namei_vfat.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 *  linux/fs/vfat/namei.c
   4 *
   5 *  Written 1992,1993 by Werner Almesberger
   6 *
   7 *  Windows95/Windows NT compatible extended MSDOS filesystem
   8 *    by Gordon Chaffee Copyright (C) 1995.  Send bug reports for the
   9 *    VFAT filesystem to <chaffee@cs.berkeley.edu>.  Specify
  10 *    what file operation caused you trouble and if you can duplicate
  11 *    the problem, send a script that demonstrates it.
  12 *
  13 *  Short name translation 1999, 2001 by Wolfram Pienkoss <wp@bszh.de>
  14 *
  15 *  Support Multibyte characters and cleanup by
  16 *				OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
  17 */
  18
  19#include <linux/module.h>
  20#include <linux/ctype.h>
  21#include <linux/slab.h>
  22#include <linux/namei.h>
  23#include <linux/kernel.h>
  24#include <linux/iversion.h>
  25#include "fat.h"
  26
  27static inline unsigned long vfat_d_version(struct dentry *dentry)
  28{
  29	return (unsigned long) dentry->d_fsdata;
  30}
  31
  32static inline void vfat_d_version_set(struct dentry *dentry,
  33				      unsigned long version)
  34{
  35	dentry->d_fsdata = (void *) version;
  36}
  37
  38/*
  39 * If new entry was created in the parent, it could create the 8.3
  40 * alias (the shortname of logname).  So, the parent may have the
  41 * negative-dentry which matches the created 8.3 alias.
  42 *
  43 * If it happened, the negative dentry isn't actually negative
  44 * anymore.  So, drop it.
  45 */
  46static bool vfat_revalidate_shortname(struct dentry *dentry, struct inode *dir)
  47{
  48	return inode_eq_iversion(dir, vfat_d_version(dentry));
  49}
  50
  51static int vfat_revalidate(struct inode *dir, const struct qstr *name,
  52			   struct dentry *dentry, unsigned int flags)
  53{
  54	if (flags & LOOKUP_RCU)
  55		return -ECHILD;
  56
  57	/* This is not negative dentry. Always valid. */
  58	if (d_really_is_positive(dentry))
  59		return 1;
  60	return vfat_revalidate_shortname(dentry, dir);
  61}
  62
  63static int vfat_revalidate_ci(struct inode *dir, const struct qstr *name,
  64			      struct dentry *dentry, unsigned int flags)
  65{
  66	if (flags & LOOKUP_RCU)
  67		return -ECHILD;
  68
  69	/*
  70	 * This is not negative dentry. Always valid.
  71	 *
  72	 * Note, rename() to existing directory entry will have ->d_inode,
  73	 * and will use existing name which isn't specified name by user.
  74	 *
  75	 * We may be able to drop this positive dentry here. But dropping
  76	 * positive dentry isn't good idea. So it's unsupported like
  77	 * rename("filename", "FILENAME") for now.
  78	 */
  79	if (d_really_is_positive(dentry))
  80		return 1;
  81
  82	/*
  83	 * This may be nfsd (or something), anyway, we can't see the
  84	 * intent of this. So, since this can be for creation, drop it.
  85	 */
  86	if (!flags)
  87		return 0;
  88
  89	/*
  90	 * Drop the negative dentry, in order to make sure to use the
  91	 * case sensitive name which is specified by user if this is
  92	 * for creation.
  93	 */
  94	if (flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET))
  95		return 0;
  96
  97	return vfat_revalidate_shortname(dentry, dir);
  98}
  99
 100/* returns the length of a struct qstr, ignoring trailing dots */
 101static unsigned int __vfat_striptail_len(unsigned int len, const char *name)
 102{
 103	while (len && name[len - 1] == '.')
 104		len--;
 105	return len;
 106}
 107
 108static unsigned int vfat_striptail_len(const struct qstr *qstr)
 109{
 110	return __vfat_striptail_len(qstr->len, qstr->name);
 111}
 112
 113/*
 114 * Compute the hash for the vfat name corresponding to the dentry.
 115 * Note: if the name is invalid, we leave the hash code unchanged so
 116 * that the existing dentry can be used. The vfat fs routines will
 117 * return ENOENT or EINVAL as appropriate.
 118 */
 119static int vfat_hash(const struct dentry *dentry, struct qstr *qstr)
 120{
 121	qstr->hash = full_name_hash(dentry, qstr->name, vfat_striptail_len(qstr));
 122	return 0;
 123}
 124
 125/*
 126 * Compute the hash for the vfat name corresponding to the dentry.
 127 * Note: if the name is invalid, we leave the hash code unchanged so
 128 * that the existing dentry can be used. The vfat fs routines will
 129 * return ENOENT or EINVAL as appropriate.
 130 */
 131static int vfat_hashi(const struct dentry *dentry, struct qstr *qstr)
 132{
 133	struct nls_table *t = MSDOS_SB(dentry->d_sb)->nls_io;
 134	const unsigned char *name;
 135	unsigned int len;
 136	unsigned long hash;
 137
 138	name = qstr->name;
 139	len = vfat_striptail_len(qstr);
 140
 141	hash = init_name_hash(dentry);
 142	while (len--)
 143		hash = partial_name_hash(nls_tolower(t, *name++), hash);
 144	qstr->hash = end_name_hash(hash);
 145
 146	return 0;
 147}
 148
 149/*
 150 * Case insensitive compare of two vfat names.
 151 */
 152static int vfat_cmpi(const struct dentry *dentry,
 153		unsigned int len, const char *str, const struct qstr *name)
 154{
 155	struct nls_table *t = MSDOS_SB(dentry->d_sb)->nls_io;
 156	unsigned int alen, blen;
 157
 158	/* A filename cannot end in '.' or we treat it like it has none */
 159	alen = vfat_striptail_len(name);
 160	blen = __vfat_striptail_len(len, str);
 161	if (alen == blen) {
 162		if (nls_strnicmp(t, name->name, str, alen) == 0)
 163			return 0;
 164	}
 165	return 1;
 166}
 167
 168/*
 169 * Case sensitive compare of two vfat names.
 170 */
 171static int vfat_cmp(const struct dentry *dentry,
 172		unsigned int len, const char *str, const struct qstr *name)
 173{
 174	unsigned int alen, blen;
 175
 176	/* A filename cannot end in '.' or we treat it like it has none */
 177	alen = vfat_striptail_len(name);
 178	blen = __vfat_striptail_len(len, str);
 179	if (alen == blen) {
 180		if (strncmp(name->name, str, alen) == 0)
 181			return 0;
 182	}
 183	return 1;
 184}
 185
 186static const struct dentry_operations vfat_ci_dentry_ops = {
 187	.d_revalidate	= vfat_revalidate_ci,
 188	.d_hash		= vfat_hashi,
 189	.d_compare	= vfat_cmpi,
 190};
 191
 192static const struct dentry_operations vfat_dentry_ops = {
 193	.d_revalidate	= vfat_revalidate,
 194	.d_hash		= vfat_hash,
 195	.d_compare	= vfat_cmp,
 196};
 197
 198/* Characters that are undesirable in an MS-DOS file name */
 199
 200static inline bool vfat_bad_char(wchar_t w)
 201{
 202	return (w < 0x0020)
 203	    || (w == '*') || (w == '?') || (w == '<') || (w == '>')
 204	    || (w == '|') || (w == '"') || (w == ':') || (w == '/')
 205	    || (w == '\\');
 206}
 207
 208static inline bool vfat_replace_char(wchar_t w)
 209{
 210	return (w == '[') || (w == ']') || (w == ';') || (w == ',')
 211	    || (w == '+') || (w == '=');
 212}
 213
 214static wchar_t vfat_skip_char(wchar_t w)
 215{
 216	return (w == '.') || (w == ' ');
 217}
 218
 219static inline int vfat_is_used_badchars(const wchar_t *s, int len)
 220{
 221	int i;
 222
 223	for (i = 0; i < len; i++)
 224		if (vfat_bad_char(s[i]))
 225			return -EINVAL;
 226
 227	if (s[i - 1] == ' ') /* last character cannot be space */
 228		return -EINVAL;
 229
 230	return 0;
 231}
 232
 233static int vfat_find_form(struct inode *dir, unsigned char *name)
 234{
 235	struct fat_slot_info sinfo;
 236	int err = fat_scan(dir, name, &sinfo);
 237	if (err)
 238		return -ENOENT;
 239	brelse(sinfo.bh);
 240	return 0;
 241}
 242
 243/*
 244 * 1) Valid characters for the 8.3 format alias are any combination of
 245 * letters, uppercase alphabets, digits, any of the
 246 * following special characters:
 247 *     $ % ' ` - @ { } ~ ! # ( ) & _ ^
 248 * In this case Longfilename is not stored in disk.
 249 *
 250 * WinNT's Extension:
 251 * File name and extension name is contain uppercase/lowercase
 252 * only. And it is expressed by CASE_LOWER_BASE and CASE_LOWER_EXT.
 253 *
 254 * 2) File name is 8.3 format, but it contain the uppercase and
 255 * lowercase char, muliti bytes char, etc. In this case numtail is not
 256 * added, but Longfilename is stored.
 257 *
 258 * 3) When the one except for the above, or the following special
 259 * character are contained:
 260 *        .   [ ] ; , + =
 261 * numtail is added, and Longfilename must be stored in disk .
 262 */
 263struct shortname_info {
 264	unsigned char lower:1,
 265		      upper:1,
 266		      valid:1;
 267};
 268#define INIT_SHORTNAME_INFO(x)	do {		\
 269	(x)->lower = 1;				\
 270	(x)->upper = 1;				\
 271	(x)->valid = 1;				\
 272} while (0)
 273
 274static inline int to_shortname_char(struct nls_table *nls,
 275				    unsigned char *buf, int buf_size,
 276				    wchar_t *src, struct shortname_info *info)
 277{
 278	int len;
 279
 280	if (vfat_skip_char(*src)) {
 281		info->valid = 0;
 282		return 0;
 283	}
 284	if (vfat_replace_char(*src)) {
 285		info->valid = 0;
 286		buf[0] = '_';
 287		return 1;
 288	}
 289
 290	len = nls->uni2char(*src, buf, buf_size);
 291	if (len <= 0) {
 292		info->valid = 0;
 293		buf[0] = '_';
 294		len = 1;
 295	} else if (len == 1) {
 296		unsigned char prev = buf[0];
 297
 298		if (buf[0] >= 0x7F) {
 299			info->lower = 0;
 300			info->upper = 0;
 301		}
 302
 303		buf[0] = nls_toupper(nls, buf[0]);
 304		if (isalpha(buf[0])) {
 305			if (buf[0] == prev)
 306				info->lower = 0;
 307			else
 308				info->upper = 0;
 309		}
 310	} else {
 311		info->lower = 0;
 312		info->upper = 0;
 313	}
 314
 315	return len;
 316}
 317
 318/*
 319 * Given a valid longname, create a unique shortname.  Make sure the
 320 * shortname does not exist
 321 * Returns negative number on error, 0 for a normal
 322 * return, and 1 for valid shortname
 323 */
 324static int vfat_create_shortname(struct inode *dir, struct nls_table *nls,
 325				 wchar_t *uname, int ulen,
 326				 unsigned char *name_res, unsigned char *lcase)
 327{
 328	struct fat_mount_options *opts = &MSDOS_SB(dir->i_sb)->options;
 329	wchar_t *ip, *ext_start, *end, *name_start;
 330	unsigned char base[9], ext[4], buf[5], *p;
 331	unsigned char charbuf[NLS_MAX_CHARSET_SIZE];
 332	int chl, chi;
 333	int sz = 0, extlen, baselen, i, numtail_baselen, numtail2_baselen;
 334	int is_shortname;
 335	struct shortname_info base_info, ext_info;
 336
 337	is_shortname = 1;
 338	INIT_SHORTNAME_INFO(&base_info);
 339	INIT_SHORTNAME_INFO(&ext_info);
 340
 341	/* Now, we need to create a shortname from the long name */
 342	ext_start = end = &uname[ulen];
 343	while (--ext_start >= uname) {
 344		if (*ext_start == 0x002E) {	/* is `.' */
 345			if (ext_start == end - 1) {
 346				sz = ulen;
 347				ext_start = NULL;
 348			}
 349			break;
 350		}
 351	}
 352
 353	if (ext_start == uname - 1) {
 354		sz = ulen;
 355		ext_start = NULL;
 356	} else if (ext_start) {
 357		/*
 358		 * Names which start with a dot could be just
 359		 * an extension eg. "...test".  In this case Win95
 360		 * uses the extension as the name and sets no extension.
 361		 */
 362		name_start = &uname[0];
 363		while (name_start < ext_start) {
 364			if (!vfat_skip_char(*name_start))
 365				break;
 366			name_start++;
 367		}
 368		if (name_start != ext_start) {
 369			sz = ext_start - uname;
 370			ext_start++;
 371		} else {
 372			sz = ulen;
 373			ext_start = NULL;
 374		}
 375	}
 376
 377	numtail_baselen = 6;
 378	numtail2_baselen = 2;
 379	for (baselen = i = 0, p = base, ip = uname; i < sz; i++, ip++) {
 380		chl = to_shortname_char(nls, charbuf, sizeof(charbuf),
 381					ip, &base_info);
 382		if (chl == 0)
 383			continue;
 384
 385		if (baselen < 2 && (baselen + chl) > 2)
 386			numtail2_baselen = baselen;
 387		if (baselen < 6 && (baselen + chl) > 6)
 388			numtail_baselen = baselen;
 389		for (chi = 0; chi < chl; chi++) {
 390			*p++ = charbuf[chi];
 391			baselen++;
 392			if (baselen >= 8)
 393				break;
 394		}
 395		if (baselen >= 8) {
 396			if ((chi < chl - 1) || (ip + 1) - uname < sz)
 397				is_shortname = 0;
 398			break;
 399		}
 400	}
 401	if (baselen == 0) {
 402		return -EINVAL;
 403	}
 404
 405	extlen = 0;
 406	if (ext_start) {
 407		for (p = ext, ip = ext_start; extlen < 3 && ip < end; ip++) {
 408			chl = to_shortname_char(nls, charbuf, sizeof(charbuf),
 409						ip, &ext_info);
 410			if (chl == 0)
 411				continue;
 412
 413			if ((extlen + chl) > 3) {
 414				is_shortname = 0;
 415				break;
 416			}
 417			for (chi = 0; chi < chl; chi++) {
 418				*p++ = charbuf[chi];
 419				extlen++;
 420			}
 421			if (extlen >= 3) {
 422				if (ip + 1 != end)
 423					is_shortname = 0;
 424				break;
 425			}
 426		}
 427	}
 428	ext[extlen] = '\0';
 429	base[baselen] = '\0';
 430
 431	/* Yes, it can happen. ".\xe5" would do it. */
 432	if (base[0] == DELETED_FLAG)
 433		base[0] = 0x05;
 434
 435	/* OK, at this point we know that base is not longer than 8 symbols,
 436	 * ext is not longer than 3, base is nonempty, both don't contain
 437	 * any bad symbols (lowercase transformed to uppercase).
 438	 */
 439
 440	memset(name_res, ' ', MSDOS_NAME);
 441	memcpy(name_res, base, baselen);
 442	memcpy(name_res + 8, ext, extlen);
 443	*lcase = 0;
 444	if (is_shortname && base_info.valid && ext_info.valid) {
 445		if (vfat_find_form(dir, name_res) == 0)
 446			return -EEXIST;
 447
 448		if (opts->shortname & VFAT_SFN_CREATE_WIN95) {
 449			return (base_info.upper && ext_info.upper);
 450		} else if (opts->shortname & VFAT_SFN_CREATE_WINNT) {
 451			if ((base_info.upper || base_info.lower) &&
 452			    (ext_info.upper || ext_info.lower)) {
 453				if (!base_info.upper && base_info.lower)
 454					*lcase |= CASE_LOWER_BASE;
 455				if (!ext_info.upper && ext_info.lower)
 456					*lcase |= CASE_LOWER_EXT;
 457				return 1;
 458			}
 459			return 0;
 460		} else {
 461			BUG();
 462		}
 463	}
 464
 465	if (opts->numtail == 0)
 466		if (vfat_find_form(dir, name_res) < 0)
 467			return 0;
 468
 469	/*
 470	 * Try to find a unique extension.  This used to
 471	 * iterate through all possibilities sequentially,
 472	 * but that gave extremely bad performance.  Windows
 473	 * only tries a few cases before using random
 474	 * values for part of the base.
 475	 */
 476
 477	if (baselen > 6) {
 478		baselen = numtail_baselen;
 479		name_res[7] = ' ';
 480	}
 481	name_res[baselen] = '~';
 482	for (i = 1; i < 10; i++) {
 483		name_res[baselen + 1] = i + '0';
 484		if (vfat_find_form(dir, name_res) < 0)
 485			return 0;
 486	}
 487
 488	i = jiffies;
 489	sz = (jiffies >> 16) & 0x7;
 490	if (baselen > 2) {
 491		baselen = numtail2_baselen;
 492		name_res[7] = ' ';
 493	}
 494	name_res[baselen + 4] = '~';
 495	name_res[baselen + 5] = '1' + sz;
 496	while (1) {
 497		snprintf(buf, sizeof(buf), "%04X", i & 0xffff);
 498		memcpy(&name_res[baselen], buf, 4);
 499		if (vfat_find_form(dir, name_res) < 0)
 500			break;
 501		i -= 11;
 502	}
 503	return 0;
 504}
 505
 506/* Translate a string, including coded sequences into Unicode */
 507static int
 508xlate_to_uni(const unsigned char *name, int len, unsigned char *outname,
 509	     int *longlen, int *outlen, int escape, int utf8,
 510	     struct nls_table *nls)
 511{
 512	const unsigned char *ip;
 513	unsigned char *op;
 514	int i, fill;
 515	int charlen;
 516
 517	if (utf8) {
 518		*outlen = utf8s_to_utf16s(name, len, UTF16_HOST_ENDIAN,
 519				(wchar_t *) outname, FAT_LFN_LEN + 2);
 520		if (*outlen < 0)
 521			return *outlen;
 522		else if (*outlen > FAT_LFN_LEN)
 523			return -ENAMETOOLONG;
 524
 525		op = &outname[*outlen * sizeof(wchar_t)];
 526	} else {
 527		for (i = 0, ip = name, op = outname, *outlen = 0;
 528			 i < len && *outlen < FAT_LFN_LEN;
 529			 *outlen += 1) {
 530			if (escape && (*ip == ':')) {
 531				u8 uc[2];
 532
 533				if (i > len - 5)
 534					return -EINVAL;
 535
 536				if (hex2bin(uc, ip + 1, 2) < 0)
 537					return -EINVAL;
 538
 539				*(wchar_t *)op = uc[0] << 8 | uc[1];
 540
 541				op += 2;
 542				ip += 5;
 543				i += 5;
 544			} else {
 545				charlen = nls->char2uni(ip, len - i,
 546							(wchar_t *)op);
 547				if (charlen < 0)
 548					return -EINVAL;
 549				ip += charlen;
 550				i += charlen;
 551				op += 2;
 552			}
 553		}
 554		if (i < len)
 555			return -ENAMETOOLONG;
 556	}
 557
 558	*longlen = *outlen;
 559	if (*outlen % 13) {
 560		*op++ = 0;
 561		*op++ = 0;
 562		*outlen += 1;
 563		if (*outlen % 13) {
 564			fill = 13 - (*outlen % 13);
 565			for (i = 0; i < fill; i++) {
 566				*op++ = 0xff;
 567				*op++ = 0xff;
 568			}
 569			*outlen += fill;
 570		}
 571	}
 572
 573	return 0;
 574}
 575
 576static int vfat_build_slots(struct inode *dir, const unsigned char *name,
 577			    int len, int is_dir, int cluster,
 578			    struct timespec64 *ts,
 579			    struct msdos_dir_slot *slots, int *nr_slots)
 580{
 581	struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
 582	struct fat_mount_options *opts = &sbi->options;
 583	struct msdos_dir_slot *ps;
 584	struct msdos_dir_entry *de;
 585	unsigned char cksum, lcase;
 586	unsigned char msdos_name[MSDOS_NAME];
 587	wchar_t *uname;
 588	__le16 time, date;
 589	u8 time_cs;
 590	int err, ulen, usize, i;
 591	loff_t offset;
 592
 593	*nr_slots = 0;
 594
 595	uname = __getname();
 596	if (!uname)
 597		return -ENOMEM;
 598
 599	err = xlate_to_uni(name, len, (unsigned char *)uname, &ulen, &usize,
 600			   opts->unicode_xlate, opts->utf8, sbi->nls_io);
 601	if (err)
 602		goto out_free;
 603
 604	err = vfat_is_used_badchars(uname, ulen);
 605	if (err)
 606		goto out_free;
 607
 608	err = vfat_create_shortname(dir, sbi->nls_disk, uname, ulen,
 609				    msdos_name, &lcase);
 610	if (err < 0)
 611		goto out_free;
 612	else if (err == 1) {
 613		de = (struct msdos_dir_entry *)slots;
 614		err = 0;
 615		goto shortname;
 616	}
 617
 618	/* build the entry of long file name */
 619	cksum = fat_checksum(msdos_name);
 620
 621	*nr_slots = usize / 13;
 622	for (ps = slots, i = *nr_slots; i > 0; i--, ps++) {
 623		ps->id = i;
 624		ps->attr = ATTR_EXT;
 625		ps->reserved = 0;
 626		ps->alias_checksum = cksum;
 627		ps->start = 0;
 628		offset = (i - 1) * 13;
 629		fatwchar_to16(ps->name0_4, uname + offset, 5);
 630		fatwchar_to16(ps->name5_10, uname + offset + 5, 6);
 631		fatwchar_to16(ps->name11_12, uname + offset + 11, 2);
 632	}
 633	slots[0].id |= 0x40;
 634	de = (struct msdos_dir_entry *)ps;
 635
 636shortname:
 637	/* build the entry of 8.3 alias name */
 638	(*nr_slots)++;
 639	memcpy(de->name, msdos_name, MSDOS_NAME);
 640	de->attr = is_dir ? ATTR_DIR : ATTR_ARCH;
 641	de->lcase = lcase;
 642	fat_time_unix2fat(sbi, ts, &time, &date, &time_cs);
 643	de->time = de->ctime = time;
 644	de->date = de->cdate = de->adate = date;
 645	de->ctime_cs = time_cs;
 646	fat_set_start(de, cluster);
 647	de->size = 0;
 648out_free:
 649	__putname(uname);
 650	return err;
 651}
 652
 653static int vfat_add_entry(struct inode *dir, const struct qstr *qname,
 654			  int is_dir, int cluster, struct timespec64 *ts,
 655			  struct fat_slot_info *sinfo)
 656{
 657	struct msdos_dir_slot *slots;
 658	unsigned int len;
 659	int err, nr_slots;
 660
 661	len = vfat_striptail_len(qname);
 662	if (len == 0)
 663		return -ENOENT;
 664
 665	slots = kmalloc_array(MSDOS_SLOTS, sizeof(*slots), GFP_NOFS);
 666	if (slots == NULL)
 667		return -ENOMEM;
 668
 669	err = vfat_build_slots(dir, qname->name, len, is_dir, cluster, ts,
 670			       slots, &nr_slots);
 671	if (err)
 672		goto cleanup;
 673
 674	err = fat_add_entries(dir, slots, nr_slots, sinfo);
 675	if (err)
 676		goto cleanup;
 677
 678	/* update timestamp */
 679	fat_truncate_time(dir, ts, S_CTIME|S_MTIME);
 680	if (IS_DIRSYNC(dir))
 681		(void)fat_sync_inode(dir);
 682	else
 683		mark_inode_dirty(dir);
 684cleanup:
 685	kfree(slots);
 686	return err;
 687}
 688
 689static int vfat_find(struct inode *dir, const struct qstr *qname,
 690		     struct fat_slot_info *sinfo)
 691{
 692	unsigned int len = vfat_striptail_len(qname);
 693	if (len == 0)
 694		return -ENOENT;
 695	return fat_search_long(dir, qname->name, len, sinfo);
 696}
 697
 698static struct dentry *vfat_lookup(struct inode *dir, struct dentry *dentry,
 699				  unsigned int flags)
 700{
 701	struct super_block *sb = dir->i_sb;
 702	struct fat_slot_info sinfo;
 703	struct inode *inode;
 704	struct dentry *alias;
 705	int err;
 706
 707	mutex_lock(&MSDOS_SB(sb)->s_lock);
 708
 709	err = vfat_find(dir, &dentry->d_name, &sinfo);
 710	if (err) {
 711		if (err == -ENOENT) {
 712			inode = NULL;
 713			goto out;
 714		}
 715		goto error;
 716	}
 717
 718	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
 719	brelse(sinfo.bh);
 720	if (IS_ERR(inode)) {
 721		err = PTR_ERR(inode);
 722		goto error;
 723	}
 724
 725	alias = d_find_alias(inode);
 726	/*
 727	 * Checking "alias->d_parent == dentry->d_parent" to make sure
 728	 * FS is not corrupted (especially double linked dir).
 729	 */
 730	if (alias && alias->d_parent == dentry->d_parent) {
 731		/*
 732		 * This inode has non anonymous-DCACHE_DISCONNECTED
 733		 * dentry. This means, the user did ->lookup() by an
 734		 * another name (longname vs 8.3 alias of it) in past.
 735		 *
 736		 * Switch to new one for reason of locality if possible.
 737		 */
 738		if (!S_ISDIR(inode->i_mode))
 739			d_move(alias, dentry);
 740		iput(inode);
 741		mutex_unlock(&MSDOS_SB(sb)->s_lock);
 742		return alias;
 743	} else
 744		dput(alias);
 745
 746out:
 747	mutex_unlock(&MSDOS_SB(sb)->s_lock);
 748	if (!inode)
 749		vfat_d_version_set(dentry, inode_query_iversion(dir));
 750	return d_splice_alias(inode, dentry);
 751error:
 752	mutex_unlock(&MSDOS_SB(sb)->s_lock);
 753	return ERR_PTR(err);
 754}
 755
 756static int vfat_create(struct mnt_idmap *idmap, struct inode *dir,
 757		       struct dentry *dentry, umode_t mode, bool excl)
 758{
 759	struct super_block *sb = dir->i_sb;
 760	struct inode *inode;
 761	struct fat_slot_info sinfo;
 762	struct timespec64 ts;
 763	int err;
 764
 765	mutex_lock(&MSDOS_SB(sb)->s_lock);
 766
 767	ts = current_time(dir);
 768	err = vfat_add_entry(dir, &dentry->d_name, 0, 0, &ts, &sinfo);
 769	if (err)
 770		goto out;
 771	inode_inc_iversion(dir);
 772
 773	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
 774	brelse(sinfo.bh);
 775	if (IS_ERR(inode)) {
 776		err = PTR_ERR(inode);
 777		goto out;
 778	}
 779	inode_inc_iversion(inode);
 780
 781	d_instantiate(dentry, inode);
 782out:
 783	mutex_unlock(&MSDOS_SB(sb)->s_lock);
 784	return err;
 785}
 786
 787static int vfat_rmdir(struct inode *dir, struct dentry *dentry)
 788{
 789	struct inode *inode = d_inode(dentry);
 790	struct super_block *sb = dir->i_sb;
 791	struct fat_slot_info sinfo;
 792	int err;
 793
 794	mutex_lock(&MSDOS_SB(sb)->s_lock);
 795
 796	err = fat_dir_empty(inode);
 797	if (err)
 798		goto out;
 799	err = vfat_find(dir, &dentry->d_name, &sinfo);
 800	if (err)
 801		goto out;
 802
 803	err = fat_remove_entries(dir, &sinfo);	/* and releases bh */
 804	if (err)
 805		goto out;
 806	if (dir->i_nlink >= 3)
 807		drop_nlink(dir);
 808	else {
 809		fat_fs_error(sb, "parent dir link count too low (%u)",
 810			dir->i_nlink);
 811	}
 812
 813	clear_nlink(inode);
 814	fat_truncate_time(inode, NULL, S_ATIME|S_MTIME);
 815	fat_detach(inode);
 816	vfat_d_version_set(dentry, inode_query_iversion(dir));
 817out:
 818	mutex_unlock(&MSDOS_SB(sb)->s_lock);
 819
 820	return err;
 821}
 822
 823static int vfat_unlink(struct inode *dir, struct dentry *dentry)
 824{
 825	struct inode *inode = d_inode(dentry);
 826	struct super_block *sb = dir->i_sb;
 827	struct fat_slot_info sinfo;
 828	int err;
 829
 830	mutex_lock(&MSDOS_SB(sb)->s_lock);
 831
 832	err = vfat_find(dir, &dentry->d_name, &sinfo);
 833	if (err)
 834		goto out;
 835
 836	err = fat_remove_entries(dir, &sinfo);	/* and releases bh */
 837	if (err)
 838		goto out;
 839	clear_nlink(inode);
 840	fat_truncate_time(inode, NULL, S_ATIME|S_MTIME);
 841	fat_detach(inode);
 842	vfat_d_version_set(dentry, inode_query_iversion(dir));
 843out:
 844	mutex_unlock(&MSDOS_SB(sb)->s_lock);
 845
 846	return err;
 847}
 848
 849static struct dentry *vfat_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 850				  struct dentry *dentry, umode_t mode)
 851{
 852	struct super_block *sb = dir->i_sb;
 853	struct inode *inode;
 854	struct fat_slot_info sinfo;
 855	struct timespec64 ts;
 856	int err, cluster;
 857
 858	mutex_lock(&MSDOS_SB(sb)->s_lock);
 859
 860	ts = current_time(dir);
 861	cluster = fat_alloc_new_dir(dir, &ts);
 862	if (cluster < 0) {
 863		err = cluster;
 864		goto out;
 865	}
 866	err = vfat_add_entry(dir, &dentry->d_name, 1, cluster, &ts, &sinfo);
 867	if (err)
 868		goto out_free;
 869	inode_inc_iversion(dir);
 870	inc_nlink(dir);
 871
 872	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
 873	brelse(sinfo.bh);
 874	if (IS_ERR(inode)) {
 875		err = PTR_ERR(inode);
 876		/* the directory was completed, just return a error */
 877		goto out;
 878	}
 879	inode_inc_iversion(inode);
 880	set_nlink(inode, 2);
 881
 882	d_instantiate(dentry, inode);
 883
 884	mutex_unlock(&MSDOS_SB(sb)->s_lock);
 885	return NULL;
 886
 887out_free:
 888	fat_free_clusters(dir, cluster);
 889out:
 890	mutex_unlock(&MSDOS_SB(sb)->s_lock);
 891	return ERR_PTR(err);
 892}
 893
 894static int vfat_get_dotdot_de(struct inode *inode, struct buffer_head **bh,
 895			      struct msdos_dir_entry **de)
 896{
 897	if (S_ISDIR(inode->i_mode)) {
 898		if (fat_get_dotdot_entry(inode, bh, de))
 899			return -EIO;
 900	}
 901	return 0;
 902}
 903
 904static int vfat_sync_ipos(struct inode *dir, struct inode *inode)
 905{
 906	if (IS_DIRSYNC(dir))
 907		return fat_sync_inode(inode);
 908	mark_inode_dirty(inode);
 909	return 0;
 910}
 911
 912static int vfat_update_dotdot_de(struct inode *dir, struct inode *inode,
 913				 struct buffer_head *dotdot_bh,
 914				 struct msdos_dir_entry *dotdot_de)
 915{
 916	fat_set_start(dotdot_de, MSDOS_I(dir)->i_logstart);
 917	mark_buffer_dirty_inode(dotdot_bh, inode);
 918	if (IS_DIRSYNC(dir))
 919		return sync_dirty_buffer(dotdot_bh);
 920	return 0;
 921}
 922
 923static void vfat_update_dir_metadata(struct inode *dir, struct timespec64 *ts)
 924{
 925	inode_inc_iversion(dir);
 926	fat_truncate_time(dir, ts, S_CTIME | S_MTIME);
 927	if (IS_DIRSYNC(dir))
 928		(void)fat_sync_inode(dir);
 929	else
 930		mark_inode_dirty(dir);
 931}
 932
 933static int vfat_rename(struct inode *old_dir, struct dentry *old_dentry,
 934		       struct inode *new_dir, struct dentry *new_dentry)
 935{
 936	struct buffer_head *dotdot_bh;
 937	struct msdos_dir_entry *dotdot_de = NULL;
 938	struct inode *old_inode, *new_inode;
 939	struct fat_slot_info old_sinfo, sinfo;
 940	struct timespec64 ts;
 941	loff_t new_i_pos;
 942	int err, is_dir, corrupt = 0;
 943	struct super_block *sb = old_dir->i_sb;
 944
 945	old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
 946	old_inode = d_inode(old_dentry);
 947	new_inode = d_inode(new_dentry);
 948	mutex_lock(&MSDOS_SB(sb)->s_lock);
 949	err = vfat_find(old_dir, &old_dentry->d_name, &old_sinfo);
 950	if (err)
 951		goto out;
 952
 953	if (old_dir != new_dir) {
 954		err = vfat_get_dotdot_de(old_inode, &dotdot_bh, &dotdot_de);
 955		if (err)
 956			goto out;
 957	}
 958
 959	is_dir = S_ISDIR(old_inode->i_mode);
 960	ts = current_time(old_dir);
 961	if (new_inode) {
 962		if (is_dir) {
 963			err = fat_dir_empty(new_inode);
 964			if (err)
 965				goto out;
 966		}
 967		new_i_pos = MSDOS_I(new_inode)->i_pos;
 968		fat_detach(new_inode);
 969	} else {
 970		err = vfat_add_entry(new_dir, &new_dentry->d_name, is_dir, 0,
 971				     &ts, &sinfo);
 972		if (err)
 973			goto out;
 974		new_i_pos = sinfo.i_pos;
 975	}
 976	inode_inc_iversion(new_dir);
 977
 978	fat_detach(old_inode);
 979	fat_attach(old_inode, new_i_pos);
 980	err = vfat_sync_ipos(new_dir, old_inode);
 981	if (err)
 982		goto error_inode;
 983
 984	if (dotdot_de) {
 985		err = vfat_update_dotdot_de(new_dir, old_inode, dotdot_bh,
 986					    dotdot_de);
 987		if (err)
 988			goto error_dotdot;
 989		drop_nlink(old_dir);
 990		if (!new_inode)
 991 			inc_nlink(new_dir);
 992	}
 993
 994	err = fat_remove_entries(old_dir, &old_sinfo);	/* and releases bh */
 995	old_sinfo.bh = NULL;
 996	if (err)
 997		goto error_dotdot;
 998	vfat_update_dir_metadata(old_dir, &ts);
 999
1000	if (new_inode) {
1001		drop_nlink(new_inode);
1002		if (is_dir)
1003			drop_nlink(new_inode);
1004		fat_truncate_time(new_inode, &ts, S_CTIME);
1005	}
1006out:
1007	brelse(sinfo.bh);
1008	brelse(dotdot_bh);
1009	brelse(old_sinfo.bh);
1010	mutex_unlock(&MSDOS_SB(sb)->s_lock);
1011
1012	return err;
1013
1014error_dotdot:
1015	/* data cluster is shared, serious corruption */
1016	corrupt = 1;
1017
1018	if (dotdot_de) {
1019		corrupt |= vfat_update_dotdot_de(old_dir, old_inode, dotdot_bh,
1020						 dotdot_de);
1021	}
1022error_inode:
1023	fat_detach(old_inode);
1024	fat_attach(old_inode, old_sinfo.i_pos);
1025	if (new_inode) {
1026		fat_attach(new_inode, new_i_pos);
1027		if (corrupt)
1028			corrupt |= fat_sync_inode(new_inode);
1029	} else {
1030		/*
1031		 * If new entry was not sharing the data cluster, it
1032		 * shouldn't be serious corruption.
1033		 */
1034		int err2 = fat_remove_entries(new_dir, &sinfo);
1035		if (corrupt)
1036			corrupt |= err2;
1037		sinfo.bh = NULL;
1038	}
1039	if (corrupt < 0) {
1040		fat_fs_error(new_dir->i_sb,
1041			     "%s: Filesystem corrupted (i_pos %lld)",
1042			     __func__, new_i_pos);
1043	}
1044	goto out;
1045}
1046
1047static void vfat_exchange_ipos(struct inode *old_inode, struct inode *new_inode,
1048			       loff_t old_i_pos, loff_t new_i_pos)
1049{
1050	fat_detach(old_inode);
1051	fat_detach(new_inode);
1052	fat_attach(old_inode, new_i_pos);
1053	fat_attach(new_inode, old_i_pos);
1054}
1055
1056static void vfat_move_nlink(struct inode *src, struct inode *dst)
1057{
1058	drop_nlink(src);
1059	inc_nlink(dst);
1060}
1061
1062static int vfat_rename_exchange(struct inode *old_dir, struct dentry *old_dentry,
1063				struct inode *new_dir, struct dentry *new_dentry)
1064{
1065	struct buffer_head *old_dotdot_bh = NULL, *new_dotdot_bh = NULL;
1066	struct msdos_dir_entry *old_dotdot_de = NULL, *new_dotdot_de = NULL;
1067	struct inode *old_inode, *new_inode;
1068	struct timespec64 ts = current_time(old_dir);
1069	loff_t old_i_pos, new_i_pos;
1070	int err, corrupt = 0;
1071	struct super_block *sb = old_dir->i_sb;
1072
1073	old_inode = d_inode(old_dentry);
1074	new_inode = d_inode(new_dentry);
1075
1076	/* Acquire super block lock for the operation to be atomic */
1077	mutex_lock(&MSDOS_SB(sb)->s_lock);
1078
1079	/* if directories are not the same, get ".." info to update */
1080	if (old_dir != new_dir) {
1081		err = vfat_get_dotdot_de(old_inode, &old_dotdot_bh,
1082					 &old_dotdot_de);
1083		if (err)
1084			goto out;
1085
1086		err = vfat_get_dotdot_de(new_inode, &new_dotdot_bh,
1087					 &new_dotdot_de);
1088		if (err)
1089			goto out;
1090	}
1091
1092	old_i_pos = MSDOS_I(old_inode)->i_pos;
1093	new_i_pos = MSDOS_I(new_inode)->i_pos;
1094
1095	vfat_exchange_ipos(old_inode, new_inode, old_i_pos, new_i_pos);
1096
1097	err = vfat_sync_ipos(old_dir, new_inode);
1098	if (err)
1099		goto error_exchange;
1100	err = vfat_sync_ipos(new_dir, old_inode);
1101	if (err)
1102		goto error_exchange;
1103
1104	/* update ".." directory entry info */
1105	if (old_dotdot_de) {
1106		err = vfat_update_dotdot_de(new_dir, old_inode, old_dotdot_bh,
1107					    old_dotdot_de);
1108		if (err)
1109			goto error_old_dotdot;
1110	}
1111	if (new_dotdot_de) {
1112		err = vfat_update_dotdot_de(old_dir, new_inode, new_dotdot_bh,
1113					    new_dotdot_de);
1114		if (err)
1115			goto error_new_dotdot;
1116	}
1117
1118	/* if cross directory and only one is a directory, adjust nlink */
1119	if (!old_dotdot_de != !new_dotdot_de) {
1120		if (old_dotdot_de)
1121			vfat_move_nlink(old_dir, new_dir);
1122		else
1123			vfat_move_nlink(new_dir, old_dir);
1124	}
1125
1126	vfat_update_dir_metadata(old_dir, &ts);
1127	/* if directories are not the same, update new_dir as well */
1128	if (old_dir != new_dir)
1129		vfat_update_dir_metadata(new_dir, &ts);
1130
1131out:
1132	brelse(old_dotdot_bh);
1133	brelse(new_dotdot_bh);
1134	mutex_unlock(&MSDOS_SB(sb)->s_lock);
1135
1136	return err;
1137
1138error_new_dotdot:
1139	if (new_dotdot_de) {
1140		corrupt |= vfat_update_dotdot_de(new_dir, new_inode,
1141						 new_dotdot_bh, new_dotdot_de);
1142	}
1143
1144error_old_dotdot:
1145	if (old_dotdot_de) {
1146		corrupt |= vfat_update_dotdot_de(old_dir, old_inode,
1147						 old_dotdot_bh, old_dotdot_de);
1148	}
1149
1150error_exchange:
1151	vfat_exchange_ipos(old_inode, new_inode, new_i_pos, old_i_pos);
1152	corrupt |= vfat_sync_ipos(new_dir, new_inode);
1153	corrupt |= vfat_sync_ipos(old_dir, old_inode);
1154
1155	if (corrupt < 0) {
1156		fat_fs_error(new_dir->i_sb,
1157			     "%s: Filesystem corrupted (i_pos %lld, %lld)",
1158			     __func__, old_i_pos, new_i_pos);
1159	}
1160	goto out;
1161}
1162
1163static int vfat_rename2(struct mnt_idmap *idmap, struct inode *old_dir,
1164			struct dentry *old_dentry, struct inode *new_dir,
1165			struct dentry *new_dentry, unsigned int flags)
1166{
1167	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
1168		return -EINVAL;
1169
1170	if (flags & RENAME_EXCHANGE) {
1171		return vfat_rename_exchange(old_dir, old_dentry,
1172					    new_dir, new_dentry);
1173	}
1174
1175	/* VFS already handled RENAME_NOREPLACE, handle it as a normal rename */
1176	return vfat_rename(old_dir, old_dentry, new_dir, new_dentry);
1177}
1178
1179static const struct inode_operations vfat_dir_inode_operations = {
1180	.create		= vfat_create,
1181	.lookup		= vfat_lookup,
1182	.unlink		= vfat_unlink,
1183	.mkdir		= vfat_mkdir,
1184	.rmdir		= vfat_rmdir,
1185	.rename		= vfat_rename2,
1186	.setattr	= fat_setattr,
1187	.getattr	= fat_getattr,
1188	.update_time	= fat_update_time,
1189};
1190
1191static void setup(struct super_block *sb)
1192{
1193	MSDOS_SB(sb)->dir_ops = &vfat_dir_inode_operations;
1194	if (MSDOS_SB(sb)->options.name_check != 's')
1195		set_default_d_op(sb, &vfat_ci_dentry_ops);
1196	else
1197		set_default_d_op(sb, &vfat_dentry_ops);
1198}
1199
1200static int vfat_fill_super(struct super_block *sb, struct fs_context *fc)
1201{
1202	return fat_fill_super(sb, fc, setup);
1203}
1204
1205static int vfat_get_tree(struct fs_context *fc)
1206{
1207	return get_tree_bdev(fc, vfat_fill_super);
1208}
1209
1210static int vfat_parse_param(struct fs_context *fc, struct fs_parameter *param)
1211{
1212	return fat_parse_param(fc, param, true);
1213}
1214
1215static const struct fs_context_operations vfat_context_ops = {
1216	.parse_param	= vfat_parse_param,
1217	.get_tree	= vfat_get_tree,
1218	.reconfigure	= fat_reconfigure,
1219	.free		= fat_free_fc,
1220};
1221
1222static int vfat_init_fs_context(struct fs_context *fc)
1223{
1224	int err;
1225
1226	/* Initialize with is_vfat == true */
1227	err = fat_init_fs_context(fc, true);
1228	if (err)
1229		return err;
1230
1231	fc->ops = &vfat_context_ops;
1232	return 0;
1233}
1234
1235static struct file_system_type vfat_fs_type = {
1236	.owner		= THIS_MODULE,
1237	.name		= "vfat",
1238	.kill_sb	= kill_block_super,
1239	.fs_flags	= FS_REQUIRES_DEV | FS_ALLOW_IDMAP,
1240	.init_fs_context = vfat_init_fs_context,
1241	.parameters     = fat_param_spec,
1242};
1243MODULE_ALIAS_FS("vfat");
1244
1245static int __init init_vfat_fs(void)
1246{
1247	return register_filesystem(&vfat_fs_type);
1248}
1249
1250static void __exit exit_vfat_fs(void)
1251{
1252	unregister_filesystem(&vfat_fs_type);
1253}
1254
1255MODULE_LICENSE("GPL");
1256MODULE_DESCRIPTION("VFAT filesystem support");
1257MODULE_AUTHOR("Gordon Chaffee");
1258
1259module_init(init_vfat_fs)
1260module_exit(exit_vfat_fs)