1146  *  1. We can't do it if dir is read-only (done in permission())
1147  *  2. We should have write and exec permissions on dir
1148  *  3. We can't remove anything from append-only dir
1149  *  4. We can't do anything with immutable dir (done in permission())
1150  *  5. If the sticky bit on dir is set we should either
1151  *      a. be owner of dir, or
1152  *      b. be owner of victim, or
1153  *      c. have CAP_FOWNER capability
1154  *  6. If the victim is append-only or immutable we can't do antyhing with
1155  *     links pointing to it.
1156  *  7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1157  *  8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1158  *  9. We can't remove a root or mountpoint.
1159  * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1160  *     nfs_async_unlink().
1161  */
1162 static inline int may_delete(struct inode *dir,struct dentry *victim,int isdir)
1163 {
1164         int error;
1165
1166         if (!victim->d_inode)
1167                 return -ENOENT;
1168
1169         BUG_ON(victim->d_parent->d_inode != dir);
1170
1171         error = permission(dir,MAY_WRITE | MAY_EXEC, NULL);
1172         if (error)
1173                 return error;
1174         if (IS_APPEND(dir))
1175                 return -EPERM;
1176         if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
1177             IS_IMMUTABLE(victim->d_inode))
1178                 return -EPERM;
1179         if (isdir) {
1180                 if (!S_ISDIR(victim->d_inode->i_mode))
1181                         return -ENOTDIR;
1182                 if (IS_ROOT(victim))
1183                         return -EBUSY;
1184         } else if (S_ISDIR(victim->d_inode->i_mode))
1185                 return -EISDIR;
1186         if (IS_DEADDIR(dir))
1187                 return -ENOENT;
1188         if (victim->d_flags & DCACHE_NFSFS_RENAMED)
1189                 return -EBUSY;
1190         return 0;
1191 }
1192
1193 /*      Check whether we can create an object with dentry child in directory
1194  *  dir.
1195  *  1. We can't do it if child already exists (open has special treatment for
1196  *     this case, but since we are inlined it's OK)
1197  *  2. We can't do it if dir is read-only (done in permission())
1198  *  3. We should have write and exec permissions on dir
1199  *  4. We can't do it if dir is immutable (done in permission())
1200  */
1201 static inline int may_create(struct inode *dir, struct dentry *child,
1202                              struct nameidata *nd)
1203 {
1204         if (child->d_inode)
1205                 return -EEXIST;
1206         if (IS_DEADDIR(dir))
1207                 return -ENOENT;
1208         return permission(dir,MAY_WRITE | MAY_EXEC, nd);
1209 }
1210
1211 /*
1212  * Special case: O_CREAT|O_EXCL implies O_NOFOLLOW for security
1213  * reasons.
1214  *
1215  * O_DIRECTORY translates into forcing a directory lookup.
1216  */
1217 static inline int lookup_flags(unsigned int f)
1218 {
1219         unsigned long retval = LOOKUP_FOLLOW;
1220
1221         if (f & O_NOFOLLOW)
1222                 retval &= ~LOOKUP_FOLLOW;
1223
1224         if ((f & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL))
1225                 retval &= ~LOOKUP_FOLLOW;
1226
1227         if (f & O_DIRECTORY)
1228                 retval |= LOOKUP_DIRECTORY;
1229
1230         return retval;
1231 }
1232
1233 /*
1234  * p1 and p2 should be directories on the same fs.
1235  */
1236 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
1237 {
1238         struct dentry *p;
1239
1240         if (p1 == p2) {
1241                 down(&p1->d_inode->i_sem);
1242                 return NULL;
1243         }
1244
1245         down(&p1->d_inode->i_sb->s_vfs_rename_sem);
1246
1247         for (p = p1; p->d_parent != p; p = p->d_parent) {
1248                 if (p->d_parent == p2) {
1249                         down(&p2->d_inode->i_sem);
1250                         down(&p1->d_inode->i_sem);
1251                         return p;
1252                 }
1253         }
1254
1255         for (p = p2; p->d_parent != p; p = p->d_parent) {
1256                 if (p->d_parent == p1) {
1257                         down(&p1->d_inode->i_sem);
1258                         down(&p2->d_inode->i_sem);
1259                         return p;
1260                 }
1261         }
1262
1263         down(&p1->d_inode->i_sem);
1264         down(&p2->d_inode->i_sem);
1265         return NULL;
1266 }
1267
1268 void unlock_rename(struct dentry *p1, struct dentry *p2)
1269 {
1270         up(&p1->d_inode->i_sem);
1271         if (p1 != p2) {
1272                 up(&p2->d_inode->i_sem);
1273                 up(&p1->d_inode->i_sb->s_vfs_rename_sem);
1274         }
1275 }
1276
1277 int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
1278                 struct nameidata *nd)
1279 {
1280         int error = may_create(dir, dentry, nd);
1281
1282         if (error)
1283                 return error;
1284
1285         if (!dir->i_op || !dir->i_op->create)
1286                 return -EACCES; /* shouldn't it be ENOSYS? */
1287         mode &= S_IALLUGO;
1288         mode |= S_IFREG;
1289         error = security_inode_create(dir, dentry, mode);
1290         if (error)
1291                 return error;
1292         DQUOT_INIT(dir);
1293         error = dir->i_op->create(dir, dentry, mode, nd);
1294         if (!error) {
1295                 inode_dir_notify(dir, DN_CREATE);
1296                 security_inode_post_create(dir, dentry, mode);
1297         }
1298         return error;
1299 }
1300
1301 int may_open(struct nameidata *nd, int acc_mode, int flag)
1302 {
1303         struct dentry *dentry = nd->dentry;
1304         struct inode *inode = dentry->d_inode;
1305         int error;
1306
1307         if (!inode)
1308                 return -ENOENT;
1309
1310         if (S_ISLNK(inode->i_mode))
1311                 return -ELOOP;
1312
1313         if (S_ISDIR(inode->i_mode) && (flag & FMODE_WRITE))
1314                 return -EISDIR;
1315
1316         error = permission(inode, acc_mode, nd);
1317         if (error)
1318                 return error;
1319
1320         /*
1321          * FIFO's, sockets and device files are special: they don't
1322          * actually live on the filesystem itself, and as such you
1323          * can write to them even if the filesystem is read-only.
1324          */
1325         if (S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
1326                 flag &= ~O_TRUNC;
1327         } else if (S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode)) {
1328                 if (nd->mnt->mnt_flags & MNT_NODEV)
1329                         return -EACCES;
1330
1331                 flag &= ~O_TRUNC;
1332         } else if (IS_RDONLY(inode) && (flag & FMODE_WRITE))
1333                 return -EROFS;
1334         /*
1335          * An append-only file must be opened in append mode for writing.
1336          */
1337         if (IS_APPEND(inode)) {
1338                 if  ((flag & FMODE_WRITE) && !(flag & O_APPEND))
1339                         return -EPERM;
1340                 if (flag & O_TRUNC)
1341                         return -EPERM;
1342         }
1343
1344         /* O_NOATIME can only be set by the owner or superuser */
1345         if (flag & O_NOATIME)
1346                 if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
1347                         return -EPERM;
1348
1349         /*
1350          * Ensure there are no outstanding leases on the file.
1351          */
1352         error = break_lease(inode, flag);
1353         if (error)
1354                 return error;
1355
1356         if (flag & O_TRUNC) {
1357                 error = get_write_access(inode);
1358                 if (error)
1359                         return error;
1360
1361                 /*
1362                  * Refuse to truncate files with mandatory locks held on them.
1363                  */
1364                 error = locks_verify_locked(inode);
1365                 if (!error) {
1366                         DQUOT_INIT(inode);
1367
1368                         error = do_truncate(dentry, 0);
1369                 }
1370                 put_write_access(inode);
1371                 if (error)
1372                         return error;
1373         } else
1374                 if (flag & FMODE_WRITE)
1375                         DQUOT_INIT(inode);
1376
1377         return 0;
1378 }
1379
1380 /*
1381  *      open_namei()
1382  *
1383  * namei for open - this is in fact almost the whole open-routine.
1384  *
1385  * Note that the low bits of "flag" aren't the same as in the open
1386  * system call - they are 00 - no permissions needed
1387  *                        01 - read permission needed
1388  *                        10 - write permission needed
1389  *                        11 - read/write permissions needed
1390  * which is a lot more logical, and also allows the "no perm" needed
1391  * for symlinks (where the permissions are checked later).
1392  * SMP-safe
1393  */
1394 int open_namei(const char * pathname, int flag, int mode, struct nameidata *nd)
1395 {
1396         int acc_mode, error = 0;
1397         struct dentry *dentry;
1398         struct dentry *dir;
1399         int count = 0;
1400
1401         acc_mode = ACC_MODE(flag);
1402
1403         /* Allow the LSM permission hook to distinguish append
1404            access from general write access. */
1405         if (flag & O_APPEND)
1406                 acc_mode |= MAY_APPEND;
1407
1408         /* Fill in the open() intent data */
1409         nd->intent.open.flags = flag;
1410         nd->intent.open.create_mode = mode;
1411
1412         /*
1413          * The simplest case - just a plain lookup.
1414          */
1415         if (!(flag & O_CREAT)) {
1416                 error = path_lookup(pathname, lookup_flags(flag)|LOOKUP_OPEN, nd);
1417                 if (error)
1418                         return error;
1419                 goto ok;
1420         }
1421
1422         /*
1423          * Create - we need to know the parent.
1424          */
1425         error = path_lookup(pathname, LOOKUP_PARENT|LOOKUP_OPEN|LOOKUP_CREATE, nd);
1426         if (error)
1427                 return error;
1428
1429         /*
1430          * We have the parent and last component. First of all, check
1431          * that we are not asked to creat(2) an obvious directory - that
1432          * will not do.
1433          */
1434         error = -EISDIR;
1435         if (nd->last_type != LAST_NORM || nd->last.name[nd->last.len])
1436                 goto exit;
1437
1438         dir = nd->dentry;
1439         nd->flags &= ~LOOKUP_PARENT;
1440         down(&dir->d_inode->i_sem);
1441         dentry = __lookup_hash(&nd->last, nd->dentry, nd);
1442
1443 do_last:
1444         error = PTR_ERR(dentry);
1445         if (IS_ERR(dentry)) {
1446                 up(&dir->d_inode->i_sem);
1447                 goto exit;
1448         }
1449
1450         /* Negative dentry, just create the file */
1451         if (!dentry->d_inode) {
1452                 if (!IS_POSIXACL(dir->d_inode))
1453                         mode &= ~current->fs->umask;
1454                 error = vfs_create(dir->d_inode, dentry, mode, nd);
1455                 up(&dir->d_inode->i_sem);
1456                 dput(nd->dentry);
1457                 nd->dentry = dentry;
1458                 if (error)
1459                         goto exit;
1460                 /* Don't check for write permission, don't truncate */
1461                 acc_mode = 0;
1462                 flag &= ~O_TRUNC;
1463                 goto ok;
1464         }
1465
1466         /*
1467          * It already exists.
1468          */
1469         up(&dir->d_inode->i_sem);
1470
1471         error = -EEXIST;
1472         if (flag & O_EXCL)
1473                 goto exit_dput;
1474
1475         if (d_mountpoint(dentry)) {
1476                 error = -ELOOP;
1477                 if (flag & O_NOFOLLOW)
1478                         goto exit_dput;
1479                 while (__follow_down(&nd->mnt,&dentry) && d_mountpoint(dentry));
1480         }
1481         error = -ENOENT;
1482         if (!dentry->d_inode)
1483                 goto exit_dput;
1484         if (dentry->d_inode->i_op && dentry->d_inode->i_op->follow_link)
1485                 goto do_link;
1486
1487         dput(nd->dentry);
1488         nd->dentry = dentry;
1489         error = -EISDIR;
1490         if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode))
1491                 goto exit;
1492 ok:
1493         error = may_open(nd, acc_mode, flag);
1494         if (error)
1495                 goto exit;
1496         return 0;
1497
1498 exit_dput:
1499         dput(dentry);
1500 exit:
1501         path_release(nd);
1502         return error;
1503
1504 do_link:
1505         error = -ELOOP;
1506         if (flag & O_NOFOLLOW)
1507                 goto exit_dput;
1508         /*
1509          * This is subtle. Instead of calling do_follow_link() we do the
1510          * thing by hands. The reason is that this way we have zero link_count
1511          * and path_walk() (called from ->follow_link) honoring LOOKUP_PARENT.
1512          * After that we have the parent and last component, i.e.
1513          * we are in the same situation as after the first path_walk().
1514          * Well, almost - if the last component is normal we get its copy
1515          * stored in nd->last.name and we will have to putname() it when we
1516          * are done. Procfs-like symlinks just set LAST_BIND.
1517          */
1518         nd->flags |= LOOKUP_PARENT;
1519         error = security_inode_follow_link(dentry, nd);
1520         if (error)
1521                 goto exit_dput;
1522         error = __do_follow_link(dentry, nd);
1523         dput(dentry);
1524         if (error)
1525                 return error;
1526         nd->flags &= ~LOOKUP_PARENT;
1527         if (nd->last_type == LAST_BIND) {
1528                 dentry = nd->dentry;
1529                 goto ok;
1530         }
1531         error = -EISDIR;
1532         if (nd->last_type != LAST_NORM)
1533                 goto exit;
1534         if (nd->last.name[nd->last.len]) {
1535                 putname(nd->last.name);
1536                 goto exit;
1537         }
1538         error = -ELOOP;
1539         if (count++==32) {
1540                 putname(nd->last.name);
1541                 goto exit;
1542         }
1543         dir = nd->dentry;
1544         down(&dir->d_inode->i_sem);
1545         dentry = __lookup_hash(&nd->last, nd->dentry, nd);
1546         putname(nd->last.name);
1547         goto do_last;
1548 }
1549
1550 /**
1551  * lookup_create - lookup a dentry, creating it if it doesn't exist
1552  * @nd: nameidata info
1553  * @is_dir: directory flag
1554  *
1555  * Simple function to lookup and return a dentry and create it
1556  * if it doesn't exist.  Is SMP-safe.
1557  */
1558 struct dentry *lookup_create(struct nameidata *nd, int is_dir)
1559 {
1560         struct dentry *dentry;
1561
1562         down(&nd->dentry->d_inode->i_sem);
1563         dentry = ERR_PTR(-EEXIST);
1564         if (nd->last_type != LAST_NORM)
1565                 goto fail;
1566         nd->flags &= ~LOOKUP_PARENT;
1567         dentry = lookup_hash(&nd->last, nd->dentry);
1568         if (IS_ERR(dentry))
1569                 goto fail;
1570         if (!is_dir && nd->last.name[nd->last.len] && !dentry->d_inode)
1571                 goto enoent;
1572         return dentry;
1573 enoent:
1574         dput(dentry);
1575         dentry = ERR_PTR(-ENOENT);
1576 fail:
1577         return dentry;
1578 }
1579
1580 int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1581 {
1582         int error = may_create(dir, dentry, NULL);
1583
1584         if (error)
1585                 return error;
1586
1587         if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
1588                 return -EPERM;
1589
1590         if (!dir->i_op || !dir->i_op->mknod)
1591                 return -EPERM;
1592
1593         error = security_inode_mknod(dir, dentry, mode, dev);
1594         if (error)
1595                 return error;
1596
1597         DQUOT_INIT(dir);
1598         error = dir->i_op->mknod(dir, dentry, mode, dev);
1599         if (!error) {
1600                 inode_dir_notify(dir, DN_CREATE);
1601                 security_inode_post_mknod(dir, dentry, mode, dev);
1602         }
1603         return error;
1604 }
1605
1606 asmlinkage long sys_mknod(const char __user * filename, int mode, unsigned dev)
1607 {
1608         int error = 0;
1609         char * tmp;
1610         struct dentry * dentry;
1611         struct nameidata nd;
1612
1613         if (S_ISDIR(mode))
1614                 return -EPERM;
1615         tmp = getname(filename);
1616         if (IS_ERR(tmp))
1617                 return PTR_ERR(tmp);
1618
1619         error = path_lookup(tmp, LOOKUP_PARENT, &nd);
1620         if (error)
1621                 goto out;
1622         dentry = lookup_create(&nd, 0);
1623         error = PTR_ERR(dentry);
1624
1625         if (!IS_POSIXACL(nd.dentry->d_inode))
1626                 mode &= ~current->fs->umask;
1627         if (!IS_ERR(dentry)) {
1628                 switch (mode & S_IFMT) {
1629                 case 0: case S_IFREG:
1630                         error = vfs_create(nd.dentry->d_inode,dentry,mode,&nd);
1631                         break;
1632                 case S_IFCHR: case S_IFBLK:
1633                         error = vfs_mknod(nd.dentry->d_inode,dentry,mode,
1634                                         new_decode_dev(dev));
1635                         break;
1636                 case S_IFIFO: case S_IFSOCK:
1637                         error = vfs_mknod(nd.dentry->d_inode,dentry,mode,0);
1638                         break;
1639                 case S_IFDIR:
1640                         error = -EPERM;
1641                         break;
1642                 default:
1643                         error = -EINVAL;
1644                 }
1645                 dput(dentry);
1646         }
1647         up(&nd.dentry->d_inode->i_sem);
1648         path_release(&nd);
1649 out:
1650         putname(tmp);
1651
1652         return error;
1653 }
1654
1655 int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1656 {
1657         int error = may_create(dir, dentry, NULL);
1658
1659         if (error)
1660                 return error;
1661
1662         if (!dir->i_op || !dir->i_op->mkdir)
1663                 return -EPERM;
1664
1665         mode &= (S_IRWXUGO|S_ISVTX);
1666         error = security_inode_mkdir(dir, dentry, mode);
1667         if (error)
1668                 return error;
1669
1670         DQUOT_INIT(dir);
1671         error = dir->i_op->mkdir(dir, dentry, mode);
1672         if (!error) {
1673                 inode_dir_notify(dir, DN_CREATE);
1674                 security_inode_post_mkdir(dir,dentry, mode);
1675         }
1676         return error;
1677 }
1678
1679 asmlinkage long sys_mkdir(const char __user * pathname, int mode)
1680 {
1681         int error = 0;
1682         char * tmp;
1683
1684         tmp = getname(pathname);
1685         error = PTR_ERR(tmp);
1686         if (!IS_ERR(tmp)) {
1687                 struct dentry *dentry;
1688                 struct nameidata nd;
1689
1690                 error = path_lookup(tmp, LOOKUP_PARENT, &nd);
1691                 if (error)
1692                         goto out;
1693                 dentry = lookup_create(&nd, 1);
1694                 error = PTR_ERR(dentry);
1695                 if (!IS_ERR(dentry)) {
1696                         if (!IS_POSIXACL(nd.dentry->d_inode))
1697                                 mode &= ~current->fs->umask;
1698                         error = vfs_mkdir(nd.dentry->d_inode, dentry, mode);
1699                         dput(dentry);
1700                 }
1701                 up(&nd.dentry->d_inode->i_sem);
1702                 path_release(&nd);
1703 out:
1704                 putname(tmp);
1705         }
1706
1707         return error;
1708 }
1709
1710 /*
1711  * We try to drop the dentry early: we should have
1712  * a usage count of 2 if we're the only user of this
1713  * dentry, and if that is true (possibly after pruning
1714  * the dcache), then we drop the dentry now.
1715  *
1716  * A low-level filesystem can, if it choses, legally
1717  * do a
1718  *
1719  *      if (!d_unhashed(dentry))
1720  *              return -EBUSY;
1721  *
1722  * if it cannot handle the case of removing a directory
1723  * that is still in use by something else..
1724  */
1725 void dentry_unhash(struct dentry *dentry)
1726 {
1727         dget(dentry);
1728         if (atomic_read(&dentry->d_count))
1729                 shrink_dcache_parent(dentry);
1730         spin_lock(&dcache_lock);
1731         spin_lock(&dentry->d_lock);
1732         if (atomic_read(&dentry->d_count) == 2)
1733                 __d_drop(dentry);
1734         spin_unlock(&dentry->d_lock);
1735         spin_unlock(&dcache_lock);
1736 }
1737
1738 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
1739 {
1740         int error = may_delete(dir, dentry, 1);
1741
1742         if (error)
1743                 return error;
1744
1745         if (!dir->i_op || !dir->i_op->rmdir)
1746                 return -EPERM;
1747
1748         DQUOT_INIT(dir);
1749
1750         down(&dentry->d_inode->i_sem);
1751         dentry_unhash(dentry);
1752         if (d_mountpoint(dentry))
1753                 error = -EBUSY;
1754         else {
1755                 error = security_inode_rmdir(dir, dentry);
1756                 if (!error) {
1757                         error = dir->i_op->rmdir(dir, dentry);
1758                         if (!error)
1759                                 dentry->d_inode->i_flags |= S_DEAD;
1760                 }
1761         }
1762         up(&dentry->d_inode->i_sem);
1763         if (!error) {
1764                 inode_dir_notify(dir, DN_DELETE);
1765                 d_delete(dentry);
1766         }
1767         dput(dentry);
1768
1769         return error;
1770 }
1771
1772 asmlinkage long sys_rmdir(const char __user * pathname)
1773 {
1774         int error = 0;
1775         char * name;
1776         struct dentry *dentry;
1777         struct nameidata nd;
1778
1779         name = getname(pathname);
1780         if(IS_ERR(name))
1781                 return PTR_ERR(name);
1782
1783         error = path_lookup(name, LOOKUP_PARENT, &nd);
1784         if (error)
1785                 goto exit;
1786
1787         switch(nd.last_type) {
1788                 case LAST_DOTDOT:
1789                         error = -ENOTEMPTY;
1790                         goto exit1;
1791                 case LAST_DOT:
1792                         error = -EINVAL;
1793                         goto exit1;
1794                 case LAST_ROOT:
1795                         error = -EBUSY;
1796                         goto exit1;
1797         }
1798         down(&nd.dentry->d_inode->i_sem);
1799         dentry = lookup_hash(&nd.last, nd.dentry);
1800         error = PTR_ERR(dentry);
1801         if (!IS_ERR(dentry)) {
1802                 error = vfs_rmdir(nd.dentry->d_inode, dentry);
1803                 dput(dentry);
1804         }
1805         up(&nd.dentry->d_inode->i_sem);
1806 exit1:
1807         path_release(&nd);
1808 exit:
1809         putname(name);
1810         return error;
1811 }
1812
1813 int vfs_unlink(struct inode *dir, struct dentry *dentry)
1814 {
1815         int error = may_delete(dir, dentry, 0);
1816
1817         if (error)
1818                 return error;
1819
1820         if (!dir->i_op || !dir->i_op->unlink)
1821                 return -EPERM;
1822
1823         DQUOT_INIT(dir);
1824
1825         down(&dentry->d_inode->i_sem);
1826         if (d_mountpoint(dentry))
1827                 error = -EBUSY;
1828         else {
1829                 error = security_inode_unlink(dir, dentry);
1830                 if (!error)
1831                         error = dir->i_op->unlink(dir, dentry);
1832         }
1833         up(&dentry->d_inode->i_sem);
1834
1835         /* We don't d_delete() NFS sillyrenamed files--they still exist. */
1836         if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
1837                 d_delete(dentry);
1838                 inode_dir_notify(dir, DN_DELETE);
1839         }
1840         return error;
1841 }
1842
1843 /*
1844  * Make sure that the actual truncation of the file will occur outside its
1845  * directory's i_sem.  Truncate can take a long time if there is a lot of
1846  * writeout happening, and we don't want to prevent access to the directory
1847  * while waiting on the I/O.
1848  */
1849 asmlinkage long sys_unlink(const char __user * pathname)
1850 {
1851         int error = 0;
1852         char * name;
1853         struct dentry *dentry;
1854         struct nameidata nd;
1855         struct inode *inode = NULL;
1856
1857         name = getname(pathname);
1858         if(IS_ERR(name))
1859                 return PTR_ERR(name);
1860
1861         error = path_lookup(name, LOOKUP_PARENT, &nd);
1862         if (error)
1863                 goto exit;
1864         error = -EISDIR;
1865         if (nd.last_type != LAST_NORM)
1866                 goto exit1;
1867         down(&nd.dentry->d_inode->i_sem);
1868         dentry = lookup_hash(&nd.last, nd.dentry);
1869         error = PTR_ERR(dentry);
1870         if (!IS_ERR(dentry)) {
1871                 /* Why not before? Because we want correct error value */
1872                 if (nd.last.name[nd.last.len])
1873                         goto slashes;
1874                 inode = dentry->d_inode;
1875                 if (inode)
1876                         atomic_inc(&inode->i_count);
1877                 error = vfs_unlink(nd.dentry->d_inode, dentry);
1878         exit2:
1879                 dput(dentry);
1880         }
1881         up(&nd.dentry->d_inode->i_sem);
1882         if (inode)
1883                 iput(inode);    /* truncate the inode here */
1884 exit1:
1885         path_release(&nd);
1886 exit:
1887         putname(name);
1888         return error;
1889
1890 slashes:
1891         error = !dentry->d_inode ? -ENOENT :
1892                 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
1893         goto exit2;
1894 }
1895
1896 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname, int mode)
1897 {
1898         int error = may_create(dir, dentry, NULL);
1899
1900         if (error)
1901                 return error;
1902
1903         if (!dir->i_op || !dir->i_op->symlink)
1904                 return -EPERM;
1905
1906         error = security_inode_symlink(dir, dentry, oldname);
1907         if (error)
1908                 return error;
1909
1910         DQUOT_INIT(dir);
1911         error = dir->i_op->symlink(dir, dentry, oldname);
1912         if (!error) {
1913                 inode_dir_notify(dir, DN_CREATE);
1914                 security_inode_post_symlink(dir, dentry, oldname);
1915         }
1916         return error;
1917 }
1918
1919 asmlinkage long sys_symlink(const char __user * oldname, const char __user * newname)
1920 {
1921         int error = 0;
1922         char * from;
1923         char * to;
1924
1925         from = getname(oldname);
1926         if(IS_ERR(from))
1927                 return PTR_ERR(from);
1928         to = getname(newname);
1929         error = PTR_ERR(to);
1930         if (!IS_ERR(to)) {
1931                 struct dentry *dentry;
1932                 struct nameidata nd;
1933
1934                 error = path_lookup(to, LOOKUP_PARENT, &nd);
1935                 if (error)
1936                         goto out;
1937                 dentry = lookup_create(&nd, 0);
1938                 error = PTR_ERR(dentry);
1939                 if (!IS_ERR(dentry)) {
1940                         error = vfs_symlink(nd.dentry->d_inode, dentry, from, S_IALLUGO);
1941                         dput(dentry);
1942                 }
1943                 up(&nd.dentry->d_inode->i_sem);
1944                 path_release(&nd);
1945 out:
1946                 putname(to);
1947         }
1948         putname(from);
1949         return error;
1950 }
1951
1952 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
1953 {
1954         struct inode *inode = old_dentry->d_inode;
1955         int error;
1956
1957         if (!inode)
1958                 return -ENOENT;
1959
1960         error = may_create(dir, new_dentry, NULL);
1961         if (error)
1962                 return error;
1963
1964         if (dir->i_sb != inode->i_sb)
1965                 return -EXDEV;
1966
1967         /*
1968          * A link to an append-only or immutable file cannot be created.
1969          */
1970         if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
1971                 return -EPERM;
1972         if (!dir->i_op || !dir->i_op->link)
1973                 return -EPERM;
1974         if (S_ISDIR(old_dentry->d_inode->i_mode))
1975                 return -EPERM;
1976
1977         error = security_inode_link(old_dentry, dir, new_dentry);
1978         if (error)
1979                 return error;
1980
1981         down(&old_dentry->d_inode->i_sem);
1982         DQUOT_INIT(dir);
1983         error = dir->i_op->link(old_dentry, dir, new_dentry);
1984         up(&old_dentry->d_inode->i_sem);
1985         if (!error) {
1986                 inode_dir_notify(dir, DN_CREATE);
1987                 security_inode_post_link(old_dentry, dir, new_dentry);
1988         }
1989         return error;
1990 }
1991
1992 /*
1993  * Hardlinks are often used in delicate situations.  We avoid
1994  * security-related surprises by not following symlinks on the
1995  * newname.  --KAB
1996  *
1997  * We don't follow them on the oldname either to be compatible
1998  * with linux 2.0, and to avoid hard-linking to directories
1999  * and other special files.  --ADM
2000  */
2001 asmlinkage long sys_link(const char __user * oldname, const char __user * newname)
2002 {
2003         struct dentry *new_dentry;
2004         struct nameidata nd, old_nd;
2005         int error;
2006         char * to;
2007
2008         to = getname(newname);
2009         if (IS_ERR(to))
2010                 return PTR_ERR(to);
2011
2012         error = __user_walk(oldname, 0, &old_nd);
2013         if (error)
2014                 goto exit;
2015         error = path_lookup(to, LOOKUP_PARENT, &nd);
2016         if (error)
2017                 goto out;
2018         error = -EXDEV;
2019         if (old_nd.mnt != nd.mnt)
2020                 goto out_release;
2021         new_dentry = lookup_create(&nd, 0);
2022         error = PTR_ERR(new_dentry);
2023         if (!IS_ERR(new_dentry)) {
2024                 error = vfs_link(old_nd.dentry, nd.dentry->d_inode, new_dentry);
2025                 dput(new_dentry);
2026         }
2027         up(&nd.dentry->d_inode->i_sem);
2028 out_release:
2029         path_release(&nd);
2030 out:
2031         path_release(&old_nd);
2032 exit:
2033         putname(to);
2034
2035         return error;
2036 }
2037
2038 /*
2039  * The worst of all namespace operations - renaming directory. "Perverted"
2040  * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
2041  * Problems:
2042  *      a) we can get into loop creation. Check is done in is_subdir().
2043  *      b) race potential - two innocent renames can create a loop together.
2044  *         That's where 4.4 screws up. Current fix: serialization on
2045  *         sb->s_vfs_rename_sem. We might be more accurate, but that's another
2046  *         story.
2047  *      c) we have to lock _three_ objects - parents and victim (if it exists).
2048  *         And that - after we got ->i_sem on parents (until then we don't know
2049  *         whether the target exists).  Solution: try to be smart with locking
2050  *         order for inodes.  We rely on the fact that tree topology may change
2051  *         only under ->s_vfs_rename_sem _and_ that parent of the object we
2052  *         move will be locked.  Thus we can rank directories by the tree
2053  *         (ancestors first) and rank all non-directories after them.
2054  *         That works since everybody except rename does "lock parent, lookup,
2055  *         lock child" and rename is under ->s_vfs_rename_sem.
2056  *         HOWEVER, it relies on the assumption that any object with ->lookup()
2057  *         has no more than 1 dentry.  If "hybrid" objects will ever appear,
2058  *         we'd better make sure that there's no link(2) for them.
2059  *      d) some filesystems don't support opened-but-unlinked directories,
2060  *         either because of layout or because they are not ready to deal with
2061  *         all cases correctly. The latter will be fixed (taking this sort of
2062  *         stuff into VFS), but the former is not going away. Solution: the same
2063  *         trick as in rmdir().
2064  *      e) conversion from fhandle to dentry may come in the wrong moment - when
2065  *         we are removing the target. Solution: we will have to grab ->i_sem
2066  *         in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
2067  *         ->i_sem on parents, which works but leads to some truely excessive
2068  *         locking].
2069  */
2070 int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
2071                struct inode *new_dir, struct dentry *new_dentry)
2072 {
2073         int error = 0;
2074         struct inode *target;
2075
2076         /*
2077          * If we are going to change the parent - check write permissions,
2078          * we'll need to flip '..'.
2079          */
2080         if (new_dir != old_dir) {
2081                 error = permission(old_dentry->d_inode, MAY_WRITE, NULL);
2082                 if (error)
2083                         return error;
2084         }
2085
2086         error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
2087         if (error)
2088                 return error;
2089
2090         target = new_dentry->d_inode;
2091         if (target) {
2092                 down(&target->i_sem);
2093                 dentry_unhash(new_dentry);
2094         }
2095         if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
2096                 error = -EBUSY;
2097         else
2098                 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
2099         if (target) {
2100                 if (!error)
2101                         target->i_flags |= S_DEAD;
2102                 up(&target->i_sem);
2103                 if (d_unhashed(new_dentry))
2104                         d_rehash(new_dentry);
2105                 dput(new_dentry);
2106         }
2107         if (!error) {
2108                 d_move(old_dentry,new_dentry);
2109                 security_inode_post_rename(old_dir, old_dentry,
2110                                            new_dir, new_dentry);
2111         }
2112         return error;
2113 }
2114
2115 int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
2116                struct inode *new_dir, struct dentry *new_dentry)
2117 {
2118         struct inode *target;
2119         int error;
2120
2121         error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
2122         if (error)
2123                 return error;
2124
2125         dget(new_dentry);
2126         target = new_dentry->d_inode;
2127         if (target)
2128                 down(&target->i_sem);
2129         if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
2130                 error = -EBUSY;
2131         else
2132                 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
2133         if (!error) {
2134                 /* The following d_move() should become unconditional */
2135                 if (!(old_dir->i_sb->s_type->fs_flags & FS_ODD_RENAME))
2136                         d_move(old_dentry, new_dentry);
2137                 security_inode_post_rename(old_dir, old_dentry, new_dir, new_dentry);
2138         }
2139         if (target)
2140                 up(&target->i_sem);
2141         dput(new_dentry);
2142         return error;
2143 }
2144
2145 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
2146                struct inode *new_dir, struct dentry *new_dentry)
2147 {
2148         int error;
2149         int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
2150
2151         if (old_dentry->d_inode == new_dentry->d_inode)
2152                 return 0;
2153
2154         error = may_delete(old_dir, old_dentry, is_dir);
2155         if (error)
2156                 return error;
2157
2158         if (!new_dentry->d_inode)
2159                 error = may_create(new_dir, new_dentry, NULL);
2160         else
2161                 error = may_delete(new_dir, new_dentry, is_dir);
2162         if (error)
2163                 return error;
2164
2165         if (!old_dir->i_op || !old_dir->i_op->rename)
2166                 return -EPERM;
2167
2168         DQUOT_INIT(old_dir);
2169         DQUOT_INIT(new_dir);
2170
2171         if (is_dir)
2172                 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
2173         else
2174                 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
2175         if (!error) {
2176                 if (old_dir == new_dir)
2177                         inode_dir_notify(old_dir, DN_RENAME);
2178                 else {
2179                         inode_dir_notify(old_dir, DN_DELETE);
2180                         inode_dir_notify(new_dir, DN_CREATE);
2181                 }
2182         }
2183         return error;
2184 }
2185
2186 static inline int do_rename(const char * oldname, const char * newname)
2187 {
2188         int error = 0;
2189         struct dentry * old_dir, * new_dir;
2190         struct dentry * old_dentry, *new_dentry;
2191         struct dentry * trap;
2192         struct nameidata oldnd, newnd;
2193
2194         error = path_lookup(oldname, LOOKUP_PARENT, &oldnd);
2195         if (error)
2196                 goto exit;
2197
2198         error = path_lookup(newname, LOOKUP_PARENT, &newnd);
2199         if (error)
2200                 goto exit1;
2201
2202         error = -EXDEV;
2203         if (oldnd.mnt != newnd.mnt)
2204                 goto exit2;
2205
2206         old_dir = oldnd.dentry;
2207         error = -EBUSY;
2208         if (oldnd.last_type != LAST_NORM)
2209                 goto exit2;
2210
2211         new_dir = newnd.dentry;
2212         if (newnd.last_type != LAST_NORM)
2213                 goto exit2;
2214
2215         trap = lock_rename(new_dir, old_dir);
2216
2217         old_dentry = lookup_hash(&oldnd.last, old_dir);
2218         error = PTR_ERR(old_dentry);
2219         if (IS_ERR(old_dentry))
2220                 goto exit3;
2221         /* source must exist */
2222         error = -ENOENT;
2223         if (!old_dentry->d_inode)
2224                 goto exit4;
2225         /* unless the source is a directory trailing slashes give -ENOTDIR */
2226         if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
2227                 error = -ENOTDIR;
2228                 if (oldnd.last.name[oldnd.last.len])
2229                         goto exit4;
2230                 if (newnd.last.name[newnd.last.len])
2231                         goto exit4;
2232         }
2233         /* source should not be ancestor of target */
2234         error = -EINVAL;
2235         if (old_dentry == trap)
2236                 goto exit4;
2237         new_dentry = lookup_hash(&newnd.last, new_dir);
2238         error = PTR_ERR(new_dentry);
2239         if (IS_ERR(new_dentry))
2240                 goto exit4;
2241         /* target should not be an ancestor of source */
2242         error = -ENOTEMPTY;
2243         if (new_dentry == trap)
2244                 goto exit5;
2245
2246         error = vfs_rename(old_dir->d_inode, old_dentry,
2247                                    new_dir->d_inode, new_dentry);
2248 exit5:
2249         dput(new_dentry);
2250 exit4:
2251         dput(old_dentry);
2252 exit3:
2253         unlock_rename(new_dir, old_dir);
2254 exit2:
2255         path_release(&newnd);
2256 exit1:
2257         path_release(&oldnd);
2258 exit:
2259         return error;
2260 }
2261
2262 asmlinkage long sys_rename(const char __user * oldname, const char __user * newname)
2263 {
2264         int error;
2265         char * from;
2266         char * to;
2267
2268         from = getname(oldname);
2269         if(IS_ERR(from))
2270                 return PTR_ERR(from);
2271         to = getname(newname);
2272         error = PTR_ERR(to);
2273         if (!IS_ERR(to)) {
2274                 error = do_rename(from,to);
2275                 putname(to);
2276         }
2277         putname(from);
2278         return error;
2279 }
2280
2281 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
2282 {
2283         int len;
2284
2285         len = PTR_ERR(link);
2286         if (IS_ERR(link))
2287                 goto out;
2288
2289         len = strlen(link);
2290         if (len > (unsigned) buflen)
2291                 len = buflen;
2292         if (copy_to_user(buffer, link, len))
2293                 len = -EFAULT;
2294 out:
2295         return len;
2296 }
2297
2298 /*
2299  * A helper for ->readlink().  This should be used *ONLY* for symlinks that
2300  * have ->follow_link() touching nd only in nd_set_link().  Using (or not
2301  * using) it for any given inode is up to filesystem.
2302  */
2303 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
2304 {
2305         struct nameidata nd;
2306         int res;
2307         nd.depth = 0;
2308         res = dentry->d_inode->i_op->follow_link(dentry, &nd);
2309         if (!res) {
2310                 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
2311                 if (dentry->d_inode->i_op->put_link)
2312                         dentry->d_inode->i_op->put_link(dentry, &nd);
2313         }
2314         return res;
2315 }
2316
2317 int vfs_follow_link(struct nameidata *nd, const char *link)
2318 {
2319         return __vfs_follow_link(nd, link);
2320 }
2321
2322 /* get the link contents into pagecache */
2323 static char *page_getlink(struct dentry * dentry, struct page **ppage)
2324 {
2325         struct page * page;
2326         struct address_space *mapping = dentry->d_inode->i_mapping;
2327         page = read_cache_page(mapping, 0, (filler_t *)mapping->a_ops->readpage,
2328                                 NULL);
2329         if (IS_ERR(page))
2330                 goto sync_fail;
2331         wait_on_page_locked(page);
2332         if (!PageUptodate(page))
2333                 goto async_fail;
2334         *ppage = page;
2335         return kmap(page);
2336
2337 async_fail:
2338         page_cache_release(page);
2339         return ERR_PTR(-EIO);
2340
2341 sync_fail:
2342         return (char*)page;
2343 }
2344
2345 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
2346 {
2347         struct page *page = NULL;
2348         char *s = page_getlink(dentry, &page);
2349         int res = vfs_readlink(dentry,buffer,buflen,s);
2350         if (page) {
2351                 kunmap(page);
2352                 page_cache_release(page);
2353         }
2354         return res;
2355 }
2356
2357 int page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
2358 {
2359         struct page *page;
2360         nd_set_link(nd, page_getlink(dentry, &page));
2361         return 0;
2362 }
2363
2364 void page_put_link(struct dentry *dentry, struct nameidata *nd)
2365 {
2366         if (!IS_ERR(nd_get_link(nd))) {
2367                 struct page *page;
2368                 page = find_get_page(dentry->d_inode->i_mapping, 0);
2369                 if (!page)
2370                         BUG();
2371                 kunmap(page);
2372                 page_cache_release(page);
2373                 page_cache_release(page);
2374         }
2375 }
2376
2377 int page_symlink(struct inode *inode, const char *symname, int len)
2378 {
2379         struct address_space *mapping = inode->i_mapping;
2380         struct page *page = grab_cache_page(mapping, 0);
2381         int err = -ENOMEM;
2382         char *kaddr;
2383
2384         if (!page)
2385                 goto fail;
2386         err = mapping->a_ops->prepare_write(NULL, page, 0, len-1);
2387         if (err)
2388                 goto fail_map;
2389         kaddr = kmap_atomic(page, KM_USER0);
2390         memcpy(kaddr, symname, len-1);
2391         kunmap_atomic(kaddr, KM_USER0);
2392         mapping->a_ops->commit_write(NULL, page, 0, len-1);
2393         /*
2394          * Notice that we are _not_ going to block here - end of page is
2395          * unmapped, so this will only try to map the rest of page, see
2396          * that it is unmapped (typically even will not look into inode -
2397          * ->i_size will be enough for everything) and zero it out.
2398          * OTOH it's obviously correct and should make the page up-to-date.
2399          */
2400         if (!PageUptodate(page)) {
2401                 err = mapping->a_ops->readpage(NULL, page);
2402                 wait_on_page_locked(page);
2403         } else {
2404                 unlock_page(page);
2405         }
2406         page_cache_release(page);
2407         if (err < 0)
2408                 goto fail;
2409         mark_inode_dirty(inode);
2410         return 0;
2411 fail_map:
2412         unlock_page(page);
2413         page_cache_release(page);
2414 fail:
2415         return err;
2416 }
2417
2418 struct inode_operations page_symlink_inode_operations = {
2419         .readlink       = generic_readlink,
2420         .follow_link    = page_follow_link_light,
2421         .put_link       = page_put_link,
2422 };
2423
2424 EXPORT_SYMBOL(__user_walk);
2425 EXPORT_SYMBOL(follow_down);
2426 EXPORT_SYMBOL(follow_up);
2427 EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
2428 EXPORT_SYMBOL(getname);
2429 EXPORT_SYMBOL(lock_rename);
2430 EXPORT_SYMBOL(lookup_hash);
2431 EXPORT_SYMBOL(lookup_one_len);
2432 EXPORT_SYMBOL(page_follow_link_light);
2433 EXPORT_SYMBOL(page_put_link);
2434 EXPORT_SYMBOL(page_readlink);
2435 EXPORT_SYMBOL(page_symlink);
2436 EXPORT_SYMBOL(page_symlink_inode_operations);
2437 EXPORT_SYMBOL(path_lookup);
2438 EXPORT_SYMBOL(path_release);
2439 EXPORT_SYMBOL(path_walk);
2440 EXPORT_SYMBOL(permission);
2441 EXPORT_SYMBOL(unlock_rename);
2442 EXPORT_SYMBOL(vfs_create);
2443 EXPORT_SYMBOL(vfs_follow_link);
2444 EXPORT_SYMBOL(vfs_link);
2445 EXPORT_SYMBOL(vfs_mkdir);
2446 EXPORT_SYMBOL(vfs_mknod);
2447 EXPORT_SYMBOL(generic_permission);
2448 EXPORT_SYMBOL(vfs_readlink);
2449 EXPORT_SYMBOL(vfs_rename);
2450 EXPORT_SYMBOL(vfs_rmdir);
2451 EXPORT_SYMBOL(vfs_symlink);
2452 EXPORT_SYMBOL(vfs_unlink);
2453 EXPORT_SYMBOL(dentry_unhash);
2454 EXPORT_SYMBOL(generic_readlink);