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TOMOYO Linux Cross Reference
Linux/fs/open.c

Version: ~ [ linux-5.6-rc1 ] ~ [ linux-5.5.2 ] ~ [ linux-5.4.17 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.102 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.170 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.213 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.213 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.81 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
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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 <asm/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(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 static 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 static 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         if (IS_APPEND(inode))
186                 goto out_putf;
187 
188         sb_start_write(inode->i_sb);
189         error = locks_verify_truncate(inode, f.file, length);
190         if (!error)
191                 error = security_path_truncate(&f.file->f_path);
192         if (!error)
193                 error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, f.file);
194         sb_end_write(inode->i_sb);
195 out_putf:
196         fdput(f);
197 out:
198         return error;
199 }
200 
201 SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
202 {
203         return do_sys_ftruncate(fd, length, 1);
204 }
205 
206 #ifdef CONFIG_COMPAT
207 COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length)
208 {
209         return do_sys_ftruncate(fd, length, 1);
210 }
211 #endif
212 
213 /* LFS versions of truncate are only needed on 32 bit machines */
214 #if BITS_PER_LONG == 32
215 SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
216 {
217         return do_sys_truncate(path, length);
218 }
219 
220 SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
221 {
222         return do_sys_ftruncate(fd, length, 0);
223 }
224 #endif /* BITS_PER_LONG == 32 */
225 
226 
227 int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
228 {
229         struct inode *inode = file_inode(file);
230         long ret;
231 
232         if (offset < 0 || len <= 0)
233                 return -EINVAL;
234 
235         /* Return error if mode is not supported */
236         if (mode & ~FALLOC_FL_SUPPORTED_MASK)
237                 return -EOPNOTSUPP;
238 
239         /* Punch hole and zero range are mutually exclusive */
240         if ((mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) ==
241             (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE))
242                 return -EOPNOTSUPP;
243 
244         /* Punch hole must have keep size set */
245         if ((mode & FALLOC_FL_PUNCH_HOLE) &&
246             !(mode & FALLOC_FL_KEEP_SIZE))
247                 return -EOPNOTSUPP;
248 
249         /* Collapse range should only be used exclusively. */
250         if ((mode & FALLOC_FL_COLLAPSE_RANGE) &&
251             (mode & ~FALLOC_FL_COLLAPSE_RANGE))
252                 return -EINVAL;
253 
254         /* Insert range should only be used exclusively. */
255         if ((mode & FALLOC_FL_INSERT_RANGE) &&
256             (mode & ~FALLOC_FL_INSERT_RANGE))
257                 return -EINVAL;
258 
259         if (!(file->f_mode & FMODE_WRITE))
260                 return -EBADF;
261 
262         /*
263          * We can only allow pure fallocate on append only files
264          */
265         if ((mode & ~FALLOC_FL_KEEP_SIZE) && IS_APPEND(inode))
266                 return -EPERM;
267 
268         if (IS_IMMUTABLE(inode))
269                 return -EPERM;
270 
271         /*
272          * We cannot allow any fallocate operation on an active swapfile
273          */
274         if (IS_SWAPFILE(inode))
275                 return -ETXTBSY;
276 
277         /*
278          * Revalidate the write permissions, in case security policy has
279          * changed since the files were opened.
280          */
281         ret = security_file_permission(file, MAY_WRITE);
282         if (ret)
283                 return ret;
284 
285         if (S_ISFIFO(inode->i_mode))
286                 return -ESPIPE;
287 
288         /*
289          * Let individual file system decide if it supports preallocation
290          * for directories or not.
291          */
292         if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
293                 return -ENODEV;
294 
295         /* Check for wrap through zero too */
296         if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
297                 return -EFBIG;
298 
299         if (!file->f_op->fallocate)
300                 return -EOPNOTSUPP;
301 
302         sb_start_write(inode->i_sb);
303         ret = file->f_op->fallocate(file, mode, offset, len);
304 
305         /*
306          * Create inotify and fanotify events.
307          *
308          * To keep the logic simple always create events if fallocate succeeds.
309          * This implies that events are even created if the file size remains
310          * unchanged, e.g. when using flag FALLOC_FL_KEEP_SIZE.
311          */
312         if (ret == 0)
313                 fsnotify_modify(file);
314 
315         sb_end_write(inode->i_sb);
316         return ret;
317 }
318 EXPORT_SYMBOL_GPL(vfs_fallocate);
319 
320 SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
321 {
322         struct fd f = fdget(fd);
323         int error = -EBADF;
324 
325         if (f.file) {
326                 error = vfs_fallocate(f.file, mode, offset, len);
327                 fdput(f);
328         }
329         return error;
330 }
331 
332 /*
333  * access() needs to use the real uid/gid, not the effective uid/gid.
334  * We do this by temporarily clearing all FS-related capabilities and
335  * switching the fsuid/fsgid around to the real ones.
336  */
337 SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
338 {
339         const struct cred *old_cred;
340         struct cred *override_cred;
341         struct path path;
342         struct inode *inode;
343         int res;
344         unsigned int lookup_flags = LOOKUP_FOLLOW;
345 
346         if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
347                 return -EINVAL;
348 
349         override_cred = prepare_creds();
350         if (!override_cred)
351                 return -ENOMEM;
352 
353         override_cred->fsuid = override_cred->uid;
354         override_cred->fsgid = override_cred->gid;
355 
356         if (!issecure(SECURE_NO_SETUID_FIXUP)) {
357                 /* Clear the capabilities if we switch to a non-root user */
358                 kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
359                 if (!uid_eq(override_cred->uid, root_uid))
360                         cap_clear(override_cred->cap_effective);
361                 else
362                         override_cred->cap_effective =
363                                 override_cred->cap_permitted;
364         }
365 
366         old_cred = override_creds(override_cred);
367 retry:
368         res = user_path_at(dfd, filename, lookup_flags, &path);
369         if (res)
370                 goto out;
371 
372         inode = d_backing_inode(path.dentry);
373 
374         if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
375                 /*
376                  * MAY_EXEC on regular files is denied if the fs is mounted
377                  * with the "noexec" flag.
378                  */
379                 res = -EACCES;
380                 if (path_noexec(&path))
381                         goto out_path_release;
382         }
383 
384         res = inode_permission(inode, mode | MAY_ACCESS);
385         /* SuS v2 requires we report a read only fs too */
386         if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
387                 goto out_path_release;
388         /*
389          * This is a rare case where using __mnt_is_readonly()
390          * is OK without a mnt_want/drop_write() pair.  Since
391          * no actual write to the fs is performed here, we do
392          * not need to telegraph to that to anyone.
393          *
394          * By doing this, we accept that this access is
395          * inherently racy and know that the fs may change
396          * state before we even see this result.
397          */
398         if (__mnt_is_readonly(path.mnt))
399                 res = -EROFS;
400 
401 out_path_release:
402         path_put(&path);
403         if (retry_estale(res, lookup_flags)) {
404                 lookup_flags |= LOOKUP_REVAL;
405                 goto retry;
406         }
407 out:
408         revert_creds(old_cred);
409         put_cred(override_cred);
410         return res;
411 }
412 
413 SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
414 {
415         return sys_faccessat(AT_FDCWD, filename, mode);
416 }
417 
418 SYSCALL_DEFINE1(chdir, const char __user *, filename)
419 {
420         struct path path;
421         int error;
422         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
423 retry:
424         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
425         if (error)
426                 goto out;
427 
428         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
429         if (error)
430                 goto dput_and_out;
431 
432         set_fs_pwd(current->fs, &path);
433 
434 dput_and_out:
435         path_put(&path);
436         if (retry_estale(error, lookup_flags)) {
437                 lookup_flags |= LOOKUP_REVAL;
438                 goto retry;
439         }
440 out:
441         return error;
442 }
443 
444 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
445 {
446         struct fd f = fdget_raw(fd);
447         struct inode *inode;
448         int error = -EBADF;
449 
450         error = -EBADF;
451         if (!f.file)
452                 goto out;
453 
454         inode = file_inode(f.file);
455 
456         error = -ENOTDIR;
457         if (!S_ISDIR(inode->i_mode))
458                 goto out_putf;
459 
460         error = inode_permission(inode, MAY_EXEC | MAY_CHDIR);
461         if (!error)
462                 set_fs_pwd(current->fs, &f.file->f_path);
463 out_putf:
464         fdput(f);
465 out:
466         return error;
467 }
468 
469 SYSCALL_DEFINE1(chroot, const char __user *, filename)
470 {
471         struct path path;
472         int error;
473         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
474 retry:
475         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
476         if (error)
477                 goto out;
478 
479         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
480         if (error)
481                 goto dput_and_out;
482 
483         error = -EPERM;
484         if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
485                 goto dput_and_out;
486         error = security_path_chroot(&path);
487         if (error)
488                 goto dput_and_out;
489 
490         set_fs_root(current->fs, &path);
491         error = 0;
492 dput_and_out:
493         path_put(&path);
494         if (retry_estale(error, lookup_flags)) {
495                 lookup_flags |= LOOKUP_REVAL;
496                 goto retry;
497         }
498 out:
499         return error;
500 }
501 
502 static int chmod_common(struct path *path, umode_t mode)
503 {
504         struct inode *inode = path->dentry->d_inode;
505         struct inode *delegated_inode = NULL;
506         struct iattr newattrs;
507         int error;
508 
509         error = mnt_want_write(path->mnt);
510         if (error)
511                 return error;
512 retry_deleg:
513         inode_lock(inode);
514         error = security_path_chmod(path, mode);
515         if (error)
516                 goto out_unlock;
517         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
518         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
519         error = notify_change(path->dentry, &newattrs, &delegated_inode);
520 out_unlock:
521         inode_unlock(inode);
522         if (delegated_inode) {
523                 error = break_deleg_wait(&delegated_inode);
524                 if (!error)
525                         goto retry_deleg;
526         }
527         mnt_drop_write(path->mnt);
528         return error;
529 }
530 
531 SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
532 {
533         struct fd f = fdget(fd);
534         int err = -EBADF;
535 
536         if (f.file) {
537                 audit_file(f.file);
538                 err = chmod_common(&f.file->f_path, mode);
539                 fdput(f);
540         }
541         return err;
542 }
543 
544 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode)
545 {
546         struct path path;
547         int error;
548         unsigned int lookup_flags = LOOKUP_FOLLOW;
549 retry:
550         error = user_path_at(dfd, filename, lookup_flags, &path);
551         if (!error) {
552                 error = chmod_common(&path, mode);
553                 path_put(&path);
554                 if (retry_estale(error, lookup_flags)) {
555                         lookup_flags |= LOOKUP_REVAL;
556                         goto retry;
557                 }
558         }
559         return error;
560 }
561 
562 SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
563 {
564         return sys_fchmodat(AT_FDCWD, filename, mode);
565 }
566 
567 static int chown_common(struct path *path, uid_t user, gid_t group)
568 {
569         struct inode *inode = path->dentry->d_inode;
570         struct inode *delegated_inode = NULL;
571         int error;
572         struct iattr newattrs;
573         kuid_t uid;
574         kgid_t gid;
575 
576         uid = make_kuid(current_user_ns(), user);
577         gid = make_kgid(current_user_ns(), group);
578 
579 retry_deleg:
580         newattrs.ia_valid =  ATTR_CTIME;
581         if (user != (uid_t) -1) {
582                 if (!uid_valid(uid))
583                         return -EINVAL;
584                 newattrs.ia_valid |= ATTR_UID;
585                 newattrs.ia_uid = uid;
586         }
587         if (group != (gid_t) -1) {
588                 if (!gid_valid(gid))
589                         return -EINVAL;
590                 newattrs.ia_valid |= ATTR_GID;
591                 newattrs.ia_gid = gid;
592         }
593         if (!S_ISDIR(inode->i_mode))
594                 newattrs.ia_valid |=
595                         ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
596         inode_lock(inode);
597         error = security_path_chown(path, uid, gid);
598         if (!error)
599                 error = notify_change(path->dentry, &newattrs, &delegated_inode);
600         inode_unlock(inode);
601         if (delegated_inode) {
602                 error = break_deleg_wait(&delegated_inode);
603                 if (!error)
604                         goto retry_deleg;
605         }
606         return error;
607 }
608 
609 SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
610                 gid_t, group, int, flag)
611 {
612         struct path path;
613         int error = -EINVAL;
614         int lookup_flags;
615 
616         if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
617                 goto out;
618 
619         lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
620         if (flag & AT_EMPTY_PATH)
621                 lookup_flags |= LOOKUP_EMPTY;
622 retry:
623         error = user_path_at(dfd, filename, lookup_flags, &path);
624         if (error)
625                 goto out;
626         error = mnt_want_write(path.mnt);
627         if (error)
628                 goto out_release;
629         error = chown_common(&path, user, group);
630         mnt_drop_write(path.mnt);
631 out_release:
632         path_put(&path);
633         if (retry_estale(error, lookup_flags)) {
634                 lookup_flags |= LOOKUP_REVAL;
635                 goto retry;
636         }
637 out:
638         return error;
639 }
640 
641 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
642 {
643         return sys_fchownat(AT_FDCWD, filename, user, group, 0);
644 }
645 
646 SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
647 {
648         return sys_fchownat(AT_FDCWD, filename, user, group,
649                             AT_SYMLINK_NOFOLLOW);
650 }
651 
652 SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
653 {
654         struct fd f = fdget(fd);
655         int error = -EBADF;
656 
657         if (!f.file)
658                 goto out;
659 
660         error = mnt_want_write_file(f.file);
661         if (error)
662                 goto out_fput;
663         audit_file(f.file);
664         error = chown_common(&f.file->f_path, user, group);
665         mnt_drop_write_file(f.file);
666 out_fput:
667         fdput(f);
668 out:
669         return error;
670 }
671 
672 int open_check_o_direct(struct file *f)
673 {
674         /* NB: we're sure to have correct a_ops only after f_op->open */
675         if (f->f_flags & O_DIRECT) {
676                 if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO)
677                         return -EINVAL;
678         }
679         return 0;
680 }
681 
682 static int do_dentry_open(struct file *f,
683                           struct inode *inode,
684                           int (*open)(struct inode *, struct file *),
685                           const struct cred *cred)
686 {
687         static const struct file_operations empty_fops = {};
688         int error;
689 
690         f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
691                                 FMODE_PREAD | FMODE_PWRITE;
692 
693         path_get(&f->f_path);
694         f->f_inode = inode;
695         f->f_mapping = inode->i_mapping;
696 
697         if (unlikely(f->f_flags & O_PATH)) {
698                 f->f_mode = FMODE_PATH;
699                 f->f_op = &empty_fops;
700                 return 0;
701         }
702 
703         if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
704                 error = get_write_access(inode);
705                 if (unlikely(error))
706                         goto cleanup_file;
707                 error = __mnt_want_write(f->f_path.mnt);
708                 if (unlikely(error)) {
709                         put_write_access(inode);
710                         goto cleanup_file;
711                 }
712                 f->f_mode |= FMODE_WRITER;
713         }
714 
715         /* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
716         if (S_ISREG(inode->i_mode))
717                 f->f_mode |= FMODE_ATOMIC_POS;
718 
719         f->f_op = fops_get(inode->i_fop);
720         if (unlikely(WARN_ON(!f->f_op))) {
721                 error = -ENODEV;
722                 goto cleanup_all;
723         }
724 
725         error = security_file_open(f, cred);
726         if (error)
727                 goto cleanup_all;
728 
729         error = break_lease(inode, f->f_flags);
730         if (error)
731                 goto cleanup_all;
732 
733         if (!open)
734                 open = f->f_op->open;
735         if (open) {
736                 error = open(inode, f);
737                 if (error)
738                         goto cleanup_all;
739         }
740         if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
741                 i_readcount_inc(inode);
742         if ((f->f_mode & FMODE_READ) &&
743              likely(f->f_op->read || f->f_op->read_iter))
744                 f->f_mode |= FMODE_CAN_READ;
745         if ((f->f_mode & FMODE_WRITE) &&
746              likely(f->f_op->write || f->f_op->write_iter))
747                 f->f_mode |= FMODE_CAN_WRITE;
748 
749         f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
750 
751         file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
752 
753         return 0;
754 
755 cleanup_all:
756         fops_put(f->f_op);
757         if (f->f_mode & FMODE_WRITER) {
758                 put_write_access(inode);
759                 __mnt_drop_write(f->f_path.mnt);
760         }
761 cleanup_file:
762         path_put(&f->f_path);
763         f->f_path.mnt = NULL;
764         f->f_path.dentry = NULL;
765         f->f_inode = NULL;
766         return error;
767 }
768 
769 /**
770  * finish_open - finish opening a file
771  * @file: file pointer
772  * @dentry: pointer to dentry
773  * @open: open callback
774  * @opened: state of open
775  *
776  * This can be used to finish opening a file passed to i_op->atomic_open().
777  *
778  * If the open callback is set to NULL, then the standard f_op->open()
779  * filesystem callback is substituted.
780  *
781  * NB: the dentry reference is _not_ consumed.  If, for example, the dentry is
782  * the return value of d_splice_alias(), then the caller needs to perform dput()
783  * on it after finish_open().
784  *
785  * On successful return @file is a fully instantiated open file.  After this, if
786  * an error occurs in ->atomic_open(), it needs to clean up with fput().
787  *
788  * Returns zero on success or -errno if the open failed.
789  */
790 int finish_open(struct file *file, struct dentry *dentry,
791                 int (*open)(struct inode *, struct file *),
792                 int *opened)
793 {
794         int error;
795         BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
796 
797         file->f_path.dentry = dentry;
798         error = do_dentry_open(file, d_backing_inode(dentry), open,
799                                current_cred());
800         if (!error)
801                 *opened |= FILE_OPENED;
802 
803         return error;
804 }
805 EXPORT_SYMBOL(finish_open);
806 
807 /**
808  * finish_no_open - finish ->atomic_open() without opening the file
809  *
810  * @file: file pointer
811  * @dentry: dentry or NULL (as returned from ->lookup())
812  *
813  * This can be used to set the result of a successful lookup in ->atomic_open().
814  *
815  * NB: unlike finish_open() this function does consume the dentry reference and
816  * the caller need not dput() it.
817  *
818  * Returns "1" which must be the return value of ->atomic_open() after having
819  * called this function.
820  */
821 int finish_no_open(struct file *file, struct dentry *dentry)
822 {
823         file->f_path.dentry = dentry;
824         return 1;
825 }
826 EXPORT_SYMBOL(finish_no_open);
827 
828 char *file_path(struct file *filp, char *buf, int buflen)
829 {
830         return d_path(&filp->f_path, buf, buflen);
831 }
832 EXPORT_SYMBOL(file_path);
833 
834 /**
835  * vfs_open - open the file at the given path
836  * @path: path to open
837  * @file: newly allocated file with f_flag initialized
838  * @cred: credentials to use
839  */
840 int vfs_open(const struct path *path, struct file *file,
841              const struct cred *cred)
842 {
843         struct inode *inode = vfs_select_inode(path->dentry, file->f_flags);
844 
845         if (IS_ERR(inode))
846                 return PTR_ERR(inode);
847 
848         file->f_path = *path;
849         return do_dentry_open(file, inode, NULL, cred);
850 }
851 
852 struct file *dentry_open(const struct path *path, int flags,
853                          const struct cred *cred)
854 {
855         int error;
856         struct file *f;
857 
858         validate_creds(cred);
859 
860         /* We must always pass in a valid mount pointer. */
861         BUG_ON(!path->mnt);
862 
863         f = get_empty_filp();
864         if (!IS_ERR(f)) {
865                 f->f_flags = flags;
866                 error = vfs_open(path, f, cred);
867                 if (!error) {
868                         /* from now on we need fput() to dispose of f */
869                         error = open_check_o_direct(f);
870                         if (error) {
871                                 fput(f);
872                                 f = ERR_PTR(error);
873                         }
874                 } else { 
875                         put_filp(f);
876                         f = ERR_PTR(error);
877                 }
878         }
879         return f;
880 }
881 EXPORT_SYMBOL(dentry_open);
882 
883 static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
884 {
885         int lookup_flags = 0;
886         int acc_mode = ACC_MODE(flags);
887 
888         if (flags & (O_CREAT | __O_TMPFILE))
889                 op->mode = (mode & S_IALLUGO) | S_IFREG;
890         else
891                 op->mode = 0;
892 
893         /* Must never be set by userspace */
894         flags &= ~FMODE_NONOTIFY & ~O_CLOEXEC;
895 
896         /*
897          * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
898          * check for O_DSYNC if the need any syncing at all we enforce it's
899          * always set instead of having to deal with possibly weird behaviour
900          * for malicious applications setting only __O_SYNC.
901          */
902         if (flags & __O_SYNC)
903                 flags |= O_DSYNC;
904 
905         if (flags & __O_TMPFILE) {
906                 if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
907                         return -EINVAL;
908                 if (!(acc_mode & MAY_WRITE))
909                         return -EINVAL;
910         } else if (flags & O_PATH) {
911                 /*
912                  * If we have O_PATH in the open flag. Then we
913                  * cannot have anything other than the below set of flags
914                  */
915                 flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
916                 acc_mode = 0;
917         }
918 
919         op->open_flag = flags;
920 
921         /* O_TRUNC implies we need access checks for write permissions */
922         if (flags & O_TRUNC)
923                 acc_mode |= MAY_WRITE;
924 
925         /* Allow the LSM permission hook to distinguish append
926            access from general write access. */
927         if (flags & O_APPEND)
928                 acc_mode |= MAY_APPEND;
929 
930         op->acc_mode = acc_mode;
931 
932         op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
933 
934         if (flags & O_CREAT) {
935                 op->intent |= LOOKUP_CREATE;
936                 if (flags & O_EXCL)
937                         op->intent |= LOOKUP_EXCL;
938         }
939 
940         if (flags & O_DIRECTORY)
941                 lookup_flags |= LOOKUP_DIRECTORY;
942         if (!(flags & O_NOFOLLOW))
943                 lookup_flags |= LOOKUP_FOLLOW;
944         op->lookup_flags = lookup_flags;
945         return 0;
946 }
947 
948 /**
949  * file_open_name - open file and return file pointer
950  *
951  * @name:       struct filename containing path to open
952  * @flags:      open flags as per the open(2) second argument
953  * @mode:       mode for the new file if O_CREAT is set, else ignored
954  *
955  * This is the helper to open a file from kernelspace if you really
956  * have to.  But in generally you should not do this, so please move
957  * along, nothing to see here..
958  */
959 struct file *file_open_name(struct filename *name, int flags, umode_t mode)
960 {
961         struct open_flags op;
962         int err = build_open_flags(flags, mode, &op);
963         return err ? ERR_PTR(err) : do_filp_open(AT_FDCWD, name, &op);
964 }
965 
966 /**
967  * filp_open - open file and return file pointer
968  *
969  * @filename:   path to open
970  * @flags:      open flags as per the open(2) second argument
971  * @mode:       mode for the new file if O_CREAT is set, else ignored
972  *
973  * This is the helper to open a file from kernelspace if you really
974  * have to.  But in generally you should not do this, so please move
975  * along, nothing to see here..
976  */
977 struct file *filp_open(const char *filename, int flags, umode_t mode)
978 {
979         struct filename *name = getname_kernel(filename);
980         struct file *file = ERR_CAST(name);
981         
982         if (!IS_ERR(name)) {
983                 file = file_open_name(name, flags, mode);
984                 putname(name);
985         }
986         return file;
987 }
988 EXPORT_SYMBOL(filp_open);
989 
990 struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
991                             const char *filename, int flags, umode_t mode)
992 {
993         struct open_flags op;
994         int err = build_open_flags(flags, mode, &op);
995         if (err)
996                 return ERR_PTR(err);
997         return do_file_open_root(dentry, mnt, filename, &op);
998 }
999 EXPORT_SYMBOL(file_open_root);
1000 
1001 long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
1002 {
1003         struct open_flags op;
1004         int fd = build_open_flags(flags, mode, &op);
1005         struct filename *tmp;
1006 
1007         if (fd)
1008                 return fd;
1009 
1010         tmp = getname(filename);
1011         if (IS_ERR(tmp))
1012                 return PTR_ERR(tmp);
1013 
1014         fd = get_unused_fd_flags(flags);
1015         if (fd >= 0) {
1016                 struct file *f = do_filp_open(dfd, tmp, &op);
1017                 if (IS_ERR(f)) {
1018                         put_unused_fd(fd);
1019                         fd = PTR_ERR(f);
1020                 } else {
1021                         fsnotify_open(f);
1022                         fd_install(fd, f);
1023                 }
1024         }
1025         putname(tmp);
1026         return fd;
1027 }
1028 
1029 SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1030 {
1031         if (force_o_largefile())
1032                 flags |= O_LARGEFILE;
1033 
1034         return do_sys_open(AT_FDCWD, filename, flags, mode);
1035 }
1036 
1037 SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1038                 umode_t, mode)
1039 {
1040         if (force_o_largefile())
1041                 flags |= O_LARGEFILE;
1042 
1043         return do_sys_open(dfd, filename, flags, mode);
1044 }
1045 
1046 #ifndef __alpha__
1047 
1048 /*
1049  * For backward compatibility?  Maybe this should be moved
1050  * into arch/i386 instead?
1051  */
1052 SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1053 {
1054         return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1055 }
1056 
1057 #endif
1058 
1059 /*
1060  * "id" is the POSIX thread ID. We use the
1061  * files pointer for this..
1062  */
1063 int filp_close(struct file *filp, fl_owner_t id)
1064 {
1065         int retval = 0;
1066 
1067         if (!file_count(filp)) {
1068                 printk(KERN_ERR "VFS: Close: file count is 0\n");
1069                 return 0;
1070         }
1071 
1072         if (filp->f_op->flush)
1073                 retval = filp->f_op->flush(filp, id);
1074 
1075         if (likely(!(filp->f_mode & FMODE_PATH))) {
1076                 dnotify_flush(filp, id);
1077                 locks_remove_posix(filp, id);
1078         }
1079         fput(filp);
1080         return retval;
1081 }
1082 
1083 EXPORT_SYMBOL(filp_close);
1084 
1085 /*
1086  * Careful here! We test whether the file pointer is NULL before
1087  * releasing the fd. This ensures that one clone task can't release
1088  * an fd while another clone is opening it.
1089  */
1090 SYSCALL_DEFINE1(close, unsigned int, fd)
1091 {
1092         int retval = __close_fd(current->files, fd);
1093 
1094         /* can't restart close syscall because file table entry was cleared */
1095         if (unlikely(retval == -ERESTARTSYS ||
1096                      retval == -ERESTARTNOINTR ||
1097                      retval == -ERESTARTNOHAND ||
1098                      retval == -ERESTART_RESTARTBLOCK))
1099                 retval = -EINTR;
1100 
1101         return retval;
1102 }
1103 EXPORT_SYMBOL(sys_close);
1104 
1105 /*
1106  * This routine simulates a hangup on the tty, to arrange that users
1107  * are given clean terminals at login time.
1108  */
1109 SYSCALL_DEFINE0(vhangup)
1110 {
1111         if (!ccs_capable(CCS_SYS_VHANGUP))
1112                 return -EPERM;
1113         if (capable(CAP_SYS_TTY_CONFIG)) {
1114                 tty_vhangup_self();
1115                 return 0;
1116         }
1117         return -EPERM;
1118 }
1119 
1120 /*
1121  * Called when an inode is about to be open.
1122  * We use this to disallow opening large files on 32bit systems if
1123  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1124  * on this flag in sys_open.
1125  */
1126 int generic_file_open(struct inode * inode, struct file * filp)
1127 {
1128         if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1129                 return -EOVERFLOW;
1130         return 0;
1131 }
1132 
1133 EXPORT_SYMBOL(generic_file_open);
1134 
1135 /*
1136  * This is used by subsystems that don't want seekable
1137  * file descriptors. The function is not supposed to ever fail, the only
1138  * reason it returns an 'int' and not 'void' is so that it can be plugged
1139  * directly into file_operations structure.
1140  */
1141 int nonseekable_open(struct inode *inode, struct file *filp)
1142 {
1143         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1144         return 0;
1145 }
1146 
1147 EXPORT_SYMBOL(nonseekable_open);
1148 

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