Root/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/fsnotify.h>
25#include <linux/personality.h>
26#include <linux/security.h>
27#include <linux/ima.h>
28#include <linux/syscalls.h>
29#include <linux/mount.h>
30#include <linux/audit.h>
31#include <linux/capability.h>
32#include <linux/file.h>
33#include <linux/fcntl.h>
34#include <linux/device_cgroup.h>
35#include <linux/fs_struct.h>
36#include <asm/uaccess.h>
37
38#define ACC_MODE(x) ("\000\004\002\006"[(x)&O_ACCMODE])
39
40/* [Feb-1997 T. Schoebel-Theuer]
41 * Fundamental changes in the pathname lookup mechanisms (namei)
42 * were necessary because of omirr. The reason is that omirr needs
43 * to know the _real_ pathname, not the user-supplied one, in case
44 * of symlinks (and also when transname replacements occur).
45 *
46 * The new code replaces the old recursive symlink resolution with
47 * an iterative one (in case of non-nested symlink chains). It does
48 * this with calls to <fs>_follow_link().
49 * As a side effect, dir_namei(), _namei() and follow_link() are now
50 * replaced with a single function lookup_dentry() that can handle all
51 * the special cases of the former code.
52 *
53 * With the new dcache, the pathname is stored at each inode, at least as
54 * long as the refcount of the inode is positive. As a side effect, the
55 * size of the dcache depends on the inode cache and thus is dynamic.
56 *
57 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
58 * resolution to correspond with current state of the code.
59 *
60 * Note that the symlink resolution is not *completely* iterative.
61 * There is still a significant amount of tail- and mid- recursion in
62 * the algorithm. Also, note that <fs>_readlink() is not used in
63 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
64 * may return different results than <fs>_follow_link(). Many virtual
65 * filesystems (including /proc) exhibit this behavior.
66 */
67
68/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
69 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
70 * and the name already exists in form of a symlink, try to create the new
71 * name indicated by the symlink. The old code always complained that the
72 * name already exists, due to not following the symlink even if its target
73 * is nonexistent. The new semantics affects also mknod() and link() when
74 * the name is a symlink pointing to a non-existant name.
75 *
76 * I don't know which semantics is the right one, since I have no access
77 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
78 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
79 * "old" one. Personally, I think the new semantics is much more logical.
80 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
81 * file does succeed in both HP-UX and SunOs, but not in Solaris
82 * and in the old Linux semantics.
83 */
84
85/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
86 * semantics. See the comments in "open_namei" and "do_link" below.
87 *
88 * [10-Sep-98 Alan Modra] Another symlink change.
89 */
90
91/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
92 * inside the path - always follow.
93 * in the last component in creation/removal/renaming - never follow.
94 * if LOOKUP_FOLLOW passed - follow.
95 * if the pathname has trailing slashes - follow.
96 * otherwise - don't follow.
97 * (applied in that order).
98 *
99 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
100 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
101 * During the 2.4 we need to fix the userland stuff depending on it -
102 * hopefully we will be able to get rid of that wart in 2.5. So far only
103 * XEmacs seems to be relying on it...
104 */
105/*
106 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
107 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
108 * any extra contention...
109 */
110
111static int __link_path_walk(const char *name, struct nameidata *nd);
112
113/* In order to reduce some races, while at the same time doing additional
114 * checking and hopefully speeding things up, we copy filenames to the
115 * kernel data space before using them..
116 *
117 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
118 * PATH_MAX includes the nul terminator --RR.
119 */
120static int do_getname(const char __user *filename, char *page)
121{
122    int retval;
123    unsigned long len = PATH_MAX;
124
125    if (!segment_eq(get_fs(), KERNEL_DS)) {
126        if ((unsigned long) filename >= TASK_SIZE)
127            return -EFAULT;
128        if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
129            len = TASK_SIZE - (unsigned long) filename;
130    }
131
132    retval = strncpy_from_user(page, filename, len);
133    if (retval > 0) {
134        if (retval < len)
135            return 0;
136        return -ENAMETOOLONG;
137    } else if (!retval)
138        retval = -ENOENT;
139    return retval;
140}
141
142char * getname(const char __user * filename)
143{
144    char *tmp, *result;
145
146    result = ERR_PTR(-ENOMEM);
147    tmp = __getname();
148    if (tmp) {
149        int retval = do_getname(filename, tmp);
150
151        result = tmp;
152        if (retval < 0) {
153            __putname(tmp);
154            result = ERR_PTR(retval);
155        }
156    }
157    audit_getname(result);
158    return result;
159}
160
161#ifdef CONFIG_AUDITSYSCALL
162void putname(const char *name)
163{
164    if (unlikely(!audit_dummy_context()))
165        audit_putname(name);
166    else
167        __putname(name);
168}
169EXPORT_SYMBOL(putname);
170#endif
171
172
173/**
174 * generic_permission - check for access rights on a Posix-like filesystem
175 * @inode: inode to check access rights for
176 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
177 * @check_acl: optional callback to check for Posix ACLs
178 *
179 * Used to check for read/write/execute permissions on a file.
180 * We use "fsuid" for this, letting us set arbitrary permissions
181 * for filesystem access without changing the "normal" uids which
182 * are used for other things..
183 */
184int generic_permission(struct inode *inode, int mask,
185        int (*check_acl)(struct inode *inode, int mask))
186{
187    umode_t mode = inode->i_mode;
188
189    mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
190
191    if (current_fsuid() == inode->i_uid)
192        mode >>= 6;
193    else {
194        if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
195            int error = check_acl(inode, mask);
196            if (error == -EACCES)
197                goto check_capabilities;
198            else if (error != -EAGAIN)
199                return error;
200        }
201
202        if (in_group_p(inode->i_gid))
203            mode >>= 3;
204    }
205
206    /*
207     * If the DACs are ok we don't need any capability check.
208     */
209    if ((mask & ~mode) == 0)
210        return 0;
211
212 check_capabilities:
213    /*
214     * Read/write DACs are always overridable.
215     * Executable DACs are overridable if at least one exec bit is set.
216     */
217    if (!(mask & MAY_EXEC) || execute_ok(inode))
218        if (capable(CAP_DAC_OVERRIDE))
219            return 0;
220
221    /*
222     * Searching includes executable on directories, else just read.
223     */
224    if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
225        if (capable(CAP_DAC_READ_SEARCH))
226            return 0;
227
228    return -EACCES;
229}
230
231/**
232 * inode_permission - check for access rights to a given inode
233 * @inode: inode to check permission on
234 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
235 *
236 * Used to check for read/write/execute permissions on an inode.
237 * We use "fsuid" for this, letting us set arbitrary permissions
238 * for filesystem access without changing the "normal" uids which
239 * are used for other things.
240 */
241int inode_permission(struct inode *inode, int mask)
242{
243    int retval;
244
245    if (mask & MAY_WRITE) {
246        umode_t mode = inode->i_mode;
247
248        /*
249         * Nobody gets write access to a read-only fs.
250         */
251        if (IS_RDONLY(inode) &&
252            (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
253            return -EROFS;
254
255        /*
256         * Nobody gets write access to an immutable file.
257         */
258        if (IS_IMMUTABLE(inode))
259            return -EACCES;
260    }
261
262    if (inode->i_op->permission)
263        retval = inode->i_op->permission(inode, mask);
264    else
265        retval = generic_permission(inode, mask, NULL);
266
267    if (retval)
268        return retval;
269
270    retval = devcgroup_inode_permission(inode, mask);
271    if (retval)
272        return retval;
273
274    return security_inode_permission(inode,
275            mask & (MAY_READ|MAY_WRITE|MAY_EXEC|MAY_APPEND));
276}
277
278/**
279 * file_permission - check for additional access rights to a given file
280 * @file: file to check access rights for
281 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
282 *
283 * Used to check for read/write/execute permissions on an already opened
284 * file.
285 *
286 * Note:
287 * Do not use this function in new code. All access checks should
288 * be done using inode_permission().
289 */
290int file_permission(struct file *file, int mask)
291{
292    return inode_permission(file->f_path.dentry->d_inode, mask);
293}
294
295/*
296 * get_write_access() gets write permission for a file.
297 * put_write_access() releases this write permission.
298 * This is used for regular files.
299 * We cannot support write (and maybe mmap read-write shared) accesses and
300 * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
301 * can have the following values:
302 * 0: no writers, no VM_DENYWRITE mappings
303 * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
304 * > 0: (i_writecount) users are writing to the file.
305 *
306 * Normally we operate on that counter with atomic_{inc,dec} and it's safe
307 * except for the cases where we don't hold i_writecount yet. Then we need to
308 * use {get,deny}_write_access() - these functions check the sign and refuse
309 * to do the change if sign is wrong. Exclusion between them is provided by
310 * the inode->i_lock spinlock.
311 */
312
313int get_write_access(struct inode * inode)
314{
315    spin_lock(&inode->i_lock);
316    if (atomic_read(&inode->i_writecount) < 0) {
317        spin_unlock(&inode->i_lock);
318        return -ETXTBSY;
319    }
320    atomic_inc(&inode->i_writecount);
321    spin_unlock(&inode->i_lock);
322
323    return 0;
324}
325
326int deny_write_access(struct file * file)
327{
328    struct inode *inode = file->f_path.dentry->d_inode;
329
330    spin_lock(&inode->i_lock);
331    if (atomic_read(&inode->i_writecount) > 0) {
332        spin_unlock(&inode->i_lock);
333        return -ETXTBSY;
334    }
335    atomic_dec(&inode->i_writecount);
336    spin_unlock(&inode->i_lock);
337
338    return 0;
339}
340
341/**
342 * path_get - get a reference to a path
343 * @path: path to get the reference to
344 *
345 * Given a path increment the reference count to the dentry and the vfsmount.
346 */
347void path_get(struct path *path)
348{
349    mntget(path->mnt);
350    dget(path->dentry);
351}
352EXPORT_SYMBOL(path_get);
353
354/**
355 * path_put - put a reference to a path
356 * @path: path to put the reference to
357 *
358 * Given a path decrement the reference count to the dentry and the vfsmount.
359 */
360void path_put(struct path *path)
361{
362    dput(path->dentry);
363    mntput(path->mnt);
364}
365EXPORT_SYMBOL(path_put);
366
367/**
368 * release_open_intent - free up open intent resources
369 * @nd: pointer to nameidata
370 */
371void release_open_intent(struct nameidata *nd)
372{
373    if (nd->intent.open.file->f_path.dentry == NULL)
374        put_filp(nd->intent.open.file);
375    else
376        fput(nd->intent.open.file);
377}
378
379static inline struct dentry *
380do_revalidate(struct dentry *dentry, struct nameidata *nd)
381{
382    int status = dentry->d_op->d_revalidate(dentry, nd);
383    if (unlikely(status <= 0)) {
384        /*
385         * The dentry failed validation.
386         * If d_revalidate returned 0 attempt to invalidate
387         * the dentry otherwise d_revalidate is asking us
388         * to return a fail status.
389         */
390        if (!status) {
391            if (!d_invalidate(dentry)) {
392                dput(dentry);
393                dentry = NULL;
394            }
395        } else {
396            dput(dentry);
397            dentry = ERR_PTR(status);
398        }
399    }
400    return dentry;
401}
402
403/*
404 * Internal lookup() using the new generic dcache.
405 * SMP-safe
406 */
407static struct dentry * cached_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
408{
409    struct dentry * dentry = __d_lookup(parent, name);
410
411    /* lockess __d_lookup may fail due to concurrent d_move()
412     * in some unrelated directory, so try with d_lookup
413     */
414    if (!dentry)
415        dentry = d_lookup(parent, name);
416
417    if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
418        dentry = do_revalidate(dentry, nd);
419
420    return dentry;
421}
422
423/*
424 * Short-cut version of permission(), for calling by
425 * path_walk(), when dcache lock is held. Combines parts
426 * of permission() and generic_permission(), and tests ONLY for
427 * MAY_EXEC permission.
428 *
429 * If appropriate, check DAC only. If not appropriate, or
430 * short-cut DAC fails, then call permission() to do more
431 * complete permission check.
432 */
433static int exec_permission_lite(struct inode *inode)
434{
435    umode_t mode = inode->i_mode;
436
437    if (inode->i_op->permission)
438        return -EAGAIN;
439
440    if (current_fsuid() == inode->i_uid)
441        mode >>= 6;
442    else if (in_group_p(inode->i_gid))
443        mode >>= 3;
444
445    if (mode & MAY_EXEC)
446        goto ok;
447
448    if ((inode->i_mode & S_IXUGO) && capable(CAP_DAC_OVERRIDE))
449        goto ok;
450
451    if (S_ISDIR(inode->i_mode) && capable(CAP_DAC_OVERRIDE))
452        goto ok;
453
454    if (S_ISDIR(inode->i_mode) && capable(CAP_DAC_READ_SEARCH))
455        goto ok;
456
457    return -EACCES;
458ok:
459    return security_inode_permission(inode, MAY_EXEC);
460}
461
462/*
463 * This is called when everything else fails, and we actually have
464 * to go to the low-level filesystem to find out what we should do..
465 *
466 * We get the directory semaphore, and after getting that we also
467 * make sure that nobody added the entry to the dcache in the meantime..
468 * SMP-safe
469 */
470static struct dentry * real_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
471{
472    struct dentry * result;
473    struct inode *dir = parent->d_inode;
474
475    mutex_lock(&dir->i_mutex);
476    /*
477     * First re-do the cached lookup just in case it was created
478     * while we waited for the directory semaphore..
479     *
480     * FIXME! This could use version numbering or similar to
481     * avoid unnecessary cache lookups.
482     *
483     * The "dcache_lock" is purely to protect the RCU list walker
484     * from concurrent renames at this point (we mustn't get false
485     * negatives from the RCU list walk here, unlike the optimistic
486     * fast walk).
487     *
488     * so doing d_lookup() (with seqlock), instead of lockfree __d_lookup
489     */
490    result = d_lookup(parent, name);
491    if (!result) {
492        struct dentry *dentry;
493
494        /* Don't create child dentry for a dead directory. */
495        result = ERR_PTR(-ENOENT);
496        if (IS_DEADDIR(dir))
497            goto out_unlock;
498
499        dentry = d_alloc(parent, name);
500        result = ERR_PTR(-ENOMEM);
501        if (dentry) {
502            result = dir->i_op->lookup(dir, dentry, nd);
503            if (result)
504                dput(dentry);
505            else
506                result = dentry;
507        }
508out_unlock:
509        mutex_unlock(&dir->i_mutex);
510        return result;
511    }
512
513    /*
514     * Uhhuh! Nasty case: the cache was re-populated while
515     * we waited on the semaphore. Need to revalidate.
516     */
517    mutex_unlock(&dir->i_mutex);
518    if (result->d_op && result->d_op->d_revalidate) {
519        result = do_revalidate(result, nd);
520        if (!result)
521            result = ERR_PTR(-ENOENT);
522    }
523    return result;
524}
525
526/*
527 * Wrapper to retry pathname resolution whenever the underlying
528 * file system returns an ESTALE.
529 *
530 * Retry the whole path once, forcing real lookup requests
531 * instead of relying on the dcache.
532 */
533static __always_inline int link_path_walk(const char *name, struct nameidata *nd)
534{
535    struct path save = nd->path;
536    int result;
537
538    /* make sure the stuff we saved doesn't go away */
539    path_get(&save);
540
541    result = __link_path_walk(name, nd);
542    if (result == -ESTALE) {
543        /* nd->path had been dropped */
544        nd->path = save;
545        path_get(&nd->path);
546        nd->flags |= LOOKUP_REVAL;
547        result = __link_path_walk(name, nd);
548    }
549
550    path_put(&save);
551
552    return result;
553}
554
555static __always_inline void set_root(struct nameidata *nd)
556{
557    if (!nd->root.mnt) {
558        struct fs_struct *fs = current->fs;
559        read_lock(&fs->lock);
560        nd->root = fs->root;
561        path_get(&nd->root);
562        read_unlock(&fs->lock);
563    }
564}
565
566static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
567{
568    int res = 0;
569    char *name;
570    if (IS_ERR(link))
571        goto fail;
572
573    if (*link == '/') {
574        set_root(nd);
575        path_put(&nd->path);
576        nd->path = nd->root;
577        path_get(&nd->root);
578    }
579
580    res = link_path_walk(link, nd);
581    if (nd->depth || res || nd->last_type!=LAST_NORM)
582        return res;
583    /*
584     * If it is an iterative symlinks resolution in open_namei() we
585     * have to copy the last component. And all that crap because of
586     * bloody create() on broken symlinks. Furrfu...
587     */
588    name = __getname();
589    if (unlikely(!name)) {
590        path_put(&nd->path);
591        return -ENOMEM;
592    }
593    strcpy(name, nd->last.name);
594    nd->last.name = name;
595    return 0;
596fail:
597    path_put(&nd->path);
598    return PTR_ERR(link);
599}
600
601static void path_put_conditional(struct path *path, struct nameidata *nd)
602{
603    dput(path->dentry);
604    if (path->mnt != nd->path.mnt)
605        mntput(path->mnt);
606}
607
608static inline void path_to_nameidata(struct path *path, struct nameidata *nd)
609{
610    dput(nd->path.dentry);
611    if (nd->path.mnt != path->mnt)
612        mntput(nd->path.mnt);
613    nd->path.mnt = path->mnt;
614    nd->path.dentry = path->dentry;
615}
616
617static __always_inline int __do_follow_link(struct path *path, struct nameidata *nd)
618{
619    int error;
620    void *cookie;
621    struct dentry *dentry = path->dentry;
622
623    touch_atime(path->mnt, dentry);
624    nd_set_link(nd, NULL);
625
626    if (path->mnt != nd->path.mnt) {
627        path_to_nameidata(path, nd);
628        dget(dentry);
629    }
630    mntget(path->mnt);
631    cookie = dentry->d_inode->i_op->follow_link(dentry, nd);
632    error = PTR_ERR(cookie);
633    if (!IS_ERR(cookie)) {
634        char *s = nd_get_link(nd);
635        error = 0;
636        if (s)
637            error = __vfs_follow_link(nd, s);
638        if (dentry->d_inode->i_op->put_link)
639            dentry->d_inode->i_op->put_link(dentry, nd, cookie);
640    }
641    path_put(path);
642
643    return error;
644}
645
646/*
647 * This limits recursive symlink follows to 8, while
648 * limiting consecutive symlinks to 40.
649 *
650 * Without that kind of total limit, nasty chains of consecutive
651 * symlinks can cause almost arbitrarily long lookups.
652 */
653static inline int do_follow_link(struct path *path, struct nameidata *nd)
654{
655    int err = -ELOOP;
656    if (current->link_count >= MAX_NESTED_LINKS)
657        goto loop;
658    if (current->total_link_count >= 40)
659        goto loop;
660    BUG_ON(nd->depth >= MAX_NESTED_LINKS);
661    cond_resched();
662    err = security_inode_follow_link(path->dentry, nd);
663    if (err)
664        goto loop;
665    current->link_count++;
666    current->total_link_count++;
667    nd->depth++;
668    err = __do_follow_link(path, nd);
669    current->link_count--;
670    nd->depth--;
671    return err;
672loop:
673    path_put_conditional(path, nd);
674    path_put(&nd->path);
675    return err;
676}
677
678int follow_up(struct path *path)
679{
680    struct vfsmount *parent;
681    struct dentry *mountpoint;
682    spin_lock(&vfsmount_lock);
683    parent = path->mnt->mnt_parent;
684    if (parent == path->mnt) {
685        spin_unlock(&vfsmount_lock);
686        return 0;
687    }
688    mntget(parent);
689    mountpoint = dget(path->mnt->mnt_mountpoint);
690    spin_unlock(&vfsmount_lock);
691    dput(path->dentry);
692    path->dentry = mountpoint;
693    mntput(path->mnt);
694    path->mnt = parent;
695    return 1;
696}
697
698/* no need for dcache_lock, as serialization is taken care in
699 * namespace.c
700 */
701static int __follow_mount(struct path *path)
702{
703    int res = 0;
704    while (d_mountpoint(path->dentry)) {
705        struct vfsmount *mounted = lookup_mnt(path);
706        if (!mounted)
707            break;
708        dput(path->dentry);
709        if (res)
710            mntput(path->mnt);
711        path->mnt = mounted;
712        path->dentry = dget(mounted->mnt_root);
713        res = 1;
714    }
715    return res;
716}
717
718static void follow_mount(struct path *path)
719{
720    while (d_mountpoint(path->dentry)) {
721        struct vfsmount *mounted = lookup_mnt(path);
722        if (!mounted)
723            break;
724        dput(path->dentry);
725        mntput(path->mnt);
726        path->mnt = mounted;
727        path->dentry = dget(mounted->mnt_root);
728    }
729}
730
731/* no need for dcache_lock, as serialization is taken care in
732 * namespace.c
733 */
734int follow_down(struct path *path)
735{
736    struct vfsmount *mounted;
737
738    mounted = lookup_mnt(path);
739    if (mounted) {
740        dput(path->dentry);
741        mntput(path->mnt);
742        path->mnt = mounted;
743        path->dentry = dget(mounted->mnt_root);
744        return 1;
745    }
746    return 0;
747}
748
749static __always_inline void follow_dotdot(struct nameidata *nd)
750{
751    set_root(nd);
752
753    while(1) {
754        struct vfsmount *parent;
755        struct dentry *old = nd->path.dentry;
756
757        if (nd->path.dentry == nd->root.dentry &&
758            nd->path.mnt == nd->root.mnt) {
759            break;
760        }
761        spin_lock(&dcache_lock);
762        if (nd->path.dentry != nd->path.mnt->mnt_root) {
763            nd->path.dentry = dget(nd->path.dentry->d_parent);
764            spin_unlock(&dcache_lock);
765            dput(old);
766            break;
767        }
768        spin_unlock(&dcache_lock);
769        spin_lock(&vfsmount_lock);
770        parent = nd->path.mnt->mnt_parent;
771        if (parent == nd->path.mnt) {
772            spin_unlock(&vfsmount_lock);
773            break;
774        }
775        mntget(parent);
776        nd->path.dentry = dget(nd->path.mnt->mnt_mountpoint);
777        spin_unlock(&vfsmount_lock);
778        dput(old);
779        mntput(nd->path.mnt);
780        nd->path.mnt = parent;
781    }
782    follow_mount(&nd->path);
783}
784
785/*
786 * It's more convoluted than I'd like it to be, but... it's still fairly
787 * small and for now I'd prefer to have fast path as straight as possible.
788 * It _is_ time-critical.
789 */
790static int do_lookup(struct nameidata *nd, struct qstr *name,
791             struct path *path)
792{
793    struct vfsmount *mnt = nd->path.mnt;
794    struct dentry *dentry = __d_lookup(nd->path.dentry, name);
795
796    if (!dentry)
797        goto need_lookup;
798    if (dentry->d_op && dentry->d_op->d_revalidate)
799        goto need_revalidate;
800done:
801    path->mnt = mnt;
802    path->dentry = dentry;
803    __follow_mount(path);
804    return 0;
805
806need_lookup:
807    dentry = real_lookup(nd->path.dentry, name, nd);
808    if (IS_ERR(dentry))
809        goto fail;
810    goto done;
811
812need_revalidate:
813    dentry = do_revalidate(dentry, nd);
814    if (!dentry)
815        goto need_lookup;
816    if (IS_ERR(dentry))
817        goto fail;
818    goto done;
819
820fail:
821    return PTR_ERR(dentry);
822}
823
824/*
825 * Name resolution.
826 * This is the basic name resolution function, turning a pathname into
827 * the final dentry. We expect 'base' to be positive and a directory.
828 *
829 * Returns 0 and nd will have valid dentry and mnt on success.
830 * Returns error and drops reference to input namei data on failure.
831 */
832static int __link_path_walk(const char *name, struct nameidata *nd)
833{
834    struct path next;
835    struct inode *inode;
836    int err;
837    unsigned int lookup_flags = nd->flags;
838    
839    while (*name=='/')
840        name++;
841    if (!*name)
842        goto return_reval;
843
844    inode = nd->path.dentry->d_inode;
845    if (nd->depth)
846        lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
847
848    /* At this point we know we have a real path component. */
849    for(;;) {
850        unsigned long hash;
851        struct qstr this;
852        unsigned int c;
853
854        nd->flags |= LOOKUP_CONTINUE;
855        err = exec_permission_lite(inode);
856        if (err == -EAGAIN)
857            err = inode_permission(nd->path.dentry->d_inode,
858                           MAY_EXEC);
859        if (!err)
860            err = ima_path_check(&nd->path, MAY_EXEC,
861                             IMA_COUNT_UPDATE);
862         if (err)
863            break;
864
865        this.name = name;
866        c = *(const unsigned char *)name;
867
868        hash = init_name_hash();
869        do {
870            name++;
871            hash = partial_name_hash(c, hash);
872            c = *(const unsigned char *)name;
873        } while (c && (c != '/'));
874        this.len = name - (const char *) this.name;
875        this.hash = end_name_hash(hash);
876
877        /* remove trailing slashes? */
878        if (!c)
879            goto last_component;
880        while (*++name == '/');
881        if (!*name)
882            goto last_with_slashes;
883
884        /*
885         * "." and ".." are special - ".." especially so because it has
886         * to be able to know about the current root directory and
887         * parent relationships.
888         */
889        if (this.name[0] == '.') switch (this.len) {
890            default:
891                break;
892            case 2:
893                if (this.name[1] != '.')
894                    break;
895                follow_dotdot(nd);
896                inode = nd->path.dentry->d_inode;
897                /* fallthrough */
898            case 1:
899                continue;
900        }
901        /*
902         * See if the low-level filesystem might want
903         * to use its own hash..
904         */
905        if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
906            err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
907                                &this);
908            if (err < 0)
909                break;
910        }
911        /* This does the actual lookups.. */
912        err = do_lookup(nd, &this, &next);
913        if (err)
914            break;
915
916        err = -ENOENT;
917        inode = next.dentry->d_inode;
918        if (!inode)
919            goto out_dput;
920
921        if (inode->i_op->follow_link) {
922            err = do_follow_link(&next, nd);
923            if (err)
924                goto return_err;
925            err = -ENOENT;
926            inode = nd->path.dentry->d_inode;
927            if (!inode)
928                break;
929        } else
930            path_to_nameidata(&next, nd);
931        err = -ENOTDIR;
932        if (!inode->i_op->lookup)
933            break;
934        continue;
935        /* here ends the main loop */
936
937last_with_slashes:
938        lookup_flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
939last_component:
940        /* Clear LOOKUP_CONTINUE iff it was previously unset */
941        nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;
942        if (lookup_flags & LOOKUP_PARENT)
943            goto lookup_parent;
944        if (this.name[0] == '.') switch (this.len) {
945            default:
946                break;
947            case 2:
948                if (this.name[1] != '.')
949                    break;
950                follow_dotdot(nd);
951                inode = nd->path.dentry->d_inode;
952                /* fallthrough */
953            case 1:
954                goto return_reval;
955        }
956        if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
957            err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
958                                &this);
959            if (err < 0)
960                break;
961        }
962        err = do_lookup(nd, &this, &next);
963        if (err)
964            break;
965        inode = next.dentry->d_inode;
966        if ((lookup_flags & LOOKUP_FOLLOW)
967            && inode && inode->i_op->follow_link) {
968            err = do_follow_link(&next, nd);
969            if (err)
970                goto return_err;
971            inode = nd->path.dentry->d_inode;
972        } else
973            path_to_nameidata(&next, nd);
974        err = -ENOENT;
975        if (!inode)
976            break;
977        if (lookup_flags & LOOKUP_DIRECTORY) {
978            err = -ENOTDIR;
979            if (!inode->i_op->lookup)
980                break;
981        }
982        goto return_base;
983lookup_parent:
984        nd->last = this;
985        nd->last_type = LAST_NORM;
986        if (this.name[0] != '.')
987            goto return_base;
988        if (this.len == 1)
989            nd->last_type = LAST_DOT;
990        else if (this.len == 2 && this.name[1] == '.')
991            nd->last_type = LAST_DOTDOT;
992        else
993            goto return_base;
994return_reval:
995        /*
996         * We bypassed the ordinary revalidation routines.
997         * We may need to check the cached dentry for staleness.
998         */
999        if (nd->path.dentry && nd->path.dentry->d_sb &&
1000            (nd->path.dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)) {
1001            err = -ESTALE;
1002            /* Note: we do not d_invalidate() */
1003            if (!nd->path.dentry->d_op->d_revalidate(
1004                    nd->path.dentry, nd))
1005                break;
1006        }
1007return_base:
1008        return 0;
1009out_dput:
1010        path_put_conditional(&next, nd);
1011        break;
1012    }
1013    path_put(&nd->path);
1014return_err:
1015    return err;
1016}
1017
1018static int path_walk(const char *name, struct nameidata *nd)
1019{
1020    current->total_link_count = 0;
1021    return link_path_walk(name, nd);
1022}
1023
1024static int path_init(int dfd, const char *name, unsigned int flags, struct nameidata *nd)
1025{
1026    int retval = 0;
1027    int fput_needed;
1028    struct file *file;
1029
1030    nd->last_type = LAST_ROOT; /* if there are only slashes... */
1031    nd->flags = flags;
1032    nd->depth = 0;
1033    nd->root.mnt = NULL;
1034
1035    if (*name=='/') {
1036        set_root(nd);
1037        nd->path = nd->root;
1038        path_get(&nd->root);
1039    } else if (dfd == AT_FDCWD) {
1040        struct fs_struct *fs = current->fs;
1041        read_lock(&fs->lock);
1042        nd->path = fs->pwd;
1043        path_get(&fs->pwd);
1044        read_unlock(&fs->lock);
1045    } else {
1046        struct dentry *dentry;
1047
1048        file = fget_light(dfd, &fput_needed);
1049        retval = -EBADF;
1050        if (!file)
1051            goto out_fail;
1052
1053        dentry = file->f_path.dentry;
1054
1055        retval = -ENOTDIR;
1056        if (!S_ISDIR(dentry->d_inode->i_mode))
1057            goto fput_fail;
1058
1059        retval = file_permission(file, MAY_EXEC);
1060        if (retval)
1061            goto fput_fail;
1062
1063        nd->path = file->f_path;
1064        path_get(&file->f_path);
1065
1066        fput_light(file, fput_needed);
1067    }
1068    return 0;
1069
1070fput_fail:
1071    fput_light(file, fput_needed);
1072out_fail:
1073    return retval;
1074}
1075
1076/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1077static int do_path_lookup(int dfd, const char *name,
1078                unsigned int flags, struct nameidata *nd)
1079{
1080    int retval = path_init(dfd, name, flags, nd);
1081    if (!retval)
1082        retval = path_walk(name, nd);
1083    if (unlikely(!retval && !audit_dummy_context() && nd->path.dentry &&
1084                nd->path.dentry->d_inode))
1085        audit_inode(name, nd->path.dentry);
1086    if (nd->root.mnt) {
1087        path_put(&nd->root);
1088        nd->root.mnt = NULL;
1089    }
1090    return retval;
1091}
1092
1093int path_lookup(const char *name, unsigned int flags,
1094            struct nameidata *nd)
1095{
1096    return do_path_lookup(AT_FDCWD, name, flags, nd);
1097}
1098
1099int kern_path(const char *name, unsigned int flags, struct path *path)
1100{
1101    struct nameidata nd;
1102    int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
1103    if (!res)
1104        *path = nd.path;
1105    return res;
1106}
1107
1108/**
1109 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1110 * @dentry: pointer to dentry of the base directory
1111 * @mnt: pointer to vfs mount of the base directory
1112 * @name: pointer to file name
1113 * @flags: lookup flags
1114 * @nd: pointer to nameidata
1115 */
1116int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
1117            const char *name, unsigned int flags,
1118            struct nameidata *nd)
1119{
1120    int retval;
1121
1122    /* same as do_path_lookup */
1123    nd->last_type = LAST_ROOT;
1124    nd->flags = flags;
1125    nd->depth = 0;
1126
1127    nd->path.dentry = dentry;
1128    nd->path.mnt = mnt;
1129    path_get(&nd->path);
1130    nd->root = nd->path;
1131    path_get(&nd->root);
1132
1133    retval = path_walk(name, nd);
1134    if (unlikely(!retval && !audit_dummy_context() && nd->path.dentry &&
1135                nd->path.dentry->d_inode))
1136        audit_inode(name, nd->path.dentry);
1137
1138    path_put(&nd->root);
1139    nd->root.mnt = NULL;
1140
1141    return retval;
1142}
1143
1144/**
1145 * path_lookup_open - lookup a file path with open intent
1146 * @dfd: the directory to use as base, or AT_FDCWD
1147 * @name: pointer to file name
1148 * @lookup_flags: lookup intent flags
1149 * @nd: pointer to nameidata
1150 * @open_flags: open intent flags
1151 */
1152static int path_lookup_open(int dfd, const char *name,
1153        unsigned int lookup_flags, struct nameidata *nd, int open_flags)
1154{
1155    struct file *filp = get_empty_filp();
1156    int err;
1157
1158    if (filp == NULL)
1159        return -ENFILE;
1160    nd->intent.open.file = filp;
1161    nd->intent.open.flags = open_flags;
1162    nd->intent.open.create_mode = 0;
1163    err = do_path_lookup(dfd, name, lookup_flags|LOOKUP_OPEN, nd);
1164    if (IS_ERR(nd->intent.open.file)) {
1165        if (err == 0) {
1166            err = PTR_ERR(nd->intent.open.file);
1167            path_put(&nd->path);
1168        }
1169    } else if (err != 0)
1170        release_open_intent(nd);
1171    return err;
1172}
1173
1174static struct dentry *__lookup_hash(struct qstr *name,
1175        struct dentry *base, struct nameidata *nd)
1176{
1177    struct dentry *dentry;
1178    struct inode *inode;
1179    int err;
1180
1181    inode = base->d_inode;
1182
1183    /*
1184     * See if the low-level filesystem might want
1185     * to use its own hash..
1186     */
1187    if (base->d_op && base->d_op->d_hash) {
1188        err = base->d_op->d_hash(base, name);
1189        dentry = ERR_PTR(err);
1190        if (err < 0)
1191            goto out;
1192    }
1193
1194    dentry = cached_lookup(base, name, nd);
1195    if (!dentry) {
1196        struct dentry *new;
1197
1198        /* Don't create child dentry for a dead directory. */
1199        dentry = ERR_PTR(-ENOENT);
1200        if (IS_DEADDIR(inode))
1201            goto out;
1202
1203        new = d_alloc(base, name);
1204        dentry = ERR_PTR(-ENOMEM);
1205        if (!new)
1206            goto out;
1207        dentry = inode->i_op->lookup(inode, new, nd);
1208        if (!dentry)
1209            dentry = new;
1210        else
1211            dput(new);
1212    }
1213out:
1214    return dentry;
1215}
1216
1217/*
1218 * Restricted form of lookup. Doesn't follow links, single-component only,
1219 * needs parent already locked. Doesn't follow mounts.
1220 * SMP-safe.
1221 */
1222static struct dentry *lookup_hash(struct nameidata *nd)
1223{
1224    int err;
1225
1226    err = inode_permission(nd->path.dentry->d_inode, MAY_EXEC);
1227    if (err)
1228        return ERR_PTR(err);
1229    return __lookup_hash(&nd->last, nd->path.dentry, nd);
1230}
1231
1232static int __lookup_one_len(const char *name, struct qstr *this,
1233        struct dentry *base, int len)
1234{
1235    unsigned long hash;
1236    unsigned int c;
1237
1238    this->name = name;
1239    this->len = len;
1240    if (!len)
1241        return -EACCES;
1242
1243    hash = init_name_hash();
1244    while (len--) {
1245        c = *(const unsigned char *)name++;
1246        if (c == '/' || c == '\0')
1247            return -EACCES;
1248        hash = partial_name_hash(c, hash);
1249    }
1250    this->hash = end_name_hash(hash);
1251    return 0;
1252}
1253
1254/**
1255 * lookup_one_len - filesystem helper to lookup single pathname component
1256 * @name: pathname component to lookup
1257 * @base: base directory to lookup from
1258 * @len: maximum length @len should be interpreted to
1259 *
1260 * Note that this routine is purely a helper for filesystem usage and should
1261 * not be called by generic code. Also note that by using this function the
1262 * nameidata argument is passed to the filesystem methods and a filesystem
1263 * using this helper needs to be prepared for that.
1264 */
1265struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
1266{
1267    int err;
1268    struct qstr this;
1269
1270    WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
1271
1272    err = __lookup_one_len(name, &this, base, len);
1273    if (err)
1274        return ERR_PTR(err);
1275
1276    err = inode_permission(base->d_inode, MAY_EXEC);
1277    if (err)
1278        return ERR_PTR(err);
1279    return __lookup_hash(&this, base, NULL);
1280}
1281
1282/**
1283 * lookup_one_noperm - bad hack for sysfs
1284 * @name: pathname component to lookup
1285 * @base: base directory to lookup from
1286 *
1287 * This is a variant of lookup_one_len that doesn't perform any permission
1288 * checks. It's a horrible hack to work around the braindead sysfs
1289 * architecture and should not be used anywhere else.
1290 *
1291 * DON'T USE THIS FUNCTION EVER, thanks.
1292 */
1293struct dentry *lookup_one_noperm(const char *name, struct dentry *base)
1294{
1295    int err;
1296    struct qstr this;
1297
1298    err = __lookup_one_len(name, &this, base, strlen(name));
1299    if (err)
1300        return ERR_PTR(err);
1301    return __lookup_hash(&this, base, NULL);
1302}
1303
1304int user_path_at(int dfd, const char __user *name, unsigned flags,
1305         struct path *path)
1306{
1307    struct nameidata nd;
1308    char *tmp = getname(name);
1309    int err = PTR_ERR(tmp);
1310    if (!IS_ERR(tmp)) {
1311
1312        BUG_ON(flags & LOOKUP_PARENT);
1313
1314        err = do_path_lookup(dfd, tmp, flags, &nd);
1315        putname(tmp);
1316        if (!err)
1317            *path = nd.path;
1318    }
1319    return err;
1320}
1321
1322static int user_path_parent(int dfd, const char __user *path,
1323            struct nameidata *nd, char **name)
1324{
1325    char *s = getname(path);
1326    int error;
1327
1328    if (IS_ERR(s))
1329        return PTR_ERR(s);
1330
1331    error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
1332    if (error)
1333        putname(s);
1334    else
1335        *name = s;
1336
1337    return error;
1338}
1339
1340/*
1341 * It's inline, so penalty for filesystems that don't use sticky bit is
1342 * minimal.
1343 */
1344static inline int check_sticky(struct inode *dir, struct inode *inode)
1345{
1346    uid_t fsuid = current_fsuid();
1347
1348    if (!(dir->i_mode & S_ISVTX))
1349        return 0;
1350    if (inode->i_uid == fsuid)
1351        return 0;
1352    if (dir->i_uid == fsuid)
1353        return 0;
1354    return !capable(CAP_FOWNER);
1355}
1356
1357/*
1358 * Check whether we can remove a link victim from directory dir, check
1359 * whether the type of victim is right.
1360 * 1. We can't do it if dir is read-only (done in permission())
1361 * 2. We should have write and exec permissions on dir
1362 * 3. We can't remove anything from append-only dir
1363 * 4. We can't do anything with immutable dir (done in permission())
1364 * 5. If the sticky bit on dir is set we should either
1365 * a. be owner of dir, or
1366 * b. be owner of victim, or
1367 * c. have CAP_FOWNER capability
1368 * 6. If the victim is append-only or immutable we can't do antyhing with
1369 * links pointing to it.
1370 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1371 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1372 * 9. We can't remove a root or mountpoint.
1373 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1374 * nfs_async_unlink().
1375 */
1376static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
1377{
1378    int error;
1379
1380    if (!victim->d_inode)
1381        return -ENOENT;
1382
1383    BUG_ON(victim->d_parent->d_inode != dir);
1384    audit_inode_child(victim->d_name.name, victim, dir);
1385
1386    error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
1387    if (error)
1388        return error;
1389    if (IS_APPEND(dir))
1390        return -EPERM;
1391    if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
1392        IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
1393        return -EPERM;
1394    if (isdir) {
1395        if (!S_ISDIR(victim->d_inode->i_mode))
1396            return -ENOTDIR;
1397        if (IS_ROOT(victim))
1398            return -EBUSY;
1399    } else if (S_ISDIR(victim->d_inode->i_mode))
1400        return -EISDIR;
1401    if (IS_DEADDIR(dir))
1402        return -ENOENT;
1403    if (victim->d_flags & DCACHE_NFSFS_RENAMED)
1404        return -EBUSY;
1405    return 0;
1406}
1407
1408/* Check whether we can create an object with dentry child in directory
1409 * dir.
1410 * 1. We can't do it if child already exists (open has special treatment for
1411 * this case, but since we are inlined it's OK)
1412 * 2. We can't do it if dir is read-only (done in permission())
1413 * 3. We should have write and exec permissions on dir
1414 * 4. We can't do it if dir is immutable (done in permission())
1415 */
1416static inline int may_create(struct inode *dir, struct dentry *child)
1417{
1418    if (child->d_inode)
1419        return -EEXIST;
1420    if (IS_DEADDIR(dir))
1421        return -ENOENT;
1422    return inode_permission(dir, MAY_WRITE | MAY_EXEC);
1423}
1424
1425/*
1426 * O_DIRECTORY translates into forcing a directory lookup.
1427 */
1428static inline int lookup_flags(unsigned int f)
1429{
1430    unsigned long retval = LOOKUP_FOLLOW;
1431
1432    if (f & O_NOFOLLOW)
1433        retval &= ~LOOKUP_FOLLOW;
1434    
1435    if (f & O_DIRECTORY)
1436        retval |= LOOKUP_DIRECTORY;
1437
1438    return retval;
1439}
1440
1441/*
1442 * p1 and p2 should be directories on the same fs.
1443 */
1444struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
1445{
1446    struct dentry *p;
1447
1448    if (p1 == p2) {
1449        mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1450        return NULL;
1451    }
1452
1453    mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
1454
1455    p = d_ancestor(p2, p1);
1456    if (p) {
1457        mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
1458        mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
1459        return p;
1460    }
1461
1462    p = d_ancestor(p1, p2);
1463    if (p) {
1464        mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1465        mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
1466        return p;
1467    }
1468
1469    mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1470    mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
1471    return NULL;
1472}
1473
1474void unlock_rename(struct dentry *p1, struct dentry *p2)
1475{
1476    mutex_unlock(&p1->d_inode->i_mutex);
1477    if (p1 != p2) {
1478        mutex_unlock(&p2->d_inode->i_mutex);
1479        mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
1480    }
1481}
1482
1483int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
1484        struct nameidata *nd)
1485{
1486    int error = may_create(dir, dentry);
1487
1488    if (error)
1489        return error;
1490
1491    if (!dir->i_op->create)
1492        return -EACCES; /* shouldn't it be ENOSYS? */
1493    mode &= S_IALLUGO;
1494    mode |= S_IFREG;
1495    error = security_inode_create(dir, dentry, mode);
1496    if (error)
1497        return error;
1498    vfs_dq_init(dir);
1499    error = dir->i_op->create(dir, dentry, mode, nd);
1500    if (!error)
1501        fsnotify_create(dir, dentry);
1502    return error;
1503}
1504
1505int may_open(struct path *path, int acc_mode, int flag)
1506{
1507    struct dentry *dentry = path->dentry;
1508    struct inode *inode = dentry->d_inode;
1509    int error;
1510
1511    if (!inode)
1512        return -ENOENT;
1513
1514    switch (inode->i_mode & S_IFMT) {
1515    case S_IFLNK:
1516        return -ELOOP;
1517    case S_IFDIR:
1518        if (acc_mode & MAY_WRITE)
1519            return -EISDIR;
1520        break;
1521    case S_IFBLK:
1522    case S_IFCHR:
1523        if (path->mnt->mnt_flags & MNT_NODEV)
1524            return -EACCES;
1525        /*FALLTHRU*/
1526    case S_IFIFO:
1527    case S_IFSOCK:
1528        flag &= ~O_TRUNC;
1529        break;
1530    }
1531
1532    error = inode_permission(inode, acc_mode);
1533    if (error)
1534        return error;
1535
1536    error = ima_path_check(path,
1537                   acc_mode & (MAY_READ | MAY_WRITE | MAY_EXEC),
1538                   IMA_COUNT_UPDATE);
1539    if (error)
1540        return error;
1541    /*
1542     * An append-only file must be opened in append mode for writing.
1543     */
1544    if (IS_APPEND(inode)) {
1545        error = -EPERM;
1546        if ((flag & FMODE_WRITE) && !(flag & O_APPEND))
1547            goto err_out;
1548        if (flag & O_TRUNC)
1549            goto err_out;
1550    }
1551
1552    /* O_NOATIME can only be set by the owner or superuser */
1553    if (flag & O_NOATIME)
1554        if (!is_owner_or_cap(inode)) {
1555            error = -EPERM;
1556            goto err_out;
1557        }
1558
1559    /*
1560     * Ensure there are no outstanding leases on the file.
1561     */
1562    error = break_lease(inode, flag);
1563    if (error)
1564        goto err_out;
1565
1566    if (flag & O_TRUNC) {
1567        error = get_write_access(inode);
1568        if (error)
1569            goto err_out;
1570
1571        /*
1572         * Refuse to truncate files with mandatory locks held on them.
1573         */
1574        error = locks_verify_locked(inode);
1575        if (!error)
1576            error = security_path_truncate(path, 0,
1577                           ATTR_MTIME|ATTR_CTIME|ATTR_OPEN);
1578        if (!error) {
1579            vfs_dq_init(inode);
1580
1581            error = do_truncate(dentry, 0,
1582                        ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
1583                        NULL);
1584        }
1585        put_write_access(inode);
1586        if (error)
1587            goto err_out;
1588    } else
1589        if (flag & FMODE_WRITE)
1590            vfs_dq_init(inode);
1591
1592    return 0;
1593err_out:
1594    ima_counts_put(path, acc_mode ?
1595               acc_mode & (MAY_READ | MAY_WRITE | MAY_EXEC) :
1596               ACC_MODE(flag) & (MAY_READ | MAY_WRITE));
1597    return error;
1598}
1599
1600/*
1601 * Be careful about ever adding any more callers of this
1602 * function. Its flags must be in the namei format, not
1603 * what get passed to sys_open().
1604 */
1605static int __open_namei_create(struct nameidata *nd, struct path *path,
1606                int flag, int mode)
1607{
1608    int error;
1609    struct dentry *dir = nd->path.dentry;
1610
1611    if (!IS_POSIXACL(dir->d_inode))
1612        mode &= ~current_umask();
1613    error = security_path_mknod(&nd->path, path->dentry, mode, 0);
1614    if (error)
1615        goto out_unlock;
1616    error = vfs_create(dir->d_inode, path->dentry, mode, nd);
1617out_unlock:
1618    mutex_unlock(&dir->d_inode->i_mutex);
1619    dput(nd->path.dentry);
1620    nd->path.dentry = path->dentry;
1621    if (error)
1622        return error;
1623    /* Don't check for write permission, don't truncate */
1624    return may_open(&nd->path, 0, flag & ~O_TRUNC);
1625}
1626
1627/*
1628 * Note that while the flag value (low two bits) for sys_open means:
1629 * 00 - read-only
1630 * 01 - write-only
1631 * 10 - read-write
1632 * 11 - special
1633 * it is changed into
1634 * 00 - no permissions needed
1635 * 01 - read-permission
1636 * 10 - write-permission
1637 * 11 - read-write
1638 * for the internal routines (ie open_namei()/follow_link() etc)
1639 * This is more logical, and also allows the 00 "no perm needed"
1640 * to be used for symlinks (where the permissions are checked
1641 * later).
1642 *
1643*/
1644static inline int open_to_namei_flags(int flag)
1645{
1646    if ((flag+1) & O_ACCMODE)
1647        flag++;
1648    return flag;
1649}
1650
1651static int open_will_write_to_fs(int flag, struct inode *inode)
1652{
1653    /*
1654     * We'll never write to the fs underlying
1655     * a device file.
1656     */
1657    if (special_file(inode->i_mode))
1658        return 0;
1659    return (flag & O_TRUNC);
1660}
1661
1662/*
1663 * Note that the low bits of the passed in "open_flag"
1664 * are not the same as in the local variable "flag". See
1665 * open_to_namei_flags() for more details.
1666 */
1667struct file *do_filp_open(int dfd, const char *pathname,
1668        int open_flag, int mode, int acc_mode)
1669{
1670    struct file *filp;
1671    struct nameidata nd;
1672    int error;
1673    struct path path;
1674    struct dentry *dir;
1675    int count = 0;
1676    int will_write;
1677    int flag = open_to_namei_flags(open_flag);
1678
1679    if (!acc_mode)
1680        acc_mode = MAY_OPEN | ACC_MODE(flag);
1681
1682    /* O_TRUNC implies we need access checks for write permissions */
1683    if (flag & O_TRUNC)
1684        acc_mode |= MAY_WRITE;
1685
1686    /* Allow the LSM permission hook to distinguish append
1687       access from general write access. */
1688    if (flag & O_APPEND)
1689        acc_mode |= MAY_APPEND;
1690
1691    /*
1692     * The simplest case - just a plain lookup.
1693     */
1694    if (!(flag & O_CREAT)) {
1695        error = path_lookup_open(dfd, pathname, lookup_flags(flag),
1696                     &nd, flag);
1697        if (error)
1698            return ERR_PTR(error);
1699        goto ok;
1700    }
1701
1702    /*
1703     * Create - we need to know the parent.
1704     */
1705    error = path_init(dfd, pathname, LOOKUP_PARENT, &nd);
1706    if (error)
1707        return ERR_PTR(error);
1708    error = path_walk(pathname, &nd);
1709    if (error) {
1710        if (nd.root.mnt)
1711            path_put(&nd.root);
1712        return ERR_PTR(error);
1713    }
1714    if (unlikely(!audit_dummy_context()))
1715        audit_inode(pathname, nd.path.dentry);
1716
1717    /*
1718     * We have the parent and last component. First of all, check
1719     * that we are not asked to creat(2) an obvious directory - that
1720     * will not do.
1721     */
1722    error = -EISDIR;
1723    if (nd.last_type != LAST_NORM || nd.last.name[nd.last.len])
1724        goto exit_parent;
1725
1726    error = -ENFILE;
1727    filp = get_empty_filp();
1728    if (filp == NULL)
1729        goto exit_parent;
1730    nd.intent.open.file = filp;
1731    nd.intent.open.flags = flag;
1732    nd.intent.open.create_mode = mode;
1733    dir = nd.path.dentry;
1734    nd.flags &= ~LOOKUP_PARENT;
1735    nd.flags |= LOOKUP_CREATE | LOOKUP_OPEN;
1736    if (flag & O_EXCL)
1737        nd.flags |= LOOKUP_EXCL;
1738    mutex_lock(&dir->d_inode->i_mutex);
1739    path.dentry = lookup_hash(&nd);
1740    path.mnt = nd.path.mnt;
1741
1742do_last:
1743    error = PTR_ERR(path.dentry);
1744    if (IS_ERR(path.dentry)) {
1745        mutex_unlock(&dir->d_inode->i_mutex);
1746        goto exit;
1747    }
1748
1749    if (IS_ERR(nd.intent.open.file)) {
1750        error = PTR_ERR(nd.intent.open.file);
1751        goto exit_mutex_unlock;
1752    }
1753
1754    /* Negative dentry, just create the file */
1755    if (!path.dentry->d_inode) {
1756        /*
1757         * This write is needed to ensure that a
1758         * ro->rw transition does not occur between
1759         * the time when the file is created and when
1760         * a permanent write count is taken through
1761         * the 'struct file' in nameidata_to_filp().
1762         */
1763        error = mnt_want_write(nd.path.mnt);
1764        if (error)
1765            goto exit_mutex_unlock;
1766        error = __open_namei_create(&nd, &path, flag, mode);
1767        if (error) {
1768            mnt_drop_write(nd.path.mnt);
1769            goto exit;
1770        }
1771        filp = nameidata_to_filp(&nd, open_flag);
1772        if (IS_ERR(filp))
1773            ima_counts_put(&nd.path,
1774                       acc_mode & (MAY_READ | MAY_WRITE |
1775                           MAY_EXEC));
1776        mnt_drop_write(nd.path.mnt);
1777        if (nd.root.mnt)
1778            path_put(&nd.root);
1779        return filp;
1780    }
1781
1782    /*
1783     * It already exists.
1784     */
1785    mutex_unlock(&dir->d_inode->i_mutex);
1786    audit_inode(pathname, path.dentry);
1787
1788    error = -EEXIST;
1789    if (flag & O_EXCL)
1790        goto exit_dput;
1791
1792    if (__follow_mount(&path)) {
1793        error = -ELOOP;
1794        if (flag & O_NOFOLLOW)
1795            goto exit_dput;
1796    }
1797
1798    error = -ENOENT;
1799    if (!path.dentry->d_inode)
1800        goto exit_dput;
1801    if (path.dentry->d_inode->i_op->follow_link)
1802        goto do_link;
1803
1804    path_to_nameidata(&path, &nd);
1805    error = -EISDIR;
1806    if (path.dentry->d_inode && S_ISDIR(path.dentry->d_inode->i_mode))
1807        goto exit;
1808ok:
1809    /*
1810     * Consider:
1811     * 1. may_open() truncates a file
1812     * 2. a rw->ro mount transition occurs
1813     * 3. nameidata_to_filp() fails due to
1814     * the ro mount.
1815     * That would be inconsistent, and should
1816     * be avoided. Taking this mnt write here
1817     * ensures that (2) can not occur.
1818     */
1819    will_write = open_will_write_to_fs(flag, nd.path.dentry->d_inode);
1820    if (will_write) {
1821        error = mnt_want_write(nd.path.mnt);
1822        if (error)
1823            goto exit;
1824    }
1825    error = may_open(&nd.path, acc_mode, flag);
1826    if (error) {
1827        if (will_write)
1828            mnt_drop_write(nd.path.mnt);
1829        goto exit;
1830    }
1831    filp = nameidata_to_filp(&nd, open_flag);
1832    if (IS_ERR(filp))
1833        ima_counts_put(&nd.path,
1834                   acc_mode & (MAY_READ | MAY_WRITE | MAY_EXEC));
1835    /*
1836     * It is now safe to drop the mnt write
1837     * because the filp has had a write taken
1838     * on its behalf.
1839     */
1840    if (will_write)
1841        mnt_drop_write(nd.path.mnt);
1842    if (nd.root.mnt)
1843        path_put(&nd.root);
1844    return filp;
1845
1846exit_mutex_unlock:
1847    mutex_unlock(&dir->d_inode->i_mutex);
1848exit_dput:
1849    path_put_conditional(&path, &nd);
1850exit:
1851    if (!IS_ERR(nd.intent.open.file))
1852        release_open_intent(&nd);
1853exit_parent:
1854    if (nd.root.mnt)
1855        path_put(&nd.root);
1856    path_put(&nd.path);
1857    return ERR_PTR(error);
1858
1859do_link:
1860    error = -ELOOP;
1861    if (flag & O_NOFOLLOW)
1862        goto exit_dput;
1863    /*
1864     * This is subtle. Instead of calling do_follow_link() we do the
1865     * thing by hands. The reason is that this way we have zero link_count
1866     * and path_walk() (called from ->follow_link) honoring LOOKUP_PARENT.
1867     * After that we have the parent and last component, i.e.
1868     * we are in the same situation as after the first path_walk().
1869     * Well, almost - if the last component is normal we get its copy
1870     * stored in nd->last.name and we will have to putname() it when we
1871     * are done. Procfs-like symlinks just set LAST_BIND.
1872     */
1873    nd.flags |= LOOKUP_PARENT;
1874    error = security_inode_follow_link(path.dentry, &nd);
1875    if (error)
1876        goto exit_dput;
1877    error = __do_follow_link(&path, &nd);
1878    if (error) {
1879        /* Does someone understand code flow here? Or it is only
1880         * me so stupid? Anathema to whoever designed this non-sense
1881         * with "intent.open".
1882         */
1883        release_open_intent(&nd);
1884        if (nd.root.mnt)
1885            path_put(&nd.root);
1886        return ERR_PTR(error);
1887    }
1888    nd.flags &= ~LOOKUP_PARENT;
1889    if (nd.last_type == LAST_BIND)
1890        goto ok;
1891    error = -EISDIR;
1892    if (nd.last_type != LAST_NORM)
1893        goto exit;
1894    if (nd.last.name[nd.last.len]) {
1895        __putname(nd.last.name);
1896        goto exit;
1897    }
1898    error = -ELOOP;
1899    if (count++==32) {
1900        __putname(nd.last.name);
1901        goto exit;
1902    }
1903    dir = nd.path.dentry;
1904    mutex_lock(&dir->d_inode->i_mutex);
1905    path.dentry = lookup_hash(&nd);
1906    path.mnt = nd.path.mnt;
1907    __putname(nd.last.name);
1908    goto do_last;
1909}
1910
1911/**
1912 * filp_open - open file and return file pointer
1913 *
1914 * @filename: path to open
1915 * @flags: open flags as per the open(2) second argument
1916 * @mode: mode for the new file if O_CREAT is set, else ignored
1917 *
1918 * This is the helper to open a file from kernelspace if you really
1919 * have to. But in generally you should not do this, so please move
1920 * along, nothing to see here..
1921 */
1922struct file *filp_open(const char *filename, int flags, int mode)
1923{
1924    return do_filp_open(AT_FDCWD, filename, flags, mode, 0);
1925}
1926EXPORT_SYMBOL(filp_open);
1927
1928/**
1929 * lookup_create - lookup a dentry, creating it if it doesn't exist
1930 * @nd: nameidata info
1931 * @is_dir: directory flag
1932 *
1933 * Simple function to lookup and return a dentry and create it
1934 * if it doesn't exist. Is SMP-safe.
1935 *
1936 * Returns with nd->path.dentry->d_inode->i_mutex locked.
1937 */
1938struct dentry *lookup_create(struct nameidata *nd, int is_dir)
1939{
1940    struct dentry *dentry = ERR_PTR(-EEXIST);
1941
1942    mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
1943    /*
1944     * Yucky last component or no last component at all?
1945     * (foo/., foo/.., /////)
1946     */
1947    if (nd->last_type != LAST_NORM)
1948        goto fail;
1949    nd->flags &= ~LOOKUP_PARENT;
1950    nd->flags |= LOOKUP_CREATE | LOOKUP_EXCL;
1951    nd->intent.open.flags = O_EXCL;
1952
1953    /*
1954     * Do the final lookup.
1955     */
1956    dentry = lookup_hash(nd);
1957    if (IS_ERR(dentry))
1958        goto fail;
1959
1960    if (dentry->d_inode)
1961        goto eexist;
1962    /*
1963     * Special case - lookup gave negative, but... we had foo/bar/
1964     * From the vfs_mknod() POV we just have a negative dentry -
1965     * all is fine. Let's be bastards - you had / on the end, you've
1966     * been asking for (non-existent) directory. -ENOENT for you.
1967     */
1968    if (unlikely(!is_dir && nd->last.name[nd->last.len])) {
1969        dput(dentry);
1970        dentry = ERR_PTR(-ENOENT);
1971    }
1972    return dentry;
1973eexist:
1974    dput(dentry);
1975    dentry = ERR_PTR(-EEXIST);
1976fail:
1977    return dentry;
1978}
1979EXPORT_SYMBOL_GPL(lookup_create);
1980
1981int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1982{
1983    int error = may_create(dir, dentry);
1984
1985    if (error)
1986        return error;
1987
1988    if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
1989        return -EPERM;
1990
1991    if (!dir->i_op->mknod)
1992        return -EPERM;
1993
1994    error = devcgroup_inode_mknod(mode, dev);
1995    if (error)
1996        return error;
1997
1998    error = security_inode_mknod(dir, dentry, mode, dev);
1999    if (error)
2000        return error;
2001
2002    vfs_dq_init(dir);
2003    error = dir->i_op->mknod(dir, dentry, mode, dev);
2004    if (!error)
2005        fsnotify_create(dir, dentry);
2006    return error;
2007}
2008
2009static int may_mknod(mode_t mode)
2010{
2011    switch (mode & S_IFMT) {
2012    case S_IFREG:
2013    case S_IFCHR:
2014    case S_IFBLK:
2015    case S_IFIFO:
2016    case S_IFSOCK:
2017    case 0: /* zero mode translates to S_IFREG */
2018        return 0;
2019    case S_IFDIR:
2020        return -EPERM;
2021    default:
2022        return -EINVAL;
2023    }
2024}
2025
2026SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, int, mode,
2027        unsigned, dev)
2028{
2029    int error;
2030    char *tmp;
2031    struct dentry *dentry;
2032    struct nameidata nd;
2033
2034    if (S_ISDIR(mode))
2035        return -EPERM;
2036
2037    error = user_path_parent(dfd, filename, &nd, &tmp);
2038    if (error)
2039        return error;
2040
2041    dentry = lookup_create(&nd, 0);
2042    if (IS_ERR(dentry)) {
2043        error = PTR_ERR(dentry);
2044        goto out_unlock;
2045    }
2046    if (!IS_POSIXACL(nd.path.dentry->d_inode))
2047        mode &= ~current_umask();
2048    error = may_mknod(mode);
2049    if (error)
2050        goto out_dput;
2051    error = mnt_want_write(nd.path.mnt);
2052    if (error)
2053        goto out_dput;
2054    error = security_path_mknod(&nd.path, dentry, mode, dev);
2055    if (error)
2056        goto out_drop_write;
2057    switch (mode & S_IFMT) {
2058        case 0: case S_IFREG:
2059            error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);
2060            break;
2061        case S_IFCHR: case S_IFBLK:
2062            error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,
2063                    new_decode_dev(dev));
2064            break;
2065        case S_IFIFO: case S_IFSOCK:
2066            error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
2067            break;
2068    }
2069out_drop_write:
2070    mnt_drop_write(nd.path.mnt);
2071out_dput:
2072    dput(dentry);
2073out_unlock:
2074    mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2075    path_put(&nd.path);
2076    putname(tmp);
2077
2078    return error;
2079}
2080
2081SYSCALL_DEFINE3(mknod, const char __user *, filename, int, mode, unsigned, dev)
2082{
2083    return sys_mknodat(AT_FDCWD, filename, mode, dev);
2084}
2085
2086int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
2087{
2088    int error = may_create(dir, dentry);
2089
2090    if (error)
2091        return error;
2092
2093    if (!dir->i_op->mkdir)
2094        return -EPERM;
2095
2096    mode &= (S_IRWXUGO|S_ISVTX);
2097    error = security_inode_mkdir(dir, dentry, mode);
2098    if (error)
2099        return error;
2100
2101    vfs_dq_init(dir);
2102    error = dir->i_op->mkdir(dir, dentry, mode);
2103    if (!error)
2104        fsnotify_mkdir(dir, dentry);
2105    return error;
2106}
2107
2108SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, int, mode)
2109{
2110    int error = 0;
2111    char * tmp;
2112    struct dentry *dentry;
2113    struct nameidata nd;
2114
2115    error = user_path_parent(dfd, pathname, &nd, &tmp);
2116    if (error)
2117        goto out_err;
2118
2119    dentry = lookup_create(&nd, 1);
2120    error = PTR_ERR(dentry);
2121    if (IS_ERR(dentry))
2122        goto out_unlock;
2123
2124    if (!IS_POSIXACL(nd.path.dentry->d_inode))
2125        mode &= ~current_umask();
2126    error = mnt_want_write(nd.path.mnt);
2127    if (error)
2128        goto out_dput;
2129    error = security_path_mkdir(&nd.path, dentry, mode);
2130    if (error)
2131        goto out_drop_write;
2132    error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
2133out_drop_write:
2134    mnt_drop_write(nd.path.mnt);
2135out_dput:
2136    dput(dentry);
2137out_unlock:
2138    mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2139    path_put(&nd.path);
2140    putname(tmp);
2141out_err:
2142    return error;
2143}
2144
2145SYSCALL_DEFINE2(mkdir, const char __user *, pathname, int, mode)
2146{
2147    return sys_mkdirat(AT_FDCWD, pathname, mode);
2148}
2149
2150/*
2151 * We try to drop the dentry early: we should have
2152 * a usage count of 2 if we're the only user of this
2153 * dentry, and if that is true (possibly after pruning
2154 * the dcache), then we drop the dentry now.
2155 *
2156 * A low-level filesystem can, if it choses, legally
2157 * do a
2158 *
2159 * if (!d_unhashed(dentry))
2160 * return -EBUSY;
2161 *
2162 * if it cannot handle the case of removing a directory
2163 * that is still in use by something else..
2164 */
2165void dentry_unhash(struct dentry *dentry)
2166{
2167    dget(dentry);
2168    shrink_dcache_parent(dentry);
2169    spin_lock(&dcache_lock);
2170    spin_lock(&dentry->d_lock);
2171    if (atomic_read(&dentry->d_count) == 2)
2172        __d_drop(dentry);
2173    spin_unlock(&dentry->d_lock);
2174    spin_unlock(&dcache_lock);
2175}
2176
2177int vfs_rmdir(struct inode *dir, struct dentry *dentry)
2178{
2179    int error = may_delete(dir, dentry, 1);
2180
2181    if (error)
2182        return error;
2183
2184    if (!dir->i_op->rmdir)
2185        return -EPERM;
2186
2187    vfs_dq_init(dir);
2188
2189    mutex_lock(&dentry->d_inode->i_mutex);
2190    dentry_unhash(dentry);
2191    if (d_mountpoint(dentry))
2192        error = -EBUSY;
2193    else {
2194        error = security_inode_rmdir(dir, dentry);
2195        if (!error) {
2196            error = dir->i_op->rmdir(dir, dentry);
2197            if (!error)
2198                dentry->d_inode->i_flags |= S_DEAD;
2199        }
2200    }
2201    mutex_unlock(&dentry->d_inode->i_mutex);
2202    if (!error) {
2203        d_delete(dentry);
2204    }
2205    dput(dentry);
2206
2207    return error;
2208}
2209
2210static long do_rmdir(int dfd, const char __user *pathname)
2211{
2212    int error = 0;
2213    char * name;
2214    struct dentry *dentry;
2215    struct nameidata nd;
2216
2217    error = user_path_parent(dfd, pathname, &nd, &name);
2218    if (error)
2219        return error;
2220
2221    switch(nd.last_type) {
2222    case LAST_DOTDOT:
2223        error = -ENOTEMPTY;
2224        goto exit1;
2225    case LAST_DOT:
2226        error = -EINVAL;
2227        goto exit1;
2228    case LAST_ROOT:
2229        error = -EBUSY;
2230        goto exit1;
2231    }
2232
2233    nd.flags &= ~LOOKUP_PARENT;
2234
2235    mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2236    dentry = lookup_hash(&nd);
2237    error = PTR_ERR(dentry);
2238    if (IS_ERR(dentry))
2239        goto exit2;
2240    error = mnt_want_write(nd.path.mnt);
2241    if (error)
2242        goto exit3;
2243    error = security_path_rmdir(&nd.path, dentry);
2244    if (error)
2245        goto exit4;
2246    error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
2247exit4:
2248    mnt_drop_write(nd.path.mnt);
2249exit3:
2250    dput(dentry);
2251exit2:
2252    mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2253exit1:
2254    path_put(&nd.path);
2255    putname(name);
2256    return error;
2257}
2258
2259SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
2260{
2261    return do_rmdir(AT_FDCWD, pathname);
2262}
2263
2264int vfs_unlink(struct inode *dir, struct dentry *dentry)
2265{
2266    int error = may_delete(dir, dentry, 0);
2267
2268    if (error)
2269        return error;
2270
2271    if (!dir->i_op->unlink)
2272        return -EPERM;
2273
2274    vfs_dq_init(dir);
2275
2276    mutex_lock(&dentry->d_inode->i_mutex);
2277    if (d_mountpoint(dentry))
2278        error = -EBUSY;
2279    else {
2280        error = security_inode_unlink(dir, dentry);
2281        if (!error)
2282            error = dir->i_op->unlink(dir, dentry);
2283    }
2284    mutex_unlock(&dentry->d_inode->i_mutex);
2285
2286    /* We don't d_delete() NFS sillyrenamed files--they still exist. */
2287    if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
2288        fsnotify_link_count(dentry->d_inode);
2289        d_delete(dentry);
2290    }
2291
2292    return error;
2293}
2294
2295/*
2296 * Make sure that the actual truncation of the file will occur outside its
2297 * directory's i_mutex. Truncate can take a long time if there is a lot of
2298 * writeout happening, and we don't want to prevent access to the directory
2299 * while waiting on the I/O.
2300 */
2301static long do_unlinkat(int dfd, const char __user *pathname)
2302{
2303    int error;
2304    char *name;
2305    struct dentry *dentry;
2306    struct nameidata nd;
2307    struct inode *inode = NULL;
2308
2309    error = user_path_parent(dfd, pathname, &nd, &name);
2310    if (error)
2311        return error;
2312
2313    error = -EISDIR;
2314    if (nd.last_type != LAST_NORM)
2315        goto exit1;
2316
2317    nd.flags &= ~LOOKUP_PARENT;
2318
2319    mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2320    dentry = lookup_hash(&nd);
2321    error = PTR_ERR(dentry);
2322    if (!IS_ERR(dentry)) {
2323        /* Why not before? Because we want correct error value */
2324        if (nd.last.name[nd.last.len])
2325            goto slashes;
2326        inode = dentry->d_inode;
2327        if (inode)
2328            atomic_inc(&inode->i_count);
2329        error = mnt_want_write(nd.path.mnt);
2330        if (error)
2331            goto exit2;
2332        error = security_path_unlink(&nd.path, dentry);
2333        if (error)
2334            goto exit3;
2335        error = vfs_unlink(nd.path.dentry->d_inode, dentry);
2336exit3:
2337        mnt_drop_write(nd.path.mnt);
2338    exit2:
2339        dput(dentry);
2340    }
2341    mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2342    if (inode)
2343        iput(inode); /* truncate the inode here */
2344exit1:
2345    path_put(&nd.path);
2346    putname(name);
2347    return error;
2348
2349slashes:
2350    error = !dentry->d_inode ? -ENOENT :
2351        S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
2352    goto exit2;
2353}
2354
2355SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
2356{
2357    if ((flag & ~AT_REMOVEDIR) != 0)
2358        return -EINVAL;
2359
2360    if (flag & AT_REMOVEDIR)
2361        return do_rmdir(dfd, pathname);
2362
2363    return do_unlinkat(dfd, pathname);
2364}
2365
2366SYSCALL_DEFINE1(unlink, const char __user *, pathname)
2367{
2368    return do_unlinkat(AT_FDCWD, pathname);
2369}
2370
2371int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
2372{
2373    int error = may_create(dir, dentry);
2374
2375    if (error)
2376        return error;
2377
2378    if (!dir->i_op->symlink)
2379        return -EPERM;
2380
2381    error = security_inode_symlink(dir, dentry, oldname);
2382    if (error)
2383        return error;
2384
2385    vfs_dq_init(dir);
2386    error = dir->i_op->symlink(dir, dentry, oldname);
2387    if (!error)
2388        fsnotify_create(dir, dentry);
2389    return error;
2390}
2391
2392SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
2393        int, newdfd, const char __user *, newname)
2394{
2395    int error;
2396    char *from;
2397    char *to;
2398    struct dentry *dentry;
2399    struct nameidata nd;
2400
2401    from = getname(oldname);
2402    if (IS_ERR(from))
2403        return PTR_ERR(from);
2404
2405    error = user_path_parent(newdfd, newname, &nd, &to);
2406    if (error)
2407        goto out_putname;
2408
2409    dentry = lookup_create(&nd, 0);
2410    error = PTR_ERR(dentry);
2411    if (IS_ERR(dentry))
2412        goto out_unlock;
2413
2414    error = mnt_want_write(nd.path.mnt);
2415    if (error)
2416        goto out_dput;
2417    error = security_path_symlink(&nd.path, dentry, from);
2418    if (error)
2419        goto out_drop_write;
2420    error = vfs_symlink(nd.path.dentry->d_inode, dentry, from);
2421out_drop_write:
2422    mnt_drop_write(nd.path.mnt);
2423out_dput:
2424    dput(dentry);
2425out_unlock:
2426    mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2427    path_put(&nd.path);
2428    putname(to);
2429out_putname:
2430    putname(from);
2431    return error;
2432}
2433
2434SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
2435{
2436    return sys_symlinkat(oldname, AT_FDCWD, newname);
2437}
2438
2439int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
2440{
2441    struct inode *inode = old_dentry->d_inode;
2442    int error;
2443
2444    if (!inode)
2445        return -ENOENT;
2446
2447    error = may_create(dir, new_dentry);
2448    if (error)
2449        return error;
2450
2451    if (dir->i_sb != inode->i_sb)
2452        return -EXDEV;
2453
2454    /*
2455     * A link to an append-only or immutable file cannot be created.
2456     */
2457    if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
2458        return -EPERM;
2459    if (!dir->i_op->link)
2460        return -EPERM;
2461    if (S_ISDIR(inode->i_mode))
2462        return -EPERM;
2463
2464    error = security_inode_link(old_dentry, dir, new_dentry);
2465    if (error)
2466        return error;
2467
2468    mutex_lock(&inode->i_mutex);
2469    vfs_dq_init(dir);
2470    error = dir->i_op->link(old_dentry, dir, new_dentry);
2471    mutex_unlock(&inode->i_mutex);
2472    if (!error)
2473        fsnotify_link(dir, inode, new_dentry);
2474    return error;
2475}
2476
2477/*
2478 * Hardlinks are often used in delicate situations. We avoid
2479 * security-related surprises by not following symlinks on the
2480 * newname. --KAB
2481 *
2482 * We don't follow them on the oldname either to be compatible
2483 * with linux 2.0, and to avoid hard-linking to directories
2484 * and other special files. --ADM
2485 */
2486SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
2487        int, newdfd, const char __user *, newname, int, flags)
2488{
2489    struct dentry *new_dentry;
2490    struct nameidata nd;
2491    struct path old_path;
2492    int error;
2493    char *to;
2494
2495    if ((flags & ~AT_SYMLINK_FOLLOW) != 0)
2496        return -EINVAL;
2497
2498    error = user_path_at(olddfd, oldname,
2499                 flags & AT_SYMLINK_FOLLOW ? LOOKUP_FOLLOW : 0,
2500                 &old_path);
2501    if (error)
2502        return error;
2503
2504    error = user_path_parent(newdfd, newname, &nd, &to);
2505    if (error)
2506        goto out;
2507    error = -EXDEV;
2508    if (old_path.mnt != nd.path.mnt)
2509        goto out_release;
2510    new_dentry = lookup_create(&nd, 0);
2511    error = PTR_ERR(new_dentry);
2512    if (IS_ERR(new_dentry))
2513        goto out_unlock;
2514    error = mnt_want_write(nd.path.mnt);
2515    if (error)
2516        goto out_dput;
2517    error = security_path_link(old_path.dentry, &nd.path, new_dentry);
2518    if (error)
2519        goto out_drop_write;
2520    error = vfs_link(old_path.dentry, nd.path.dentry->d_inode, new_dentry);
2521out_drop_write:
2522    mnt_drop_write(nd.path.mnt);
2523out_dput:
2524    dput(new_dentry);
2525out_unlock:
2526    mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2527out_release:
2528    path_put(&nd.path);
2529    putname(to);
2530out:
2531    path_put(&old_path);
2532
2533    return error;
2534}
2535
2536SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
2537{
2538    return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
2539}
2540
2541/*
2542 * The worst of all namespace operations - renaming directory. "Perverted"
2543 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
2544 * Problems:
2545 * a) we can get into loop creation. Check is done in is_subdir().
2546 * b) race potential - two innocent renames can create a loop together.
2547 * That's where 4.4 screws up. Current fix: serialization on
2548 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
2549 * story.
2550 * c) we have to lock _three_ objects - parents and victim (if it exists).
2551 * And that - after we got ->i_mutex on parents (until then we don't know
2552 * whether the target exists). Solution: try to be smart with locking
2553 * order for inodes. We rely on the fact that tree topology may change
2554 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
2555 * move will be locked. Thus we can rank directories by the tree
2556 * (ancestors first) and rank all non-directories after them.
2557 * That works since everybody except rename does "lock parent, lookup,
2558 * lock child" and rename is under ->s_vfs_rename_mutex.
2559 * HOWEVER, it relies on the assumption that any object with ->lookup()
2560 * has no more than 1 dentry. If "hybrid" objects will ever appear,
2561 * we'd better make sure that there's no link(2) for them.
2562 * d) some filesystems don't support opened-but-unlinked directories,
2563 * either because of layout or because they are not ready to deal with
2564 * all cases correctly. The latter will be fixed (taking this sort of
2565 * stuff into VFS), but the former is not going away. Solution: the same
2566 * trick as in rmdir().
2567 * e) conversion from fhandle to dentry may come in the wrong moment - when
2568 * we are removing the target. Solution: we will have to grab ->i_mutex
2569 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
2570 * ->i_mutex on parents, which works but leads to some truely excessive
2571 * locking].
2572 */
2573static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
2574              struct inode *new_dir, struct dentry *new_dentry)
2575{
2576    int error = 0;
2577    struct inode *target;
2578
2579    /*
2580     * If we are going to change the parent - check write permissions,
2581     * we'll need to flip '..'.
2582     */
2583    if (new_dir != old_dir) {
2584        error = inode_permission(old_dentry->d_inode, MAY_WRITE);
2585        if (error)
2586            return error;
2587    }
2588
2589    error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
2590    if (error)
2591        return error;
2592
2593    target = new_dentry->d_inode;
2594    if (target) {
2595        mutex_lock(&target->i_mutex);
2596        dentry_unhash(new_dentry);
2597    }
2598    if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
2599        error = -EBUSY;
2600    else
2601        error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
2602    if (target) {
2603        if (!error)
2604            target->i_flags |= S_DEAD;
2605        mutex_unlock(&target->i_mutex);
2606        if (d_unhashed(new_dentry))
2607            d_rehash(new_dentry);
2608        dput(new_dentry);
2609    }
2610    if (!error)
2611        if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
2612            d_move(old_dentry,new_dentry);
2613    return error;
2614}
2615
2616static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
2617                struct inode *new_dir, struct dentry *new_dentry)
2618{
2619    struct inode *target;
2620    int error;
2621
2622    error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
2623    if (error)
2624        return error;
2625
2626    dget(new_dentry);
2627    target = new_dentry->d_inode;
2628    if (target)
2629        mutex_lock(&target->i_mutex);
2630    if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
2631        error = -EBUSY;
2632    else
2633        error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
2634    if (!error) {
2635        if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
2636            d_move(old_dentry, new_dentry);
2637    }
2638    if (target)
2639        mutex_unlock(&target->i_mutex);
2640    dput(new_dentry);
2641    return error;
2642}
2643
2644int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
2645           struct inode *new_dir, struct dentry *new_dentry)
2646{
2647    int error;
2648    int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
2649    const char *old_name;
2650
2651    if (old_dentry->d_inode == new_dentry->d_inode)
2652         return 0;
2653 
2654    error = may_delete(old_dir, old_dentry, is_dir);
2655    if (error)
2656        return error;
2657
2658    if (!new_dentry->d_inode)
2659        error = may_create(new_dir, new_dentry);
2660    else
2661        error = may_delete(new_dir, new_dentry, is_dir);
2662    if (error)
2663        return error;
2664
2665    if (!old_dir->i_op->rename)
2666        return -EPERM;
2667
2668    vfs_dq_init(old_dir);
2669    vfs_dq_init(new_dir);
2670
2671    old_name = fsnotify_oldname_init(old_dentry->d_name.name);
2672
2673    if (is_dir)
2674        error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
2675    else
2676        error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
2677    if (!error) {
2678        const char *new_name = old_dentry->d_name.name;
2679        fsnotify_move(old_dir, new_dir, old_name, new_name, is_dir,
2680                  new_dentry->d_inode, old_dentry);
2681    }
2682    fsnotify_oldname_free(old_name);
2683
2684    return error;
2685}
2686
2687SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
2688        int, newdfd, const char __user *, newname)
2689{
2690    struct dentry *old_dir, *new_dir;
2691    struct dentry *old_dentry, *new_dentry;
2692    struct dentry *trap;
2693    struct nameidata oldnd, newnd;
2694    char *from;
2695    char *to;
2696    int error;
2697
2698    error = user_path_parent(olddfd, oldname, &oldnd, &from);
2699    if (error)
2700        goto exit;
2701
2702    error = user_path_parent(newdfd, newname, &newnd, &to);
2703    if (error)
2704        goto exit1;
2705
2706    error = -EXDEV;
2707    if (oldnd.path.mnt != newnd.path.mnt)
2708        goto exit2;
2709
2710    old_dir = oldnd.path.dentry;
2711    error = -EBUSY;
2712    if (oldnd.last_type != LAST_NORM)
2713        goto exit2;
2714
2715    new_dir = newnd.path.dentry;
2716    if (newnd.last_type != LAST_NORM)
2717        goto exit2;
2718
2719    oldnd.flags &= ~LOOKUP_PARENT;
2720    newnd.flags &= ~LOOKUP_PARENT;
2721    newnd.flags |= LOOKUP_RENAME_TARGET;
2722
2723    trap = lock_rename(new_dir, old_dir);
2724
2725    old_dentry = lookup_hash(&oldnd);
2726    error = PTR_ERR(old_dentry);
2727    if (IS_ERR(old_dentry))
2728        goto exit3;
2729    /* source must exist */
2730    error = -ENOENT;
2731    if (!old_dentry->d_inode)
2732        goto exit4;
2733    /* unless the source is a directory trailing slashes give -ENOTDIR */
2734    if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
2735        error = -ENOTDIR;
2736        if (oldnd.last.name[oldnd.last.len])
2737            goto exit4;
2738        if (newnd.last.name[newnd.last.len])
2739            goto exit4;
2740    }
2741    /* source should not be ancestor of target */
2742    error = -EINVAL;
2743    if (old_dentry == trap)
2744        goto exit4;
2745    new_dentry = lookup_hash(&newnd);
2746    error = PTR_ERR(new_dentry);
2747    if (IS_ERR(new_dentry))
2748        goto exit4;
2749    /* target should not be an ancestor of source */
2750    error = -ENOTEMPTY;
2751    if (new_dentry == trap)
2752        goto exit5;
2753
2754    error = mnt_want_write(oldnd.path.mnt);
2755    if (error)
2756        goto exit5;
2757    error = security_path_rename(&oldnd.path, old_dentry,
2758                     &newnd.path, new_dentry);
2759    if (error)
2760        goto exit6;
2761    error = vfs_rename(old_dir->d_inode, old_dentry,
2762                   new_dir->d_inode, new_dentry);
2763exit6:
2764    mnt_drop_write(oldnd.path.mnt);
2765exit5:
2766    dput(new_dentry);
2767exit4:
2768    dput(old_dentry);
2769exit3:
2770    unlock_rename(new_dir, old_dir);
2771exit2:
2772    path_put(&newnd.path);
2773    putname(to);
2774exit1:
2775    path_put(&oldnd.path);
2776    putname(from);
2777exit:
2778    return error;
2779}
2780
2781SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
2782{
2783    return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
2784}
2785
2786int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
2787{
2788    int len;
2789
2790    len = PTR_ERR(link);
2791    if (IS_ERR(link))
2792        goto out;
2793
2794    len = strlen(link);
2795    if (len > (unsigned) buflen)
2796        len = buflen;
2797    if (copy_to_user(buffer, link, len))
2798        len = -EFAULT;
2799out:
2800    return len;
2801}
2802
2803/*
2804 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
2805 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
2806 * using) it for any given inode is up to filesystem.
2807 */
2808int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
2809{
2810    struct nameidata nd;
2811    void *cookie;
2812    int res;
2813
2814    nd.depth = 0;
2815    cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
2816    if (IS_ERR(cookie))
2817        return PTR_ERR(cookie);
2818
2819    res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
2820    if (dentry->d_inode->i_op->put_link)
2821        dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
2822    return res;
2823}
2824
2825int vfs_follow_link(struct nameidata *nd, const char *link)
2826{
2827    return __vfs_follow_link(nd, link);
2828}
2829
2830/* get the link contents into pagecache */
2831static char *page_getlink(struct dentry * dentry, struct page **ppage)
2832{
2833    char *kaddr;
2834    struct page *page;
2835    struct address_space *mapping = dentry->d_inode->i_mapping;
2836    page = read_mapping_page(mapping, 0, NULL);
2837    if (IS_ERR(page))
2838        return (char*)page;
2839    *ppage = page;
2840    kaddr = kmap(page);
2841    nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
2842    return kaddr;
2843}
2844
2845int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
2846{
2847    struct page *page = NULL;
2848    char *s = page_getlink(dentry, &page);
2849    int res = vfs_readlink(dentry,buffer,buflen,s);
2850    if (page) {
2851        kunmap(page);
2852        page_cache_release(page);
2853    }
2854    return res;
2855}
2856
2857void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
2858{
2859    struct page *page = NULL;
2860    nd_set_link(nd, page_getlink(dentry, &page));
2861    return page;
2862}
2863
2864void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2865{
2866    struct page *page = cookie;
2867
2868    if (page) {
2869        kunmap(page);
2870        page_cache_release(page);
2871    }
2872}
2873
2874/*
2875 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
2876 */
2877int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
2878{
2879    struct address_space *mapping = inode->i_mapping;
2880    struct page *page;
2881    void *fsdata;
2882    int err;
2883    char *kaddr;
2884    unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
2885    if (nofs)
2886        flags |= AOP_FLAG_NOFS;
2887
2888retry:
2889    err = pagecache_write_begin(NULL, mapping, 0, len-1,
2890                flags, &page, &fsdata);
2891    if (err)
2892        goto fail;
2893
2894    kaddr = kmap_atomic(page, KM_USER0);
2895    memcpy(kaddr, symname, len-1);
2896    kunmap_atomic(kaddr, KM_USER0);
2897
2898    err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
2899                            page, fsdata);
2900    if (err < 0)
2901        goto fail;
2902    if (err < len-1)
2903        goto retry;
2904
2905    mark_inode_dirty(inode);
2906    return 0;
2907fail:
2908    return err;
2909}
2910
2911int page_symlink(struct inode *inode, const char *symname, int len)
2912{
2913    return __page_symlink(inode, symname, len,
2914            !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
2915}
2916
2917const struct inode_operations page_symlink_inode_operations = {
2918    .readlink = generic_readlink,
2919    .follow_link = page_follow_link_light,
2920    .put_link = page_put_link,
2921};
2922
2923EXPORT_SYMBOL(user_path_at);
2924EXPORT_SYMBOL(follow_down);
2925EXPORT_SYMBOL(follow_up);
2926EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
2927EXPORT_SYMBOL(getname);
2928EXPORT_SYMBOL(lock_rename);
2929EXPORT_SYMBOL(lookup_one_len);
2930EXPORT_SYMBOL(page_follow_link_light);
2931EXPORT_SYMBOL(page_put_link);
2932EXPORT_SYMBOL(page_readlink);
2933EXPORT_SYMBOL(__page_symlink);
2934EXPORT_SYMBOL(page_symlink);
2935EXPORT_SYMBOL(page_symlink_inode_operations);
2936EXPORT_SYMBOL(path_lookup);
2937EXPORT_SYMBOL(kern_path);
2938EXPORT_SYMBOL(vfs_path_lookup);
2939EXPORT_SYMBOL(inode_permission);
2940EXPORT_SYMBOL(file_permission);
2941EXPORT_SYMBOL(unlock_rename);
2942EXPORT_SYMBOL(vfs_create);
2943EXPORT_SYMBOL(vfs_follow_link);
2944EXPORT_SYMBOL(vfs_link);
2945EXPORT_SYMBOL(vfs_mkdir);
2946EXPORT_SYMBOL(vfs_mknod);
2947EXPORT_SYMBOL(generic_permission);
2948EXPORT_SYMBOL(vfs_readlink);
2949EXPORT_SYMBOL(vfs_rename);
2950EXPORT_SYMBOL(vfs_rmdir);
2951EXPORT_SYMBOL(vfs_symlink);
2952EXPORT_SYMBOL(vfs_unlink);
2953EXPORT_SYMBOL(dentry_unhash);
2954EXPORT_SYMBOL(generic_readlink);
2955

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