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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         struct dentry *upperdentry;
 72         long error;
 73 
 74         inode = path->dentry->d_inode;
 75 
 76         /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
 77         if (S_ISDIR(inode->i_mode))
 78                 return -EISDIR;
 79         if (!S_ISREG(inode->i_mode))
 80                 return -EINVAL;
 81 
 82         error = mnt_want_write(path->mnt);
 83         if (error)
 84                 goto out;
 85 
 86         error = inode_permission(inode, MAY_WRITE);
 87         if (error)
 88                 goto mnt_drop_write_and_out;
 89 
 90         error = -EPERM;
 91         if (IS_APPEND(inode))
 92                 goto mnt_drop_write_and_out;
 93 
 94         /*
 95          * If this is an overlayfs then do as if opening the file so we get
 96          * write access on the upper inode, not on the overlay inode.  For
 97          * non-overlay filesystems d_real() is an identity function.
 98          */
 99         upperdentry = d_real(path->dentry, NULL, O_WRONLY, 0);
100         error = PTR_ERR(upperdentry);
101         if (IS_ERR(upperdentry))
102                 goto mnt_drop_write_and_out;
103 
104         error = get_write_access(upperdentry->d_inode);
105         if (error)
106                 goto mnt_drop_write_and_out;
107 
108         /*
109          * Make sure that there are no leases.  get_write_access() protects
110          * against the truncate racing with a lease-granting setlease().
111          */
112         error = break_lease(inode, O_WRONLY);
113         if (error)
114                 goto put_write_and_out;
115 
116         error = locks_verify_truncate(inode, NULL, length);
117         if (!error)
118                 error = security_path_truncate(path);
119         if (!error)
120                 error = do_truncate(path->dentry, length, 0, NULL);
121 
122 put_write_and_out:
123         put_write_access(upperdentry->d_inode);
124 mnt_drop_write_and_out:
125         mnt_drop_write(path->mnt);
126 out:
127         return error;
128 }
129 EXPORT_SYMBOL_GPL(vfs_truncate);
130 
131 long do_sys_truncate(const char __user *pathname, loff_t length)
132 {
133         unsigned int lookup_flags = LOOKUP_FOLLOW;
134         struct path path;
135         int error;
136 
137         if (length < 0) /* sorry, but loff_t says... */
138                 return -EINVAL;
139 
140 retry:
141         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
142         if (!error) {
143                 error = vfs_truncate(&path, length);
144                 path_put(&path);
145         }
146         if (retry_estale(error, lookup_flags)) {
147                 lookup_flags |= LOOKUP_REVAL;
148                 goto retry;
149         }
150         return error;
151 }
152 
153 SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
154 {
155         return do_sys_truncate(path, length);
156 }
157 
158 #ifdef CONFIG_COMPAT
159 COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
160 {
161         return do_sys_truncate(path, length);
162 }
163 #endif
164 
165 long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
166 {
167         struct inode *inode;
168         struct dentry *dentry;
169         struct fd f;
170         int error;
171 
172         error = -EINVAL;
173         if (length < 0)
174                 goto out;
175         error = -EBADF;
176         f = fdget(fd);
177         if (!f.file)
178                 goto out;
179 
180         /* explicitly opened as large or we are on 64-bit box */
181         if (f.file->f_flags & O_LARGEFILE)
182                 small = 0;
183 
184         dentry = f.file->f_path.dentry;
185         inode = dentry->d_inode;
186         error = -EINVAL;
187         if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
188                 goto out_putf;
189 
190         error = -EINVAL;
191         /* Cannot ftruncate over 2^31 bytes without large file support */
192         if (small && length > MAX_NON_LFS)
193                 goto out_putf;
194 
195         error = -EPERM;
196         /* Check IS_APPEND on real upper inode */
197         if (IS_APPEND(file_inode(f.file)))
198                 goto out_putf;
199 
200         sb_start_write(inode->i_sb);
201         error = locks_verify_truncate(inode, f.file, length);
202         if (!error)
203                 error = security_path_truncate(&f.file->f_path);
204         if (!error)
205                 error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, f.file);
206         sb_end_write(inode->i_sb);
207 out_putf:
208         fdput(f);
209 out:
210         return error;
211 }
212 
213 SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
214 {
215         return do_sys_ftruncate(fd, length, 1);
216 }
217 
218 #ifdef CONFIG_COMPAT
219 COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length)
220 {
221         return do_sys_ftruncate(fd, length, 1);
222 }
223 #endif
224 
225 /* LFS versions of truncate are only needed on 32 bit machines */
226 #if BITS_PER_LONG == 32
227 SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
228 {
229         return do_sys_truncate(path, length);
230 }
231 
232 SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
233 {
234         return do_sys_ftruncate(fd, length, 0);
235 }
236 #endif /* BITS_PER_LONG == 32 */
237 
238 
239 int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
240 {
241         struct inode *inode = file_inode(file);
242         long ret;
243 
244         if (offset < 0 || len <= 0)
245                 return -EINVAL;
246 
247         /* Return error if mode is not supported */
248         if (mode & ~FALLOC_FL_SUPPORTED_MASK)
249                 return -EOPNOTSUPP;
250 
251         /* Punch hole and zero range are mutually exclusive */
252         if ((mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) ==
253             (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE))
254                 return -EOPNOTSUPP;
255 
256         /* Punch hole must have keep size set */
257         if ((mode & FALLOC_FL_PUNCH_HOLE) &&
258             !(mode & FALLOC_FL_KEEP_SIZE))
259                 return -EOPNOTSUPP;
260 
261         /* Collapse range should only be used exclusively. */
262         if ((mode & FALLOC_FL_COLLAPSE_RANGE) &&
263             (mode & ~FALLOC_FL_COLLAPSE_RANGE))
264                 return -EINVAL;
265 
266         /* Insert range should only be used exclusively. */
267         if ((mode & FALLOC_FL_INSERT_RANGE) &&
268             (mode & ~FALLOC_FL_INSERT_RANGE))
269                 return -EINVAL;
270 
271         /* Unshare range should only be used with allocate mode. */
272         if ((mode & FALLOC_FL_UNSHARE_RANGE) &&
273             (mode & ~(FALLOC_FL_UNSHARE_RANGE | FALLOC_FL_KEEP_SIZE)))
274                 return -EINVAL;
275 
276         if (!(file->f_mode & FMODE_WRITE))
277                 return -EBADF;
278 
279         /*
280          * We can only allow pure fallocate on append only files
281          */
282         if ((mode & ~FALLOC_FL_KEEP_SIZE) && IS_APPEND(inode))
283                 return -EPERM;
284 
285         if (IS_IMMUTABLE(inode))
286                 return -EPERM;
287 
288         /*
289          * We cannot allow any fallocate operation on an active swapfile
290          */
291         if (IS_SWAPFILE(inode))
292                 return -ETXTBSY;
293 
294         /*
295          * Revalidate the write permissions, in case security policy has
296          * changed since the files were opened.
297          */
298         ret = security_file_permission(file, MAY_WRITE);
299         if (ret)
300                 return ret;
301 
302         if (S_ISFIFO(inode->i_mode))
303                 return -ESPIPE;
304 
305         if (S_ISDIR(inode->i_mode))
306                 return -EISDIR;
307 
308         if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
309                 return -ENODEV;
310 
311         /* Check for wrap through zero too */
312         if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
313                 return -EFBIG;
314 
315         if (!file->f_op->fallocate)
316                 return -EOPNOTSUPP;
317 
318         file_start_write(file);
319         ret = file->f_op->fallocate(file, mode, offset, len);
320 
321         /*
322          * Create inotify and fanotify events.
323          *
324          * To keep the logic simple always create events if fallocate succeeds.
325          * This implies that events are even created if the file size remains
326          * unchanged, e.g. when using flag FALLOC_FL_KEEP_SIZE.
327          */
328         if (ret == 0)
329                 fsnotify_modify(file);
330 
331         file_end_write(file);
332         return ret;
333 }
334 EXPORT_SYMBOL_GPL(vfs_fallocate);
335 
336 int ksys_fallocate(int fd, int mode, loff_t offset, loff_t len)
337 {
338         struct fd f = fdget(fd);
339         int error = -EBADF;
340 
341         if (f.file) {
342                 error = vfs_fallocate(f.file, mode, offset, len);
343                 fdput(f);
344         }
345         return error;
346 }
347 
348 SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
349 {
350         return ksys_fallocate(fd, mode, offset, len);
351 }
352 
353 /*
354  * access() needs to use the real uid/gid, not the effective uid/gid.
355  * We do this by temporarily clearing all FS-related capabilities and
356  * switching the fsuid/fsgid around to the real ones.
357  */
358 long do_faccessat(int dfd, const char __user *filename, int mode)
359 {
360         const struct cred *old_cred;
361         struct cred *override_cred;
362         struct path path;
363         struct inode *inode;
364         int res;
365         unsigned int lookup_flags = LOOKUP_FOLLOW;
366 
367         if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
368                 return -EINVAL;
369 
370         override_cred = prepare_creds();
371         if (!override_cred)
372                 return -ENOMEM;
373 
374         override_cred->fsuid = override_cred->uid;
375         override_cred->fsgid = override_cred->gid;
376 
377         if (!issecure(SECURE_NO_SETUID_FIXUP)) {
378                 /* Clear the capabilities if we switch to a non-root user */
379                 kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
380                 if (!uid_eq(override_cred->uid, root_uid))
381                         cap_clear(override_cred->cap_effective);
382                 else
383                         override_cred->cap_effective =
384                                 override_cred->cap_permitted;
385         }
386 
387         old_cred = override_creds(override_cred);
388 retry:
389         res = user_path_at(dfd, filename, lookup_flags, &path);
390         if (res)
391                 goto out;
392 
393         inode = d_backing_inode(path.dentry);
394 
395         if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
396                 /*
397                  * MAY_EXEC on regular files is denied if the fs is mounted
398                  * with the "noexec" flag.
399                  */
400                 res = -EACCES;
401                 if (path_noexec(&path))
402                         goto out_path_release;
403         }
404 
405         res = inode_permission(inode, mode | MAY_ACCESS);
406         /* SuS v2 requires we report a read only fs too */
407         if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
408                 goto out_path_release;
409         /*
410          * This is a rare case where using __mnt_is_readonly()
411          * is OK without a mnt_want/drop_write() pair.  Since
412          * no actual write to the fs is performed here, we do
413          * not need to telegraph to that to anyone.
414          *
415          * By doing this, we accept that this access is
416          * inherently racy and know that the fs may change
417          * state before we even see this result.
418          */
419         if (__mnt_is_readonly(path.mnt))
420                 res = -EROFS;
421 
422 out_path_release:
423         path_put(&path);
424         if (retry_estale(res, lookup_flags)) {
425                 lookup_flags |= LOOKUP_REVAL;
426                 goto retry;
427         }
428 out:
429         revert_creds(old_cred);
430         put_cred(override_cred);
431         return res;
432 }
433 
434 SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
435 {
436         return do_faccessat(dfd, filename, mode);
437 }
438 
439 SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
440 {
441         return do_faccessat(AT_FDCWD, filename, mode);
442 }
443 
444 int ksys_chdir(const char __user *filename)
445 {
446         struct path path;
447         int error;
448         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
449 retry:
450         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
451         if (error)
452                 goto out;
453 
454         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
455         if (error)
456                 goto dput_and_out;
457 
458         set_fs_pwd(current->fs, &path);
459 
460 dput_and_out:
461         path_put(&path);
462         if (retry_estale(error, lookup_flags)) {
463                 lookup_flags |= LOOKUP_REVAL;
464                 goto retry;
465         }
466 out:
467         return error;
468 }
469 
470 SYSCALL_DEFINE1(chdir, const char __user *, filename)
471 {
472         return ksys_chdir(filename);
473 }
474 
475 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
476 {
477         struct fd f = fdget_raw(fd);
478         int error;
479 
480         error = -EBADF;
481         if (!f.file)
482                 goto out;
483 
484         error = -ENOTDIR;
485         if (!d_can_lookup(f.file->f_path.dentry))
486                 goto out_putf;
487 
488         error = inode_permission(file_inode(f.file), MAY_EXEC | MAY_CHDIR);
489         if (!error)
490                 set_fs_pwd(current->fs, &f.file->f_path);
491 out_putf:
492         fdput(f);
493 out:
494         return error;
495 }
496 
497 int ksys_chroot(const char __user *filename)
498 {
499         struct path path;
500         int error;
501         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
502 retry:
503         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
504         if (error)
505                 goto out;
506 
507         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
508         if (error)
509                 goto dput_and_out;
510 
511         error = -EPERM;
512         if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
513                 goto dput_and_out;
514         error = security_path_chroot(&path);
515         if (error)
516                 goto dput_and_out;
517 
518         set_fs_root(current->fs, &path);
519         error = 0;
520 dput_and_out:
521         path_put(&path);
522         if (retry_estale(error, lookup_flags)) {
523                 lookup_flags |= LOOKUP_REVAL;
524                 goto retry;
525         }
526 out:
527         return error;
528 }
529 
530 SYSCALL_DEFINE1(chroot, const char __user *, filename)
531 {
532         return ksys_chroot(filename);
533 }
534 
535 static int chmod_common(const struct path *path, umode_t mode)
536 {
537         struct inode *inode = path->dentry->d_inode;
538         struct inode *delegated_inode = NULL;
539         struct iattr newattrs;
540         int error;
541 
542         error = mnt_want_write(path->mnt);
543         if (error)
544                 return error;
545 retry_deleg:
546         inode_lock(inode);
547         error = security_path_chmod(path, mode);
548         if (error)
549                 goto out_unlock;
550         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
551         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
552         error = notify_change(path->dentry, &newattrs, &delegated_inode);
553 out_unlock:
554         inode_unlock(inode);
555         if (delegated_inode) {
556                 error = break_deleg_wait(&delegated_inode);
557                 if (!error)
558                         goto retry_deleg;
559         }
560         mnt_drop_write(path->mnt);
561         return error;
562 }
563 
564 int ksys_fchmod(unsigned int fd, umode_t mode)
565 {
566         struct fd f = fdget(fd);
567         int err = -EBADF;
568 
569         if (f.file) {
570                 audit_file(f.file);
571                 err = chmod_common(&f.file->f_path, mode);
572                 fdput(f);
573         }
574         return err;
575 }
576 
577 SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
578 {
579         return ksys_fchmod(fd, mode);
580 }
581 
582 int do_fchmodat(int dfd, const char __user *filename, umode_t mode)
583 {
584         struct path path;
585         int error;
586         unsigned int lookup_flags = LOOKUP_FOLLOW;
587 retry:
588         error = user_path_at(dfd, filename, lookup_flags, &path);
589         if (!error) {
590                 error = chmod_common(&path, mode);
591                 path_put(&path);
592                 if (retry_estale(error, lookup_flags)) {
593                         lookup_flags |= LOOKUP_REVAL;
594                         goto retry;
595                 }
596         }
597         return error;
598 }
599 
600 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename,
601                 umode_t, mode)
602 {
603         return do_fchmodat(dfd, filename, mode);
604 }
605 
606 SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
607 {
608         return do_fchmodat(AT_FDCWD, filename, mode);
609 }
610 
611 static int chown_common(const struct path *path, uid_t user, gid_t group)
612 {
613         struct inode *inode = path->dentry->d_inode;
614         struct inode *delegated_inode = NULL;
615         int error;
616         struct iattr newattrs;
617         kuid_t uid;
618         kgid_t gid;
619 
620         uid = make_kuid(current_user_ns(), user);
621         gid = make_kgid(current_user_ns(), group);
622 
623 retry_deleg:
624         newattrs.ia_valid =  ATTR_CTIME;
625         if (user != (uid_t) -1) {
626                 if (!uid_valid(uid))
627                         return -EINVAL;
628                 newattrs.ia_valid |= ATTR_UID;
629                 newattrs.ia_uid = uid;
630         }
631         if (group != (gid_t) -1) {
632                 if (!gid_valid(gid))
633                         return -EINVAL;
634                 newattrs.ia_valid |= ATTR_GID;
635                 newattrs.ia_gid = gid;
636         }
637         if (!S_ISDIR(inode->i_mode))
638                 newattrs.ia_valid |=
639                         ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
640         inode_lock(inode);
641         error = security_path_chown(path, uid, gid);
642         if (!error)
643                 error = notify_change(path->dentry, &newattrs, &delegated_inode);
644         inode_unlock(inode);
645         if (delegated_inode) {
646                 error = break_deleg_wait(&delegated_inode);
647                 if (!error)
648                         goto retry_deleg;
649         }
650         return error;
651 }
652 
653 int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
654                 int flag)
655 {
656         struct path path;
657         int error = -EINVAL;
658         int lookup_flags;
659 
660         if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
661                 goto out;
662 
663         lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
664         if (flag & AT_EMPTY_PATH)
665                 lookup_flags |= LOOKUP_EMPTY;
666 retry:
667         error = user_path_at(dfd, filename, lookup_flags, &path);
668         if (error)
669                 goto out;
670         error = mnt_want_write(path.mnt);
671         if (error)
672                 goto out_release;
673         error = chown_common(&path, user, group);
674         mnt_drop_write(path.mnt);
675 out_release:
676         path_put(&path);
677         if (retry_estale(error, lookup_flags)) {
678                 lookup_flags |= LOOKUP_REVAL;
679                 goto retry;
680         }
681 out:
682         return error;
683 }
684 
685 SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
686                 gid_t, group, int, flag)
687 {
688         return do_fchownat(dfd, filename, user, group, flag);
689 }
690 
691 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
692 {
693         return do_fchownat(AT_FDCWD, filename, user, group, 0);
694 }
695 
696 SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
697 {
698         return do_fchownat(AT_FDCWD, filename, user, group,
699                            AT_SYMLINK_NOFOLLOW);
700 }
701 
702 int ksys_fchown(unsigned int fd, uid_t user, gid_t group)
703 {
704         struct fd f = fdget(fd);
705         int error = -EBADF;
706 
707         if (!f.file)
708                 goto out;
709 
710         error = mnt_want_write_file_path(f.file);
711         if (error)
712                 goto out_fput;
713         audit_file(f.file);
714         error = chown_common(&f.file->f_path, user, group);
715         mnt_drop_write_file_path(f.file);
716 out_fput:
717         fdput(f);
718 out:
719         return error;
720 }
721 
722 SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
723 {
724         return ksys_fchown(fd, user, group);
725 }
726 
727 int open_check_o_direct(struct file *f)
728 {
729         /* NB: we're sure to have correct a_ops only after f_op->open */
730         if (f->f_flags & O_DIRECT) {
731                 if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO)
732                         return -EINVAL;
733         }
734         return 0;
735 }
736 
737 static int do_dentry_open(struct file *f,
738                           struct inode *inode,
739                           int (*open)(struct inode *, struct file *),
740                           const struct cred *cred)
741 {
742         static const struct file_operations empty_fops = {};
743         int error;
744 
745         f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
746                                 FMODE_PREAD | FMODE_PWRITE;
747 
748         path_get(&f->f_path);
749         f->f_inode = inode;
750         f->f_mapping = inode->i_mapping;
751 
752         /* Ensure that we skip any errors that predate opening of the file */
753         f->f_wb_err = filemap_sample_wb_err(f->f_mapping);
754 
755         if (unlikely(f->f_flags & O_PATH)) {
756                 f->f_mode = FMODE_PATH;
757                 f->f_op = &empty_fops;
758                 return 0;
759         }
760 
761         if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
762                 error = get_write_access(inode);
763                 if (unlikely(error))
764                         goto cleanup_file;
765                 error = __mnt_want_write(f->f_path.mnt);
766                 if (unlikely(error)) {
767                         put_write_access(inode);
768                         goto cleanup_file;
769                 }
770                 f->f_mode |= FMODE_WRITER;
771         }
772 
773         /* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
774         if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))
775                 f->f_mode |= FMODE_ATOMIC_POS;
776 
777         f->f_op = fops_get(inode->i_fop);
778         if (unlikely(WARN_ON(!f->f_op))) {
779                 error = -ENODEV;
780                 goto cleanup_all;
781         }
782 
783         error = security_file_open(f, cred);
784         if (error)
785                 goto cleanup_all;
786 
787         error = break_lease(locks_inode(f), f->f_flags);
788         if (error)
789                 goto cleanup_all;
790 
791         if (!open)
792                 open = f->f_op->open;
793         if (open) {
794                 error = open(inode, f);
795                 if (error)
796                         goto cleanup_all;
797         }
798         if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
799                 i_readcount_inc(inode);
800         if ((f->f_mode & FMODE_READ) &&
801              likely(f->f_op->read || f->f_op->read_iter))
802                 f->f_mode |= FMODE_CAN_READ;
803         if ((f->f_mode & FMODE_WRITE) &&
804              likely(f->f_op->write || f->f_op->write_iter))
805                 f->f_mode |= FMODE_CAN_WRITE;
806 
807         f->f_write_hint = WRITE_LIFE_NOT_SET;
808         f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
809 
810         file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
811 
812         return 0;
813 
814 cleanup_all:
815         fops_put(f->f_op);
816         if (f->f_mode & FMODE_WRITER) {
817                 put_write_access(inode);
818                 __mnt_drop_write(f->f_path.mnt);
819         }
820 cleanup_file:
821         path_put(&f->f_path);
822         f->f_path.mnt = NULL;
823         f->f_path.dentry = NULL;
824         f->f_inode = NULL;
825         return error;
826 }
827 
828 /**
829  * finish_open - finish opening a file
830  * @file: file pointer
831  * @dentry: pointer to dentry
832  * @open: open callback
833  * @opened: state of open
834  *
835  * This can be used to finish opening a file passed to i_op->atomic_open().
836  *
837  * If the open callback is set to NULL, then the standard f_op->open()
838  * filesystem callback is substituted.
839  *
840  * NB: the dentry reference is _not_ consumed.  If, for example, the dentry is
841  * the return value of d_splice_alias(), then the caller needs to perform dput()
842  * on it after finish_open().
843  *
844  * On successful return @file is a fully instantiated open file.  After this, if
845  * an error occurs in ->atomic_open(), it needs to clean up with fput().
846  *
847  * Returns zero on success or -errno if the open failed.
848  */
849 int finish_open(struct file *file, struct dentry *dentry,
850                 int (*open)(struct inode *, struct file *),
851                 int *opened)
852 {
853         int error;
854         BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
855 
856         file->f_path.dentry = dentry;
857         error = do_dentry_open(file, d_backing_inode(dentry), open,
858                                current_cred());
859         if (!error)
860                 *opened |= FILE_OPENED;
861 
862         return error;
863 }
864 EXPORT_SYMBOL(finish_open);
865 
866 /**
867  * finish_no_open - finish ->atomic_open() without opening the file
868  *
869  * @file: file pointer
870  * @dentry: dentry or NULL (as returned from ->lookup())
871  *
872  * This can be used to set the result of a successful lookup in ->atomic_open().
873  *
874  * NB: unlike finish_open() this function does consume the dentry reference and
875  * the caller need not dput() it.
876  *
877  * Returns "1" which must be the return value of ->atomic_open() after having
878  * called this function.
879  */
880 int finish_no_open(struct file *file, struct dentry *dentry)
881 {
882         file->f_path.dentry = dentry;
883         return 1;
884 }
885 EXPORT_SYMBOL(finish_no_open);
886 
887 char *file_path(struct file *filp, char *buf, int buflen)
888 {
889         return d_path(&filp->f_path, buf, buflen);
890 }
891 EXPORT_SYMBOL(file_path);
892 
893 /**
894  * vfs_open - open the file at the given path
895  * @path: path to open
896  * @file: newly allocated file with f_flag initialized
897  * @cred: credentials to use
898  */
899 int vfs_open(const struct path *path, struct file *file,
900              const struct cred *cred)
901 {
902         struct dentry *dentry = d_real(path->dentry, NULL, file->f_flags, 0);
903 
904         if (IS_ERR(dentry))
905                 return PTR_ERR(dentry);
906 
907         file->f_path = *path;
908         return do_dentry_open(file, d_backing_inode(dentry), NULL, cred);
909 }
910 
911 struct file *dentry_open(const struct path *path, int flags,
912                          const struct cred *cred)
913 {
914         int error;
915         struct file *f;
916 
917         validate_creds(cred);
918 
919         /* We must always pass in a valid mount pointer. */
920         BUG_ON(!path->mnt);
921 
922         f = get_empty_filp();
923         if (!IS_ERR(f)) {
924                 f->f_flags = flags;
925                 error = vfs_open(path, f, cred);
926                 if (!error) {
927                         /* from now on we need fput() to dispose of f */
928                         error = open_check_o_direct(f);
929                         if (error) {
930                                 fput(f);
931                                 f = ERR_PTR(error);
932                         }
933                 } else { 
934                         put_filp(f);
935                         f = ERR_PTR(error);
936                 }
937         }
938         return f;
939 }
940 EXPORT_SYMBOL(dentry_open);
941 
942 static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
943 {
944         int lookup_flags = 0;
945         int acc_mode = ACC_MODE(flags);
946 
947         /*
948          * Clear out all open flags we don't know about so that we don't report
949          * them in fcntl(F_GETFD) or similar interfaces.
950          */
951         flags &= VALID_OPEN_FLAGS;
952 
953         if (flags & (O_CREAT | __O_TMPFILE))
954                 op->mode = (mode & S_IALLUGO) | S_IFREG;
955         else
956                 op->mode = 0;
957 
958         /* Must never be set by userspace */
959         flags &= ~FMODE_NONOTIFY & ~O_CLOEXEC;
960 
961         /*
962          * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
963          * check for O_DSYNC if the need any syncing at all we enforce it's
964          * always set instead of having to deal with possibly weird behaviour
965          * for malicious applications setting only __O_SYNC.
966          */
967         if (flags & __O_SYNC)
968                 flags |= O_DSYNC;
969 
970         if (flags & __O_TMPFILE) {
971                 if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
972                         return -EINVAL;
973                 if (!(acc_mode & MAY_WRITE))
974                         return -EINVAL;
975         } else if (flags & O_PATH) {
976                 /*
977                  * If we have O_PATH in the open flag. Then we
978                  * cannot have anything other than the below set of flags
979                  */
980                 flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
981                 acc_mode = 0;
982         }
983 
984         op->open_flag = flags;
985 
986         /* O_TRUNC implies we need access checks for write permissions */
987         if (flags & O_TRUNC)
988                 acc_mode |= MAY_WRITE;
989 
990         /* Allow the LSM permission hook to distinguish append
991            access from general write access. */
992         if (flags & O_APPEND)
993                 acc_mode |= MAY_APPEND;
994 
995         op->acc_mode = acc_mode;
996 
997         op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
998 
999         if (flags & O_CREAT) {
1000                 op->intent |= LOOKUP_CREATE;
1001                 if (flags & O_EXCL)
1002                         op->intent |= LOOKUP_EXCL;
1003         }
1004 
1005         if (flags & O_DIRECTORY)
1006                 lookup_flags |= LOOKUP_DIRECTORY;
1007         if (!(flags & O_NOFOLLOW))
1008                 lookup_flags |= LOOKUP_FOLLOW;
1009         op->lookup_flags = lookup_flags;
1010         return 0;
1011 }
1012 
1013 /**
1014  * file_open_name - open file and return file pointer
1015  *
1016  * @name:       struct filename containing 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 *file_open_name(struct filename *name, int flags, umode_t mode)
1025 {
1026         struct open_flags op;
1027         int err = build_open_flags(flags, mode, &op);
1028         return err ? ERR_PTR(err) : do_filp_open(AT_FDCWD, name, &op);
1029 }
1030 
1031 /**
1032  * filp_open - open file and return file pointer
1033  *
1034  * @filename:   path to open
1035  * @flags:      open flags as per the open(2) second argument
1036  * @mode:       mode for the new file if O_CREAT is set, else ignored
1037  *
1038  * This is the helper to open a file from kernelspace if you really
1039  * have to.  But in generally you should not do this, so please move
1040  * along, nothing to see here..
1041  */
1042 struct file *filp_open(const char *filename, int flags, umode_t mode)
1043 {
1044         struct filename *name = getname_kernel(filename);
1045         struct file *file = ERR_CAST(name);
1046         
1047         if (!IS_ERR(name)) {
1048                 file = file_open_name(name, flags, mode);
1049                 putname(name);
1050         }
1051         return file;
1052 }
1053 EXPORT_SYMBOL(filp_open);
1054 
1055 struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
1056                             const char *filename, int flags, umode_t mode)
1057 {
1058         struct open_flags op;
1059         int err = build_open_flags(flags, mode, &op);
1060         if (err)
1061                 return ERR_PTR(err);
1062         return do_file_open_root(dentry, mnt, filename, &op);
1063 }
1064 EXPORT_SYMBOL(file_open_root);
1065 
1066 struct file *filp_clone_open(struct file *oldfile)
1067 {
1068         struct file *file;
1069         int retval;
1070 
1071         file = get_empty_filp();
1072         if (IS_ERR(file))
1073                 return file;
1074 
1075         file->f_flags = oldfile->f_flags;
1076         retval = vfs_open(&oldfile->f_path, file, oldfile->f_cred);
1077         if (retval) {
1078                 put_filp(file);
1079                 return ERR_PTR(retval);
1080         }
1081 
1082         return file;
1083 }
1084 EXPORT_SYMBOL(filp_clone_open);
1085 
1086 long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
1087 {
1088         struct open_flags op;
1089         int fd = build_open_flags(flags, mode, &op);
1090         struct filename *tmp;
1091 
1092         if (fd)
1093                 return fd;
1094 
1095         tmp = getname(filename);
1096         if (IS_ERR(tmp))
1097                 return PTR_ERR(tmp);
1098 
1099         fd = get_unused_fd_flags(flags);
1100         if (fd >= 0) {
1101                 struct file *f = do_filp_open(dfd, tmp, &op);
1102                 if (IS_ERR(f)) {
1103                         put_unused_fd(fd);
1104                         fd = PTR_ERR(f);
1105                 } else {
1106                         fsnotify_open(f);
1107                         fd_install(fd, f);
1108                 }
1109         }
1110         putname(tmp);
1111         return fd;
1112 }
1113 
1114 SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1115 {
1116         if (force_o_largefile())
1117                 flags |= O_LARGEFILE;
1118 
1119         return do_sys_open(AT_FDCWD, filename, flags, mode);
1120 }
1121 
1122 SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1123                 umode_t, mode)
1124 {
1125         if (force_o_largefile())
1126                 flags |= O_LARGEFILE;
1127 
1128         return do_sys_open(dfd, filename, flags, mode);
1129 }
1130 
1131 #ifdef CONFIG_COMPAT
1132 /*
1133  * Exactly like sys_open(), except that it doesn't set the
1134  * O_LARGEFILE flag.
1135  */
1136 COMPAT_SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1137 {
1138         return do_sys_open(AT_FDCWD, filename, flags, mode);
1139 }
1140 
1141 /*
1142  * Exactly like sys_openat(), except that it doesn't set the
1143  * O_LARGEFILE flag.
1144  */
1145 COMPAT_SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags, umode_t, mode)
1146 {
1147         return do_sys_open(dfd, filename, flags, mode);
1148 }
1149 #endif
1150 
1151 #ifndef __alpha__
1152 
1153 /*
1154  * For backward compatibility?  Maybe this should be moved
1155  * into arch/i386 instead?
1156  */
1157 SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1158 {
1159         return ksys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1160 }
1161 
1162 #endif
1163 
1164 /*
1165  * "id" is the POSIX thread ID. We use the
1166  * files pointer for this..
1167  */
1168 int filp_close(struct file *filp, fl_owner_t id)
1169 {
1170         int retval = 0;
1171 
1172         if (!file_count(filp)) {
1173                 printk(KERN_ERR "VFS: Close: file count is 0\n");
1174                 return 0;
1175         }
1176 
1177         if (filp->f_op->flush)
1178                 retval = filp->f_op->flush(filp, id);
1179 
1180         if (likely(!(filp->f_mode & FMODE_PATH))) {
1181                 dnotify_flush(filp, id);
1182                 locks_remove_posix(filp, id);
1183         }
1184         fput(filp);
1185         return retval;
1186 }
1187 
1188 EXPORT_SYMBOL(filp_close);
1189 
1190 /*
1191  * Careful here! We test whether the file pointer is NULL before
1192  * releasing the fd. This ensures that one clone task can't release
1193  * an fd while another clone is opening it.
1194  */
1195 SYSCALL_DEFINE1(close, unsigned int, fd)
1196 {
1197         int retval = __close_fd(current->files, fd);
1198 
1199         /* can't restart close syscall because file table entry was cleared */
1200         if (unlikely(retval == -ERESTARTSYS ||
1201                      retval == -ERESTARTNOINTR ||
1202                      retval == -ERESTARTNOHAND ||
1203                      retval == -ERESTART_RESTARTBLOCK))
1204                 retval = -EINTR;
1205 
1206         return retval;
1207 }
1208 
1209 /*
1210  * This routine simulates a hangup on the tty, to arrange that users
1211  * are given clean terminals at login time.
1212  */
1213 SYSCALL_DEFINE0(vhangup)
1214 {
1215         if (!ccs_capable(CCS_SYS_VHANGUP))
1216                 return -EPERM;
1217         if (capable(CAP_SYS_TTY_CONFIG)) {
1218                 tty_vhangup_self();
1219                 return 0;
1220         }
1221         return -EPERM;
1222 }
1223 
1224 /*
1225  * Called when an inode is about to be open.
1226  * We use this to disallow opening large files on 32bit systems if
1227  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1228  * on this flag in sys_open.
1229  */
1230 int generic_file_open(struct inode * inode, struct file * filp)
1231 {
1232         if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1233                 return -EOVERFLOW;
1234         return 0;
1235 }
1236 
1237 EXPORT_SYMBOL(generic_file_open);
1238 
1239 /*
1240  * This is used by subsystems that don't want seekable
1241  * file descriptors. The function is not supposed to ever fail, the only
1242  * reason it returns an 'int' and not 'void' is so that it can be plugged
1243  * directly into file_operations structure.
1244  */
1245 int nonseekable_open(struct inode *inode, struct file *filp)
1246 {
1247         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1248         return 0;
1249 }
1250 
1251 EXPORT_SYMBOL(nonseekable_open);
1252 

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