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TOMOYO Linux Cross Reference
Linux/fs/open.c

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  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/fsnotify.h>
 12 #include <linux/module.h>
 13 #include <linux/tty.h>
 14 #include <linux/namei.h>
 15 #include <linux/backing-dev.h>
 16 #include <linux/capability.h>
 17 #include <linux/securebits.h>
 18 #include <linux/security.h>
 19 #include <linux/mount.h>
 20 #include <linux/fcntl.h>
 21 #include <linux/slab.h>
 22 #include <linux/uaccess.h>
 23 #include <linux/fs.h>
 24 #include <linux/personality.h>
 25 #include <linux/pagemap.h>
 26 #include <linux/syscalls.h>
 27 #include <linux/rcupdate.h>
 28 #include <linux/audit.h>
 29 #include <linux/falloc.h>
 30 #include <linux/fs_struct.h>
 31 #include <linux/ima.h>
 32 #include <linux/dnotify.h>
 33 #include <linux/compat.h>
 34 
 35 #include "internal.h"
 36 
 37 int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
 38         struct file *filp)
 39 {
 40         int ret;
 41         struct iattr newattrs;
 42 
 43         /* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
 44         if (length < 0)
 45                 return -EINVAL;
 46 
 47         newattrs.ia_size = length;
 48         newattrs.ia_valid = ATTR_SIZE | time_attrs;
 49         if (filp) {
 50                 newattrs.ia_file = filp;
 51                 newattrs.ia_valid |= ATTR_FILE;
 52         }
 53 
 54         /* Remove suid, sgid, and file capabilities on truncate too */
 55         ret = dentry_needs_remove_privs(dentry);
 56         if (ret < 0)
 57                 return ret;
 58         if (ret)
 59                 newattrs.ia_valid |= ret | ATTR_FORCE;
 60 
 61         inode_lock(dentry->d_inode);
 62         /* Note any delegations or leases have already been broken: */
 63         ret = notify_change(dentry, &newattrs, NULL);
 64         inode_unlock(dentry->d_inode);
 65         return ret;
 66 }
 67 
 68 long vfs_truncate(const struct path *path, loff_t length)
 69 {
 70         struct inode *inode;
 71         long error;
 72 
 73         inode = path->dentry->d_inode;
 74 
 75         /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
 76         if (S_ISDIR(inode->i_mode))
 77                 return -EISDIR;
 78         if (!S_ISREG(inode->i_mode))
 79                 return -EINVAL;
 80 
 81         error = mnt_want_write(path->mnt);
 82         if (error)
 83                 goto out;
 84 
 85         error = inode_permission(inode, MAY_WRITE);
 86         if (error)
 87                 goto mnt_drop_write_and_out;
 88 
 89         error = -EPERM;
 90         if (IS_APPEND(inode))
 91                 goto mnt_drop_write_and_out;
 92 
 93         error = get_write_access(inode);
 94         if (error)
 95                 goto mnt_drop_write_and_out;
 96 
 97         /*
 98          * Make sure that there are no leases.  get_write_access() protects
 99          * against the truncate racing with a lease-granting setlease().
100          */
101         error = break_lease(inode, O_WRONLY);
102         if (error)
103                 goto put_write_and_out;
104 
105         error = locks_verify_truncate(inode, NULL, length);
106         if (!error)
107                 error = security_path_truncate(path);
108         if (!error)
109                 error = do_truncate(path->dentry, length, 0, NULL);
110 
111 put_write_and_out:
112         put_write_access(inode);
113 mnt_drop_write_and_out:
114         mnt_drop_write(path->mnt);
115 out:
116         return error;
117 }
118 EXPORT_SYMBOL_GPL(vfs_truncate);
119 
120 long do_sys_truncate(const char __user *pathname, loff_t length)
121 {
122         unsigned int lookup_flags = LOOKUP_FOLLOW;
123         struct path path;
124         int error;
125 
126         if (length < 0) /* sorry, but loff_t says... */
127                 return -EINVAL;
128 
129 retry:
130         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
131         if (!error) {
132                 error = vfs_truncate(&path, length);
133                 path_put(&path);
134         }
135         if (retry_estale(error, lookup_flags)) {
136                 lookup_flags |= LOOKUP_REVAL;
137                 goto retry;
138         }
139         return error;
140 }
141 
142 SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
143 {
144         return do_sys_truncate(path, length);
145 }
146 
147 #ifdef CONFIG_COMPAT
148 COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
149 {
150         return do_sys_truncate(path, length);
151 }
152 #endif
153 
154 long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
155 {
156         struct inode *inode;
157         struct dentry *dentry;
158         struct fd f;
159         int error;
160 
161         error = -EINVAL;
162         if (length < 0)
163                 goto out;
164         error = -EBADF;
165         f = fdget(fd);
166         if (!f.file)
167                 goto out;
168 
169         /* explicitly opened as large or we are on 64-bit box */
170         if (f.file->f_flags & O_LARGEFILE)
171                 small = 0;
172 
173         dentry = f.file->f_path.dentry;
174         inode = dentry->d_inode;
175         error = -EINVAL;
176         if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
177                 goto out_putf;
178 
179         error = -EINVAL;
180         /* Cannot ftruncate over 2^31 bytes without large file support */
181         if (small && length > MAX_NON_LFS)
182                 goto out_putf;
183 
184         error = -EPERM;
185         /* Check IS_APPEND on real upper inode */
186         if (IS_APPEND(file_inode(f.file)))
187                 goto out_putf;
188 
189         sb_start_write(inode->i_sb);
190         error = locks_verify_truncate(inode, f.file, length);
191         if (!error)
192                 error = security_path_truncate(&f.file->f_path);
193         if (!error)
194                 error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, f.file);
195         sb_end_write(inode->i_sb);
196 out_putf:
197         fdput(f);
198 out:
199         return error;
200 }
201 
202 SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
203 {
204         return do_sys_ftruncate(fd, length, 1);
205 }
206 
207 #ifdef CONFIG_COMPAT
208 COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length)
209 {
210         return do_sys_ftruncate(fd, length, 1);
211 }
212 #endif
213 
214 /* LFS versions of truncate are only needed on 32 bit machines */
215 #if BITS_PER_LONG == 32
216 SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
217 {
218         return do_sys_truncate(path, length);
219 }
220 
221 SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
222 {
223         return do_sys_ftruncate(fd, length, 0);
224 }
225 #endif /* BITS_PER_LONG == 32 */
226 
227 
228 int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
229 {
230         struct inode *inode = file_inode(file);
231         long ret;
232 
233         if (offset < 0 || len <= 0)
234                 return -EINVAL;
235 
236         /* Return error if mode is not supported */
237         if (mode & ~FALLOC_FL_SUPPORTED_MASK)
238                 return -EOPNOTSUPP;
239 
240         /* Punch hole and zero range are mutually exclusive */
241         if ((mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) ==
242             (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE))
243                 return -EOPNOTSUPP;
244 
245         /* Punch hole must have keep size set */
246         if ((mode & FALLOC_FL_PUNCH_HOLE) &&
247             !(mode & FALLOC_FL_KEEP_SIZE))
248                 return -EOPNOTSUPP;
249 
250         /* Collapse range should only be used exclusively. */
251         if ((mode & FALLOC_FL_COLLAPSE_RANGE) &&
252             (mode & ~FALLOC_FL_COLLAPSE_RANGE))
253                 return -EINVAL;
254 
255         /* Insert range should only be used exclusively. */
256         if ((mode & FALLOC_FL_INSERT_RANGE) &&
257             (mode & ~FALLOC_FL_INSERT_RANGE))
258                 return -EINVAL;
259 
260         /* Unshare range should only be used with allocate mode. */
261         if ((mode & FALLOC_FL_UNSHARE_RANGE) &&
262             (mode & ~(FALLOC_FL_UNSHARE_RANGE | FALLOC_FL_KEEP_SIZE)))
263                 return -EINVAL;
264 
265         if (!(file->f_mode & FMODE_WRITE))
266                 return -EBADF;
267 
268         /*
269          * We can only allow pure fallocate on append only files
270          */
271         if ((mode & ~FALLOC_FL_KEEP_SIZE) && IS_APPEND(inode))
272                 return -EPERM;
273 
274         if (IS_IMMUTABLE(inode))
275                 return -EPERM;
276 
277         /*
278          * We cannot allow any fallocate operation on an active swapfile
279          */
280         if (IS_SWAPFILE(inode))
281                 return -ETXTBSY;
282 
283         /*
284          * Revalidate the write permissions, in case security policy has
285          * changed since the files were opened.
286          */
287         ret = security_file_permission(file, MAY_WRITE);
288         if (ret)
289                 return ret;
290 
291         if (S_ISFIFO(inode->i_mode))
292                 return -ESPIPE;
293 
294         if (S_ISDIR(inode->i_mode))
295                 return -EISDIR;
296 
297         if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
298                 return -ENODEV;
299 
300         /* Check for wrap through zero too */
301         if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
302                 return -EFBIG;
303 
304         if (!file->f_op->fallocate)
305                 return -EOPNOTSUPP;
306 
307         file_start_write(file);
308         ret = file->f_op->fallocate(file, mode, offset, len);
309 
310         /*
311          * Create inotify and fanotify events.
312          *
313          * To keep the logic simple always create events if fallocate succeeds.
314          * This implies that events are even created if the file size remains
315          * unchanged, e.g. when using flag FALLOC_FL_KEEP_SIZE.
316          */
317         if (ret == 0)
318                 fsnotify_modify(file);
319 
320         file_end_write(file);
321         return ret;
322 }
323 EXPORT_SYMBOL_GPL(vfs_fallocate);
324 
325 int ksys_fallocate(int fd, int mode, loff_t offset, loff_t len)
326 {
327         struct fd f = fdget(fd);
328         int error = -EBADF;
329 
330         if (f.file) {
331                 error = vfs_fallocate(f.file, mode, offset, len);
332                 fdput(f);
333         }
334         return error;
335 }
336 
337 SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
338 {
339         return ksys_fallocate(fd, mode, offset, len);
340 }
341 
342 /*
343  * access() needs to use the real uid/gid, not the effective uid/gid.
344  * We do this by temporarily clearing all FS-related capabilities and
345  * switching the fsuid/fsgid around to the real ones.
346  */
347 long do_faccessat(int dfd, const char __user *filename, int mode)
348 {
349         const struct cred *old_cred;
350         struct cred *override_cred;
351         struct path path;
352         struct inode *inode;
353         int res;
354         unsigned int lookup_flags = LOOKUP_FOLLOW;
355 
356         if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
357                 return -EINVAL;
358 
359         override_cred = prepare_creds();
360         if (!override_cred)
361                 return -ENOMEM;
362 
363         override_cred->fsuid = override_cred->uid;
364         override_cred->fsgid = override_cred->gid;
365 
366         if (!issecure(SECURE_NO_SETUID_FIXUP)) {
367                 /* Clear the capabilities if we switch to a non-root user */
368                 kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
369                 if (!uid_eq(override_cred->uid, root_uid))
370                         cap_clear(override_cred->cap_effective);
371                 else
372                         override_cred->cap_effective =
373                                 override_cred->cap_permitted;
374         }
375 
376         old_cred = override_creds(override_cred);
377 retry:
378         res = user_path_at(dfd, filename, lookup_flags, &path);
379         if (res)
380                 goto out;
381 
382         inode = d_backing_inode(path.dentry);
383 
384         if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
385                 /*
386                  * MAY_EXEC on regular files is denied if the fs is mounted
387                  * with the "noexec" flag.
388                  */
389                 res = -EACCES;
390                 if (path_noexec(&path))
391                         goto out_path_release;
392         }
393 
394         res = inode_permission(inode, mode | MAY_ACCESS);
395         /* SuS v2 requires we report a read only fs too */
396         if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
397                 goto out_path_release;
398         /*
399          * This is a rare case where using __mnt_is_readonly()
400          * is OK without a mnt_want/drop_write() pair.  Since
401          * no actual write to the fs is performed here, we do
402          * not need to telegraph to that to anyone.
403          *
404          * By doing this, we accept that this access is
405          * inherently racy and know that the fs may change
406          * state before we even see this result.
407          */
408         if (__mnt_is_readonly(path.mnt))
409                 res = -EROFS;
410 
411 out_path_release:
412         path_put(&path);
413         if (retry_estale(res, lookup_flags)) {
414                 lookup_flags |= LOOKUP_REVAL;
415                 goto retry;
416         }
417 out:
418         revert_creds(old_cred);
419         put_cred(override_cred);
420         return res;
421 }
422 
423 SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
424 {
425         return do_faccessat(dfd, filename, mode);
426 }
427 
428 SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
429 {
430         return do_faccessat(AT_FDCWD, filename, mode);
431 }
432 
433 int ksys_chdir(const char __user *filename)
434 {
435         struct path path;
436         int error;
437         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
438 retry:
439         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
440         if (error)
441                 goto out;
442 
443         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
444         if (error)
445                 goto dput_and_out;
446 
447         set_fs_pwd(current->fs, &path);
448 
449 dput_and_out:
450         path_put(&path);
451         if (retry_estale(error, lookup_flags)) {
452                 lookup_flags |= LOOKUP_REVAL;
453                 goto retry;
454         }
455 out:
456         return error;
457 }
458 
459 SYSCALL_DEFINE1(chdir, const char __user *, filename)
460 {
461         return ksys_chdir(filename);
462 }
463 
464 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
465 {
466         struct fd f = fdget_raw(fd);
467         int error;
468 
469         error = -EBADF;
470         if (!f.file)
471                 goto out;
472 
473         error = -ENOTDIR;
474         if (!d_can_lookup(f.file->f_path.dentry))
475                 goto out_putf;
476 
477         error = inode_permission(file_inode(f.file), MAY_EXEC | MAY_CHDIR);
478         if (!error)
479                 set_fs_pwd(current->fs, &f.file->f_path);
480 out_putf:
481         fdput(f);
482 out:
483         return error;
484 }
485 
486 int ksys_chroot(const char __user *filename)
487 {
488         struct path path;
489         int error;
490         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
491 retry:
492         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
493         if (error)
494                 goto out;
495 
496         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
497         if (error)
498                 goto dput_and_out;
499 
500         error = -EPERM;
501         if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
502                 goto dput_and_out;
503         error = security_path_chroot(&path);
504         if (error)
505                 goto dput_and_out;
506 
507         set_fs_root(current->fs, &path);
508         error = 0;
509 dput_and_out:
510         path_put(&path);
511         if (retry_estale(error, lookup_flags)) {
512                 lookup_flags |= LOOKUP_REVAL;
513                 goto retry;
514         }
515 out:
516         return error;
517 }
518 
519 SYSCALL_DEFINE1(chroot, const char __user *, filename)
520 {
521         return ksys_chroot(filename);
522 }
523 
524 static int chmod_common(const struct path *path, umode_t mode)
525 {
526         struct inode *inode = path->dentry->d_inode;
527         struct inode *delegated_inode = NULL;
528         struct iattr newattrs;
529         int error;
530 
531         error = mnt_want_write(path->mnt);
532         if (error)
533                 return error;
534 retry_deleg:
535         inode_lock(inode);
536         error = security_path_chmod(path, mode);
537         if (error)
538                 goto out_unlock;
539         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
540         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
541         error = notify_change(path->dentry, &newattrs, &delegated_inode);
542 out_unlock:
543         inode_unlock(inode);
544         if (delegated_inode) {
545                 error = break_deleg_wait(&delegated_inode);
546                 if (!error)
547                         goto retry_deleg;
548         }
549         mnt_drop_write(path->mnt);
550         return error;
551 }
552 
553 int ksys_fchmod(unsigned int fd, umode_t mode)
554 {
555         struct fd f = fdget(fd);
556         int err = -EBADF;
557 
558         if (f.file) {
559                 audit_file(f.file);
560                 err = chmod_common(&f.file->f_path, mode);
561                 fdput(f);
562         }
563         return err;
564 }
565 
566 SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
567 {
568         return ksys_fchmod(fd, mode);
569 }
570 
571 int do_fchmodat(int dfd, const char __user *filename, umode_t mode)
572 {
573         struct path path;
574         int error;
575         unsigned int lookup_flags = LOOKUP_FOLLOW;
576 retry:
577         error = user_path_at(dfd, filename, lookup_flags, &path);
578         if (!error) {
579                 error = chmod_common(&path, mode);
580                 path_put(&path);
581                 if (retry_estale(error, lookup_flags)) {
582                         lookup_flags |= LOOKUP_REVAL;
583                         goto retry;
584                 }
585         }
586         return error;
587 }
588 
589 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename,
590                 umode_t, mode)
591 {
592         return do_fchmodat(dfd, filename, mode);
593 }
594 
595 SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
596 {
597         return do_fchmodat(AT_FDCWD, filename, mode);
598 }
599 
600 static int chown_common(const struct path *path, uid_t user, gid_t group)
601 {
602         struct inode *inode = path->dentry->d_inode;
603         struct inode *delegated_inode = NULL;
604         int error;
605         struct iattr newattrs;
606         kuid_t uid;
607         kgid_t gid;
608 
609         uid = make_kuid(current_user_ns(), user);
610         gid = make_kgid(current_user_ns(), group);
611 
612 retry_deleg:
613         newattrs.ia_valid =  ATTR_CTIME;
614         if (user != (uid_t) -1) {
615                 if (!uid_valid(uid))
616                         return -EINVAL;
617                 newattrs.ia_valid |= ATTR_UID;
618                 newattrs.ia_uid = uid;
619         }
620         if (group != (gid_t) -1) {
621                 if (!gid_valid(gid))
622                         return -EINVAL;
623                 newattrs.ia_valid |= ATTR_GID;
624                 newattrs.ia_gid = gid;
625         }
626         if (!S_ISDIR(inode->i_mode))
627                 newattrs.ia_valid |=
628                         ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
629         inode_lock(inode);
630         error = security_path_chown(path, uid, gid);
631         if (!error)
632                 error = notify_change(path->dentry, &newattrs, &delegated_inode);
633         inode_unlock(inode);
634         if (delegated_inode) {
635                 error = break_deleg_wait(&delegated_inode);
636                 if (!error)
637                         goto retry_deleg;
638         }
639         return error;
640 }
641 
642 int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
643                 int flag)
644 {
645         struct path path;
646         int error = -EINVAL;
647         int lookup_flags;
648 
649         if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
650                 goto out;
651 
652         lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
653         if (flag & AT_EMPTY_PATH)
654                 lookup_flags |= LOOKUP_EMPTY;
655 retry:
656         error = user_path_at(dfd, filename, lookup_flags, &path);
657         if (error)
658                 goto out;
659         error = mnt_want_write(path.mnt);
660         if (error)
661                 goto out_release;
662         error = chown_common(&path, user, group);
663         mnt_drop_write(path.mnt);
664 out_release:
665         path_put(&path);
666         if (retry_estale(error, lookup_flags)) {
667                 lookup_flags |= LOOKUP_REVAL;
668                 goto retry;
669         }
670 out:
671         return error;
672 }
673 
674 SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
675                 gid_t, group, int, flag)
676 {
677         return do_fchownat(dfd, filename, user, group, flag);
678 }
679 
680 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
681 {
682         return do_fchownat(AT_FDCWD, filename, user, group, 0);
683 }
684 
685 SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
686 {
687         return do_fchownat(AT_FDCWD, filename, user, group,
688                            AT_SYMLINK_NOFOLLOW);
689 }
690 
691 int ksys_fchown(unsigned int fd, uid_t user, gid_t group)
692 {
693         struct fd f = fdget(fd);
694         int error = -EBADF;
695 
696         if (!f.file)
697                 goto out;
698 
699         error = mnt_want_write_file(f.file);
700         if (error)
701                 goto out_fput;
702         audit_file(f.file);
703         error = chown_common(&f.file->f_path, user, group);
704         mnt_drop_write_file(f.file);
705 out_fput:
706         fdput(f);
707 out:
708         return error;
709 }
710 
711 SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
712 {
713         return ksys_fchown(fd, user, group);
714 }
715 
716 static int do_dentry_open(struct file *f,
717                           struct inode *inode,
718                           int (*open)(struct inode *, struct file *))
719 {
720         static const struct file_operations empty_fops = {};
721         int error;
722 
723         path_get(&f->f_path);
724         f->f_inode = inode;
725         f->f_mapping = inode->i_mapping;
726 
727         /* Ensure that we skip any errors that predate opening of the file */
728         f->f_wb_err = filemap_sample_wb_err(f->f_mapping);
729 
730         if (unlikely(f->f_flags & O_PATH)) {
731                 f->f_mode = FMODE_PATH | FMODE_OPENED;
732                 f->f_op = &empty_fops;
733                 return 0;
734         }
735 
736         if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
737                 error = get_write_access(inode);
738                 if (unlikely(error))
739                         goto cleanup_file;
740                 error = __mnt_want_write(f->f_path.mnt);
741                 if (unlikely(error)) {
742                         put_write_access(inode);
743                         goto cleanup_file;
744                 }
745                 f->f_mode |= FMODE_WRITER;
746         }
747 
748         /* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
749         if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))
750                 f->f_mode |= FMODE_ATOMIC_POS;
751 
752         f->f_op = fops_get(inode->i_fop);
753         if (unlikely(WARN_ON(!f->f_op))) {
754                 error = -ENODEV;
755                 goto cleanup_all;
756         }
757 
758         error = security_file_open(f);
759         if (error)
760                 goto cleanup_all;
761 
762         error = break_lease(locks_inode(f), f->f_flags);
763         if (error)
764                 goto cleanup_all;
765 
766         /* normally all 3 are set; ->open() can clear them if needed */
767         f->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
768         if (!open)
769                 open = f->f_op->open;
770         if (open) {
771                 error = open(inode, f);
772                 if (error)
773                         goto cleanup_all;
774         }
775         f->f_mode |= FMODE_OPENED;
776         if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
777                 i_readcount_inc(inode);
778         if ((f->f_mode & FMODE_READ) &&
779              likely(f->f_op->read || f->f_op->read_iter))
780                 f->f_mode |= FMODE_CAN_READ;
781         if ((f->f_mode & FMODE_WRITE) &&
782              likely(f->f_op->write || f->f_op->write_iter))
783                 f->f_mode |= FMODE_CAN_WRITE;
784 
785         f->f_write_hint = WRITE_LIFE_NOT_SET;
786         f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
787 
788         file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
789 
790         /* NB: we're sure to have correct a_ops only after f_op->open */
791         if (f->f_flags & O_DIRECT) {
792                 if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO)
793                         return -EINVAL;
794         }
795         return 0;
796 
797 cleanup_all:
798         if (WARN_ON_ONCE(error > 0))
799                 error = -EINVAL;
800         fops_put(f->f_op);
801         if (f->f_mode & FMODE_WRITER) {
802                 put_write_access(inode);
803                 __mnt_drop_write(f->f_path.mnt);
804         }
805 cleanup_file:
806         path_put(&f->f_path);
807         f->f_path.mnt = NULL;
808         f->f_path.dentry = NULL;
809         f->f_inode = NULL;
810         return error;
811 }
812 
813 /**
814  * finish_open - finish opening a file
815  * @file: file pointer
816  * @dentry: pointer to dentry
817  * @open: open callback
818  * @opened: state of open
819  *
820  * This can be used to finish opening a file passed to i_op->atomic_open().
821  *
822  * If the open callback is set to NULL, then the standard f_op->open()
823  * filesystem callback is substituted.
824  *
825  * NB: the dentry reference is _not_ consumed.  If, for example, the dentry is
826  * the return value of d_splice_alias(), then the caller needs to perform dput()
827  * on it after finish_open().
828  *
829  * On successful return @file is a fully instantiated open file.  After this, if
830  * an error occurs in ->atomic_open(), it needs to clean up with fput().
831  *
832  * Returns zero on success or -errno if the open failed.
833  */
834 int finish_open(struct file *file, struct dentry *dentry,
835                 int (*open)(struct inode *, struct file *))
836 {
837         BUG_ON(file->f_mode & FMODE_OPENED); /* once it's opened, it's opened */
838 
839         file->f_path.dentry = dentry;
840         return do_dentry_open(file, d_backing_inode(dentry), open);
841 }
842 EXPORT_SYMBOL(finish_open);
843 
844 /**
845  * finish_no_open - finish ->atomic_open() without opening the file
846  *
847  * @file: file pointer
848  * @dentry: dentry or NULL (as returned from ->lookup())
849  *
850  * This can be used to set the result of a successful lookup in ->atomic_open().
851  *
852  * NB: unlike finish_open() this function does consume the dentry reference and
853  * the caller need not dput() it.
854  *
855  * Returns "" which must be the return value of ->atomic_open() after having
856  * called this function.
857  */
858 int finish_no_open(struct file *file, struct dentry *dentry)
859 {
860         file->f_path.dentry = dentry;
861         return 0;
862 }
863 EXPORT_SYMBOL(finish_no_open);
864 
865 char *file_path(struct file *filp, char *buf, int buflen)
866 {
867         return d_path(&filp->f_path, buf, buflen);
868 }
869 EXPORT_SYMBOL(file_path);
870 
871 /**
872  * vfs_open - open the file at the given path
873  * @path: path to open
874  * @file: newly allocated file with f_flag initialized
875  * @cred: credentials to use
876  */
877 int vfs_open(const struct path *path, struct file *file)
878 {
879         file->f_path = *path;
880         return do_dentry_open(file, d_backing_inode(path->dentry), NULL);
881 }
882 
883 struct file *dentry_open(const struct path *path, int flags,
884                          const struct cred *cred)
885 {
886         int error;
887         struct file *f;
888 
889         validate_creds(cred);
890 
891         /* We must always pass in a valid mount pointer. */
892         BUG_ON(!path->mnt);
893 
894         f = alloc_empty_file(flags, cred);
895         if (!IS_ERR(f)) {
896                 error = vfs_open(path, f);
897                 if (error) {
898                         fput(f);
899                         f = ERR_PTR(error);
900                 }
901         }
902         return f;
903 }
904 EXPORT_SYMBOL(dentry_open);
905 
906 struct file *open_with_fake_path(const struct path *path, int flags,
907                                 struct inode *inode, const struct cred *cred)
908 {
909         struct file *f = alloc_empty_file_noaccount(flags, cred);
910         if (!IS_ERR(f)) {
911                 int error;
912 
913                 f->f_path = *path;
914                 error = do_dentry_open(f, inode, NULL);
915                 if (error) {
916                         fput(f);
917                         f = ERR_PTR(error);
918                 }
919         }
920         return f;
921 }
922 EXPORT_SYMBOL(open_with_fake_path);
923 
924 static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
925 {
926         int lookup_flags = 0;
927         int acc_mode = ACC_MODE(flags);
928 
929         /*
930          * Clear out all open flags we don't know about so that we don't report
931          * them in fcntl(F_GETFD) or similar interfaces.
932          */
933         flags &= VALID_OPEN_FLAGS;
934 
935         if (flags & (O_CREAT | __O_TMPFILE))
936                 op->mode = (mode & S_IALLUGO) | S_IFREG;
937         else
938                 op->mode = 0;
939 
940         /* Must never be set by userspace */
941         flags &= ~FMODE_NONOTIFY & ~O_CLOEXEC;
942 
943         /*
944          * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
945          * check for O_DSYNC if the need any syncing at all we enforce it's
946          * always set instead of having to deal with possibly weird behaviour
947          * for malicious applications setting only __O_SYNC.
948          */
949         if (flags & __O_SYNC)
950                 flags |= O_DSYNC;
951 
952         if (flags & __O_TMPFILE) {
953                 if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
954                         return -EINVAL;
955                 if (!(acc_mode & MAY_WRITE))
956                         return -EINVAL;
957         } else if (flags & O_PATH) {
958                 /*
959                  * If we have O_PATH in the open flag. Then we
960                  * cannot have anything other than the below set of flags
961                  */
962                 flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
963                 acc_mode = 0;
964         }
965 
966         op->open_flag = flags;
967 
968         /* O_TRUNC implies we need access checks for write permissions */
969         if (flags & O_TRUNC)
970                 acc_mode |= MAY_WRITE;
971 
972         /* Allow the LSM permission hook to distinguish append
973            access from general write access. */
974         if (flags & O_APPEND)
975                 acc_mode |= MAY_APPEND;
976 
977         op->acc_mode = acc_mode;
978 
979         op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
980 
981         if (flags & O_CREAT) {
982                 op->intent |= LOOKUP_CREATE;
983                 if (flags & O_EXCL)
984                         op->intent |= LOOKUP_EXCL;
985         }
986 
987         if (flags & O_DIRECTORY)
988                 lookup_flags |= LOOKUP_DIRECTORY;
989         if (!(flags & O_NOFOLLOW))
990                 lookup_flags |= LOOKUP_FOLLOW;
991         op->lookup_flags = lookup_flags;
992         return 0;
993 }
994 
995 /**
996  * file_open_name - open file and return file pointer
997  *
998  * @name:       struct filename containing path to open
999  * @flags:      open flags as per the open(2) second argument
1000  * @mode:       mode for the new file if O_CREAT is set, else ignored
1001  *
1002  * This is the helper to open a file from kernelspace if you really
1003  * have to.  But in generally you should not do this, so please move
1004  * along, nothing to see here..
1005  */
1006 struct file *file_open_name(struct filename *name, int flags, umode_t mode)
1007 {
1008         struct open_flags op;
1009         int err = build_open_flags(flags, mode, &op);
1010         return err ? ERR_PTR(err) : do_filp_open(AT_FDCWD, name, &op);
1011 }
1012 
1013 /**
1014  * filp_open - open file and return file pointer
1015  *
1016  * @filename:   path to open
1017  * @flags:      open flags as per the open(2) second argument
1018  * @mode:       mode for the new file if O_CREAT is set, else ignored
1019  *
1020  * This is the helper to open a file from kernelspace if you really
1021  * have to.  But in generally you should not do this, so please move
1022  * along, nothing to see here..
1023  */
1024 struct file *filp_open(const char *filename, int flags, umode_t mode)
1025 {
1026         struct filename *name = getname_kernel(filename);
1027         struct file *file = ERR_CAST(name);
1028         
1029         if (!IS_ERR(name)) {
1030                 file = file_open_name(name, flags, mode);
1031                 putname(name);
1032         }
1033         return file;
1034 }
1035 EXPORT_SYMBOL(filp_open);
1036 
1037 struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
1038                             const char *filename, int flags, umode_t mode)
1039 {
1040         struct open_flags op;
1041         int err = build_open_flags(flags, mode, &op);
1042         if (err)
1043                 return ERR_PTR(err);
1044         return do_file_open_root(dentry, mnt, filename, &op);
1045 }
1046 EXPORT_SYMBOL(file_open_root);
1047 
1048 long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
1049 {
1050         struct open_flags op;
1051         int fd = build_open_flags(flags, mode, &op);
1052         struct filename *tmp;
1053 
1054         if (fd)
1055                 return fd;
1056 
1057         tmp = getname(filename);
1058         if (IS_ERR(tmp))
1059                 return PTR_ERR(tmp);
1060 
1061         fd = get_unused_fd_flags(flags);
1062         if (fd >= 0) {
1063                 struct file *f = do_filp_open(dfd, tmp, &op);
1064                 if (IS_ERR(f)) {
1065                         put_unused_fd(fd);
1066                         fd = PTR_ERR(f);
1067                 } else {
1068                         fsnotify_open(f);
1069                         fd_install(fd, f);
1070                 }
1071         }
1072         putname(tmp);
1073         return fd;
1074 }
1075 
1076 SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1077 {
1078         if (force_o_largefile())
1079                 flags |= O_LARGEFILE;
1080 
1081         return do_sys_open(AT_FDCWD, filename, flags, mode);
1082 }
1083 
1084 SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1085                 umode_t, mode)
1086 {
1087         if (force_o_largefile())
1088                 flags |= O_LARGEFILE;
1089 
1090         return do_sys_open(dfd, filename, flags, mode);
1091 }
1092 
1093 #ifdef CONFIG_COMPAT
1094 /*
1095  * Exactly like sys_open(), except that it doesn't set the
1096  * O_LARGEFILE flag.
1097  */
1098 COMPAT_SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1099 {
1100         return do_sys_open(AT_FDCWD, filename, flags, mode);
1101 }
1102 
1103 /*
1104  * Exactly like sys_openat(), except that it doesn't set the
1105  * O_LARGEFILE flag.
1106  */
1107 COMPAT_SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags, umode_t, mode)
1108 {
1109         return do_sys_open(dfd, filename, flags, mode);
1110 }
1111 #endif
1112 
1113 #ifndef __alpha__
1114 
1115 /*
1116  * For backward compatibility?  Maybe this should be moved
1117  * into arch/i386 instead?
1118  */
1119 SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1120 {
1121         return ksys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1122 }
1123 
1124 #endif
1125 
1126 /*
1127  * "id" is the POSIX thread ID. We use the
1128  * files pointer for this..
1129  */
1130 int filp_close(struct file *filp, fl_owner_t id)
1131 {
1132         int retval = 0;
1133 
1134         if (!file_count(filp)) {
1135                 printk(KERN_ERR "VFS: Close: file count is 0\n");
1136                 return 0;
1137         }
1138 
1139         if (filp->f_op->flush)
1140                 retval = filp->f_op->flush(filp, id);
1141 
1142         if (likely(!(filp->f_mode & FMODE_PATH))) {
1143                 dnotify_flush(filp, id);
1144                 locks_remove_posix(filp, id);
1145         }
1146         fput(filp);
1147         return retval;
1148 }
1149 
1150 EXPORT_SYMBOL(filp_close);
1151 
1152 /*
1153  * Careful here! We test whether the file pointer is NULL before
1154  * releasing the fd. This ensures that one clone task can't release
1155  * an fd while another clone is opening it.
1156  */
1157 SYSCALL_DEFINE1(close, unsigned int, fd)
1158 {
1159         int retval = __close_fd(current->files, fd);
1160 
1161         /* can't restart close syscall because file table entry was cleared */
1162         if (unlikely(retval == -ERESTARTSYS ||
1163                      retval == -ERESTARTNOINTR ||
1164                      retval == -ERESTARTNOHAND ||
1165                      retval == -ERESTART_RESTARTBLOCK))
1166                 retval = -EINTR;
1167 
1168         return retval;
1169 }
1170 
1171 /*
1172  * This routine simulates a hangup on the tty, to arrange that users
1173  * are given clean terminals at login time.
1174  */
1175 SYSCALL_DEFINE0(vhangup)
1176 {
1177         if (!ccs_capable(CCS_SYS_VHANGUP))
1178                 return -EPERM;
1179         if (capable(CAP_SYS_TTY_CONFIG)) {
1180                 tty_vhangup_self();
1181                 return 0;
1182         }
1183         return -EPERM;
1184 }
1185 
1186 /*
1187  * Called when an inode is about to be open.
1188  * We use this to disallow opening large files on 32bit systems if
1189  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1190  * on this flag in sys_open.
1191  */
1192 int generic_file_open(struct inode * inode, struct file * filp)
1193 {
1194         if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1195                 return -EOVERFLOW;
1196         return 0;
1197 }
1198 
1199 EXPORT_SYMBOL(generic_file_open);
1200 
1201 /*
1202  * This is used by subsystems that don't want seekable
1203  * file descriptors. The function is not supposed to ever fail, the only
1204  * reason it returns an 'int' and not 'void' is so that it can be plugged
1205  * directly into file_operations structure.
1206  */
1207 int nonseekable_open(struct inode *inode, struct file *filp)
1208 {
1209         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1210         return 0;
1211 }
1212 
1213 EXPORT_SYMBOL(nonseekable_open);
1214 

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