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/fs/open.c

https://bitbucket.org/emiliolopez/linux
C | 1208 lines | 844 code | 173 blank | 191 comment | 166 complexity | d67f0a4c07695a3657654167c86cb725 MD5 | raw file
   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
  37int 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
  68long 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);
 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
 122put_write_and_out:
 123	put_write_access(upperdentry->d_inode);
 124mnt_drop_write_and_out:
 125	mnt_drop_write(path->mnt);
 126out:
 127	return error;
 128}
 129EXPORT_SYMBOL_GPL(vfs_truncate);
 130
 131static 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
 140retry:
 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
 153SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
 154{
 155	return do_sys_truncate(path, length);
 156}
 157
 158#ifdef CONFIG_COMPAT
 159COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
 160{
 161	return do_sys_truncate(path, length);
 162}
 163#endif
 164
 165static 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);
 207out_putf:
 208	fdput(f);
 209out:
 210	return error;
 211}
 212
 213SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
 214{
 215	return do_sys_ftruncate(fd, length, 1);
 216}
 217
 218#ifdef CONFIG_COMPAT
 219COMPAT_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
 227SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
 228{
 229	return do_sys_truncate(path, length);
 230}
 231
 232SYSCALL_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
 239int 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}
 334EXPORT_SYMBOL_GPL(vfs_fallocate);
 335
 336SYSCALL_DEFINE4(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/*
 349 * access() needs to use the real uid/gid, not the effective uid/gid.
 350 * We do this by temporarily clearing all FS-related capabilities and
 351 * switching the fsuid/fsgid around to the real ones.
 352 */
 353SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
 354{
 355	const struct cred *old_cred;
 356	struct cred *override_cred;
 357	struct path path;
 358	struct inode *inode;
 359	int res;
 360	unsigned int lookup_flags = LOOKUP_FOLLOW;
 361
 362	if (mode & ~S_IRWXO)	/* where's F_OK, X_OK, W_OK, R_OK? */
 363		return -EINVAL;
 364
 365	override_cred = prepare_creds();
 366	if (!override_cred)
 367		return -ENOMEM;
 368
 369	override_cred->fsuid = override_cred->uid;
 370	override_cred->fsgid = override_cred->gid;
 371
 372	if (!issecure(SECURE_NO_SETUID_FIXUP)) {
 373		/* Clear the capabilities if we switch to a non-root user */
 374		kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
 375		if (!uid_eq(override_cred->uid, root_uid))
 376			cap_clear(override_cred->cap_effective);
 377		else
 378			override_cred->cap_effective =
 379				override_cred->cap_permitted;
 380	}
 381
 382	old_cred = override_creds(override_cred);
 383retry:
 384	res = user_path_at(dfd, filename, lookup_flags, &path);
 385	if (res)
 386		goto out;
 387
 388	inode = d_backing_inode(path.dentry);
 389
 390	if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
 391		/*
 392		 * MAY_EXEC on regular files is denied if the fs is mounted
 393		 * with the "noexec" flag.
 394		 */
 395		res = -EACCES;
 396		if (path_noexec(&path))
 397			goto out_path_release;
 398	}
 399
 400	res = inode_permission(inode, mode | MAY_ACCESS);
 401	/* SuS v2 requires we report a read only fs too */
 402	if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
 403		goto out_path_release;
 404	/*
 405	 * This is a rare case where using __mnt_is_readonly()
 406	 * is OK without a mnt_want/drop_write() pair.  Since
 407	 * no actual write to the fs is performed here, we do
 408	 * not need to telegraph to that to anyone.
 409	 *
 410	 * By doing this, we accept that this access is
 411	 * inherently racy and know that the fs may change
 412	 * state before we even see this result.
 413	 */
 414	if (__mnt_is_readonly(path.mnt))
 415		res = -EROFS;
 416
 417out_path_release:
 418	path_put(&path);
 419	if (retry_estale(res, lookup_flags)) {
 420		lookup_flags |= LOOKUP_REVAL;
 421		goto retry;
 422	}
 423out:
 424	revert_creds(old_cred);
 425	put_cred(override_cred);
 426	return res;
 427}
 428
 429SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
 430{
 431	return sys_faccessat(AT_FDCWD, filename, mode);
 432}
 433
 434SYSCALL_DEFINE1(chdir, const char __user *, filename)
 435{
 436	struct path path;
 437	int error;
 438	unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 439retry:
 440	error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 441	if (error)
 442		goto out;
 443
 444	error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 445	if (error)
 446		goto dput_and_out;
 447
 448	set_fs_pwd(current->fs, &path);
 449
 450dput_and_out:
 451	path_put(&path);
 452	if (retry_estale(error, lookup_flags)) {
 453		lookup_flags |= LOOKUP_REVAL;
 454		goto retry;
 455	}
 456out:
 457	return error;
 458}
 459
 460SYSCALL_DEFINE1(fchdir, unsigned int, fd)
 461{
 462	struct fd f = fdget_raw(fd);
 463	int error;
 464
 465	error = -EBADF;
 466	if (!f.file)
 467		goto out;
 468
 469	error = -ENOTDIR;
 470	if (!d_can_lookup(f.file->f_path.dentry))
 471		goto out_putf;
 472
 473	error = inode_permission(file_inode(f.file), MAY_EXEC | MAY_CHDIR);
 474	if (!error)
 475		set_fs_pwd(current->fs, &f.file->f_path);
 476out_putf:
 477	fdput(f);
 478out:
 479	return error;
 480}
 481
 482SYSCALL_DEFINE1(chroot, const char __user *, filename)
 483{
 484	struct path path;
 485	int error;
 486	unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 487retry:
 488	error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 489	if (error)
 490		goto out;
 491
 492	error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 493	if (error)
 494		goto dput_and_out;
 495
 496	error = -EPERM;
 497	if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
 498		goto dput_and_out;
 499	error = security_path_chroot(&path);
 500	if (error)
 501		goto dput_and_out;
 502
 503	set_fs_root(current->fs, &path);
 504	error = 0;
 505dput_and_out:
 506	path_put(&path);
 507	if (retry_estale(error, lookup_flags)) {
 508		lookup_flags |= LOOKUP_REVAL;
 509		goto retry;
 510	}
 511out:
 512	return error;
 513}
 514
 515static int chmod_common(const struct path *path, umode_t mode)
 516{
 517	struct inode *inode = path->dentry->d_inode;
 518	struct inode *delegated_inode = NULL;
 519	struct iattr newattrs;
 520	int error;
 521
 522	error = mnt_want_write(path->mnt);
 523	if (error)
 524		return error;
 525retry_deleg:
 526	inode_lock(inode);
 527	error = security_path_chmod(path, mode);
 528	if (error)
 529		goto out_unlock;
 530	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 531	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 532	error = notify_change(path->dentry, &newattrs, &delegated_inode);
 533out_unlock:
 534	inode_unlock(inode);
 535	if (delegated_inode) {
 536		error = break_deleg_wait(&delegated_inode);
 537		if (!error)
 538			goto retry_deleg;
 539	}
 540	mnt_drop_write(path->mnt);
 541	return error;
 542}
 543
 544SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
 545{
 546	struct fd f = fdget(fd);
 547	int err = -EBADF;
 548
 549	if (f.file) {
 550		audit_file(f.file);
 551		err = chmod_common(&f.file->f_path, mode);
 552		fdput(f);
 553	}
 554	return err;
 555}
 556
 557SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode)
 558{
 559	struct path path;
 560	int error;
 561	unsigned int lookup_flags = LOOKUP_FOLLOW;
 562retry:
 563	error = user_path_at(dfd, filename, lookup_flags, &path);
 564	if (!error) {
 565		error = chmod_common(&path, mode);
 566		path_put(&path);
 567		if (retry_estale(error, lookup_flags)) {
 568			lookup_flags |= LOOKUP_REVAL;
 569			goto retry;
 570		}
 571	}
 572	return error;
 573}
 574
 575SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
 576{
 577	return sys_fchmodat(AT_FDCWD, filename, mode);
 578}
 579
 580static int chown_common(const struct path *path, uid_t user, gid_t group)
 581{
 582	struct inode *inode = path->dentry->d_inode;
 583	struct inode *delegated_inode = NULL;
 584	int error;
 585	struct iattr newattrs;
 586	kuid_t uid;
 587	kgid_t gid;
 588
 589	uid = make_kuid(current_user_ns(), user);
 590	gid = make_kgid(current_user_ns(), group);
 591
 592retry_deleg:
 593	newattrs.ia_valid =  ATTR_CTIME;
 594	if (user != (uid_t) -1) {
 595		if (!uid_valid(uid))
 596			return -EINVAL;
 597		newattrs.ia_valid |= ATTR_UID;
 598		newattrs.ia_uid = uid;
 599	}
 600	if (group != (gid_t) -1) {
 601		if (!gid_valid(gid))
 602			return -EINVAL;
 603		newattrs.ia_valid |= ATTR_GID;
 604		newattrs.ia_gid = gid;
 605	}
 606	if (!S_ISDIR(inode->i_mode))
 607		newattrs.ia_valid |=
 608			ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
 609	inode_lock(inode);
 610	error = security_path_chown(path, uid, gid);
 611	if (!error)
 612		error = notify_change(path->dentry, &newattrs, &delegated_inode);
 613	inode_unlock(inode);
 614	if (delegated_inode) {
 615		error = break_deleg_wait(&delegated_inode);
 616		if (!error)
 617			goto retry_deleg;
 618	}
 619	return error;
 620}
 621
 622SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
 623		gid_t, group, int, flag)
 624{
 625	struct path path;
 626	int error = -EINVAL;
 627	int lookup_flags;
 628
 629	if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 630		goto out;
 631
 632	lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
 633	if (flag & AT_EMPTY_PATH)
 634		lookup_flags |= LOOKUP_EMPTY;
 635retry:
 636	error = user_path_at(dfd, filename, lookup_flags, &path);
 637	if (error)
 638		goto out;
 639	error = mnt_want_write(path.mnt);
 640	if (error)
 641		goto out_release;
 642	error = chown_common(&path, user, group);
 643	mnt_drop_write(path.mnt);
 644out_release:
 645	path_put(&path);
 646	if (retry_estale(error, lookup_flags)) {
 647		lookup_flags |= LOOKUP_REVAL;
 648		goto retry;
 649	}
 650out:
 651	return error;
 652}
 653
 654SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
 655{
 656	return sys_fchownat(AT_FDCWD, filename, user, group, 0);
 657}
 658
 659SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
 660{
 661	return sys_fchownat(AT_FDCWD, filename, user, group,
 662			    AT_SYMLINK_NOFOLLOW);
 663}
 664
 665SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
 666{
 667	struct fd f = fdget(fd);
 668	int error = -EBADF;
 669
 670	if (!f.file)
 671		goto out;
 672
 673	error = mnt_want_write_file(f.file);
 674	if (error)
 675		goto out_fput;
 676	audit_file(f.file);
 677	error = chown_common(&f.file->f_path, user, group);
 678	mnt_drop_write_file(f.file);
 679out_fput:
 680	fdput(f);
 681out:
 682	return error;
 683}
 684
 685int open_check_o_direct(struct file *f)
 686{
 687	/* NB: we're sure to have correct a_ops only after f_op->open */
 688	if (f->f_flags & O_DIRECT) {
 689		if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO)
 690			return -EINVAL;
 691	}
 692	return 0;
 693}
 694
 695static int do_dentry_open(struct file *f,
 696			  struct inode *inode,
 697			  int (*open)(struct inode *, struct file *),
 698			  const struct cred *cred)
 699{
 700	static const struct file_operations empty_fops = {};
 701	int error;
 702
 703	f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
 704				FMODE_PREAD | FMODE_PWRITE;
 705
 706	path_get(&f->f_path);
 707	f->f_inode = inode;
 708	f->f_mapping = inode->i_mapping;
 709
 710	/* Ensure that we skip any errors that predate opening of the file */
 711	f->f_wb_err = filemap_sample_wb_err(f->f_mapping);
 712
 713	if (unlikely(f->f_flags & O_PATH)) {
 714		f->f_mode = FMODE_PATH;
 715		f->f_op = &empty_fops;
 716		return 0;
 717	}
 718
 719	if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
 720		error = get_write_access(inode);
 721		if (unlikely(error))
 722			goto cleanup_file;
 723		error = __mnt_want_write(f->f_path.mnt);
 724		if (unlikely(error)) {
 725			put_write_access(inode);
 726			goto cleanup_file;
 727		}
 728		f->f_mode |= FMODE_WRITER;
 729	}
 730
 731	/* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
 732	if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))
 733		f->f_mode |= FMODE_ATOMIC_POS;
 734
 735	f->f_op = fops_get(inode->i_fop);
 736	if (unlikely(WARN_ON(!f->f_op))) {
 737		error = -ENODEV;
 738		goto cleanup_all;
 739	}
 740
 741	error = security_file_open(f, cred);
 742	if (error)
 743		goto cleanup_all;
 744
 745	error = break_lease(locks_inode(f), f->f_flags);
 746	if (error)
 747		goto cleanup_all;
 748
 749	if (!open)
 750		open = f->f_op->open;
 751	if (open) {
 752		error = open(inode, f);
 753		if (error)
 754			goto cleanup_all;
 755	}
 756	if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 757		i_readcount_inc(inode);
 758	if ((f->f_mode & FMODE_READ) &&
 759	     likely(f->f_op->read || f->f_op->read_iter))
 760		f->f_mode |= FMODE_CAN_READ;
 761	if ((f->f_mode & FMODE_WRITE) &&
 762	     likely(f->f_op->write || f->f_op->write_iter))
 763		f->f_mode |= FMODE_CAN_WRITE;
 764
 765	f->f_write_hint = WRITE_LIFE_NOT_SET;
 766	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 767
 768	file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
 769
 770	return 0;
 771
 772cleanup_all:
 773	fops_put(f->f_op);
 774	if (f->f_mode & FMODE_WRITER) {
 775		put_write_access(inode);
 776		__mnt_drop_write(f->f_path.mnt);
 777	}
 778cleanup_file:
 779	path_put(&f->f_path);
 780	f->f_path.mnt = NULL;
 781	f->f_path.dentry = NULL;
 782	f->f_inode = NULL;
 783	return error;
 784}
 785
 786/**
 787 * finish_open - finish opening a file
 788 * @file: file pointer
 789 * @dentry: pointer to dentry
 790 * @open: open callback
 791 * @opened: state of open
 792 *
 793 * This can be used to finish opening a file passed to i_op->atomic_open().
 794 *
 795 * If the open callback is set to NULL, then the standard f_op->open()
 796 * filesystem callback is substituted.
 797 *
 798 * NB: the dentry reference is _not_ consumed.  If, for example, the dentry is
 799 * the return value of d_splice_alias(), then the caller needs to perform dput()
 800 * on it after finish_open().
 801 *
 802 * On successful return @file is a fully instantiated open file.  After this, if
 803 * an error occurs in ->atomic_open(), it needs to clean up with fput().
 804 *
 805 * Returns zero on success or -errno if the open failed.
 806 */
 807int finish_open(struct file *file, struct dentry *dentry,
 808		int (*open)(struct inode *, struct file *),
 809		int *opened)
 810{
 811	int error;
 812	BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
 813
 814	file->f_path.dentry = dentry;
 815	error = do_dentry_open(file, d_backing_inode(dentry), open,
 816			       current_cred());
 817	if (!error)
 818		*opened |= FILE_OPENED;
 819
 820	return error;
 821}
 822EXPORT_SYMBOL(finish_open);
 823
 824/**
 825 * finish_no_open - finish ->atomic_open() without opening the file
 826 *
 827 * @file: file pointer
 828 * @dentry: dentry or NULL (as returned from ->lookup())
 829 *
 830 * This can be used to set the result of a successful lookup in ->atomic_open().
 831 *
 832 * NB: unlike finish_open() this function does consume the dentry reference and
 833 * the caller need not dput() it.
 834 *
 835 * Returns "1" which must be the return value of ->atomic_open() after having
 836 * called this function.
 837 */
 838int finish_no_open(struct file *file, struct dentry *dentry)
 839{
 840	file->f_path.dentry = dentry;
 841	return 1;
 842}
 843EXPORT_SYMBOL(finish_no_open);
 844
 845char *file_path(struct file *filp, char *buf, int buflen)
 846{
 847	return d_path(&filp->f_path, buf, buflen);
 848}
 849EXPORT_SYMBOL(file_path);
 850
 851/**
 852 * vfs_open - open the file at the given path
 853 * @path: path to open
 854 * @file: newly allocated file with f_flag initialized
 855 * @cred: credentials to use
 856 */
 857int vfs_open(const struct path *path, struct file *file,
 858	     const struct cred *cred)
 859{
 860	struct dentry *dentry = d_real(path->dentry, NULL, file->f_flags);
 861
 862	if (IS_ERR(dentry))
 863		return PTR_ERR(dentry);
 864
 865	file->f_path = *path;
 866	return do_dentry_open(file, d_backing_inode(dentry), NULL, cred);
 867}
 868
 869struct file *dentry_open(const struct path *path, int flags,
 870			 const struct cred *cred)
 871{
 872	int error;
 873	struct file *f;
 874
 875	validate_creds(cred);
 876
 877	/* We must always pass in a valid mount pointer. */
 878	BUG_ON(!path->mnt);
 879
 880	f = get_empty_filp();
 881	if (!IS_ERR(f)) {
 882		f->f_flags = flags;
 883		error = vfs_open(path, f, cred);
 884		if (!error) {
 885			/* from now on we need fput() to dispose of f */
 886			error = open_check_o_direct(f);
 887			if (error) {
 888				fput(f);
 889				f = ERR_PTR(error);
 890			}
 891		} else { 
 892			put_filp(f);
 893			f = ERR_PTR(error);
 894		}
 895	}
 896	return f;
 897}
 898EXPORT_SYMBOL(dentry_open);
 899
 900static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
 901{
 902	int lookup_flags = 0;
 903	int acc_mode = ACC_MODE(flags);
 904
 905	/*
 906	 * Clear out all open flags we don't know about so that we don't report
 907	 * them in fcntl(F_GETFD) or similar interfaces.
 908	 */
 909	flags &= VALID_OPEN_FLAGS;
 910
 911	if (flags & (O_CREAT | __O_TMPFILE))
 912		op->mode = (mode & S_IALLUGO) | S_IFREG;
 913	else
 914		op->mode = 0;
 915
 916	/* Must never be set by userspace */
 917	flags &= ~FMODE_NONOTIFY & ~O_CLOEXEC;
 918
 919	/*
 920	 * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
 921	 * check for O_DSYNC if the need any syncing at all we enforce it's
 922	 * always set instead of having to deal with possibly weird behaviour
 923	 * for malicious applications setting only __O_SYNC.
 924	 */
 925	if (flags & __O_SYNC)
 926		flags |= O_DSYNC;
 927
 928	if (flags & __O_TMPFILE) {
 929		if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
 930			return -EINVAL;
 931		if (!(acc_mode & MAY_WRITE))
 932			return -EINVAL;
 933	} else if (flags & O_PATH) {
 934		/*
 935		 * If we have O_PATH in the open flag. Then we
 936		 * cannot have anything other than the below set of flags
 937		 */
 938		flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
 939		acc_mode = 0;
 940	}
 941
 942	op->open_flag = flags;
 943
 944	/* O_TRUNC implies we need access checks for write permissions */
 945	if (flags & O_TRUNC)
 946		acc_mode |= MAY_WRITE;
 947
 948	/* Allow the LSM permission hook to distinguish append
 949	   access from general write access. */
 950	if (flags & O_APPEND)
 951		acc_mode |= MAY_APPEND;
 952
 953	op->acc_mode = acc_mode;
 954
 955	op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
 956
 957	if (flags & O_CREAT) {
 958		op->intent |= LOOKUP_CREATE;
 959		if (flags & O_EXCL)
 960			op->intent |= LOOKUP_EXCL;
 961	}
 962
 963	if (flags & O_DIRECTORY)
 964		lookup_flags |= LOOKUP_DIRECTORY;
 965	if (!(flags & O_NOFOLLOW))
 966		lookup_flags |= LOOKUP_FOLLOW;
 967	op->lookup_flags = lookup_flags;
 968	return 0;
 969}
 970
 971/**
 972 * file_open_name - open file and return file pointer
 973 *
 974 * @name:	struct filename containing path to open
 975 * @flags:	open flags as per the open(2) second argument
 976 * @mode:	mode for the new file if O_CREAT is set, else ignored
 977 *
 978 * This is the helper to open a file from kernelspace if you really
 979 * have to.  But in generally you should not do this, so please move
 980 * along, nothing to see here..
 981 */
 982struct file *file_open_name(struct filename *name, int flags, umode_t mode)
 983{
 984	struct open_flags op;
 985	int err = build_open_flags(flags, mode, &op);
 986	return err ? ERR_PTR(err) : do_filp_open(AT_FDCWD, name, &op);
 987}
 988
 989/**
 990 * filp_open - open file and return file pointer
 991 *
 992 * @filename:	path to open
 993 * @flags:	open flags as per the open(2) second argument
 994 * @mode:	mode for the new file if O_CREAT is set, else ignored
 995 *
 996 * This is the helper to open a file from kernelspace if you really
 997 * have to.  But in generally you should not do this, so please move
 998 * along, nothing to see here..
 999 */
1000struct file *filp_open(const char *filename, int flags, umode_t mode)
1001{
1002	struct filename *name = getname_kernel(filename);
1003	struct file *file = ERR_CAST(name);
1004	
1005	if (!IS_ERR(name)) {
1006		file = file_open_name(name, flags, mode);
1007		putname(name);
1008	}
1009	return file;
1010}
1011EXPORT_SYMBOL(filp_open);
1012
1013struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
1014			    const char *filename, int flags, umode_t mode)
1015{
1016	struct open_flags op;
1017	int err = build_open_flags(flags, mode, &op);
1018	if (err)
1019		return ERR_PTR(err);
1020	return do_file_open_root(dentry, mnt, filename, &op);
1021}
1022EXPORT_SYMBOL(file_open_root);
1023
1024struct file *filp_clone_open(struct file *oldfile)
1025{
1026	struct file *file;
1027	int retval;
1028
1029	file = get_empty_filp();
1030	if (IS_ERR(file))
1031		return file;
1032
1033	file->f_flags = oldfile->f_flags;
1034	retval = vfs_open(&oldfile->f_path, file, oldfile->f_cred);
1035	if (retval) {
1036		put_filp(file);
1037		return ERR_PTR(retval);
1038	}
1039
1040	return file;
1041}
1042EXPORT_SYMBOL(filp_clone_open);
1043
1044long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
1045{
1046	struct open_flags op;
1047	int fd = build_open_flags(flags, mode, &op);
1048	struct filename *tmp;
1049
1050	if (fd)
1051		return fd;
1052
1053	tmp = getname(filename);
1054	if (IS_ERR(tmp))
1055		return PTR_ERR(tmp);
1056
1057	fd = get_unused_fd_flags(flags);
1058	if (fd >= 0) {
1059		struct file *f = do_filp_open(dfd, tmp, &op);
1060		if (IS_ERR(f)) {
1061			put_unused_fd(fd);
1062			fd = PTR_ERR(f);
1063		} else {
1064			fsnotify_open(f);
1065			fd_install(fd, f);
1066		}
1067	}
1068	putname(tmp);
1069	return fd;
1070}
1071
1072SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1073{
1074	if (force_o_largefile())
1075		flags |= O_LARGEFILE;
1076
1077	return do_sys_open(AT_FDCWD, filename, flags, mode);
1078}
1079
1080SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1081		umode_t, mode)
1082{
1083	if (force_o_largefile())
1084		flags |= O_LARGEFILE;
1085
1086	return do_sys_open(dfd, filename, flags, mode);
1087}
1088
1089#ifdef CONFIG_COMPAT
1090/*
1091 * Exactly like sys_open(), except that it doesn't set the
1092 * O_LARGEFILE flag.
1093 */
1094COMPAT_SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1095{
1096	return do_sys_open(AT_FDCWD, filename, flags, mode);
1097}
1098
1099/*
1100 * Exactly like sys_openat(), except that it doesn't set the
1101 * O_LARGEFILE flag.
1102 */
1103COMPAT_SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags, umode_t, mode)
1104{
1105	return do_sys_open(dfd, filename, flags, mode);
1106}
1107#endif
1108
1109#ifndef __alpha__
1110
1111/*
1112 * For backward compatibility?  Maybe this should be moved
1113 * into arch/i386 instead?
1114 */
1115SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1116{
1117	return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1118}
1119
1120#endif
1121
1122/*
1123 * "id" is the POSIX thread ID. We use the
1124 * files pointer for this..
1125 */
1126int filp_close(struct file *filp, fl_owner_t id)
1127{
1128	int retval = 0;
1129
1130	if (!file_count(filp)) {
1131		printk(KERN_ERR "VFS: Close: file count is 0\n");
1132		return 0;
1133	}
1134
1135	if (filp->f_op->flush)
1136		retval = filp->f_op->flush(filp, id);
1137
1138	if (likely(!(filp->f_mode & FMODE_PATH))) {
1139		dnotify_flush(filp, id);
1140		locks_remove_posix(filp, id);
1141	}
1142	fput(filp);
1143	return retval;
1144}
1145
1146EXPORT_SYMBOL(filp_close);
1147
1148/*
1149 * Careful here! We test whether the file pointer is NULL before
1150 * releasing the fd. This ensures that one clone task can't release
1151 * an fd while another clone is opening it.
1152 */
1153SYSCALL_DEFINE1(close, unsigned int, fd)
1154{
1155	int retval = __close_fd(current->files, fd);
1156
1157	/* can't restart close syscall because file table entry was cleared */
1158	if (unlikely(retval == -ERESTARTSYS ||
1159		     retval == -ERESTARTNOINTR ||
1160		     retval == -ERESTARTNOHAND ||
1161		     retval == -ERESTART_RESTARTBLOCK))
1162		retval = -EINTR;
1163
1164	return retval;
1165}
1166EXPORT_SYMBOL(sys_close);
1167
1168/*
1169 * This routine simulates a hangup on the tty, to arrange that users
1170 * are given clean terminals at login time.
1171 */
1172SYSCALL_DEFINE0(vhangup)
1173{
1174	if (capable(CAP_SYS_TTY_CONFIG)) {
1175		tty_vhangup_self();
1176		return 0;
1177	}
1178	return -EPERM;
1179}
1180
1181/*
1182 * Called when an inode is about to be open.
1183 * We use this to disallow opening large files on 32bit systems if
1184 * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1185 * on this flag in sys_open.
1186 */
1187int generic_file_open(struct inode * inode, struct file * filp)
1188{
1189	if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1190		return -EOVERFLOW;
1191	return 0;
1192}
1193
1194EXPORT_SYMBOL(generic_file_open);
1195
1196/*
1197 * This is used by subsystems that don't want seekable
1198 * file descriptors. The function is not supposed to ever fail, the only
1199 * reason it returns an 'int' and not 'void' is so that it can be plugged
1200 * directly into file_operations structure.
1201 */
1202int nonseekable_open(struct inode *inode, struct file *filp)
1203{
1204	filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1205	return 0;
1206}
1207
1208EXPORT_SYMBOL(nonseekable_open);