xref: /openbmc/linux/fs/open.c (revision 8569c914)
1  /*
2   *  linux/fs/open.c
3   *
4   *  Copyright (C) 1991, 1992  Linus Torvalds
5   */
6  
7  #include <linux/string.h>
8  #include <linux/mm.h>
9  #include <linux/file.h>
10  #include <linux/fdtable.h>
11  #include <linux/quotaops.h>
12  #include <linux/fsnotify.h>
13  #include <linux/module.h>
14  #include <linux/slab.h>
15  #include <linux/tty.h>
16  #include <linux/namei.h>
17  #include <linux/backing-dev.h>
18  #include <linux/capability.h>
19  #include <linux/securebits.h>
20  #include <linux/security.h>
21  #include <linux/mount.h>
22  #include <linux/vfs.h>
23  #include <linux/fcntl.h>
24  #include <asm/uaccess.h>
25  #include <linux/fs.h>
26  #include <linux/personality.h>
27  #include <linux/pagemap.h>
28  #include <linux/syscalls.h>
29  #include <linux/rcupdate.h>
30  #include <linux/audit.h>
31  #include <linux/falloc.h>
32  
33  int vfs_statfs(struct dentry *dentry, struct kstatfs *buf)
34  {
35  	int retval = -ENODEV;
36  
37  	if (dentry) {
38  		retval = -ENOSYS;
39  		if (dentry->d_sb->s_op->statfs) {
40  			memset(buf, 0, sizeof(*buf));
41  			retval = security_sb_statfs(dentry);
42  			if (retval)
43  				return retval;
44  			retval = dentry->d_sb->s_op->statfs(dentry, buf);
45  			if (retval == 0 && buf->f_frsize == 0)
46  				buf->f_frsize = buf->f_bsize;
47  		}
48  	}
49  	return retval;
50  }
51  
52  EXPORT_SYMBOL(vfs_statfs);
53  
54  static int vfs_statfs_native(struct dentry *dentry, struct statfs *buf)
55  {
56  	struct kstatfs st;
57  	int retval;
58  
59  	retval = vfs_statfs(dentry, &st);
60  	if (retval)
61  		return retval;
62  
63  	if (sizeof(*buf) == sizeof(st))
64  		memcpy(buf, &st, sizeof(st));
65  	else {
66  		if (sizeof buf->f_blocks == 4) {
67  			if ((st.f_blocks | st.f_bfree | st.f_bavail |
68  			     st.f_bsize | st.f_frsize) &
69  			    0xffffffff00000000ULL)
70  				return -EOVERFLOW;
71  			/*
72  			 * f_files and f_ffree may be -1; it's okay to stuff
73  			 * that into 32 bits
74  			 */
75  			if (st.f_files != -1 &&
76  			    (st.f_files & 0xffffffff00000000ULL))
77  				return -EOVERFLOW;
78  			if (st.f_ffree != -1 &&
79  			    (st.f_ffree & 0xffffffff00000000ULL))
80  				return -EOVERFLOW;
81  		}
82  
83  		buf->f_type = st.f_type;
84  		buf->f_bsize = st.f_bsize;
85  		buf->f_blocks = st.f_blocks;
86  		buf->f_bfree = st.f_bfree;
87  		buf->f_bavail = st.f_bavail;
88  		buf->f_files = st.f_files;
89  		buf->f_ffree = st.f_ffree;
90  		buf->f_fsid = st.f_fsid;
91  		buf->f_namelen = st.f_namelen;
92  		buf->f_frsize = st.f_frsize;
93  		memset(buf->f_spare, 0, sizeof(buf->f_spare));
94  	}
95  	return 0;
96  }
97  
98  static int vfs_statfs64(struct dentry *dentry, struct statfs64 *buf)
99  {
100  	struct kstatfs st;
101  	int retval;
102  
103  	retval = vfs_statfs(dentry, &st);
104  	if (retval)
105  		return retval;
106  
107  	if (sizeof(*buf) == sizeof(st))
108  		memcpy(buf, &st, sizeof(st));
109  	else {
110  		buf->f_type = st.f_type;
111  		buf->f_bsize = st.f_bsize;
112  		buf->f_blocks = st.f_blocks;
113  		buf->f_bfree = st.f_bfree;
114  		buf->f_bavail = st.f_bavail;
115  		buf->f_files = st.f_files;
116  		buf->f_ffree = st.f_ffree;
117  		buf->f_fsid = st.f_fsid;
118  		buf->f_namelen = st.f_namelen;
119  		buf->f_frsize = st.f_frsize;
120  		memset(buf->f_spare, 0, sizeof(buf->f_spare));
121  	}
122  	return 0;
123  }
124  
125  asmlinkage long sys_statfs(const char __user *pathname, struct statfs __user * buf)
126  {
127  	struct path path;
128  	int error;
129  
130  	error = user_path(pathname, &path);
131  	if (!error) {
132  		struct statfs tmp;
133  		error = vfs_statfs_native(path.dentry, &tmp);
134  		if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
135  			error = -EFAULT;
136  		path_put(&path);
137  	}
138  	return error;
139  }
140  
141  
142  asmlinkage long sys_statfs64(const char __user *pathname, size_t sz, struct statfs64 __user *buf)
143  {
144  	struct path path;
145  	long error;
146  
147  	if (sz != sizeof(*buf))
148  		return -EINVAL;
149  	error = user_path(pathname, &path);
150  	if (!error) {
151  		struct statfs64 tmp;
152  		error = vfs_statfs64(path.dentry, &tmp);
153  		if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
154  			error = -EFAULT;
155  		path_put(&path);
156  	}
157  	return error;
158  }
159  
160  
161  asmlinkage long sys_fstatfs(unsigned int fd, struct statfs __user * buf)
162  {
163  	struct file * file;
164  	struct statfs tmp;
165  	int error;
166  
167  	error = -EBADF;
168  	file = fget(fd);
169  	if (!file)
170  		goto out;
171  	error = vfs_statfs_native(file->f_path.dentry, &tmp);
172  	if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
173  		error = -EFAULT;
174  	fput(file);
175  out:
176  	return error;
177  }
178  
179  asmlinkage long sys_fstatfs64(unsigned int fd, size_t sz, struct statfs64 __user *buf)
180  {
181  	struct file * file;
182  	struct statfs64 tmp;
183  	int error;
184  
185  	if (sz != sizeof(*buf))
186  		return -EINVAL;
187  
188  	error = -EBADF;
189  	file = fget(fd);
190  	if (!file)
191  		goto out;
192  	error = vfs_statfs64(file->f_path.dentry, &tmp);
193  	if (!error && copy_to_user(buf, &tmp, sizeof(tmp)))
194  		error = -EFAULT;
195  	fput(file);
196  out:
197  	return error;
198  }
199  
200  int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
201  	struct file *filp)
202  {
203  	int err;
204  	struct iattr newattrs;
205  
206  	/* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
207  	if (length < 0)
208  		return -EINVAL;
209  
210  	newattrs.ia_size = length;
211  	newattrs.ia_valid = ATTR_SIZE | time_attrs;
212  	if (filp) {
213  		newattrs.ia_file = filp;
214  		newattrs.ia_valid |= ATTR_FILE;
215  	}
216  
217  	/* Remove suid/sgid on truncate too */
218  	newattrs.ia_valid |= should_remove_suid(dentry);
219  
220  	mutex_lock(&dentry->d_inode->i_mutex);
221  	err = notify_change(dentry, &newattrs);
222  	mutex_unlock(&dentry->d_inode->i_mutex);
223  	return err;
224  }
225  
226  static long do_sys_truncate(const char __user *pathname, loff_t length)
227  {
228  	struct path path;
229  	struct inode *inode;
230  	int error;
231  
232  	error = -EINVAL;
233  	if (length < 0)	/* sorry, but loff_t says... */
234  		goto out;
235  
236  	error = user_path(pathname, &path);
237  	if (error)
238  		goto out;
239  	inode = path.dentry->d_inode;
240  
241  	/* For directories it's -EISDIR, for other non-regulars - -EINVAL */
242  	error = -EISDIR;
243  	if (S_ISDIR(inode->i_mode))
244  		goto dput_and_out;
245  
246  	error = -EINVAL;
247  	if (!S_ISREG(inode->i_mode))
248  		goto dput_and_out;
249  
250  	error = mnt_want_write(path.mnt);
251  	if (error)
252  		goto dput_and_out;
253  
254  	error = inode_permission(inode, MAY_WRITE);
255  	if (error)
256  		goto mnt_drop_write_and_out;
257  
258  	error = -EPERM;
259  	if (IS_APPEND(inode))
260  		goto mnt_drop_write_and_out;
261  
262  	error = get_write_access(inode);
263  	if (error)
264  		goto mnt_drop_write_and_out;
265  
266  	/*
267  	 * Make sure that there are no leases.  get_write_access() protects
268  	 * against the truncate racing with a lease-granting setlease().
269  	 */
270  	error = break_lease(inode, FMODE_WRITE);
271  	if (error)
272  		goto put_write_and_out;
273  
274  	error = locks_verify_truncate(inode, NULL, length);
275  	if (!error) {
276  		DQUOT_INIT(inode);
277  		error = do_truncate(path.dentry, length, 0, NULL);
278  	}
279  
280  put_write_and_out:
281  	put_write_access(inode);
282  mnt_drop_write_and_out:
283  	mnt_drop_write(path.mnt);
284  dput_and_out:
285  	path_put(&path);
286  out:
287  	return error;
288  }
289  
290  asmlinkage long sys_truncate(const char __user * path, unsigned long length)
291  {
292  	/* on 32-bit boxen it will cut the range 2^31--2^32-1 off */
293  	return do_sys_truncate(path, (long)length);
294  }
295  
296  static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
297  {
298  	struct inode * inode;
299  	struct dentry *dentry;
300  	struct file * file;
301  	int error;
302  
303  	error = -EINVAL;
304  	if (length < 0)
305  		goto out;
306  	error = -EBADF;
307  	file = fget(fd);
308  	if (!file)
309  		goto out;
310  
311  	/* explicitly opened as large or we are on 64-bit box */
312  	if (file->f_flags & O_LARGEFILE)
313  		small = 0;
314  
315  	dentry = file->f_path.dentry;
316  	inode = dentry->d_inode;
317  	error = -EINVAL;
318  	if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
319  		goto out_putf;
320  
321  	error = -EINVAL;
322  	/* Cannot ftruncate over 2^31 bytes without large file support */
323  	if (small && length > MAX_NON_LFS)
324  		goto out_putf;
325  
326  	error = -EPERM;
327  	if (IS_APPEND(inode))
328  		goto out_putf;
329  
330  	error = locks_verify_truncate(inode, file, length);
331  	if (!error)
332  		error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
333  out_putf:
334  	fput(file);
335  out:
336  	return error;
337  }
338  
339  asmlinkage long sys_ftruncate(unsigned int fd, unsigned long length)
340  {
341  	long ret = do_sys_ftruncate(fd, length, 1);
342  	/* avoid REGPARM breakage on x86: */
343  	asmlinkage_protect(2, ret, fd, length);
344  	return ret;
345  }
346  
347  /* LFS versions of truncate are only needed on 32 bit machines */
348  #if BITS_PER_LONG == 32
349  asmlinkage long sys_truncate64(const char __user * path, loff_t length)
350  {
351  	return do_sys_truncate(path, length);
352  }
353  
354  asmlinkage long sys_ftruncate64(unsigned int fd, loff_t length)
355  {
356  	long ret = do_sys_ftruncate(fd, length, 0);
357  	/* avoid REGPARM breakage on x86: */
358  	asmlinkage_protect(2, ret, fd, length);
359  	return ret;
360  }
361  #endif
362  
363  asmlinkage long sys_fallocate(int fd, int mode, loff_t offset, loff_t len)
364  {
365  	struct file *file;
366  	struct inode *inode;
367  	long ret = -EINVAL;
368  
369  	if (offset < 0 || len <= 0)
370  		goto out;
371  
372  	/* Return error if mode is not supported */
373  	ret = -EOPNOTSUPP;
374  	if (mode && !(mode & FALLOC_FL_KEEP_SIZE))
375  		goto out;
376  
377  	ret = -EBADF;
378  	file = fget(fd);
379  	if (!file)
380  		goto out;
381  	if (!(file->f_mode & FMODE_WRITE))
382  		goto out_fput;
383  	/*
384  	 * Revalidate the write permissions, in case security policy has
385  	 * changed since the files were opened.
386  	 */
387  	ret = security_file_permission(file, MAY_WRITE);
388  	if (ret)
389  		goto out_fput;
390  
391  	inode = file->f_path.dentry->d_inode;
392  
393  	ret = -ESPIPE;
394  	if (S_ISFIFO(inode->i_mode))
395  		goto out_fput;
396  
397  	ret = -ENODEV;
398  	/*
399  	 * Let individual file system decide if it supports preallocation
400  	 * for directories or not.
401  	 */
402  	if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
403  		goto out_fput;
404  
405  	ret = -EFBIG;
406  	/* Check for wrap through zero too */
407  	if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
408  		goto out_fput;
409  
410  	if (inode->i_op && inode->i_op->fallocate)
411  		ret = inode->i_op->fallocate(inode, mode, offset, len);
412  	else
413  		ret = -EOPNOTSUPP;
414  
415  out_fput:
416  	fput(file);
417  out:
418  	return ret;
419  }
420  
421  /*
422   * access() needs to use the real uid/gid, not the effective uid/gid.
423   * We do this by temporarily clearing all FS-related capabilities and
424   * switching the fsuid/fsgid around to the real ones.
425   */
426  asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode)
427  {
428  	struct path path;
429  	struct inode *inode;
430  	int old_fsuid, old_fsgid;
431  	kernel_cap_t uninitialized_var(old_cap);  /* !SECURE_NO_SETUID_FIXUP */
432  	int res;
433  
434  	if (mode & ~S_IRWXO)	/* where's F_OK, X_OK, W_OK, R_OK? */
435  		return -EINVAL;
436  
437  	old_fsuid = current->fsuid;
438  	old_fsgid = current->fsgid;
439  
440  	current->fsuid = current->uid;
441  	current->fsgid = current->gid;
442  
443  	if (!issecure(SECURE_NO_SETUID_FIXUP)) {
444  		/*
445  		 * Clear the capabilities if we switch to a non-root user
446  		 */
447  #ifndef CONFIG_SECURITY_FILE_CAPABILITIES
448  		/*
449  		 * FIXME: There is a race here against sys_capset.  The
450  		 * capabilities can change yet we will restore the old
451  		 * value below.  We should hold task_capabilities_lock,
452  		 * but we cannot because user_path_at can sleep.
453  		 */
454  #endif /* ndef CONFIG_SECURITY_FILE_CAPABILITIES */
455  		if (current->uid)
456  			old_cap = cap_set_effective(__cap_empty_set);
457  		else
458  			old_cap = cap_set_effective(current->cap_permitted);
459  	}
460  
461  	res = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
462  	if (res)
463  		goto out;
464  
465  	inode = path.dentry->d_inode;
466  
467  	if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
468  		/*
469  		 * MAY_EXEC on regular files is denied if the fs is mounted
470  		 * with the "noexec" flag.
471  		 */
472  		res = -EACCES;
473  		if (path.mnt->mnt_flags & MNT_NOEXEC)
474  			goto out_path_release;
475  	}
476  
477  	res = inode_permission(inode, mode | MAY_ACCESS);
478  	/* SuS v2 requires we report a read only fs too */
479  	if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
480  		goto out_path_release;
481  	/*
482  	 * This is a rare case where using __mnt_is_readonly()
483  	 * is OK without a mnt_want/drop_write() pair.  Since
484  	 * no actual write to the fs is performed here, we do
485  	 * not need to telegraph to that to anyone.
486  	 *
487  	 * By doing this, we accept that this access is
488  	 * inherently racy and know that the fs may change
489  	 * state before we even see this result.
490  	 */
491  	if (__mnt_is_readonly(path.mnt))
492  		res = -EROFS;
493  
494  out_path_release:
495  	path_put(&path);
496  out:
497  	current->fsuid = old_fsuid;
498  	current->fsgid = old_fsgid;
499  
500  	if (!issecure(SECURE_NO_SETUID_FIXUP))
501  		cap_set_effective(old_cap);
502  
503  	return res;
504  }
505  
506  asmlinkage long sys_access(const char __user *filename, int mode)
507  {
508  	return sys_faccessat(AT_FDCWD, filename, mode);
509  }
510  
511  asmlinkage long sys_chdir(const char __user * filename)
512  {
513  	struct path path;
514  	int error;
515  
516  	error = user_path_dir(filename, &path);
517  	if (error)
518  		goto out;
519  
520  	error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_ACCESS);
521  	if (error)
522  		goto dput_and_out;
523  
524  	set_fs_pwd(current->fs, &path);
525  
526  dput_and_out:
527  	path_put(&path);
528  out:
529  	return error;
530  }
531  
532  asmlinkage long sys_fchdir(unsigned int fd)
533  {
534  	struct file *file;
535  	struct inode *inode;
536  	int error;
537  
538  	error = -EBADF;
539  	file = fget(fd);
540  	if (!file)
541  		goto out;
542  
543  	inode = file->f_path.dentry->d_inode;
544  
545  	error = -ENOTDIR;
546  	if (!S_ISDIR(inode->i_mode))
547  		goto out_putf;
548  
549  	error = inode_permission(inode, MAY_EXEC | MAY_ACCESS);
550  	if (!error)
551  		set_fs_pwd(current->fs, &file->f_path);
552  out_putf:
553  	fput(file);
554  out:
555  	return error;
556  }
557  
558  asmlinkage long sys_chroot(const char __user * filename)
559  {
560  	struct path path;
561  	int error;
562  
563  	error = user_path_dir(filename, &path);
564  	if (error)
565  		goto out;
566  
567  	error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_ACCESS);
568  	if (error)
569  		goto dput_and_out;
570  
571  	error = -EPERM;
572  	if (!capable(CAP_SYS_CHROOT))
573  		goto dput_and_out;
574  
575  	set_fs_root(current->fs, &path);
576  	error = 0;
577  dput_and_out:
578  	path_put(&path);
579  out:
580  	return error;
581  }
582  
583  asmlinkage long sys_fchmod(unsigned int fd, mode_t mode)
584  {
585  	struct inode * inode;
586  	struct dentry * dentry;
587  	struct file * file;
588  	int err = -EBADF;
589  	struct iattr newattrs;
590  
591  	file = fget(fd);
592  	if (!file)
593  		goto out;
594  
595  	dentry = file->f_path.dentry;
596  	inode = dentry->d_inode;
597  
598  	audit_inode(NULL, dentry);
599  
600  	err = mnt_want_write(file->f_path.mnt);
601  	if (err)
602  		goto out_putf;
603  	mutex_lock(&inode->i_mutex);
604  	if (mode == (mode_t) -1)
605  		mode = inode->i_mode;
606  	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
607  	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
608  	err = notify_change(dentry, &newattrs);
609  	mutex_unlock(&inode->i_mutex);
610  	mnt_drop_write(file->f_path.mnt);
611  out_putf:
612  	fput(file);
613  out:
614  	return err;
615  }
616  
617  asmlinkage long sys_fchmodat(int dfd, const char __user *filename,
618  			     mode_t mode)
619  {
620  	struct path path;
621  	struct inode *inode;
622  	int error;
623  	struct iattr newattrs;
624  
625  	error = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
626  	if (error)
627  		goto out;
628  	inode = path.dentry->d_inode;
629  
630  	error = mnt_want_write(path.mnt);
631  	if (error)
632  		goto dput_and_out;
633  	mutex_lock(&inode->i_mutex);
634  	if (mode == (mode_t) -1)
635  		mode = inode->i_mode;
636  	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
637  	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
638  	error = notify_change(path.dentry, &newattrs);
639  	mutex_unlock(&inode->i_mutex);
640  	mnt_drop_write(path.mnt);
641  dput_and_out:
642  	path_put(&path);
643  out:
644  	return error;
645  }
646  
647  asmlinkage long sys_chmod(const char __user *filename, mode_t mode)
648  {
649  	return sys_fchmodat(AT_FDCWD, filename, mode);
650  }
651  
652  static int chown_common(struct dentry * dentry, uid_t user, gid_t group)
653  {
654  	struct inode *inode = dentry->d_inode;
655  	int error;
656  	struct iattr newattrs;
657  
658  	newattrs.ia_valid =  ATTR_CTIME;
659  	if (user != (uid_t) -1) {
660  		newattrs.ia_valid |= ATTR_UID;
661  		newattrs.ia_uid = user;
662  	}
663  	if (group != (gid_t) -1) {
664  		newattrs.ia_valid |= ATTR_GID;
665  		newattrs.ia_gid = group;
666  	}
667  	if (!S_ISDIR(inode->i_mode))
668  		newattrs.ia_valid |=
669  			ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
670  	mutex_lock(&inode->i_mutex);
671  	error = notify_change(dentry, &newattrs);
672  	mutex_unlock(&inode->i_mutex);
673  
674  	return error;
675  }
676  
677  asmlinkage long sys_chown(const char __user * filename, uid_t user, gid_t group)
678  {
679  	struct path path;
680  	int error;
681  
682  	error = user_path(filename, &path);
683  	if (error)
684  		goto out;
685  	error = mnt_want_write(path.mnt);
686  	if (error)
687  		goto out_release;
688  	error = chown_common(path.dentry, user, group);
689  	mnt_drop_write(path.mnt);
690  out_release:
691  	path_put(&path);
692  out:
693  	return error;
694  }
695  
696  asmlinkage long sys_fchownat(int dfd, const char __user *filename, uid_t user,
697  			     gid_t group, int flag)
698  {
699  	struct path path;
700  	int error = -EINVAL;
701  	int follow;
702  
703  	if ((flag & ~AT_SYMLINK_NOFOLLOW) != 0)
704  		goto out;
705  
706  	follow = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
707  	error = user_path_at(dfd, filename, follow, &path);
708  	if (error)
709  		goto out;
710  	error = mnt_want_write(path.mnt);
711  	if (error)
712  		goto out_release;
713  	error = chown_common(path.dentry, user, group);
714  	mnt_drop_write(path.mnt);
715  out_release:
716  	path_put(&path);
717  out:
718  	return error;
719  }
720  
721  asmlinkage long sys_lchown(const char __user * filename, uid_t user, gid_t group)
722  {
723  	struct path path;
724  	int error;
725  
726  	error = user_lpath(filename, &path);
727  	if (error)
728  		goto out;
729  	error = mnt_want_write(path.mnt);
730  	if (error)
731  		goto out_release;
732  	error = chown_common(path.dentry, user, group);
733  	mnt_drop_write(path.mnt);
734  out_release:
735  	path_put(&path);
736  out:
737  	return error;
738  }
739  
740  
741  asmlinkage long sys_fchown(unsigned int fd, uid_t user, gid_t group)
742  {
743  	struct file * file;
744  	int error = -EBADF;
745  	struct dentry * dentry;
746  
747  	file = fget(fd);
748  	if (!file)
749  		goto out;
750  
751  	error = mnt_want_write(file->f_path.mnt);
752  	if (error)
753  		goto out_fput;
754  	dentry = file->f_path.dentry;
755  	audit_inode(NULL, dentry);
756  	error = chown_common(dentry, user, group);
757  	mnt_drop_write(file->f_path.mnt);
758  out_fput:
759  	fput(file);
760  out:
761  	return error;
762  }
763  
764  /*
765   * You have to be very careful that these write
766   * counts get cleaned up in error cases and
767   * upon __fput().  This should probably never
768   * be called outside of __dentry_open().
769   */
770  static inline int __get_file_write_access(struct inode *inode,
771  					  struct vfsmount *mnt)
772  {
773  	int error;
774  	error = get_write_access(inode);
775  	if (error)
776  		return error;
777  	/*
778  	 * Do not take mount writer counts on
779  	 * special files since no writes to
780  	 * the mount itself will occur.
781  	 */
782  	if (!special_file(inode->i_mode)) {
783  		/*
784  		 * Balanced in __fput()
785  		 */
786  		error = mnt_want_write(mnt);
787  		if (error)
788  			put_write_access(inode);
789  	}
790  	return error;
791  }
792  
793  static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
794  					int flags, struct file *f,
795  					int (*open)(struct inode *, struct file *))
796  {
797  	struct inode *inode;
798  	int error;
799  
800  	f->f_flags = flags;
801  	f->f_mode = ((flags+1) & O_ACCMODE) | FMODE_LSEEK |
802  				FMODE_PREAD | FMODE_PWRITE;
803  	inode = dentry->d_inode;
804  	if (f->f_mode & FMODE_WRITE) {
805  		error = __get_file_write_access(inode, mnt);
806  		if (error)
807  			goto cleanup_file;
808  		if (!special_file(inode->i_mode))
809  			file_take_write(f);
810  	}
811  
812  	f->f_mapping = inode->i_mapping;
813  	f->f_path.dentry = dentry;
814  	f->f_path.mnt = mnt;
815  	f->f_pos = 0;
816  	f->f_op = fops_get(inode->i_fop);
817  	file_move(f, &inode->i_sb->s_files);
818  
819  	error = security_dentry_open(f);
820  	if (error)
821  		goto cleanup_all;
822  
823  	if (!open && f->f_op)
824  		open = f->f_op->open;
825  	if (open) {
826  		error = open(inode, f);
827  		if (error)
828  			goto cleanup_all;
829  	}
830  
831  	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
832  
833  	file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
834  
835  	/* NB: we're sure to have correct a_ops only after f_op->open */
836  	if (f->f_flags & O_DIRECT) {
837  		if (!f->f_mapping->a_ops ||
838  		    ((!f->f_mapping->a_ops->direct_IO) &&
839  		    (!f->f_mapping->a_ops->get_xip_mem))) {
840  			fput(f);
841  			f = ERR_PTR(-EINVAL);
842  		}
843  	}
844  
845  	return f;
846  
847  cleanup_all:
848  	fops_put(f->f_op);
849  	if (f->f_mode & FMODE_WRITE) {
850  		put_write_access(inode);
851  		if (!special_file(inode->i_mode)) {
852  			/*
853  			 * We don't consider this a real
854  			 * mnt_want/drop_write() pair
855  			 * because it all happenend right
856  			 * here, so just reset the state.
857  			 */
858  			file_reset_write(f);
859  			mnt_drop_write(mnt);
860  		}
861  	}
862  	file_kill(f);
863  	f->f_path.dentry = NULL;
864  	f->f_path.mnt = NULL;
865  cleanup_file:
866  	put_filp(f);
867  	dput(dentry);
868  	mntput(mnt);
869  	return ERR_PTR(error);
870  }
871  
872  /**
873   * lookup_instantiate_filp - instantiates the open intent filp
874   * @nd: pointer to nameidata
875   * @dentry: pointer to dentry
876   * @open: open callback
877   *
878   * Helper for filesystems that want to use lookup open intents and pass back
879   * a fully instantiated struct file to the caller.
880   * This function is meant to be called from within a filesystem's
881   * lookup method.
882   * Beware of calling it for non-regular files! Those ->open methods might block
883   * (e.g. in fifo_open), leaving you with parent locked (and in case of fifo,
884   * leading to a deadlock, as nobody can open that fifo anymore, because
885   * another process to open fifo will block on locked parent when doing lookup).
886   * Note that in case of error, nd->intent.open.file is destroyed, but the
887   * path information remains valid.
888   * If the open callback is set to NULL, then the standard f_op->open()
889   * filesystem callback is substituted.
890   */
891  struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
892  		int (*open)(struct inode *, struct file *))
893  {
894  	if (IS_ERR(nd->intent.open.file))
895  		goto out;
896  	if (IS_ERR(dentry))
897  		goto out_err;
898  	nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->path.mnt),
899  					     nd->intent.open.flags - 1,
900  					     nd->intent.open.file,
901  					     open);
902  out:
903  	return nd->intent.open.file;
904  out_err:
905  	release_open_intent(nd);
906  	nd->intent.open.file = (struct file *)dentry;
907  	goto out;
908  }
909  EXPORT_SYMBOL_GPL(lookup_instantiate_filp);
910  
911  /**
912   * nameidata_to_filp - convert a nameidata to an open filp.
913   * @nd: pointer to nameidata
914   * @flags: open flags
915   *
916   * Note that this function destroys the original nameidata
917   */
918  struct file *nameidata_to_filp(struct nameidata *nd, int flags)
919  {
920  	struct file *filp;
921  
922  	/* Pick up the filp from the open intent */
923  	filp = nd->intent.open.file;
924  	/* Has the filesystem initialised the file for us? */
925  	if (filp->f_path.dentry == NULL)
926  		filp = __dentry_open(nd->path.dentry, nd->path.mnt, flags, filp,
927  				     NULL);
928  	else
929  		path_put(&nd->path);
930  	return filp;
931  }
932  
933  /*
934   * dentry_open() will have done dput(dentry) and mntput(mnt) if it returns an
935   * error.
936   */
937  struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags)
938  {
939  	int error;
940  	struct file *f;
941  
942  	/*
943  	 * We must always pass in a valid mount pointer.   Historically
944  	 * callers got away with not passing it, but we must enforce this at
945  	 * the earliest possible point now to avoid strange problems deep in the
946  	 * filesystem stack.
947  	 */
948  	if (!mnt) {
949  		printk(KERN_WARNING "%s called with NULL vfsmount\n", __func__);
950  		dump_stack();
951  		return ERR_PTR(-EINVAL);
952  	}
953  
954  	error = -ENFILE;
955  	f = get_empty_filp();
956  	if (f == NULL) {
957  		dput(dentry);
958  		mntput(mnt);
959  		return ERR_PTR(error);
960  	}
961  
962  	return __dentry_open(dentry, mnt, flags, f, NULL);
963  }
964  EXPORT_SYMBOL(dentry_open);
965  
966  static void __put_unused_fd(struct files_struct *files, unsigned int fd)
967  {
968  	struct fdtable *fdt = files_fdtable(files);
969  	__FD_CLR(fd, fdt->open_fds);
970  	if (fd < files->next_fd)
971  		files->next_fd = fd;
972  }
973  
974  void put_unused_fd(unsigned int fd)
975  {
976  	struct files_struct *files = current->files;
977  	spin_lock(&files->file_lock);
978  	__put_unused_fd(files, fd);
979  	spin_unlock(&files->file_lock);
980  }
981  
982  EXPORT_SYMBOL(put_unused_fd);
983  
984  /*
985   * Install a file pointer in the fd array.
986   *
987   * The VFS is full of places where we drop the files lock between
988   * setting the open_fds bitmap and installing the file in the file
989   * array.  At any such point, we are vulnerable to a dup2() race
990   * installing a file in the array before us.  We need to detect this and
991   * fput() the struct file we are about to overwrite in this case.
992   *
993   * It should never happen - if we allow dup2() do it, _really_ bad things
994   * will follow.
995   */
996  
997  void fd_install(unsigned int fd, struct file *file)
998  {
999  	struct files_struct *files = current->files;
1000  	struct fdtable *fdt;
1001  	spin_lock(&files->file_lock);
1002  	fdt = files_fdtable(files);
1003  	BUG_ON(fdt->fd[fd] != NULL);
1004  	rcu_assign_pointer(fdt->fd[fd], file);
1005  	spin_unlock(&files->file_lock);
1006  }
1007  
1008  EXPORT_SYMBOL(fd_install);
1009  
1010  long do_sys_open(int dfd, const char __user *filename, int flags, int mode)
1011  {
1012  	char *tmp = getname(filename);
1013  	int fd = PTR_ERR(tmp);
1014  
1015  	if (!IS_ERR(tmp)) {
1016  		fd = get_unused_fd_flags(flags);
1017  		if (fd >= 0) {
1018  			struct file *f = do_filp_open(dfd, tmp, flags, mode);
1019  			if (IS_ERR(f)) {
1020  				put_unused_fd(fd);
1021  				fd = PTR_ERR(f);
1022  			} else {
1023  				fsnotify_open(f->f_path.dentry);
1024  				fd_install(fd, f);
1025  			}
1026  		}
1027  		putname(tmp);
1028  	}
1029  	return fd;
1030  }
1031  
1032  asmlinkage long sys_open(const char __user *filename, int flags, int mode)
1033  {
1034  	long ret;
1035  
1036  	if (force_o_largefile())
1037  		flags |= O_LARGEFILE;
1038  
1039  	ret = do_sys_open(AT_FDCWD, filename, flags, mode);
1040  	/* avoid REGPARM breakage on x86: */
1041  	asmlinkage_protect(3, ret, filename, flags, mode);
1042  	return ret;
1043  }
1044  
1045  asmlinkage long sys_openat(int dfd, const char __user *filename, int flags,
1046  			   int mode)
1047  {
1048  	long ret;
1049  
1050  	if (force_o_largefile())
1051  		flags |= O_LARGEFILE;
1052  
1053  	ret = do_sys_open(dfd, filename, flags, mode);
1054  	/* avoid REGPARM breakage on x86: */
1055  	asmlinkage_protect(4, ret, dfd, filename, flags, mode);
1056  	return ret;
1057  }
1058  
1059  #ifndef __alpha__
1060  
1061  /*
1062   * For backward compatibility?  Maybe this should be moved
1063   * into arch/i386 instead?
1064   */
1065  asmlinkage long sys_creat(const char __user * pathname, int mode)
1066  {
1067  	return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1068  }
1069  
1070  #endif
1071  
1072  /*
1073   * "id" is the POSIX thread ID. We use the
1074   * files pointer for this..
1075   */
1076  int filp_close(struct file *filp, fl_owner_t id)
1077  {
1078  	int retval = 0;
1079  
1080  	if (!file_count(filp)) {
1081  		printk(KERN_ERR "VFS: Close: file count is 0\n");
1082  		return 0;
1083  	}
1084  
1085  	if (filp->f_op && filp->f_op->flush)
1086  		retval = filp->f_op->flush(filp, id);
1087  
1088  	dnotify_flush(filp, id);
1089  	locks_remove_posix(filp, id);
1090  	fput(filp);
1091  	return retval;
1092  }
1093  
1094  EXPORT_SYMBOL(filp_close);
1095  
1096  /*
1097   * Careful here! We test whether the file pointer is NULL before
1098   * releasing the fd. This ensures that one clone task can't release
1099   * an fd while another clone is opening it.
1100   */
1101  asmlinkage long sys_close(unsigned int fd)
1102  {
1103  	struct file * filp;
1104  	struct files_struct *files = current->files;
1105  	struct fdtable *fdt;
1106  	int retval;
1107  
1108  	spin_lock(&files->file_lock);
1109  	fdt = files_fdtable(files);
1110  	if (fd >= fdt->max_fds)
1111  		goto out_unlock;
1112  	filp = fdt->fd[fd];
1113  	if (!filp)
1114  		goto out_unlock;
1115  	rcu_assign_pointer(fdt->fd[fd], NULL);
1116  	FD_CLR(fd, fdt->close_on_exec);
1117  	__put_unused_fd(files, fd);
1118  	spin_unlock(&files->file_lock);
1119  	retval = filp_close(filp, files);
1120  
1121  	/* can't restart close syscall because file table entry was cleared */
1122  	if (unlikely(retval == -ERESTARTSYS ||
1123  		     retval == -ERESTARTNOINTR ||
1124  		     retval == -ERESTARTNOHAND ||
1125  		     retval == -ERESTART_RESTARTBLOCK))
1126  		retval = -EINTR;
1127  
1128  	return retval;
1129  
1130  out_unlock:
1131  	spin_unlock(&files->file_lock);
1132  	return -EBADF;
1133  }
1134  
1135  EXPORT_SYMBOL(sys_close);
1136  
1137  /*
1138   * This routine simulates a hangup on the tty, to arrange that users
1139   * are given clean terminals at login time.
1140   */
1141  asmlinkage long sys_vhangup(void)
1142  {
1143  	if (capable(CAP_SYS_TTY_CONFIG)) {
1144  		tty_vhangup_self();
1145  		return 0;
1146  	}
1147  	return -EPERM;
1148  }
1149  
1150  /*
1151   * Called when an inode is about to be open.
1152   * We use this to disallow opening large files on 32bit systems if
1153   * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1154   * on this flag in sys_open.
1155   */
1156  int generic_file_open(struct inode * inode, struct file * filp)
1157  {
1158  	if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1159  		return -EOVERFLOW;
1160  	return 0;
1161  }
1162  
1163  EXPORT_SYMBOL(generic_file_open);
1164  
1165  /*
1166   * This is used by subsystems that don't want seekable
1167   * file descriptors
1168   */
1169  int nonseekable_open(struct inode *inode, struct file *filp)
1170  {
1171  	filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1172  	return 0;
1173  }
1174  
1175  EXPORT_SYMBOL(nonseekable_open);
1176