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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/pagemap.h>
23	#include <linux/fsnotify.h>
24	#include <linux/personality.h>
25	#include <linux/security.h>
26	#include <linux/ima.h>
27	#include <linux/syscalls.h>
28	#include <linux/mount.h>
29	#include <linux/audit.h>
30	#include <linux/capability.h>
31	#include <linux/file.h>
32	#include <linux/fcntl.h>
33	#include <linux/device_cgroup.h>
34	#include <linux/fs_struct.h>
35	#include <asm/uaccess.h>
36
37	#include "internal.h"
38
39	/* [Feb-1997 T. Schoebel-Theuer]
40	* Fundamental changes in the pathname lookup mechanisms (namei)
41	* were necessary because of omirr. The reason is that omirr needs
42	* to know the _real_ pathname, not the user-supplied one, in case
43	* of symlinks (and also when transname replacements occur).
44	*
45	* The new code replaces the old recursive symlink resolution with
46	* an iterative one (in case of non-nested symlink chains). It does
47	* this with calls to <fs>_follow_link().
48	* As a side effect, dir_namei(), _namei() and follow_link() are now
49	* replaced with a single function lookup_dentry() that can handle all
50	* the special cases of the former code.
51	*
52	* With the new dcache, the pathname is stored at each inode, at least as
53	* long as the refcount of the inode is positive. As a side effect, the
54	* size of the dcache depends on the inode cache and thus is dynamic.
55	*
56	* [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
57	* resolution to correspond with current state of the code.
58	*
59	* Note that the symlink resolution is not completely iterative.
60	* There is still a significant amount of tail- and mid- recursion in
61	* the algorithm. Also, note that <fs>_readlink() is not used in
62	* lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
63	* may return different results than <fs>_follow_link(). Many virtual
64	* filesystems (including /proc) exhibit this behavior.
65	*/
66
67	/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
68	* New symlink semantics: when open() is called with flags O_CREAT \| O_EXCL
69	* and the name already exists in form of a symlink, try to create the new
70	* name indicated by the symlink. The old code always complained that the
71	* name already exists, due to not following the symlink even if its target
72	* is nonexistent. The new semantics affects also mknod() and link() when
73	* the name is a symlink pointing to a non-existent name.
74	*
75	* I don't know which semantics is the right one, since I have no access
76	* to standards. But I found by trial that HP-UX 9.0 has the full "new"
77	* semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
78	* "old" one. Personally, I think the new semantics is much more logical.
79	* Note that "ln old new" where "new" is a symlink pointing to a non-existing
80	* file does succeed in both HP-UX and SunOs, but not in Solaris
81	* and in the old Linux semantics.
82	*/
83
84	/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
85	* semantics. See the comments in "open_namei" and "do_link" below.
86	*
87	* [10-Sep-98 Alan Modra] Another symlink change.
88	*/
89
90	/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
91	* inside the path - always follow.
92	* in the last component in creation/removal/renaming - never follow.
93	* if LOOKUP_FOLLOW passed - follow.
94	* if the pathname has trailing slashes - follow.
95	* otherwise - don't follow.
96	* (applied in that order).
97	*
98	* [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
99	* restored for 2.4. This is the last surviving part of old 4.2BSD bug.
100	* During the 2.4 we need to fix the userland stuff depending on it -
101	* hopefully we will be able to get rid of that wart in 2.5. So far only
102	* XEmacs seems to be relying on it...
103	*/
104	/*
105	* [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
106	* implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
107	* any extra contention...
108	*/
109
110	/* In order to reduce some races, while at the same time doing additional
111	* checking and hopefully speeding things up, we copy filenames to the
112	* kernel data space before using them..
113	*
114	* POSIX.1 2.4: an empty pathname is invalid (ENOENT).
115	* PATH_MAX includes the nul terminator --RR.
116	*/
117	static int do_getname(const char __user filename, char page)
118	{
119	int retval;
120	unsigned long len = PATH_MAX;
121
122	if (!segment_eq(get_fs(), KERNEL_DS)) {
123	if ((unsigned long) filename >= TASK_SIZE)
124	return -EFAULT;
125	if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
126	len = TASK_SIZE - (unsigned long) filename;
127	}
128
129	retval = strncpy_from_user(page, filename, len);
130	if (retval > 0) {
131	if (retval < len)
132	return 0;
133	return -ENAMETOOLONG;
134	} else if (!retval)
135	retval = -ENOENT;
136	return retval;
137	}
138
139	static char getname_flags(const char __user filename, int flags)
140	{
141	char tmp, result;
142
143	result = ERR_PTR(-ENOMEM);
144	tmp = __getname();
145	if (tmp) {
146	int retval = do_getname(filename, tmp);
147
148	result = tmp;
149	if (retval < 0) {
150	if (retval != -ENOENT \|\| !(flags & LOOKUP_EMPTY)) {
151	__putname(tmp);
152	result = ERR_PTR(retval);
153	}
154	}
155	}
156	audit_getname(result);
157	return result;
158	}
159
160	char getname(const char __user filename)
161	{
162	return getname_flags(filename, 0);
163	}
164
165	#ifdef CONFIG_AUDITSYSCALL
166	void putname(const char *name)
167	{
168	if (unlikely(!audit_dummy_context()))
169	audit_putname(name);
170	else
171	__putname(name);
172	}
173	EXPORT_SYMBOL(putname);
174	#endif
175
176	/*
177	* This does basic POSIX ACL permission checking
178	*/
179	static int acl_permission_check(struct inode *inode, int mask, unsigned int flags,
180	int (check_acl)(struct inode inode, int mask, unsigned int flags))
181	{
182	unsigned int mode = inode->i_mode;
183
184	mask &= MAY_READ \| MAY_WRITE \| MAY_EXEC;
185
186	if (current_user_ns() != inode_userns(inode))
187	goto other_perms;
188
189	if (current_fsuid() == inode->i_uid)
190	mode >>= 6;
191	else {
192	if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
193	int error = check_acl(inode, mask, flags);
194	if (error != -EAGAIN)
195	return error;
196	}
197
198	if (in_group_p(inode->i_gid))
199	mode >>= 3;
200	}
201
202	other_perms:
203	/*
204	* If the DACs are ok we don't need any capability check.
205	*/
206	if ((mask & ~mode) == 0)
207	return 0;
208	return -EACCES;
209	}
210
211	/**
212	* generic_permission - check for access rights on a Posix-like filesystem
213	* @inode: inode to check access rights for
214	* @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
215	* @check_acl: optional callback to check for Posix ACLs
216	* @flags: IPERM_FLAG_ flags.
217	*
218	* Used to check for read/write/execute permissions on a file.
219	* We use "fsuid" for this, letting us set arbitrary permissions
220	* for filesystem access without changing the "normal" uids which
221	* are used for other things.
222	*
223	* generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
224	* request cannot be satisfied (eg. requires blocking or too much complexity).
225	* It would then be called again in ref-walk mode.
226	*/
227	int generic_permission(struct inode *inode, int mask, unsigned int flags,
228	int (check_acl)(struct inode inode, int mask, unsigned int flags))
229	{
230	int ret;
231
232	/*
233	* Do the basic POSIX ACL permission checks.
234	*/
235	ret = acl_permission_check(inode, mask, flags, check_acl);
236	if (ret != -EACCES)
237	return ret;
238
239	/*
240	* Read/write DACs are always overridable.
241	* Executable DACs are overridable for all directories and
242	* for non-directories that have least one exec bit set.
243	*/
244	if (!(mask & MAY_EXEC) \|\| execute_ok(inode))
245	if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
246	return 0;
247
248	/*
249	* Searching includes executable on directories, else just read.
250	*/
251	mask &= MAY_READ \| MAY_WRITE \| MAY_EXEC;
252	if (mask == MAY_READ \|\| (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
253	if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
254	return 0;
255
256	return -EACCES;
257	}
258
259	/**
260	* inode_permission - check for access rights to a given inode
261	* @inode: inode to check permission on
262	* @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
263	*
264	* Used to check for read/write/execute permissions on an inode.
265	* We use "fsuid" for this, letting us set arbitrary permissions
266	* for filesystem access without changing the "normal" uids which
267	* are used for other things.
268	*/
269	int inode_permission(struct inode *inode, int mask)
270	{
271	int retval;
272
273	if (mask & MAY_WRITE) {
274	umode_t mode = inode->i_mode;
275
276	/*
277	* Nobody gets write access to a read-only fs.
278	*/
279	if (IS_RDONLY(inode) &&
280	(S_ISREG(mode) \|\| S_ISDIR(mode) \|\| S_ISLNK(mode)))
281	return -EROFS;
282
283	/*
284	* Nobody gets write access to an immutable file.
285	*/
286	if (IS_IMMUTABLE(inode))
287	return -EACCES;
288	}
289
290	if (inode->i_op->permission)
291	retval = inode->i_op->permission(inode, mask, 0);
292	else
293	retval = generic_permission(inode, mask, 0,
294	inode->i_op->check_acl);
295
296	if (retval)
297	return retval;
298
299	retval = devcgroup_inode_permission(inode, mask);
300	if (retval)
301	return retval;
302
303	return security_inode_permission(inode, mask);
304	}
305
306	/**
307	* file_permission - check for additional access rights to a given file
308	* @file: file to check access rights for
309	* @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
310	*
311	* Used to check for read/write/execute permissions on an already opened
312	* file.
313	*
314	* Note:
315	* Do not use this function in new code. All access checks should
316	* be done using inode_permission().
317	*/
318	int file_permission(struct file *file, int mask)
319	{
320	return inode_permission(file->f_path.dentry->d_inode, mask);
321	}
322
323	/*
324	* get_write_access() gets write permission for a file.
325	* put_write_access() releases this write permission.
326	* This is used for regular files.
327	* We cannot support write (and maybe mmap read-write shared) accesses and
328	* MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
329	* can have the following values:
330	* 0: no writers, no VM_DENYWRITE mappings
331	* < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
332	* > 0: (i_writecount) users are writing to the file.
333	*
334	* Normally we operate on that counter with atomic_{inc,dec} and it's safe
335	* except for the cases where we don't hold i_writecount yet. Then we need to
336	* use {get,deny}_write_access() - these functions check the sign and refuse
337	* to do the change if sign is wrong. Exclusion between them is provided by
338	* the inode->i_lock spinlock.
339	*/
340
341	int get_write_access(struct inode * inode)
342	{
343	spin_lock(&inode->i_lock);
344	if (atomic_read(&inode->i_writecount) < 0) {
345	spin_unlock(&inode->i_lock);
346	return -ETXTBSY;
347	}
348	atomic_inc(&inode->i_writecount);
349	spin_unlock(&inode->i_lock);
350
351	return 0;
352	}
353
354	int deny_write_access(struct file * file)
355	{
356	struct inode *inode = file->f_path.dentry->d_inode;
357
358	spin_lock(&inode->i_lock);
359	if (atomic_read(&inode->i_writecount) > 0) {
360	spin_unlock(&inode->i_lock);
361	return -ETXTBSY;
362	}
363	atomic_dec(&inode->i_writecount);
364	spin_unlock(&inode->i_lock);
365
366	return 0;
367	}
368
369	/**
370	* path_get - get a reference to a path
371	* @path: path to get the reference to
372	*
373	* Given a path increment the reference count to the dentry and the vfsmount.
374	*/
375	void path_get(struct path *path)
376	{
377	mntget(path->mnt);
378	dget(path->dentry);
379	}
380	EXPORT_SYMBOL(path_get);
381
382	/**
383	* path_put - put a reference to a path
384	* @path: path to put the reference to
385	*
386	* Given a path decrement the reference count to the dentry and the vfsmount.
387	*/
388	void path_put(struct path *path)
389	{
390	dput(path->dentry);
391	mntput(path->mnt);
392	}
393	EXPORT_SYMBOL(path_put);
394
395	/*
396	* Path walking has 2 modes, rcu-walk and ref-walk (see
397	* Documentation/filesystems/path-lookup.txt). In situations when we can't
398	* continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
399	* normal reference counts on dentries and vfsmounts to transition to rcu-walk
400	* mode. Refcounts are grabbed at the last known good point before rcu-walk
401	* got stuck, so ref-walk may continue from there. If this is not successful
402	* (eg. a seqcount has changed), then failure is returned and it's up to caller
403	* to restart the path walk from the beginning in ref-walk mode.
404	*/
405
406	/**
407	* unlazy_walk - try to switch to ref-walk mode.
408	* @nd: nameidata pathwalk data
409	* @dentry: child of nd->path.dentry or NULL
410	* Returns: 0 on success, -ECHILD on failure
411	*
412	* unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
413	* for ref-walk mode. @dentry must be a path found by a do_lookup call on
414	* @nd or NULL. Must be called from rcu-walk context.
415	*/
416	static int unlazy_walk(struct nameidata nd, struct dentry dentry)
417	{
418	struct fs_struct *fs = current->fs;
419	struct dentry *parent = nd->path.dentry;
420	int want_root = 0;
421
422	BUG_ON(!(nd->flags & LOOKUP_RCU));
423	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
424	want_root = 1;
425	spin_lock(&fs->lock);
426	if (nd->root.mnt != fs->root.mnt \|\|
427	nd->root.dentry != fs->root.dentry)
428	goto err_root;
429	}
430	spin_lock(&parent->d_lock);
431	if (!dentry) {
432	if (!__d_rcu_to_refcount(parent, nd->seq))
433	goto err_parent;
434	BUG_ON(nd->inode != parent->d_inode);
435	} else {
436	if (dentry->d_parent != parent)
437	goto err_parent;
438	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
439	if (!__d_rcu_to_refcount(dentry, nd->seq))
440	goto err_child;
441	/*
442	* If the sequence check on the child dentry passed, then
443	* the child has not been removed from its parent. This
444	* means the parent dentry must be valid and able to take
445	* a reference at this point.
446	*/
447	BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
448	BUG_ON(!parent->d_count);
449	parent->d_count++;
450	spin_unlock(&dentry->d_lock);
451	}
452	spin_unlock(&parent->d_lock);
453	if (want_root) {
454	path_get(&nd->root);
455	spin_unlock(&fs->lock);
456	}
457	mntget(nd->path.mnt);
458
459	rcu_read_unlock();
460	br_read_unlock(vfsmount_lock);
461	nd->flags &= ~LOOKUP_RCU;
462	return 0;
463
464	err_child:
465	spin_unlock(&dentry->d_lock);
466	err_parent:
467	spin_unlock(&parent->d_lock);
468	err_root:
469	if (want_root)
470	spin_unlock(&fs->lock);
471	return -ECHILD;
472	}
473
474	/**
475	* release_open_intent - free up open intent resources
476	* @nd: pointer to nameidata
477	*/
478	void release_open_intent(struct nameidata *nd)
479	{
480	struct file *file = nd->intent.open.file;
481
482	if (file && !IS_ERR(file)) {
483	if (file->f_path.dentry == NULL)
484	put_filp(file);
485	else
486	fput(file);
487	}
488	}
489
490	static inline int d_revalidate(struct dentry dentry, struct nameidata nd)
491	{
492	return dentry->d_op->d_revalidate(dentry, nd);
493	}
494
495	static struct dentry *
496	do_revalidate(struct dentry dentry, struct nameidata nd)
497	{
498	int status = d_revalidate(dentry, nd);
499	if (unlikely(status <= 0)) {
500	/*
501	* The dentry failed validation.
502	* If d_revalidate returned 0 attempt to invalidate
503	* the dentry otherwise d_revalidate is asking us
504	* to return a fail status.
505	*/
506	if (status < 0) {
507	dput(dentry);
508	dentry = ERR_PTR(status);
509	} else if (!d_invalidate(dentry)) {
510	dput(dentry);
511	dentry = NULL;
512	}
513	}
514	return dentry;
515	}
516
517	/**
518	* complete_walk - successful completion of path walk
519	* @nd: pointer nameidata
520	*
521	* If we had been in RCU mode, drop out of it and legitimize nd->path.
522	* Revalidate the final result, unless we'd already done that during
523	* the path walk or the filesystem doesn't ask for it. Return 0 on
524	* success, -error on failure. In case of failure caller does not
525	* need to drop nd->path.
526	*/
527	static int complete_walk(struct nameidata *nd)
528	{
529	struct dentry *dentry = nd->path.dentry;
530	int status;
531
532	if (nd->flags & LOOKUP_RCU) {
533	nd->flags &= ~LOOKUP_RCU;
534	if (!(nd->flags & LOOKUP_ROOT))
535	nd->root.mnt = NULL;
536	spin_lock(&dentry->d_lock);
537	if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) {
538	spin_unlock(&dentry->d_lock);
539	rcu_read_unlock();
540	br_read_unlock(vfsmount_lock);
541	return -ECHILD;
542	}
543	BUG_ON(nd->inode != dentry->d_inode);
544	spin_unlock(&dentry->d_lock);
545	mntget(nd->path.mnt);
546	rcu_read_unlock();
547	br_read_unlock(vfsmount_lock);
548	}
549
550	if (likely(!(nd->flags & LOOKUP_JUMPED)))
551	return 0;
552
553	if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
554	return 0;
555
556	if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
557	return 0;
558
559	/* Note: we do not d_invalidate() */
560	status = d_revalidate(dentry, nd);
561	if (status > 0)
562	return 0;
563
564	if (!status)
565	status = -ESTALE;
566
567	path_put(&nd->path);
568	return status;
569	}
570
571	/*
572	* Short-cut version of permission(), for calling on directories
573	* during pathname resolution. Combines parts of permission()
574	* and generic_permission(), and tests ONLY for MAY_EXEC permission.
575	*
576	* If appropriate, check DAC only. If not appropriate, or
577	* short-cut DAC fails, then call ->permission() to do more
578	* complete permission check.
579	*/
580	static inline int exec_permission(struct inode *inode, unsigned int flags)
581	{
582	int ret;
583	struct user_namespace *ns = inode_userns(inode);
584
585	if (inode->i_op->permission) {
586	ret = inode->i_op->permission(inode, MAY_EXEC, flags);
587	} else {
588	ret = acl_permission_check(inode, MAY_EXEC, flags,
589	inode->i_op->check_acl);
590	}
591	if (likely(!ret))
592	goto ok;
593	if (ret == -ECHILD)
594	return ret;
595
596	if (ns_capable(ns, CAP_DAC_OVERRIDE) \|\|
597	ns_capable(ns, CAP_DAC_READ_SEARCH))
598	goto ok;
599
600	return ret;
601	ok:
602	return security_inode_exec_permission(inode, flags);
603	}
604
605	static __always_inline void set_root(struct nameidata *nd)
606	{
607	if (!nd->root.mnt)
608	get_fs_root(current->fs, &nd->root);
609	}
610
611	static int link_path_walk(const char , struct nameidata );
612
613	static __always_inline void set_root_rcu(struct nameidata *nd)
614	{
615	if (!nd->root.mnt) {
616	struct fs_struct *fs = current->fs;
617	unsigned seq;
618
619	do {
620	seq = read_seqcount_begin(&fs->seq);
621	nd->root = fs->root;
622	nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
623	} while (read_seqcount_retry(&fs->seq, seq));
624	}
625	}
626
627	static __always_inline int __vfs_follow_link(struct nameidata nd, const char link)
628	{
629	int ret;
630
631	if (IS_ERR(link))
632	goto fail;
633
634	if (*link == '/') {
635	set_root(nd);
636	path_put(&nd->path);
637	nd->path = nd->root;
638	path_get(&nd->root);
639	nd->flags \|= LOOKUP_JUMPED;
640	}
641	nd->inode = nd->path.dentry->d_inode;
642
643	ret = link_path_walk(link, nd);
644	return ret;
645	fail:
646	path_put(&nd->path);
647	return PTR_ERR(link);
648	}
649
650	static void path_put_conditional(struct path path, struct nameidata nd)
651	{
652	dput(path->dentry);
653	if (path->mnt != nd->path.mnt)
654	mntput(path->mnt);
655	}
656
657	static inline void path_to_nameidata(const struct path *path,
658	struct nameidata *nd)
659	{
660	if (!(nd->flags & LOOKUP_RCU)) {
661	dput(nd->path.dentry);
662	if (nd->path.mnt != path->mnt)
663	mntput(nd->path.mnt);
664	}
665	nd->path.mnt = path->mnt;
666	nd->path.dentry = path->dentry;
667	}
668
669	static inline void put_link(struct nameidata nd, struct path link, void *cookie)
670	{
671	struct inode *inode = link->dentry->d_inode;
672	if (!IS_ERR(cookie) && inode->i_op->put_link)
673	inode->i_op->put_link(link->dentry, nd, cookie);
674	path_put(link);
675	}
676
677	static __always_inline int
678	follow_link(struct path link, struct nameidata nd, void **p)
679	{
680	int error;
681	struct dentry *dentry = link->dentry;
682
683	BUG_ON(nd->flags & LOOKUP_RCU);
684
685	if (link->mnt == nd->path.mnt)
686	mntget(link->mnt);
687
688	if (unlikely(current->total_link_count >= 40)) {
689	p = ERR_PTR(-ELOOP); / no ->put_link(), please */
690	path_put(&nd->path);
691	return -ELOOP;
692	}
693	cond_resched();
694	current->total_link_count++;
695
696	touch_atime(link->mnt, dentry);
697	nd_set_link(nd, NULL);
698
699	error = security_inode_follow_link(link->dentry, nd);
700	if (error) {
701	p = ERR_PTR(error); / no ->put_link(), please */
702	path_put(&nd->path);
703	return error;
704	}
705
706	nd->last_type = LAST_BIND;
707	*p = dentry->d_inode->i_op->follow_link(dentry, nd);
708	error = PTR_ERR(*p);
709	if (!IS_ERR(*p)) {
710	char *s = nd_get_link(nd);
711	error = 0;
712	if (s)
713	error = __vfs_follow_link(nd, s);
714	else if (nd->last_type == LAST_BIND) {
715	nd->flags \|= LOOKUP_JUMPED;
716	nd->inode = nd->path.dentry->d_inode;
717	if (nd->inode->i_op->follow_link) {
718	/* stepped on a _really_ weird one */
719	path_put(&nd->path);
720	error = -ELOOP;
721	}
722	}
723	}
724	return error;
725	}
726
727	static int follow_up_rcu(struct path *path)
728	{
729	struct vfsmount *parent;
730	struct dentry *mountpoint;
731
732	parent = path->mnt->mnt_parent;
733	if (parent == path->mnt)
734	return 0;
735	mountpoint = path->mnt->mnt_mountpoint;
736	path->dentry = mountpoint;
737	path->mnt = parent;
738	return 1;
739	}
740
741	int follow_up(struct path *path)
742	{
743	struct vfsmount *parent;
744	struct dentry *mountpoint;
745
746	br_read_lock(vfsmount_lock);
747	parent = path->mnt->mnt_parent;
748	if (parent == path->mnt) {
749	br_read_unlock(vfsmount_lock);
750	return 0;
751	}
752	mntget(parent);
753	mountpoint = dget(path->mnt->mnt_mountpoint);
754	br_read_unlock(vfsmount_lock);
755	dput(path->dentry);
756	path->dentry = mountpoint;
757	mntput(path->mnt);
758	path->mnt = parent;
759	return 1;
760	}
761
762	/*
763	* Perform an automount
764	* - return -EISDIR to tell follow_managed() to stop and return the path we
765	* were called with.
766	*/
767	static int follow_automount(struct path *path, unsigned flags,
768	bool *need_mntput)
769	{
770	struct vfsmount *mnt;
771	int err;
772
773	if (!path->dentry->d_op \|\| !path->dentry->d_op->d_automount)
774	return -EREMOTE;
775
776	/* We don't want to mount if someone supplied AT_NO_AUTOMOUNT
777	* and this is the terminal part of the path.
778	*/
779	if ((flags & LOOKUP_NO_AUTOMOUNT) && !(flags & LOOKUP_CONTINUE))
780	return -EISDIR; /* we actually want to stop here */
781
782	/* We want to mount if someone is trying to open/create a file of any
783	* type under the mountpoint, wants to traverse through the mountpoint
784	* or wants to open the mounted directory.
785	*
786	* We don't want to mount if someone's just doing a stat and they've
787	* set AT_SYMLINK_NOFOLLOW - unless they're stat'ing a directory and
788	* appended a '/' to the name.
789	*/
790	if (!(flags & LOOKUP_FOLLOW) &&
791	!(flags & (LOOKUP_CONTINUE \| LOOKUP_DIRECTORY \|
792	LOOKUP_OPEN \| LOOKUP_CREATE)))
793	return -EISDIR;
794
795	current->total_link_count++;
796	if (current->total_link_count >= 40)
797	return -ELOOP;
798
799	mnt = path->dentry->d_op->d_automount(path);
800	if (IS_ERR(mnt)) {
801	/*
802	* The filesystem is allowed to return -EISDIR here to indicate
803	* it doesn't want to automount. For instance, autofs would do
804	* this so that its userspace daemon can mount on this dentry.
805	*
806	* However, we can only permit this if it's a terminal point in
807	* the path being looked up; if it wasn't then the remainder of
808	* the path is inaccessible and we should say so.
809	*/
810	if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_CONTINUE))
811	return -EREMOTE;
812	return PTR_ERR(mnt);
813	}
814
815	if (!mnt) /* mount collision */
816	return 0;
817
818	if (!*need_mntput) {
819	/* lock_mount() may release path->mnt on error */
820	mntget(path->mnt);
821	*need_mntput = true;
822	}
823	err = finish_automount(mnt, path);
824
825	switch (err) {
826	case -EBUSY:
827	/* Someone else made a mount here whilst we were busy */
828	return 0;
829	case 0:
830	path_put(path);
831	path->mnt = mnt;
832	path->dentry = dget(mnt->mnt_root);
833	return 0;
834	default:
835	return err;
836	}
837
838	}
839
840	/*
841	* Handle a dentry that is managed in some way.
842	* - Flagged for transit management (autofs)
843	* - Flagged as mountpoint
844	* - Flagged as automount point
845	*
846	* This may only be called in refwalk mode.
847	*
848	* Serialization is taken care of in namespace.c
849	*/
850	static int follow_managed(struct path *path, unsigned flags)
851	{
852	struct vfsmount mnt = path->mnt; / held by caller, must be left alone */
853	unsigned managed;
854	bool need_mntput = false;
855	int ret = 0;
856
857	/* Given that we're not holding a lock here, we retain the value in a
858	* local variable for each dentry as we look at it so that we don't see
859	* the components of that value change under us */
860	while (managed = ACCESS_ONCE(path->dentry->d_flags),
861	managed &= DCACHE_MANAGED_DENTRY,
862	unlikely(managed != 0)) {
863	/* Allow the filesystem to manage the transit without i_mutex
864	* being held. */
865	if (managed & DCACHE_MANAGE_TRANSIT) {
866	BUG_ON(!path->dentry->d_op);
867	BUG_ON(!path->dentry->d_op->d_manage);
868	ret = path->dentry->d_op->d_manage(path->dentry, false);
869	if (ret < 0)
870	break;
871	}
872
873	/* Transit to a mounted filesystem. */
874	if (managed & DCACHE_MOUNTED) {
875	struct vfsmount *mounted = lookup_mnt(path);
876	if (mounted) {
877	dput(path->dentry);
878	if (need_mntput)
879	mntput(path->mnt);
880	path->mnt = mounted;
881	path->dentry = dget(mounted->mnt_root);
882	need_mntput = true;
883	continue;
884	}
885
886	/* Something is mounted on this dentry in another
887	* namespace and/or whatever was mounted there in this
888	* namespace got unmounted before we managed to get the
889	* vfsmount_lock */
890	}
891
892	/* Handle an automount point */
893	if (managed & DCACHE_NEED_AUTOMOUNT) {
894	ret = follow_automount(path, flags, &need_mntput);
895	if (ret < 0)
896	break;
897	continue;
898	}
899
900	/* We didn't change the current path point */
901	break;
902	}
903
904	if (need_mntput && path->mnt == mnt)
905	mntput(path->mnt);
906	if (ret == -EISDIR)
907	ret = 0;
908	return ret;
909	}
910
911	int follow_down_one(struct path *path)
912	{
913	struct vfsmount *mounted;
914
915	mounted = lookup_mnt(path);
916	if (mounted) {
917	dput(path->dentry);
918	mntput(path->mnt);
919	path->mnt = mounted;
920	path->dentry = dget(mounted->mnt_root);
921	return 1;
922	}
923	return 0;
924	}
925
926	static inline bool managed_dentry_might_block(struct dentry *dentry)
927	{
928	return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
929	dentry->d_op->d_manage(dentry, true) < 0);
930	}
931
932	/*
933	* Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
934	* we meet a managed dentry that would need blocking.
935	*/
936	static bool __follow_mount_rcu(struct nameidata nd, struct path path,
937	struct inode **inode)
938	{
939	for (;;) {
940	struct vfsmount *mounted;
941	/*
942	* Don't forget we might have a non-mountpoint managed dentry
943	* that wants to block transit.
944	*/
945	if (unlikely(managed_dentry_might_block(path->dentry)))
946	return false;
947
948	if (!d_mountpoint(path->dentry))
949	break;
950
951	mounted = __lookup_mnt(path->mnt, path->dentry, 1);
952	if (!mounted)
953	break;
954	path->mnt = mounted;
955	path->dentry = mounted->mnt_root;
956	nd->seq = read_seqcount_begin(&path->dentry->d_seq);
957	/*
958	* Update the inode too. We don't need to re-check the
959	* dentry sequence number here after this d_inode read,
960	* because a mount-point is always pinned.
961	*/
962	*inode = path->dentry->d_inode;
963	}
964	return true;
965	}
966
967	static void follow_mount_rcu(struct nameidata *nd)
968	{
969	while (d_mountpoint(nd->path.dentry)) {
970	struct vfsmount *mounted;
971	mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1);
972	if (!mounted)
973	break;
974	nd->path.mnt = mounted;
975	nd->path.dentry = mounted->mnt_root;
976	nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
977	}
978	}
979
980	static int follow_dotdot_rcu(struct nameidata *nd)
981	{
982	set_root_rcu(nd);
983
984	while (1) {
985	if (nd->path.dentry == nd->root.dentry &&
986	nd->path.mnt == nd->root.mnt) {
987	break;
988	}
989	if (nd->path.dentry != nd->path.mnt->mnt_root) {
990	struct dentry *old = nd->path.dentry;
991	struct dentry *parent = old->d_parent;
992	unsigned seq;
993
994	seq = read_seqcount_begin(&parent->d_seq);
995	if (read_seqcount_retry(&old->d_seq, nd->seq))
996	goto failed;
997	nd->path.dentry = parent;
998	nd->seq = seq;
999	break;
1000	}
1001	if (!follow_up_rcu(&nd->path))
1002	break;
1003	nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1004	}
1005	follow_mount_rcu(nd);
1006	nd->inode = nd->path.dentry->d_inode;
1007	return 0;
1008
1009	failed:
1010	nd->flags &= ~LOOKUP_RCU;
1011	if (!(nd->flags & LOOKUP_ROOT))
1012	nd->root.mnt = NULL;
1013	rcu_read_unlock();
1014	br_read_unlock(vfsmount_lock);
1015	return -ECHILD;
1016	}
1017
1018	/*
1019	* Follow down to the covering mount currently visible to userspace. At each
1020	* point, the filesystem owning that dentry may be queried as to whether the
1021	* caller is permitted to proceed or not.
1022	*/
1023	int follow_down(struct path *path)
1024	{
1025	unsigned managed;
1026	int ret;
1027
1028	while (managed = ACCESS_ONCE(path->dentry->d_flags),
1029	unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1030	/* Allow the filesystem to manage the transit without i_mutex
1031	* being held.
1032	*
1033	* We indicate to the filesystem if someone is trying to mount
1034	* something here. This gives autofs the chance to deny anyone
1035	* other than its daemon the right to mount on its
1036	* superstructure.
1037	*
1038	* The filesystem may sleep at this point.
1039	*/
1040	if (managed & DCACHE_MANAGE_TRANSIT) {
1041	BUG_ON(!path->dentry->d_op);
1042	BUG_ON(!path->dentry->d_op->d_manage);
1043	ret = path->dentry->d_op->d_manage(
1044	path->dentry, false);
1045	if (ret < 0)
1046	return ret == -EISDIR ? 0 : ret;
1047	}
1048
1049	/* Transit to a mounted filesystem. */
1050	if (managed & DCACHE_MOUNTED) {
1051	struct vfsmount *mounted = lookup_mnt(path);
1052	if (!mounted)
1053	break;
1054	dput(path->dentry);
1055	mntput(path->mnt);
1056	path->mnt = mounted;
1057	path->dentry = dget(mounted->mnt_root);
1058	continue;
1059	}
1060
1061	/* Don't handle automount points here */
1062	break;
1063	}
1064	return 0;
1065	}
1066
1067	/*
1068	* Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1069	*/
1070	static void follow_mount(struct path *path)
1071	{
1072	while (d_mountpoint(path->dentry)) {
1073	struct vfsmount *mounted = lookup_mnt(path);
1074	if (!mounted)
1075	break;
1076	dput(path->dentry);
1077	mntput(path->mnt);
1078	path->mnt = mounted;
1079	path->dentry = dget(mounted->mnt_root);
1080	}
1081	}
1082
1083	static void follow_dotdot(struct nameidata *nd)
1084	{
1085	set_root(nd);
1086
1087	while(1) {
1088	struct dentry *old = nd->path.dentry;
1089
1090	if (nd->path.dentry == nd->root.dentry &&
1091	nd->path.mnt == nd->root.mnt) {
1092	break;
1093	}
1094	if (nd->path.dentry != nd->path.mnt->mnt_root) {
1095	/* rare case of legitimate dget_parent()... */
1096	nd->path.dentry = dget_parent(nd->path.dentry);
1097	dput(old);
1098	break;
1099	}
1100	if (!follow_up(&nd->path))
1101	break;
1102	}
1103	follow_mount(&nd->path);
1104	nd->inode = nd->path.dentry->d_inode;
1105	}
1106
1107	/*
1108	* Allocate a dentry with name and parent, and perform a parent
1109	* directory ->lookup on it. Returns the new dentry, or ERR_PTR
1110	* on error. parent->d_inode->i_mutex must be held. d_lookup must
1111	* have verified that no child exists while under i_mutex.
1112	*/
1113	static struct dentry d_alloc_and_lookup(struct dentry parent,
1114	struct qstr name, struct nameidata nd)
1115	{
1116	struct inode *inode = parent->d_inode;
1117	struct dentry *dentry;
1118	struct dentry *old;
1119
1120	/* Don't create child dentry for a dead directory. */
1121	if (unlikely(IS_DEADDIR(inode)))
1122	return ERR_PTR(-ENOENT);
1123
1124	dentry = d_alloc(parent, name);
1125	if (unlikely(!dentry))
1126	return ERR_PTR(-ENOMEM);
1127
1128	old = inode->i_op->lookup(inode, dentry, nd);
1129	if (unlikely(old)) {
1130	dput(dentry);
1131	dentry = old;
1132	}
1133	return dentry;
1134	}
1135
1136	/*
1137	* It's more convoluted than I'd like it to be, but... it's still fairly
1138	* small and for now I'd prefer to have fast path as straight as possible.
1139	* It _is_ time-critical.
1140	*/
1141	static int do_lookup(struct nameidata nd, struct qstr name,
1142	struct path path, struct inode *inode)
1143	{
1144	struct vfsmount *mnt = nd->path.mnt;
1145	struct dentry dentry, parent = nd->path.dentry;
1146	int need_reval = 1;
1147	int status = 1;
1148	int err;
1149
1150	/*
1151	* Rename seqlock is not required here because in the off chance
1152	* of a false negative due to a concurrent rename, we're going to
1153	* do the non-racy lookup, below.
1154	*/
1155	if (nd->flags & LOOKUP_RCU) {
1156	unsigned seq;
1157	*inode = nd->inode;
1158	dentry = __d_lookup_rcu(parent, name, &seq, inode);
1159	if (!dentry)
1160	goto unlazy;
1161
1162	/* Memory barrier in read_seqcount_begin of child is enough */
1163	if (__read_seqcount_retry(&parent->d_seq, nd->seq))
1164	return -ECHILD;
1165	nd->seq = seq;
1166
1167	if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1168	status = d_revalidate(dentry, nd);
1169	if (unlikely(status <= 0)) {
1170	if (status != -ECHILD)
1171	need_reval = 0;
1172	goto unlazy;
1173	}
1174	}
1175	path->mnt = mnt;
1176	path->dentry = dentry;
1177	if (unlikely(!__follow_mount_rcu(nd, path, inode)))
1178	goto unlazy;
1179	if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
1180	goto unlazy;
1181	return 0;
1182	unlazy:
1183	if (unlazy_walk(nd, dentry))
1184	return -ECHILD;
1185	} else {
1186	dentry = __d_lookup(parent, name);
1187	}
1188
1189	retry:
1190	if (unlikely(!dentry)) {
1191	struct inode *dir = parent->d_inode;
1192	BUG_ON(nd->inode != dir);
1193
1194	mutex_lock(&dir->i_mutex);
1195	dentry = d_lookup(parent, name);
1196	if (likely(!dentry)) {
1197	dentry = d_alloc_and_lookup(parent, name, nd);
1198	if (IS_ERR(dentry)) {
1199	mutex_unlock(&dir->i_mutex);
1200	return PTR_ERR(dentry);
1201	}
1202	/* known good */
1203	need_reval = 0;
1204	status = 1;
1205	}
1206	mutex_unlock(&dir->i_mutex);
1207	}
1208	if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
1209	status = d_revalidate(dentry, nd);
1210	if (unlikely(status <= 0)) {
1211	if (status < 0) {
1212	dput(dentry);
1213	return status;
1214	}
1215	if (!d_invalidate(dentry)) {
1216	dput(dentry);
1217	dentry = NULL;
1218	need_reval = 1;
1219	goto retry;
1220	}
1221	}
1222
1223	path->mnt = mnt;
1224	path->dentry = dentry;
1225	err = follow_managed(path, nd->flags);
1226	if (unlikely(err < 0)) {
1227	path_put_conditional(path, nd);
1228	return err;
1229	}
1230	*inode = path->dentry->d_inode;
1231	return 0;
1232	}
1233
1234	static inline int may_lookup(struct nameidata *nd)
1235	{
1236	if (nd->flags & LOOKUP_RCU) {
1237	int err = exec_permission(nd->inode, IPERM_FLAG_RCU);
1238	if (err != -ECHILD)
1239	return err;
1240	if (unlazy_walk(nd, NULL))
1241	return -ECHILD;
1242	}
1243	return exec_permission(nd->inode, 0);
1244	}
1245
1246	static inline int handle_dots(struct nameidata *nd, int type)
1247	{
1248	if (type == LAST_DOTDOT) {
1249	if (nd->flags & LOOKUP_RCU) {
1250	if (follow_dotdot_rcu(nd))
1251	return -ECHILD;
1252	} else
1253	follow_dotdot(nd);
1254	}
1255	return 0;
1256	}
1257
1258	static void terminate_walk(struct nameidata *nd)
1259	{
1260	if (!(nd->flags & LOOKUP_RCU)) {
1261	path_put(&nd->path);
1262	} else {
1263	nd->flags &= ~LOOKUP_RCU;
1264	if (!(nd->flags & LOOKUP_ROOT))
1265	nd->root.mnt = NULL;
1266	rcu_read_unlock();
1267	br_read_unlock(vfsmount_lock);
1268	}
1269	}
1270
1271	static inline int walk_component(struct nameidata nd, struct path path,
1272	struct qstr *name, int type, int follow)
1273	{
1274	struct inode *inode;
1275	int err;
1276	/*
1277	* "." and ".." are special - ".." especially so because it has
1278	* to be able to know about the current root directory and
1279	* parent relationships.
1280	*/
1281	if (unlikely(type != LAST_NORM))
1282	return handle_dots(nd, type);
1283	err = do_lookup(nd, name, path, &inode);
1284	if (unlikely(err)) {
1285	terminate_walk(nd);
1286	return err;
1287	}
1288	if (!inode) {
1289	path_to_nameidata(path, nd);
1290	terminate_walk(nd);
1291	return -ENOENT;
1292	}
1293	if (unlikely(inode->i_op->follow_link) && follow) {
1294	if (nd->flags & LOOKUP_RCU) {
1295	if (unlikely(unlazy_walk(nd, path->dentry))) {
1296	terminate_walk(nd);
1297	return -ECHILD;
1298	}
1299	}
1300	BUG_ON(inode != path->dentry->d_inode);
1301	return 1;
1302	}
1303	path_to_nameidata(path, nd);
1304	nd->inode = inode;
1305	return 0;
1306	}
1307
1308	/*
1309	* This limits recursive symlink follows to 8, while
1310	* limiting consecutive symlinks to 40.
1311	*
1312	* Without that kind of total limit, nasty chains of consecutive
1313	* symlinks can cause almost arbitrarily long lookups.
1314	*/
1315	static inline int nested_symlink(struct path path, struct nameidata nd)
1316	{
1317	int res;
1318
1319	if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
1320	path_put_conditional(path, nd);
1321	path_put(&nd->path);
1322	return -ELOOP;
1323	}
1324	BUG_ON(nd->depth >= MAX_NESTED_LINKS);
1325
1326	nd->depth++;
1327	current->link_count++;
1328
1329	do {
1330	struct path link = *path;
1331	void *cookie;
1332
1333	res = follow_link(&link, nd, &cookie);
1334	if (!res)
1335	res = walk_component(nd, path, &nd->last,
1336	nd->last_type, LOOKUP_FOLLOW);
1337	put_link(nd, &link, cookie);
1338	} while (res > 0);
1339
1340	current->link_count--;
1341	nd->depth--;
1342	return res;
1343	}
1344
1345	/*
1346	* Name resolution.
1347	* This is the basic name resolution function, turning a pathname into
1348	* the final dentry. We expect 'base' to be positive and a directory.
1349	*
1350	* Returns 0 and nd will have valid dentry and mnt on success.
1351	* Returns error and drops reference to input namei data on failure.
1352	*/
1353	static int link_path_walk(const char name, struct nameidata nd)
1354	{
1355	struct path next;
1356	int err;
1357	unsigned int lookup_flags = nd->flags;
1358
1359	while (*name=='/')
1360	name++;
1361	if (!*name)
1362	return 0;
1363
1364	/* At this point we know we have a real path component. */
1365	for(;;) {
1366	unsigned long hash;
1367	struct qstr this;
1368	unsigned int c;
1369	int type;
1370
1371	nd->flags \|= LOOKUP_CONTINUE;
1372
1373	err = may_lookup(nd);
1374	if (err)
1375	break;
1376
1377	this.name = name;
1378	c = (const unsigned char )name;
1379
1380	hash = init_name_hash();
1381	do {
1382	name++;
1383	hash = partial_name_hash(c, hash);
1384	c = (const unsigned char )name;
1385	} while (c && (c != '/'));
1386	this.len = name - (const char *) this.name;
1387	this.hash = end_name_hash(hash);
1388
1389	type = LAST_NORM;
1390	if (this.name[0] == '.') switch (this.len) {
1391	case 2:
1392	if (this.name[1] == '.') {
1393	type = LAST_DOTDOT;
1394	nd->flags \|= LOOKUP_JUMPED;
1395	}
1396	break;
1397	case 1:
1398	type = LAST_DOT;
1399	}
1400	if (likely(type == LAST_NORM)) {
1401	struct dentry *parent = nd->path.dentry;
1402	nd->flags &= ~LOOKUP_JUMPED;
1403	if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1404	err = parent->d_op->d_hash(parent, nd->inode,
1405	&this);
1406	if (err < 0)
1407	break;
1408	}
1409	}
1410
1411	/* remove trailing slashes? */
1412	if (!c)
1413	goto last_component;
1414	while (*++name == '/');
1415	if (!*name)
1416	goto last_component;
1417
1418	err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
1419	if (err < 0)
1420	return err;
1421
1422	if (err) {
1423	err = nested_symlink(&next, nd);
1424	if (err)
1425	return err;
1426	}
1427	err = -ENOTDIR;
1428	if (!nd->inode->i_op->lookup)
1429	break;
1430	continue;
1431	/* here ends the main loop */
1432
1433	last_component:
1434	/* Clear LOOKUP_CONTINUE iff it was previously unset */
1435	nd->flags &= lookup_flags \| ~LOOKUP_CONTINUE;
1436	nd->last = this;
1437	nd->last_type = type;
1438	return 0;
1439	}
1440	terminate_walk(nd);
1441	return err;
1442	}
1443
1444	static int path_init(int dfd, const char *name, unsigned int flags,
1445	struct nameidata nd, struct file *fp)
1446	{
1447	int retval = 0;
1448	int fput_needed;
1449	struct file *file;
1450
1451	nd->last_type = LAST_ROOT; /* if there are only slashes... */
1452	nd->flags = flags \| LOOKUP_JUMPED;
1453	nd->depth = 0;
1454	if (flags & LOOKUP_ROOT) {
1455	struct inode *inode = nd->root.dentry->d_inode;
1456	if (*name) {
1457	if (!inode->i_op->lookup)
1458	return -ENOTDIR;
1459	retval = inode_permission(inode, MAY_EXEC);
1460	if (retval)
1461	return retval;
1462	}
1463	nd->path = nd->root;
1464	nd->inode = inode;
1465	if (flags & LOOKUP_RCU) {
1466	br_read_lock(vfsmount_lock);
1467	rcu_read_lock();
1468	nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1469	} else {
1470	path_get(&nd->path);
1471	}
1472	return 0;
1473	}
1474
1475	nd->root.mnt = NULL;
1476
1477	if (*name=='/') {
1478	if (flags & LOOKUP_RCU) {
1479	br_read_lock(vfsmount_lock);
1480	rcu_read_lock();
1481	set_root_rcu(nd);
1482	} else {
1483	set_root(nd);
1484	path_get(&nd->root);
1485	}
1486	nd->path = nd->root;
1487	} else if (dfd == AT_FDCWD) {
1488	if (flags & LOOKUP_RCU) {
1489	struct fs_struct *fs = current->fs;
1490	unsigned seq;
1491
1492	br_read_lock(vfsmount_lock);
1493	rcu_read_lock();
1494
1495	do {
1496	seq = read_seqcount_begin(&fs->seq);
1497	nd->path = fs->pwd;
1498	nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1499	} while (read_seqcount_retry(&fs->seq, seq));
1500	} else {
1501	get_fs_pwd(current->fs, &nd->path);
1502	}
1503	} else {
1504	struct dentry *dentry;
1505
1506	file = fget_raw_light(dfd, &fput_needed);
1507	retval = -EBADF;
1508	if (!file)
1509	goto out_fail;
1510
1511	dentry = file->f_path.dentry;
1512
1513	if (*name) {
1514	retval = -ENOTDIR;
1515	if (!S_ISDIR(dentry->d_inode->i_mode))
1516	goto fput_fail;
1517
1518	retval = file_permission(file, MAY_EXEC);
1519	if (retval)
1520	goto fput_fail;
1521	}
1522
1523	nd->path = file->f_path;
1524	if (flags & LOOKUP_RCU) {
1525	if (fput_needed)
1526	*fp = file;
1527	nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1528	br_read_lock(vfsmount_lock);
1529	rcu_read_lock();
1530	} else {
1531	path_get(&file->f_path);
1532	fput_light(file, fput_needed);
1533	}
1534	}
1535
1536	nd->inode = nd->path.dentry->d_inode;
1537	return 0;
1538
1539	fput_fail:
1540	fput_light(file, fput_needed);
1541	out_fail:
1542	return retval;
1543	}
1544
1545	static inline int lookup_last(struct nameidata nd, struct path path)
1546	{
1547	if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
1548	nd->flags \|= LOOKUP_FOLLOW \| LOOKUP_DIRECTORY;
1549
1550	nd->flags &= ~LOOKUP_PARENT;
1551	return walk_component(nd, path, &nd->last, nd->last_type,
1552	nd->flags & LOOKUP_FOLLOW);
1553	}
1554
1555	/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1556	static int path_lookupat(int dfd, const char *name,
1557	unsigned int flags, struct nameidata *nd)
1558	{
1559	struct file *base = NULL;
1560	struct path path;
1561	int err;
1562
1563	/*
1564	* Path walking is largely split up into 2 different synchronisation
1565	* schemes, rcu-walk and ref-walk (explained in
1566	* Documentation/filesystems/path-lookup.txt). These share much of the
1567	* path walk code, but some things particularly setup, cleanup, and
1568	* following mounts are sufficiently divergent that functions are
1569	* duplicated. Typically there is a function foo(), and its RCU
1570	* analogue, foo_rcu().
1571	*
1572	* -ECHILD is the error number of choice (just to avoid clashes) that
1573	* is returned if some aspect of an rcu-walk fails. Such an error must
1574	* be handled by restarting a traditional ref-walk (which will always
1575	* be able to complete).
1576	*/
1577	err = path_init(dfd, name, flags \| LOOKUP_PARENT, nd, &base);
1578
1579	if (unlikely(err))
1580	return err;
1581
1582	current->total_link_count = 0;
1583	err = link_path_walk(name, nd);
1584
1585	if (!err && !(flags & LOOKUP_PARENT)) {
1586	err = lookup_last(nd, &path);
1587	while (err > 0) {
1588	void *cookie;
1589	struct path link = path;
1590	nd->flags \|= LOOKUP_PARENT;
1591	err = follow_link(&link, nd, &cookie);
1592	if (!err)
1593	err = lookup_last(nd, &path);
1594	put_link(nd, &link, cookie);
1595	}
1596	}
1597
1598	if (!err)
1599	err = complete_walk(nd);
1600
1601	if (!err && nd->flags & LOOKUP_DIRECTORY) {
1602	if (!nd->inode->i_op->lookup) {
1603	path_put(&nd->path);
1604	err = -ENOTDIR;
1605	}
1606	}
1607
1608	if (base)
1609	fput(base);
1610
1611	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
1612	path_put(&nd->root);
1613	nd->root.mnt = NULL;
1614	}
1615	return err;
1616	}
1617
1618	static int do_path_lookup(int dfd, const char *name,
1619	unsigned int flags, struct nameidata *nd)
1620	{
1621	int retval = path_lookupat(dfd, name, flags \| LOOKUP_RCU, nd);
1622	if (unlikely(retval == -ECHILD))
1623	retval = path_lookupat(dfd, name, flags, nd);
1624	if (unlikely(retval == -ESTALE))
1625	retval = path_lookupat(dfd, name, flags \| LOOKUP_REVAL, nd);
1626
1627	if (likely(!retval)) {
1628	if (unlikely(!audit_dummy_context())) {
1629	if (nd->path.dentry && nd->inode)
1630	audit_inode(name, nd->path.dentry);
1631	}
1632	}
1633	return retval;
1634	}
1635
1636	int kern_path_parent(const char name, struct nameidata nd)
1637	{
1638	return do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, nd);
1639	}
1640
1641	int kern_path(const char name, unsigned int flags, struct path path)
1642	{
1643	struct nameidata nd;
1644	int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
1645	if (!res)
1646	*path = nd.path;
1647	return res;
1648	}
1649
1650	/**
1651	* vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1652	* @dentry: pointer to dentry of the base directory
1653	* @mnt: pointer to vfs mount of the base directory
1654	* @name: pointer to file name
1655	* @flags: lookup flags
1656	* @nd: pointer to nameidata
1657	*/
1658	int vfs_path_lookup(struct dentry dentry, struct vfsmount mnt,
1659	const char *name, unsigned int flags,
1660	struct nameidata *nd)
1661	{
1662	nd->root.dentry = dentry;
1663	nd->root.mnt = mnt;
1664	/* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
1665	return do_path_lookup(AT_FDCWD, name, flags \| LOOKUP_ROOT, nd);
1666	}
1667
1668	static struct dentry __lookup_hash(struct qstr name,
1669	struct dentry base, struct nameidata nd)
1670	{
1671	struct inode *inode = base->d_inode;
1672	struct dentry *dentry;
1673	int err;
1674
1675	err = exec_permission(inode, 0);
1676	if (err)
1677	return ERR_PTR(err);
1678
1679	/*
1680	* Don't bother with __d_lookup: callers are for creat as
1681	* well as unlink, so a lot of the time it would cost
1682	* a double lookup.
1683	*/
1684	dentry = d_lookup(base, name);
1685
1686	if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE))
1687	dentry = do_revalidate(dentry, nd);
1688
1689	if (!dentry)
1690	dentry = d_alloc_and_lookup(base, name, nd);
1691
1692	return dentry;
1693	}
1694
1695	/*
1696	* Restricted form of lookup. Doesn't follow links, single-component only,
1697	* needs parent already locked. Doesn't follow mounts.
1698	* SMP-safe.
1699	*/
1700	static struct dentry lookup_hash(struct nameidata nd)
1701	{
1702	return __lookup_hash(&nd->last, nd->path.dentry, nd);
1703	}
1704
1705	/**
1706	* lookup_one_len - filesystem helper to lookup single pathname component
1707	* @name: pathname component to lookup
1708	* @base: base directory to lookup from
1709	* @len: maximum length @len should be interpreted to
1710	*
1711	* Note that this routine is purely a helper for filesystem usage and should
1712	* not be called by generic code. Also note that by using this function the
1713	* nameidata argument is passed to the filesystem methods and a filesystem
1714	* using this helper needs to be prepared for that.
1715	*/
1716	struct dentry lookup_one_len(const char name, struct dentry *base, int len)
1717	{
1718	struct qstr this;
1719	unsigned long hash;
1720	unsigned int c;
1721
1722	WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
1723
1724	this.name = name;
1725	this.len = len;
1726	if (!len)
1727	return ERR_PTR(-EACCES);
1728
1729	hash = init_name_hash();
1730	while (len--) {
1731	c = (const unsigned char )name++;
1732	if (c == '/' \|\| c == '\0')
1733	return ERR_PTR(-EACCES);
1734	hash = partial_name_hash(c, hash);
1735	}
1736	this.hash = end_name_hash(hash);
1737	/*
1738	* See if the low-level filesystem might want
1739	* to use its own hash..
1740	*/
1741	if (base->d_flags & DCACHE_OP_HASH) {
1742	int err = base->d_op->d_hash(base, base->d_inode, &this);
1743	if (err < 0)
1744	return ERR_PTR(err);
1745	}
1746
1747	return __lookup_hash(&this, base, NULL);
1748	}
1749
1750	int user_path_at(int dfd, const char __user *name, unsigned flags,
1751	struct path *path)
1752	{
1753	struct nameidata nd;
1754	char *tmp = getname_flags(name, flags);
1755	int err = PTR_ERR(tmp);
1756	if (!IS_ERR(tmp)) {
1757
1758	BUG_ON(flags & LOOKUP_PARENT);
1759
1760	err = do_path_lookup(dfd, tmp, flags, &nd);
1761	putname(tmp);
1762	if (!err)
1763	*path = nd.path;
1764	}
1765	return err;
1766	}
1767
1768	static int user_path_parent(int dfd, const char __user *path,
1769	struct nameidata nd, char *name)
1770	{
1771	char *s = getname(path);
1772	int error;
1773
1774	if (IS_ERR(s))
1775	return PTR_ERR(s);
1776
1777	error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
1778	if (error)
1779	putname(s);
1780	else
1781	*name = s;
1782
1783	return error;
1784	}
1785
1786	/*
1787	* It's inline, so penalty for filesystems that don't use sticky bit is
1788	* minimal.
1789	*/
1790	static inline int check_sticky(struct inode dir, struct inode inode)
1791	{
1792	uid_t fsuid = current_fsuid();
1793
1794	if (!(dir->i_mode & S_ISVTX))
1795	return 0;
1796	if (current_user_ns() != inode_userns(inode))
1797	goto other_userns;
1798	if (inode->i_uid == fsuid)
1799	return 0;
1800	if (dir->i_uid == fsuid)
1801	return 0;
1802
1803	other_userns:
1804	return !ns_capable(inode_userns(inode), CAP_FOWNER);
1805	}
1806
1807	/*
1808	* Check whether we can remove a link victim from directory dir, check
1809	* whether the type of victim is right.
1810	* 1. We can't do it if dir is read-only (done in permission())
1811	* 2. We should have write and exec permissions on dir
1812	* 3. We can't remove anything from append-only dir
1813	* 4. We can't do anything with immutable dir (done in permission())
1814	* 5. If the sticky bit on dir is set we should either
1815	* a. be owner of dir, or
1816	* b. be owner of victim, or
1817	* c. have CAP_FOWNER capability
1818	* 6. If the victim is append-only or immutable we can't do antyhing with
1819	* links pointing to it.
1820	* 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1821	* 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1822	* 9. We can't remove a root or mountpoint.
1823	* 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1824	* nfs_async_unlink().
1825	*/
1826	static int may_delete(struct inode dir,struct dentry victim,int isdir)
1827	{
1828	int error;
1829
1830	if (!victim->d_inode)
1831	return -ENOENT;
1832
1833	BUG_ON(victim->d_parent->d_inode != dir);
1834	audit_inode_child(victim, dir);
1835
1836	error = inode_permission(dir, MAY_WRITE \| MAY_EXEC);
1837	if (error)
1838	return error;
1839	if (IS_APPEND(dir))
1840	return -EPERM;
1841	if (check_sticky(dir, victim->d_inode)\|\|IS_APPEND(victim->d_inode)\|\|
1842	IS_IMMUTABLE(victim->d_inode) \|\| IS_SWAPFILE(victim->d_inode))
1843	return -EPERM;
1844	if (isdir) {
1845	if (!S_ISDIR(victim->d_inode->i_mode))
1846	return -ENOTDIR;
1847	if (IS_ROOT(victim))
1848	return -EBUSY;
1849	} else if (S_ISDIR(victim->d_inode->i_mode))
1850	return -EISDIR;
1851	if (IS_DEADDIR(dir))
1852	return -ENOENT;
1853	if (victim->d_flags & DCACHE_NFSFS_RENAMED)
1854	return -EBUSY;
1855	return 0;
1856	}
1857
1858	/* Check whether we can create an object with dentry child in directory
1859	* dir.
1860	* 1. We can't do it if child already exists (open has special treatment for
1861	* this case, but since we are inlined it's OK)
1862	* 2. We can't do it if dir is read-only (done in permission())
1863	* 3. We should have write and exec permissions on dir
1864	* 4. We can't do it if dir is immutable (done in permission())
1865	*/
1866	static inline int may_create(struct inode dir, struct dentry child)
1867	{
1868	if (child->d_inode)
1869	return -EEXIST;
1870	if (IS_DEADDIR(dir))
1871	return -ENOENT;
1872	return inode_permission(dir, MAY_WRITE \| MAY_EXEC);
1873	}
1874
1875	/*
1876	* p1 and p2 should be directories on the same fs.
1877	*/
1878	struct dentry lock_rename(struct dentry p1, struct dentry *p2)
1879	{
1880	struct dentry *p;
1881
1882	if (p1 == p2) {
1883	mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1884	return NULL;
1885	}
1886
1887	mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
1888
1889	p = d_ancestor(p2, p1);
1890	if (p) {
1891	mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
1892	mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
1893	return p;
1894	}
1895
1896	p = d_ancestor(p1, p2);
1897	if (p) {
1898	mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1899	mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
1900	return p;
1901	}
1902
1903	mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
1904	mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
1905	return NULL;
1906	}
1907
1908	void unlock_rename(struct dentry p1, struct dentry p2)
1909	{
1910	mutex_unlock(&p1->d_inode->i_mutex);
1911	if (p1 != p2) {
1912	mutex_unlock(&p2->d_inode->i_mutex);
1913	mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
1914	}
1915	}
1916
1917	int vfs_create(struct inode dir, struct dentry dentry, int mode,
1918	struct nameidata *nd)
1919	{
1920	int error = may_create(dir, dentry);
1921
1922	if (error)
1923	return error;
1924
1925	if (!dir->i_op->create)
1926	return -EACCES; /* shouldn't it be ENOSYS? */
1927	mode &= S_IALLUGO;
1928	mode \|= S_IFREG;
1929	error = security_inode_create(dir, dentry, mode);
1930	if (error)
1931	return error;
1932	error = dir->i_op->create(dir, dentry, mode, nd);
1933	if (!error)
1934	fsnotify_create(dir, dentry);
1935	return error;
1936	}
1937
1938	static int may_open(struct path *path, int acc_mode, int flag)
1939	{
1940	struct dentry *dentry = path->dentry;
1941	struct inode *inode = dentry->d_inode;
1942	int error;
1943
1944	/* O_PATH? */
1945	if (!acc_mode)
1946	return 0;
1947
1948	if (!inode)
1949	return -ENOENT;
1950
1951	switch (inode->i_mode & S_IFMT) {
1952	case S_IFLNK:
1953	return -ELOOP;
1954	case S_IFDIR:
1955	if (acc_mode & MAY_WRITE)
1956	return -EISDIR;
1957	break;
1958	case S_IFBLK:
1959	case S_IFCHR:
1960	if (path->mnt->mnt_flags & MNT_NODEV)
1961	return -EACCES;
1962	/FALLTHRU/
1963	case S_IFIFO:
1964	case S_IFSOCK:
1965	flag &= ~O_TRUNC;
1966	break;
1967	}
1968
1969	error = inode_permission(inode, acc_mode);
1970	if (error)
1971	return error;
1972
1973	/*
1974	* An append-only file must be opened in append mode for writing.
1975	*/
1976	if (IS_APPEND(inode)) {
1977	if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
1978	return -EPERM;
1979	if (flag & O_TRUNC)
1980	return -EPERM;
1981	}
1982
1983	/* O_NOATIME can only be set by the owner or superuser */
1984	if (flag & O_NOATIME && !inode_owner_or_capable(inode))
1985	return -EPERM;
1986
1987	/*
1988	* Ensure there are no outstanding leases on the file.
1989	*/
1990	return break_lease(inode, flag);
1991	}
1992
1993	static int handle_truncate(struct file *filp)
1994	{
1995	struct path *path = &filp->f_path;
1996	struct inode *inode = path->dentry->d_inode;
1997	int error = get_write_access(inode);
1998	if (error)
1999	return error;
2000	/*
2001	* Refuse to truncate files with mandatory locks held on them.
2002	*/
2003	error = locks_verify_locked(inode);
2004	if (!error)
2005	error = security_path_truncate(path);
2006	if (!error) {
2007	error = do_truncate(path->dentry, 0,
2008	ATTR_MTIME\|ATTR_CTIME\|ATTR_OPEN,
2009	filp);
2010	}
2011	put_write_access(inode);
2012	return error;
2013	}
2014
2015	/*
2016	* Note that while the flag value (low two bits) for sys_open means:
2017	* 00 - read-only
2018	* 01 - write-only
2019	* 10 - read-write
2020	* 11 - special
2021	* it is changed into
2022	* 00 - no permissions needed
2023	* 01 - read-permission
2024	* 10 - write-permission
2025	* 11 - read-write
2026	* for the internal routines (ie open_namei()/follow_link() etc)
2027	* This is more logical, and also allows the 00 "no perm needed"
2028	* to be used for symlinks (where the permissions are checked
2029	* later).
2030	*
2031	*/
2032	static inline int open_to_namei_flags(int flag)
2033	{
2034	if ((flag+1) & O_ACCMODE)
2035	flag++;
2036	return flag;
2037	}
2038
2039	/*
2040	* Handle the last step of open()
2041	*/
2042	static struct file do_last(struct nameidata nd, struct path *path,
2043	const struct open_flags op, const char pathname)
2044	{
2045	struct dentry *dir = nd->path.dentry;
2046	struct dentry *dentry;
2047	int open_flag = op->open_flag;
2048	int will_truncate = open_flag & O_TRUNC;
2049	int want_write = 0;
2050	int acc_mode = op->acc_mode;
2051	struct file *filp;
2052	int error;
2053
2054	nd->flags &= ~LOOKUP_PARENT;
2055	nd->flags \|= op->intent;
2056
2057	switch (nd->last_type) {
2058	case LAST_DOTDOT:
2059	case LAST_DOT:
2060	error = handle_dots(nd, nd->last_type);
2061	if (error)
2062	return ERR_PTR(error);
2063	/* fallthrough */
2064	case LAST_ROOT:
2065	error = complete_walk(nd);
2066	if (error)
2067	return ERR_PTR(error);
2068	audit_inode(pathname, nd->path.dentry);
2069	if (open_flag & O_CREAT) {
2070	error = -EISDIR;
2071	goto exit;
2072	}
2073	goto ok;
2074	case LAST_BIND:
2075	error = complete_walk(nd);
2076	if (error)
2077	return ERR_PTR(error);
2078	audit_inode(pathname, dir);
2079	goto ok;
2080	}
2081
2082	if (!(open_flag & O_CREAT)) {
2083	int symlink_ok = 0;
2084	if (nd->last.name[nd->last.len])
2085	nd->flags \|= LOOKUP_FOLLOW \| LOOKUP_DIRECTORY;
2086	if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
2087	symlink_ok = 1;
2088	/* we _can_ be in RCU mode here */
2089	error = walk_component(nd, path, &nd->last, LAST_NORM,
2090	!symlink_ok);
2091	if (error < 0)
2092	return ERR_PTR(error);
2093	if (error) /* symlink */
2094	return NULL;
2095	/* sayonara */
2096	error = complete_walk(nd);
2097	if (error)
2098	return ERR_PTR(-ECHILD);
2099
2100	error = -ENOTDIR;
2101	if (nd->flags & LOOKUP_DIRECTORY) {
2102	if (!nd->inode->i_op->lookup)
2103	goto exit;
2104	}
2105	audit_inode(pathname, nd->path.dentry);
2106	goto ok;
2107	}
2108
2109	/* create side of things */
2110	error = complete_walk(nd);
2111	if (error)
2112	return ERR_PTR(error);
2113
2114	audit_inode(pathname, dir);
2115	error = -EISDIR;
2116	/* trailing slashes? */
2117	if (nd->last.name[nd->last.len])
2118	goto exit;
2119
2120	mutex_lock(&dir->d_inode->i_mutex);
2121
2122	dentry = lookup_hash(nd);
2123	error = PTR_ERR(dentry);
2124	if (IS_ERR(dentry)) {
2125	mutex_unlock(&dir->d_inode->i_mutex);
2126	goto exit;
2127	}
2128
2129	path->dentry = dentry;
2130	path->mnt = nd->path.mnt;
2131
2132	/* Negative dentry, just create the file */
2133	if (!dentry->d_inode) {
2134	int mode = op->mode;
2135	if (!IS_POSIXACL(dir->d_inode))
2136	mode &= ~current_umask();
2137	/*
2138	* This write is needed to ensure that a
2139	* rw->ro transition does not occur between
2140	* the time when the file is created and when
2141	* a permanent write count is taken through
2142	* the 'struct file' in nameidata_to_filp().
2143	*/
2144	error = mnt_want_write(nd->path.mnt);
2145	if (error)
2146	goto exit_mutex_unlock;
2147	want_write = 1;
2148	/* Don't check for write permission, don't truncate */
2149	open_flag &= ~O_TRUNC;
2150	will_truncate = 0;
2151	acc_mode = MAY_OPEN;
2152	error = security_path_mknod(&nd->path, dentry, mode, 0);
2153	if (error)
2154	goto exit_mutex_unlock;
2155	error = vfs_create(dir->d_inode, dentry, mode, nd);
2156	if (error)
2157	goto exit_mutex_unlock;
2158	mutex_unlock(&dir->d_inode->i_mutex);
2159	dput(nd->path.dentry);
2160	nd->path.dentry = dentry;
2161	goto common;
2162	}
2163
2164	/*
2165	* It already exists.
2166	*/
2167	mutex_unlock(&dir->d_inode->i_mutex);
2168	audit_inode(pathname, path->dentry);
2169
2170	error = -EEXIST;
2171	if (open_flag & O_EXCL)
2172	goto exit_dput;
2173
2174	error = follow_managed(path, nd->flags);
2175	if (error < 0)
2176	goto exit_dput;
2177
2178	error = -ENOENT;
2179	if (!path->dentry->d_inode)
2180	goto exit_dput;
2181
2182	if (path->dentry->d_inode->i_op->follow_link)
2183	return NULL;
2184
2185	path_to_nameidata(path, nd);
2186	nd->inode = path->dentry->d_inode;
2187	error = -EISDIR;
2188	if (S_ISDIR(nd->inode->i_mode))
2189	goto exit;
2190	ok:
2191	if (!S_ISREG(nd->inode->i_mode))
2192	will_truncate = 0;
2193
2194	if (will_truncate) {
2195	error = mnt_want_write(nd->path.mnt);
2196	if (error)
2197	goto exit;
2198	want_write = 1;
2199	}
2200	common:
2201	error = may_open(&nd->path, acc_mode, open_flag);
2202	if (error)
2203	goto exit;
2204	filp = nameidata_to_filp(nd);
2205	if (!IS_ERR(filp)) {
2206	error = ima_file_check(filp, op->acc_mode);
2207	if (error) {
2208	fput(filp);
2209	filp = ERR_PTR(error);
2210	}
2211	}
2212	if (!IS_ERR(filp)) {
2213	if (will_truncate) {
2214	error = handle_truncate(filp);
2215	if (error) {
2216	fput(filp);
2217	filp = ERR_PTR(error);
2218	}
2219	}
2220	}
2221	out:
2222	if (want_write)
2223	mnt_drop_write(nd->path.mnt);
2224	path_put(&nd->path);
2225	return filp;
2226
2227	exit_mutex_unlock:
2228	mutex_unlock(&dir->d_inode->i_mutex);
2229	exit_dput:
2230	path_put_conditional(path, nd);
2231	exit:
2232	filp = ERR_PTR(error);
2233	goto out;
2234	}
2235
2236	static struct file path_openat(int dfd, const char pathname,
2237	struct nameidata nd, const struct open_flags op, int flags)
2238	{
2239	struct file *base = NULL;
2240	struct file *filp;
2241	struct path path;
2242	int error;
2243
2244	filp = get_empty_filp();
2245	if (!filp)
2246	return ERR_PTR(-ENFILE);
2247
2248	filp->f_flags = op->open_flag;
2249	nd->intent.open.file = filp;
2250	nd->intent.open.flags = open_to_namei_flags(op->open_flag);
2251	nd->intent.open.create_mode = op->mode;
2252
2253	error = path_init(dfd, pathname, flags \| LOOKUP_PARENT, nd, &base);
2254	if (unlikely(error))
2255	goto out_filp;
2256
2257	current->total_link_count = 0;
2258	error = link_path_walk(pathname, nd);
2259	if (unlikely(error))
2260	goto out_filp;
2261
2262	filp = do_last(nd, &path, op, pathname);
2263	while (unlikely(!filp)) { /* trailing symlink */
2264	struct path link = path;
2265	void *cookie;
2266	if (!(nd->flags & LOOKUP_FOLLOW)) {
2267	path_put_conditional(&path, nd);
2268	path_put(&nd->path);
2269	filp = ERR_PTR(-ELOOP);
2270	break;
2271	}
2272	nd->flags \|= LOOKUP_PARENT;
2273	nd->flags &= ~(LOOKUP_OPEN\|LOOKUP_CREATE\|LOOKUP_EXCL);
2274	error = follow_link(&link, nd, &cookie);
2275	if (unlikely(error))
2276	filp = ERR_PTR(error);
2277	else
2278	filp = do_last(nd, &path, op, pathname);
2279	put_link(nd, &link, cookie);
2280	}
2281	out:
2282	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
2283	path_put(&nd->root);
2284	if (base)
2285	fput(base);
2286	release_open_intent(nd);
2287	return filp;
2288
2289	out_filp:
2290	filp = ERR_PTR(error);
2291	goto out;
2292	}
2293
2294	struct file do_filp_open(int dfd, const char pathname,
2295	const struct open_flags *op, int flags)
2296	{
2297	struct nameidata nd;
2298	struct file *filp;
2299
2300	filp = path_openat(dfd, pathname, &nd, op, flags \| LOOKUP_RCU);
2301	if (unlikely(filp == ERR_PTR(-ECHILD)))
2302	filp = path_openat(dfd, pathname, &nd, op, flags);
2303	if (unlikely(filp == ERR_PTR(-ESTALE)))
2304	filp = path_openat(dfd, pathname, &nd, op, flags \| LOOKUP_REVAL);
2305	return filp;
2306	}
2307
2308	struct file do_file_open_root(struct dentry dentry, struct vfsmount *mnt,
2309	const char name, const struct open_flags op, int flags)
2310	{
2311	struct nameidata nd;
2312	struct file *file;
2313
2314	nd.root.mnt = mnt;
2315	nd.root.dentry = dentry;
2316
2317	flags \|= LOOKUP_ROOT;
2318
2319	if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
2320	return ERR_PTR(-ELOOP);
2321
2322	file = path_openat(-1, name, &nd, op, flags \| LOOKUP_RCU);
2323	if (unlikely(file == ERR_PTR(-ECHILD)))
2324	file = path_openat(-1, name, &nd, op, flags);
2325	if (unlikely(file == ERR_PTR(-ESTALE)))
2326	file = path_openat(-1, name, &nd, op, flags \| LOOKUP_REVAL);
2327	return file;
2328	}
2329
2330	/**
2331	* lookup_create - lookup a dentry, creating it if it doesn't exist
2332	* @nd: nameidata info
2333	* @is_dir: directory flag
2334	*
2335	* Simple function to lookup and return a dentry and create it
2336	* if it doesn't exist. Is SMP-safe.
2337	*
2338	* Returns with nd->path.dentry->d_inode->i_mutex locked.
2339	*/
2340	struct dentry lookup_create(struct nameidata nd, int is_dir)
2341	{
2342	struct dentry *dentry = ERR_PTR(-EEXIST);
2343
2344	mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2345	/*
2346	* Yucky last component or no last component at all?
2347	* (foo/., foo/.., /////)
2348	*/
2349	if (nd->last_type != LAST_NORM)
2350	goto fail;
2351	nd->flags &= ~LOOKUP_PARENT;
2352	nd->flags \|= LOOKUP_CREATE \| LOOKUP_EXCL;
2353	nd->intent.open.flags = O_EXCL;
2354
2355	/*
2356	* Do the final lookup.
2357	*/
2358	dentry = lookup_hash(nd);
2359	if (IS_ERR(dentry))
2360	goto fail;
2361
2362	if (dentry->d_inode)
2363	goto eexist;
2364	/*
2365	* Special case - lookup gave negative, but... we had foo/bar/
2366	* From the vfs_mknod() POV we just have a negative dentry -
2367	* all is fine. Let's be bastards - you had / on the end, you've
2368	* been asking for (non-existent) directory. -ENOENT for you.
2369	*/
2370	if (unlikely(!is_dir && nd->last.name[nd->last.len])) {
2371	dput(dentry);
2372	dentry = ERR_PTR(-ENOENT);
2373	}
2374	return dentry;
2375	eexist:
2376	dput(dentry);
2377	dentry = ERR_PTR(-EEXIST);
2378	fail:
2379	return dentry;
2380	}
2381	EXPORT_SYMBOL_GPL(lookup_create);
2382
2383	int vfs_mknod(struct inode dir, struct dentry dentry, int mode, dev_t dev)
2384	{
2385	int error = may_create(dir, dentry);
2386
2387	if (error)
2388	return error;
2389
2390	if ((S_ISCHR(mode) \|\| S_ISBLK(mode)) &&
2391	!ns_capable(inode_userns(dir), CAP_MKNOD))
2392	return -EPERM;
2393
2394	if (!dir->i_op->mknod)
2395	return -EPERM;
2396
2397	error = devcgroup_inode_mknod(mode, dev);
2398	if (error)
2399	return error;
2400
2401	error = security_inode_mknod(dir, dentry, mode, dev);
2402	if (error)
2403	return error;
2404
2405	error = dir->i_op->mknod(dir, dentry, mode, dev);
2406	if (!error)
2407	fsnotify_create(dir, dentry);
2408	return error;
2409	}
2410
2411	static int may_mknod(mode_t mode)
2412	{
2413	switch (mode & S_IFMT) {
2414	case S_IFREG:
2415	case S_IFCHR:
2416	case S_IFBLK:
2417	case S_IFIFO:
2418	case S_IFSOCK:
2419	case 0: /* zero mode translates to S_IFREG */
2420	return 0;
2421	case S_IFDIR:
2422	return -EPERM;
2423	default:
2424	return -EINVAL;
2425	}
2426	}
2427
2428	SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, int, mode,
2429	unsigned, dev)
2430	{
2431	int error;
2432	char *tmp;
2433	struct dentry *dentry;
2434	struct nameidata nd;
2435
2436	if (S_ISDIR(mode))
2437	return -EPERM;
2438
2439	error = user_path_parent(dfd, filename, &nd, &tmp);
2440	if (error)
2441	return error;
2442
2443	dentry = lookup_create(&nd, 0);
2444	if (IS_ERR(dentry)) {
2445	error = PTR_ERR(dentry);
2446	goto out_unlock;
2447	}
2448	if (!IS_POSIXACL(nd.path.dentry->d_inode))
2449	mode &= ~current_umask();
2450	error = may_mknod(mode);
2451	if (error)
2452	goto out_dput;
2453	error = mnt_want_write(nd.path.mnt);
2454	if (error)
2455	goto out_dput;
2456	error = security_path_mknod(&nd.path, dentry, mode, dev);
2457	if (error)
2458	goto out_drop_write;
2459	switch (mode & S_IFMT) {
2460	case 0: case S_IFREG:
2461	error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);
2462	break;
2463	case S_IFCHR: case S_IFBLK:
2464	error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,
2465	new_decode_dev(dev));
2466	break;
2467	case S_IFIFO: case S_IFSOCK:
2468	error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
2469	break;
2470	}
2471	out_drop_write:
2472	mnt_drop_write(nd.path.mnt);
2473	out_dput:
2474	dput(dentry);
2475	out_unlock:
2476	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2477	path_put(&nd.path);
2478	putname(tmp);
2479
2480	return error;
2481	}
2482
2483	SYSCALL_DEFINE3(mknod, const char __user *, filename, int, mode, unsigned, dev)
2484	{
2485	return sys_mknodat(AT_FDCWD, filename, mode, dev);
2486	}
2487
2488	int vfs_mkdir(struct inode dir, struct dentry dentry, int mode)
2489	{
2490	int error = may_create(dir, dentry);
2491
2492	if (error)
2493	return error;
2494
2495	if (!dir->i_op->mkdir)
2496	return -EPERM;
2497
2498	mode &= (S_IRWXUGO\|S_ISVTX);
2499	error = security_inode_mkdir(dir, dentry, mode);
2500	if (error)
2501	return error;
2502
2503	error = dir->i_op->mkdir(dir, dentry, mode);
2504	if (!error)
2505	fsnotify_mkdir(dir, dentry);
2506	return error;
2507	}
2508
2509	SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, int, mode)
2510	{
2511	int error = 0;
2512	char * tmp;
2513	struct dentry *dentry;
2514	struct nameidata nd;
2515
2516	error = user_path_parent(dfd, pathname, &nd, &tmp);
2517	if (error)
2518	goto out_err;
2519
2520	dentry = lookup_create(&nd, 1);
2521	error = PTR_ERR(dentry);
2522	if (IS_ERR(dentry))
2523	goto out_unlock;
2524
2525	if (!IS_POSIXACL(nd.path.dentry->d_inode))
2526	mode &= ~current_umask();
2527	error = mnt_want_write(nd.path.mnt);
2528	if (error)
2529	goto out_dput;
2530	error = security_path_mkdir(&nd.path, dentry, mode);
2531	if (error)
2532	goto out_drop_write;
2533	error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
2534	out_drop_write:
2535	mnt_drop_write(nd.path.mnt);
2536	out_dput:
2537	dput(dentry);
2538	out_unlock:
2539	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2540	path_put(&nd.path);
2541	putname(tmp);
2542	out_err:
2543	return error;
2544	}
2545
2546	SYSCALL_DEFINE2(mkdir, const char __user *, pathname, int, mode)
2547	{
2548	return sys_mkdirat(AT_FDCWD, pathname, mode);
2549	}
2550
2551	/*
2552	* The dentry_unhash() helper will try to drop the dentry early: we
2553	* should have a usage count of 2 if we're the only user of this
2554	* dentry, and if that is true (possibly after pruning the dcache),
2555	* then we drop the dentry now.
2556	*
2557	* A low-level filesystem can, if it choses, legally
2558	* do a
2559	*
2560	* if (!d_unhashed(dentry))
2561	* return -EBUSY;
2562	*
2563	* if it cannot handle the case of removing a directory
2564	* that is still in use by something else..
2565	*/
2566	void dentry_unhash(struct dentry *dentry)
2567	{
2568	shrink_dcache_parent(dentry);
2569	spin_lock(&dentry->d_lock);
2570	if (dentry->d_count == 1)
2571	__d_drop(dentry);
2572	spin_unlock(&dentry->d_lock);
2573	}
2574
2575	int vfs_rmdir(struct inode dir, struct dentry dentry)
2576	{
2577	int error = may_delete(dir, dentry, 1);
2578
2579	if (error)
2580	return error;
2581
2582	if (!dir->i_op->rmdir)
2583	return -EPERM;
2584
2585	mutex_lock(&dentry->d_inode->i_mutex);
2586
2587	error = -EBUSY;
2588	if (d_mountpoint(dentry))
2589	goto out;
2590
2591	error = security_inode_rmdir(dir, dentry);
2592	if (error)
2593	goto out;
2594
2595	shrink_dcache_parent(dentry);
2596	error = dir->i_op->rmdir(dir, dentry);
2597	if (error)
2598	goto out;
2599
2600	dentry->d_inode->i_flags \|= S_DEAD;
2601	dont_mount(dentry);
2602
2603	out:
2604	mutex_unlock(&dentry->d_inode->i_mutex);
2605	if (!error)
2606	d_delete(dentry);
2607	return error;
2608	}
2609
2610	static long do_rmdir(int dfd, const char __user *pathname)
2611	{
2612	int error = 0;
2613	char * name;
2614	struct dentry *dentry;
2615	struct nameidata nd;
2616
2617	error = user_path_parent(dfd, pathname, &nd, &name);
2618	if (error)
2619	return error;
2620
2621	switch(nd.last_type) {
2622	case LAST_DOTDOT:
2623	error = -ENOTEMPTY;
2624	goto exit1;
2625	case LAST_DOT:
2626	error = -EINVAL;
2627	goto exit1;
2628	case LAST_ROOT:
2629	error = -EBUSY;
2630	goto exit1;
2631	}
2632
2633	nd.flags &= ~LOOKUP_PARENT;
2634
2635	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2636	dentry = lookup_hash(&nd);
2637	error = PTR_ERR(dentry);
2638	if (IS_ERR(dentry))
2639	goto exit2;
2640	if (!dentry->d_inode) {
2641	error = -ENOENT;
2642	goto exit3;
2643	}
2644	error = mnt_want_write(nd.path.mnt);
2645	if (error)
2646	goto exit3;
2647	error = security_path_rmdir(&nd.path, dentry);
2648	if (error)
2649	goto exit4;
2650	error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
2651	exit4:
2652	mnt_drop_write(nd.path.mnt);
2653	exit3:
2654	dput(dentry);
2655	exit2:
2656	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2657	exit1:
2658	path_put(&nd.path);
2659	putname(name);
2660	return error;
2661	}
2662
2663	SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
2664	{
2665	return do_rmdir(AT_FDCWD, pathname);
2666	}
2667
2668	int vfs_unlink(struct inode dir, struct dentry dentry)
2669	{
2670	int error = may_delete(dir, dentry, 0);
2671
2672	if (error)
2673	return error;
2674
2675	if (!dir->i_op->unlink)
2676	return -EPERM;
2677
2678	mutex_lock(&dentry->d_inode->i_mutex);
2679	if (d_mountpoint(dentry))
2680	error = -EBUSY;
2681	else {
2682	error = security_inode_unlink(dir, dentry);
2683	if (!error) {
2684	error = dir->i_op->unlink(dir, dentry);
2685	if (!error)
2686	dont_mount(dentry);
2687	}
2688	}
2689	mutex_unlock(&dentry->d_inode->i_mutex);
2690
2691	/* We don't d_delete() NFS sillyrenamed files--they still exist. */
2692	if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
2693	fsnotify_link_count(dentry->d_inode);
2694	d_delete(dentry);
2695	}
2696
2697	return error;
2698	}
2699
2700	/*
2701	* Make sure that the actual truncation of the file will occur outside its
2702	* directory's i_mutex. Truncate can take a long time if there is a lot of
2703	* writeout happening, and we don't want to prevent access to the directory
2704	* while waiting on the I/O.
2705	*/
2706	static long do_unlinkat(int dfd, const char __user *pathname)
2707	{
2708	int error;
2709	char *name;
2710	struct dentry *dentry;
2711	struct nameidata nd;
2712	struct inode *inode = NULL;
2713
2714	error = user_path_parent(dfd, pathname, &nd, &name);
2715	if (error)
2716	return error;
2717
2718	error = -EISDIR;
2719	if (nd.last_type != LAST_NORM)
2720	goto exit1;
2721
2722	nd.flags &= ~LOOKUP_PARENT;
2723
2724	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2725	dentry = lookup_hash(&nd);
2726	error = PTR_ERR(dentry);
2727	if (!IS_ERR(dentry)) {
2728	/* Why not before? Because we want correct error value */
2729	if (nd.last.name[nd.last.len])
2730	goto slashes;
2731	inode = dentry->d_inode;
2732	if (!inode)
2733	goto slashes;
2734	ihold(inode);
2735	error = mnt_want_write(nd.path.mnt);
2736	if (error)
2737	goto exit2;
2738	error = security_path_unlink(&nd.path, dentry);
2739	if (error)
2740	goto exit3;
2741	error = vfs_unlink(nd.path.dentry->d_inode, dentry);
2742	exit3:
2743	mnt_drop_write(nd.path.mnt);
2744	exit2:
2745	dput(dentry);
2746	}
2747	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2748	if (inode)
2749	iput(inode); /* truncate the inode here */
2750	exit1:
2751	path_put(&nd.path);
2752	putname(name);
2753	return error;
2754
2755	slashes:
2756	error = !dentry->d_inode ? -ENOENT :
2757	S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
2758	goto exit2;
2759	}
2760
2761	SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
2762	{
2763	if ((flag & ~AT_REMOVEDIR) != 0)
2764	return -EINVAL;
2765
2766	if (flag & AT_REMOVEDIR)
2767	return do_rmdir(dfd, pathname);
2768
2769	return do_unlinkat(dfd, pathname);
2770	}
2771
2772	SYSCALL_DEFINE1(unlink, const char __user *, pathname)
2773	{
2774	return do_unlinkat(AT_FDCWD, pathname);
2775	}
2776
2777	int vfs_symlink(struct inode dir, struct dentry dentry, const char *oldname)
2778	{
2779	int error = may_create(dir, dentry);
2780
2781	if (error)
2782	return error;
2783
2784	if (!dir->i_op->symlink)
2785	return -EPERM;
2786
2787	error = security_inode_symlink(dir, dentry, oldname);
2788	if (error)
2789	return error;
2790
2791	error = dir->i_op->symlink(dir, dentry, oldname);
2792	if (!error)
2793	fsnotify_create(dir, dentry);
2794	return error;
2795	}
2796
2797	SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
2798	int, newdfd, const char __user *, newname)
2799	{
2800	int error;
2801	char *from;
2802	char *to;
2803	struct dentry *dentry;
2804	struct nameidata nd;
2805
2806	from = getname(oldname);
2807	if (IS_ERR(from))
2808	return PTR_ERR(from);
2809
2810	error = user_path_parent(newdfd, newname, &nd, &to);
2811	if (error)
2812	goto out_putname;
2813
2814	dentry = lookup_create(&nd, 0);
2815	error = PTR_ERR(dentry);
2816	if (IS_ERR(dentry))
2817	goto out_unlock;
2818
2819	error = mnt_want_write(nd.path.mnt);
2820	if (error)
2821	goto out_dput;
2822	error = security_path_symlink(&nd.path, dentry, from);
2823	if (error)
2824	goto out_drop_write;
2825	error = vfs_symlink(nd.path.dentry->d_inode, dentry, from);
2826	out_drop_write:
2827	mnt_drop_write(nd.path.mnt);
2828	out_dput:
2829	dput(dentry);
2830	out_unlock:
2831	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2832	path_put(&nd.path);
2833	putname(to);
2834	out_putname:
2835	putname(from);
2836	return error;
2837	}
2838
2839	SYSCALL_DEFINE2(symlink, const char __user , oldname, const char __user , newname)
2840	{
2841	return sys_symlinkat(oldname, AT_FDCWD, newname);
2842	}
2843
2844	int vfs_link(struct dentry old_dentry, struct inode dir, struct dentry *new_dentry)
2845	{
2846	struct inode *inode = old_dentry->d_inode;
2847	int error;
2848
2849	if (!inode)
2850	return -ENOENT;
2851
2852	error = may_create(dir, new_dentry);
2853	if (error)
2854	return error;
2855
2856	if (dir->i_sb != inode->i_sb)
2857	return -EXDEV;
2858
2859	/*
2860	* A link to an append-only or immutable file cannot be created.
2861	*/
2862	if (IS_APPEND(inode) \|\| IS_IMMUTABLE(inode))
2863	return -EPERM;
2864	if (!dir->i_op->link)
2865	return -EPERM;
2866	if (S_ISDIR(inode->i_mode))
2867	return -EPERM;
2868
2869	error = security_inode_link(old_dentry, dir, new_dentry);
2870	if (error)
2871	return error;
2872
2873	mutex_lock(&inode->i_mutex);
2874	/* Make sure we don't allow creating hardlink to an unlinked file */
2875	if (inode->i_nlink == 0)
2876	error = -ENOENT;
2877	else
2878	error = dir->i_op->link(old_dentry, dir, new_dentry);
2879	mutex_unlock(&inode->i_mutex);
2880	if (!error)
2881	fsnotify_link(dir, inode, new_dentry);
2882	return error;
2883	}
2884
2885	/*
2886	* Hardlinks are often used in delicate situations. We avoid
2887	* security-related surprises by not following symlinks on the
2888	* newname. --KAB
2889	*
2890	* We don't follow them on the oldname either to be compatible
2891	* with linux 2.0, and to avoid hard-linking to directories
2892	* and other special files. --ADM
2893	*/
2894	SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
2895	int, newdfd, const char __user *, newname, int, flags)
2896	{
2897	struct dentry *new_dentry;
2898	struct nameidata nd;
2899	struct path old_path;
2900	int how = 0;
2901	int error;
2902	char *to;
2903
2904	if ((flags & ~(AT_SYMLINK_FOLLOW \| AT_EMPTY_PATH)) != 0)
2905	return -EINVAL;
2906	/*
2907	* To use null names we require CAP_DAC_READ_SEARCH
2908	* This ensures that not everyone will be able to create
2909	* handlink using the passed filedescriptor.
2910	*/
2911	if (flags & AT_EMPTY_PATH) {
2912	if (!capable(CAP_DAC_READ_SEARCH))
2913	return -ENOENT;
2914	how = LOOKUP_EMPTY;
2915	}
2916
2917	if (flags & AT_SYMLINK_FOLLOW)
2918	how \|= LOOKUP_FOLLOW;
2919
2920	error = user_path_at(olddfd, oldname, how, &old_path);
2921	if (error)
2922	return error;
2923
2924	error = user_path_parent(newdfd, newname, &nd, &to);
2925	if (error)
2926	goto out;
2927	error = -EXDEV;
2928	if (old_path.mnt != nd.path.mnt)
2929	goto out_release;
2930	new_dentry = lookup_create(&nd, 0);
2931	error = PTR_ERR(new_dentry);
2932	if (IS_ERR(new_dentry))
2933	goto out_unlock;
2934	error = mnt_want_write(nd.path.mnt);
2935	if (error)
2936	goto out_dput;
2937	error = security_path_link(old_path.dentry, &nd.path, new_dentry);
2938	if (error)
2939	goto out_drop_write;
2940	error = vfs_link(old_path.dentry, nd.path.dentry->d_inode, new_dentry);
2941	out_drop_write:
2942	mnt_drop_write(nd.path.mnt);
2943	out_dput:
2944	dput(new_dentry);
2945	out_unlock:
2946	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2947	out_release:
2948	path_put(&nd.path);
2949	putname(to);
2950	out:
2951	path_put(&old_path);
2952
2953	return error;
2954	}
2955
2956	SYSCALL_DEFINE2(link, const char __user , oldname, const char __user , newname)
2957	{
2958	return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
2959	}
2960
2961	/*
2962	* The worst of all namespace operations - renaming directory. "Perverted"
2963	* doesn't even start to describe it. Somebody in UCB had a heck of a trip...
2964	* Problems:
2965	* a) we can get into loop creation. Check is done in is_subdir().
2966	* b) race potential - two innocent renames can create a loop together.
2967	* That's where 4.4 screws up. Current fix: serialization on
2968	* sb->s_vfs_rename_mutex. We might be more accurate, but that's another
2969	* story.
2970	* c) we have to lock _three_ objects - parents and victim (if it exists).
2971	* And that - after we got ->i_mutex on parents (until then we don't know
2972	* whether the target exists). Solution: try to be smart with locking
2973	* order for inodes. We rely on the fact that tree topology may change
2974	* only under ->s_vfs_rename_mutex _and_ that parent of the object we
2975	* move will be locked. Thus we can rank directories by the tree
2976	* (ancestors first) and rank all non-directories after them.
2977	* That works since everybody except rename does "lock parent, lookup,
2978	* lock child" and rename is under ->s_vfs_rename_mutex.
2979	* HOWEVER, it relies on the assumption that any object with ->lookup()
2980	* has no more than 1 dentry. If "hybrid" objects will ever appear,
2981	* we'd better make sure that there's no link(2) for them.
2982	* d) conversion from fhandle to dentry may come in the wrong moment - when
2983	* we are removing the target. Solution: we will have to grab ->i_mutex
2984	* in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
2985	* ->i_mutex on parents, which works but leads to some truly excessive
2986	* locking].
2987	*/
2988	static int vfs_rename_dir(struct inode old_dir, struct dentry old_dentry,
2989	struct inode new_dir, struct dentry new_dentry)
2990	{
2991	int error = 0;
2992	struct inode *target = new_dentry->d_inode;
2993
2994	/*
2995	* If we are going to change the parent - check write permissions,
2996	* we'll need to flip '..'.
2997	*/
2998	if (new_dir != old_dir) {
2999	error = inode_permission(old_dentry->d_inode, MAY_WRITE);
3000	if (error)
3001	return error;
3002	}
3003
3004	error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3005	if (error)
3006	return error;
3007
3008	if (target)
3009	mutex_lock(&target->i_mutex);
3010
3011	error = -EBUSY;
3012	if (d_mountpoint(old_dentry) \|\| d_mountpoint(new_dentry))
3013	goto out;
3014
3015	if (target)
3016	shrink_dcache_parent(new_dentry);
3017	error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3018	if (error)
3019	goto out;
3020
3021	if (target) {
3022	target->i_flags \|= S_DEAD;
3023	dont_mount(new_dentry);
3024	}
3025	out:
3026	if (target)
3027	mutex_unlock(&target->i_mutex);
3028	if (!error)
3029	if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3030	d_move(old_dentry,new_dentry);
3031	return error;
3032	}
3033
3034	static int vfs_rename_other(struct inode old_dir, struct dentry old_dentry,
3035	struct inode new_dir, struct dentry new_dentry)
3036	{
3037	struct inode *target = new_dentry->d_inode;
3038	int error;
3039
3040	error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3041	if (error)
3042	return error;
3043
3044	dget(new_dentry);
3045	if (target)
3046	mutex_lock(&target->i_mutex);
3047
3048	error = -EBUSY;
3049	if (d_mountpoint(old_dentry)\|\|d_mountpoint(new_dentry))
3050	goto out;
3051
3052	error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3053	if (error)
3054	goto out;
3055
3056	if (target)
3057	dont_mount(new_dentry);
3058	if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3059	d_move(old_dentry, new_dentry);
3060	out:
3061	if (target)
3062	mutex_unlock(&target->i_mutex);
3063	dput(new_dentry);
3064	return error;
3065	}
3066
3067	int vfs_rename(struct inode old_dir, struct dentry old_dentry,
3068	struct inode new_dir, struct dentry new_dentry)
3069	{
3070	int error;
3071	int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
3072	const unsigned char *old_name;
3073
3074	if (old_dentry->d_inode == new_dentry->d_inode)
3075	return 0;
3076
3077	error = may_delete(old_dir, old_dentry, is_dir);
3078	if (error)
3079	return error;
3080
3081	if (!new_dentry->d_inode)
3082	error = may_create(new_dir, new_dentry);
3083	else
3084	error = may_delete(new_dir, new_dentry, is_dir);
3085	if (error)
3086	return error;
3087
3088	if (!old_dir->i_op->rename)
3089	return -EPERM;
3090
3091	old_name = fsnotify_oldname_init(old_dentry->d_name.name);
3092
3093	if (is_dir)
3094	error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
3095	else
3096	error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
3097	if (!error)
3098	fsnotify_move(old_dir, new_dir, old_name, is_dir,
3099	new_dentry->d_inode, old_dentry);
3100	fsnotify_oldname_free(old_name);
3101
3102	return error;
3103	}
3104
3105	SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
3106	int, newdfd, const char __user *, newname)
3107	{
3108	struct dentry old_dir, new_dir;
3109	struct dentry old_dentry, new_dentry;
3110	struct dentry *trap;
3111	struct nameidata oldnd, newnd;
3112	char *from;
3113	char *to;
3114	int error;
3115
3116	error = user_path_parent(olddfd, oldname, &oldnd, &from);
3117	if (error)
3118	goto exit;
3119
3120	error = user_path_parent(newdfd, newname, &newnd, &to);
3121	if (error)
3122	goto exit1;
3123
3124	error = -EXDEV;
3125	if (oldnd.path.mnt != newnd.path.mnt)
3126	goto exit2;
3127
3128	old_dir = oldnd.path.dentry;
3129	error = -EBUSY;
3130	if (oldnd.last_type != LAST_NORM)
3131	goto exit2;
3132
3133	new_dir = newnd.path.dentry;
3134	if (newnd.last_type != LAST_NORM)
3135	goto exit2;
3136
3137	oldnd.flags &= ~LOOKUP_PARENT;
3138	newnd.flags &= ~LOOKUP_PARENT;
3139	newnd.flags \|= LOOKUP_RENAME_TARGET;
3140
3141	trap = lock_rename(new_dir, old_dir);
3142
3143	old_dentry = lookup_hash(&oldnd);
3144	error = PTR_ERR(old_dentry);
3145	if (IS_ERR(old_dentry))
3146	goto exit3;
3147	/* source must exist */
3148	error = -ENOENT;
3149	if (!old_dentry->d_inode)
3150	goto exit4;
3151	/* unless the source is a directory trailing slashes give -ENOTDIR */
3152	if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
3153	error = -ENOTDIR;
3154	if (oldnd.last.name[oldnd.last.len])
3155	goto exit4;
3156	if (newnd.last.name[newnd.last.len])
3157	goto exit4;
3158	}
3159	/* source should not be ancestor of target */
3160	error = -EINVAL;
3161	if (old_dentry == trap)
3162	goto exit4;
3163	new_dentry = lookup_hash(&newnd);
3164	error = PTR_ERR(new_dentry);
3165	if (IS_ERR(new_dentry))
3166	goto exit4;
3167	/* target should not be an ancestor of source */
3168	error = -ENOTEMPTY;
3169	if (new_dentry == trap)
3170	goto exit5;
3171
3172	error = mnt_want_write(oldnd.path.mnt);
3173	if (error)
3174	goto exit5;
3175	error = security_path_rename(&oldnd.path, old_dentry,
3176	&newnd.path, new_dentry);
3177	if (error)
3178	goto exit6;
3179	error = vfs_rename(old_dir->d_inode, old_dentry,
3180	new_dir->d_inode, new_dentry);
3181	exit6:
3182	mnt_drop_write(oldnd.path.mnt);
3183	exit5:
3184	dput(new_dentry);
3185	exit4:
3186	dput(old_dentry);
3187	exit3:
3188	unlock_rename(new_dir, old_dir);
3189	exit2:
3190	path_put(&newnd.path);
3191	putname(to);
3192	exit1:
3193	path_put(&oldnd.path);
3194	putname(from);
3195	exit:
3196	return error;
3197	}
3198
3199	SYSCALL_DEFINE2(rename, const char __user , oldname, const char __user , newname)
3200	{
3201	return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
3202	}
3203
3204	int vfs_readlink(struct dentry dentry, char __user buffer, int buflen, const char *link)
3205	{
3206	int len;
3207
3208	len = PTR_ERR(link);
3209	if (IS_ERR(link))
3210	goto out;
3211
3212	len = strlen(link);
3213	if (len > (unsigned) buflen)
3214	len = buflen;
3215	if (copy_to_user(buffer, link, len))
3216	len = -EFAULT;
3217	out:
3218	return len;
3219	}
3220
3221	/*
3222	* A helper for ->readlink(). This should be used ONLY for symlinks that
3223	* have ->follow_link() touching nd only in nd_set_link(). Using (or not
3224	* using) it for any given inode is up to filesystem.
3225	*/
3226	int generic_readlink(struct dentry dentry, char __user buffer, int buflen)
3227	{
3228	struct nameidata nd;
3229	void *cookie;
3230	int res;
3231
3232	nd.depth = 0;
3233	cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
3234	if (IS_ERR(cookie))
3235	return PTR_ERR(cookie);
3236
3237	res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
3238	if (dentry->d_inode->i_op->put_link)
3239	dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
3240	return res;
3241	}
3242
3243	int vfs_follow_link(struct nameidata nd, const char link)
3244	{
3245	return __vfs_follow_link(nd, link);
3246	}
3247
3248	/* get the link contents into pagecache */
3249	static char page_getlink(struct dentry dentry, struct page **ppage)
3250	{
3251	char *kaddr;
3252	struct page *page;
3253	struct address_space *mapping = dentry->d_inode->i_mapping;
3254	page = read_mapping_page(mapping, 0, NULL);
3255	if (IS_ERR(page))
3256	return (char*)page;
3257	*ppage = page;
3258	kaddr = kmap(page);
3259	nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
3260	return kaddr;
3261	}
3262
3263	int page_readlink(struct dentry dentry, char __user buffer, int buflen)
3264	{
3265	struct page *page = NULL;
3266	char *s = page_getlink(dentry, &page);
3267	int res = vfs_readlink(dentry,buffer,buflen,s);
3268	if (page) {
3269	kunmap(page);
3270	page_cache_release(page);
3271	}
3272	return res;
3273	}
3274
3275	void page_follow_link_light(struct dentry dentry, struct nameidata *nd)
3276	{
3277	struct page *page = NULL;
3278	nd_set_link(nd, page_getlink(dentry, &page));
3279	return page;
3280	}
3281
3282	void page_put_link(struct dentry dentry, struct nameidata nd, void *cookie)
3283	{
3284	struct page *page = cookie;
3285
3286	if (page) {
3287	kunmap(page);
3288	page_cache_release(page);
3289	}
3290	}
3291
3292	/*
3293	* The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
3294	*/
3295	int __page_symlink(struct inode inode, const char symname, int len, int nofs)
3296	{
3297	struct address_space *mapping = inode->i_mapping;
3298	struct page *page;
3299	void *fsdata;
3300	int err;
3301	char *kaddr;
3302	unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
3303	if (nofs)
3304	flags \|= AOP_FLAG_NOFS;
3305
3306	retry:
3307	err = pagecache_write_begin(NULL, mapping, 0, len-1,
3308	flags, &page, &fsdata);
3309	if (err)
3310	goto fail;
3311
3312	kaddr = kmap_atomic(page, KM_USER0);
3313	memcpy(kaddr, symname, len-1);
3314	kunmap_atomic(kaddr, KM_USER0);
3315
3316	err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
3317	page, fsdata);
3318	if (err < 0)
3319	goto fail;
3320	if (err < len-1)
3321	goto retry;
3322
3323	mark_inode_dirty(inode);
3324	return 0;
3325	fail:
3326	return err;
3327	}
3328
3329	int page_symlink(struct inode inode, const char symname, int len)
3330	{
3331	return __page_symlink(inode, symname, len,
3332	!(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
3333	}
3334
3335	const struct inode_operations page_symlink_inode_operations = {
3336	.readlink = generic_readlink,
3337	.follow_link = page_follow_link_light,
3338	.put_link = page_put_link,
3339	};
3340
3341	EXPORT_SYMBOL(user_path_at);
3342	EXPORT_SYMBOL(follow_down_one);
3343	EXPORT_SYMBOL(follow_down);
3344	EXPORT_SYMBOL(follow_up);
3345	EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
3346	EXPORT_SYMBOL(getname);
3347	EXPORT_SYMBOL(lock_rename);
3348	EXPORT_SYMBOL(lookup_one_len);
3349	EXPORT_SYMBOL(page_follow_link_light);
3350	EXPORT_SYMBOL(page_put_link);
3351	EXPORT_SYMBOL(page_readlink);
3352	EXPORT_SYMBOL(__page_symlink);
3353	EXPORT_SYMBOL(page_symlink);
3354	EXPORT_SYMBOL(page_symlink_inode_operations);
3355	EXPORT_SYMBOL(kern_path_parent);
3356	EXPORT_SYMBOL(kern_path);
3357	EXPORT_SYMBOL(vfs_path_lookup);
3358	EXPORT_SYMBOL(inode_permission);
3359	EXPORT_SYMBOL(file_permission);
3360	EXPORT_SYMBOL(unlock_rename);
3361	EXPORT_SYMBOL(vfs_create);
3362	EXPORT_SYMBOL(vfs_follow_link);
3363	EXPORT_SYMBOL(vfs_link);
3364	EXPORT_SYMBOL(vfs_mkdir);
3365	EXPORT_SYMBOL(vfs_mknod);
3366	EXPORT_SYMBOL(generic_permission);
3367	EXPORT_SYMBOL(vfs_readlink);
3368	EXPORT_SYMBOL(vfs_rename);
3369	EXPORT_SYMBOL(vfs_rmdir);
3370	EXPORT_SYMBOL(vfs_symlink);
3371	EXPORT_SYMBOL(vfs_unlink);
3372	EXPORT_SYMBOL(dentry_unhash);
3373	EXPORT_SYMBOL(generic_readlink);
3374

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