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Linux/fs/fat/namei_vfat.c

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  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 
 27 static inline unsigned long vfat_d_version(struct dentry *dentry)
 28 {
 29         return (unsigned long) dentry->d_fsdata;
 30 }
 31 
 32 static 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  */
 46 static int vfat_revalidate_shortname(struct dentry *dentry)
 47 {
 48         int ret = 1;
 49         spin_lock(&dentry->d_lock);
 50         if (!inode_eq_iversion(d_inode(dentry->d_parent), vfat_d_version(dentry)))
 51                 ret = 0;
 52         spin_unlock(&dentry->d_lock);
 53         return ret;
 54 }
 55 
 56 static int vfat_revalidate(struct dentry *dentry, unsigned int flags)
 57 {
 58         if (flags & LOOKUP_RCU)
 59                 return -ECHILD;
 60 
 61         /* This is not negative dentry. Always valid. */
 62         if (d_really_is_positive(dentry))
 63                 return 1;
 64         return vfat_revalidate_shortname(dentry);
 65 }
 66 
 67 static int vfat_revalidate_ci(struct dentry *dentry, unsigned int flags)
 68 {
 69         if (flags & LOOKUP_RCU)
 70                 return -ECHILD;
 71 
 72         /*
 73          * This is not negative dentry. Always valid.
 74          *
 75          * Note, rename() to existing directory entry will have ->d_inode,
 76          * and will use existing name which isn't specified name by user.
 77          *
 78          * We may be able to drop this positive dentry here. But dropping
 79          * positive dentry isn't good idea. So it's unsupported like
 80          * rename("filename", "FILENAME") for now.
 81          */
 82         if (d_really_is_positive(dentry))
 83                 return 1;
 84 
 85         /*
 86          * This may be nfsd (or something), anyway, we can't see the
 87          * intent of this. So, since this can be for creation, drop it.
 88          */
 89         if (!flags)
 90                 return 0;
 91 
 92         /*
 93          * Drop the negative dentry, in order to make sure to use the
 94          * case sensitive name which is specified by user if this is
 95          * for creation.
 96          */
 97         if (flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET))
 98                 return 0;
 99 
100         return vfat_revalidate_shortname(dentry);
101 }
102 
103 /* returns the length of a struct qstr, ignoring trailing dots */
104 static unsigned int __vfat_striptail_len(unsigned int len, const char *name)
105 {
106         while (len && name[len - 1] == '.')
107                 len--;
108         return len;
109 }
110 
111 static unsigned int vfat_striptail_len(const struct qstr *qstr)
112 {
113         return __vfat_striptail_len(qstr->len, qstr->name);
114 }
115 
116 /*
117  * Compute the hash for the vfat name corresponding to the dentry.
118  * Note: if the name is invalid, we leave the hash code unchanged so
119  * that the existing dentry can be used. The vfat fs routines will
120  * return ENOENT or EINVAL as appropriate.
121  */
122 static int vfat_hash(const struct dentry *dentry, struct qstr *qstr)
123 {
124         qstr->hash = full_name_hash(dentry, qstr->name, vfat_striptail_len(qstr));
125         return 0;
126 }
127 
128 /*
129  * Compute the hash for the vfat name corresponding to the dentry.
130  * Note: if the name is invalid, we leave the hash code unchanged so
131  * that the existing dentry can be used. The vfat fs routines will
132  * return ENOENT or EINVAL as appropriate.
133  */
134 static int vfat_hashi(const struct dentry *dentry, struct qstr *qstr)
135 {
136         struct nls_table *t = MSDOS_SB(dentry->d_sb)->nls_io;
137         const unsigned char *name;
138         unsigned int len;
139         unsigned long hash;
140 
141         name = qstr->name;
142         len = vfat_striptail_len(qstr);
143 
144         hash = init_name_hash(dentry);
145         while (len--)
146                 hash = partial_name_hash(nls_tolower(t, *name++), hash);
147         qstr->hash = end_name_hash(hash);
148 
149         return 0;
150 }
151 
152 /*
153  * Case insensitive compare of two vfat names.
154  */
155 static int vfat_cmpi(const struct dentry *dentry,
156                 unsigned int len, const char *str, const struct qstr *name)
157 {
158         struct nls_table *t = MSDOS_SB(dentry->d_sb)->nls_io;
159         unsigned int alen, blen;
160 
161         /* A filename cannot end in '.' or we treat it like it has none */
162         alen = vfat_striptail_len(name);
163         blen = __vfat_striptail_len(len, str);
164         if (alen == blen) {
165                 if (nls_strnicmp(t, name->name, str, alen) == 0)
166                         return 0;
167         }
168         return 1;
169 }
170 
171 /*
172  * Case sensitive compare of two vfat names.
173  */
174 static int vfat_cmp(const struct dentry *dentry,
175                 unsigned int len, const char *str, const struct qstr *name)
176 {
177         unsigned int alen, blen;
178 
179         /* A filename cannot end in '.' or we treat it like it has none */
180         alen = vfat_striptail_len(name);
181         blen = __vfat_striptail_len(len, str);
182         if (alen == blen) {
183                 if (strncmp(name->name, str, alen) == 0)
184                         return 0;
185         }
186         return 1;
187 }
188 
189 static const struct dentry_operations vfat_ci_dentry_ops = {
190         .d_revalidate   = vfat_revalidate_ci,
191         .d_hash         = vfat_hashi,
192         .d_compare      = vfat_cmpi,
193 };
194 
195 static const struct dentry_operations vfat_dentry_ops = {
196         .d_revalidate   = vfat_revalidate,
197         .d_hash         = vfat_hash,
198         .d_compare      = vfat_cmp,
199 };
200 
201 /* Characters that are undesirable in an MS-DOS file name */
202 
203 static inline wchar_t vfat_bad_char(wchar_t w)
204 {
205         return (w < 0x0020)
206             || (w == '*') || (w == '?') || (w == '<') || (w == '>')
207             || (w == '|') || (w == '"') || (w == ':') || (w == '/')
208             || (w == '\\');
209 }
210 
211 static inline wchar_t vfat_replace_char(wchar_t w)
212 {
213         return (w == '[') || (w == ']') || (w == ';') || (w == ',')
214             || (w == '+') || (w == '=');
215 }
216 
217 static wchar_t vfat_skip_char(wchar_t w)
218 {
219         return (w == '.') || (w == ' ');
220 }
221 
222 static inline int vfat_is_used_badchars(const wchar_t *s, int len)
223 {
224         int i;
225 
226         for (i = 0; i < len; i++)
227                 if (vfat_bad_char(s[i]))
228                         return -EINVAL;
229 
230         if (s[i - 1] == ' ') /* last character cannot be space */
231                 return -EINVAL;
232 
233         return 0;
234 }
235 
236 static int vfat_find_form(struct inode *dir, unsigned char *name)
237 {
238         struct fat_slot_info sinfo;
239         int err = fat_scan(dir, name, &sinfo);
240         if (err)
241                 return -ENOENT;
242         brelse(sinfo.bh);
243         return 0;
244 }
245 
246 /*
247  * 1) Valid characters for the 8.3 format alias are any combination of
248  * letters, uppercase alphabets, digits, any of the
249  * following special characters:
250  *     $ % ' ` - @ { } ~ ! # ( ) & _ ^
251  * In this case Longfilename is not stored in disk.
252  *
253  * WinNT's Extension:
254  * File name and extension name is contain uppercase/lowercase
255  * only. And it is expressed by CASE_LOWER_BASE and CASE_LOWER_EXT.
256  *
257  * 2) File name is 8.3 format, but it contain the uppercase and
258  * lowercase char, muliti bytes char, etc. In this case numtail is not
259  * added, but Longfilename is stored.
260  *
261  * 3) When the one except for the above, or the following special
262  * character are contained:
263  *        .   [ ] ; , + =
264  * numtail is added, and Longfilename must be stored in disk .
265  */
266 struct shortname_info {
267         unsigned char lower:1,
268                       upper:1,
269                       valid:1;
270 };
271 #define INIT_SHORTNAME_INFO(x)  do {            \
272         (x)->lower = 1;                         \
273         (x)->upper = 1;                         \
274         (x)->valid = 1;                         \
275 } while (0)
276 
277 static inline int to_shortname_char(struct nls_table *nls,
278                                     unsigned char *buf, int buf_size,
279                                     wchar_t *src, struct shortname_info *info)
280 {
281         int len;
282 
283         if (vfat_skip_char(*src)) {
284                 info->valid = 0;
285                 return 0;
286         }
287         if (vfat_replace_char(*src)) {
288                 info->valid = 0;
289                 buf[0] = '_';
290                 return 1;
291         }
292 
293         len = nls->uni2char(*src, buf, buf_size);
294         if (len <= 0) {
295                 info->valid = 0;
296                 buf[0] = '_';
297                 len = 1;
298         } else if (len == 1) {
299                 unsigned char prev = buf[0];
300 
301                 if (buf[0] >= 0x7F) {
302                         info->lower = 0;
303                         info->upper = 0;
304                 }
305 
306                 buf[0] = nls_toupper(nls, buf[0]);
307                 if (isalpha(buf[0])) {
308                         if (buf[0] == prev)
309                                 info->lower = 0;
310                         else
311                                 info->upper = 0;
312                 }
313         } else {
314                 info->lower = 0;
315                 info->upper = 0;
316         }
317 
318         return len;
319 }
320 
321 /*
322  * Given a valid longname, create a unique shortname.  Make sure the
323  * shortname does not exist
324  * Returns negative number on error, 0 for a normal
325  * return, and 1 for valid shortname
326  */
327 static int vfat_create_shortname(struct inode *dir, struct nls_table *nls,
328                                  wchar_t *uname, int ulen,
329                                  unsigned char *name_res, unsigned char *lcase)
330 {
331         struct fat_mount_options *opts = &MSDOS_SB(dir->i_sb)->options;
332         wchar_t *ip, *ext_start, *end, *name_start;
333         unsigned char base[9], ext[4], buf[5], *p;
334         unsigned char charbuf[NLS_MAX_CHARSET_SIZE];
335         int chl, chi;
336         int sz = 0, extlen, baselen, i, numtail_baselen, numtail2_baselen;
337         int is_shortname;
338         struct shortname_info base_info, ext_info;
339 
340         is_shortname = 1;
341         INIT_SHORTNAME_INFO(&base_info);
342         INIT_SHORTNAME_INFO(&ext_info);
343 
344         /* Now, we need to create a shortname from the long name */
345         ext_start = end = &uname[ulen];
346         while (--ext_start >= uname) {
347                 if (*ext_start == 0x002E) {     /* is `.' */
348                         if (ext_start == end - 1) {
349                                 sz = ulen;
350                                 ext_start = NULL;
351                         }
352                         break;
353                 }
354         }
355 
356         if (ext_start == uname - 1) {
357                 sz = ulen;
358                 ext_start = NULL;
359         } else if (ext_start) {
360                 /*
361                  * Names which start with a dot could be just
362                  * an extension eg. "...test".  In this case Win95
363                  * uses the extension as the name and sets no extension.
364                  */
365                 name_start = &uname[0];
366                 while (name_start < ext_start) {
367                         if (!vfat_skip_char(*name_start))
368                                 break;
369                         name_start++;
370                 }
371                 if (name_start != ext_start) {
372                         sz = ext_start - uname;
373                         ext_start++;
374                 } else {
375                         sz = ulen;
376                         ext_start = NULL;
377                 }
378         }
379 
380         numtail_baselen = 6;
381         numtail2_baselen = 2;
382         for (baselen = i = 0, p = base, ip = uname; i < sz; i++, ip++) {
383                 chl = to_shortname_char(nls, charbuf, sizeof(charbuf),
384                                         ip, &base_info);
385                 if (chl == 0)
386                         continue;
387 
388                 if (baselen < 2 && (baselen + chl) > 2)
389                         numtail2_baselen = baselen;
390                 if (baselen < 6 && (baselen + chl) > 6)
391                         numtail_baselen = baselen;
392                 for (chi = 0; chi < chl; chi++) {
393                         *p++ = charbuf[chi];
394                         baselen++;
395                         if (baselen >= 8)
396                                 break;
397                 }
398                 if (baselen >= 8) {
399                         if ((chi < chl - 1) || (ip + 1) - uname < sz)
400                                 is_shortname = 0;
401                         break;
402                 }
403         }
404         if (baselen == 0) {
405                 return -EINVAL;
406         }
407 
408         extlen = 0;
409         if (ext_start) {
410                 for (p = ext, ip = ext_start; extlen < 3 && ip < end; ip++) {
411                         chl = to_shortname_char(nls, charbuf, sizeof(charbuf),
412                                                 ip, &ext_info);
413                         if (chl == 0)
414                                 continue;
415 
416                         if ((extlen + chl) > 3) {
417                                 is_shortname = 0;
418                                 break;
419                         }
420                         for (chi = 0; chi < chl; chi++) {
421                                 *p++ = charbuf[chi];
422                                 extlen++;
423                         }
424                         if (extlen >= 3) {
425                                 if (ip + 1 != end)
426                                         is_shortname = 0;
427                                 break;
428                         }
429                 }
430         }
431         ext[extlen] = '\0';
432         base[baselen] = '\0';
433 
434         /* Yes, it can happen. ".\xe5" would do it. */
435         if (base[0] == DELETED_FLAG)
436                 base[0] = 0x05;
437 
438         /* OK, at this point we know that base is not longer than 8 symbols,
439          * ext is not longer than 3, base is nonempty, both don't contain
440          * any bad symbols (lowercase transformed to uppercase).
441          */
442 
443         memset(name_res, ' ', MSDOS_NAME);
444         memcpy(name_res, base, baselen);
445         memcpy(name_res + 8, ext, extlen);
446         *lcase = 0;
447         if (is_shortname && base_info.valid && ext_info.valid) {
448                 if (vfat_find_form(dir, name_res) == 0)
449                         return -EEXIST;
450 
451                 if (opts->shortname & VFAT_SFN_CREATE_WIN95) {
452                         return (base_info.upper && ext_info.upper);
453                 } else if (opts->shortname & VFAT_SFN_CREATE_WINNT) {
454                         if ((base_info.upper || base_info.lower) &&
455                             (ext_info.upper || ext_info.lower)) {
456                                 if (!base_info.upper && base_info.lower)
457                                         *lcase |= CASE_LOWER_BASE;
458                                 if (!ext_info.upper && ext_info.lower)
459                                         *lcase |= CASE_LOWER_EXT;
460                                 return 1;
461                         }
462                         return 0;
463                 } else {
464                         BUG();
465                 }
466         }
467 
468         if (opts->numtail == 0)
469                 if (vfat_find_form(dir, name_res) < 0)
470                         return 0;
471 
472         /*
473          * Try to find a unique extension.  This used to
474          * iterate through all possibilities sequentially,
475          * but that gave extremely bad performance.  Windows
476          * only tries a few cases before using random
477          * values for part of the base.
478          */
479 
480         if (baselen > 6) {
481                 baselen = numtail_baselen;
482                 name_res[7] = ' ';
483         }
484         name_res[baselen] = '~';
485         for (i = 1; i < 10; i++) {
486                 name_res[baselen + 1] = i + '';
487                 if (vfat_find_form(dir, name_res) < 0)
488                         return 0;
489         }
490 
491         i = jiffies;
492         sz = (jiffies >> 16) & 0x7;
493         if (baselen > 2) {
494                 baselen = numtail2_baselen;
495                 name_res[7] = ' ';
496         }
497         name_res[baselen + 4] = '~';
498         name_res[baselen + 5] = '1' + sz;
499         while (1) {
500                 snprintf(buf, sizeof(buf), "%04X", i & 0xffff);
501                 memcpy(&name_res[baselen], buf, 4);
502                 if (vfat_find_form(dir, name_res) < 0)
503                         break;
504                 i -= 11;
505         }
506         return 0;
507 }
508 
509 /* Translate a string, including coded sequences into Unicode */
510 static int
511 xlate_to_uni(const unsigned char *name, int len, unsigned char *outname,
512              int *longlen, int *outlen, int escape, int utf8,
513              struct nls_table *nls)
514 {
515         const unsigned char *ip;
516         unsigned char *op;
517         int i, fill;
518         int charlen;
519 
520         if (utf8) {
521                 *outlen = utf8s_to_utf16s(name, len, UTF16_HOST_ENDIAN,
522                                 (wchar_t *) outname, FAT_LFN_LEN + 2);
523                 if (*outlen < 0)
524                         return *outlen;
525                 else if (*outlen > FAT_LFN_LEN)
526                         return -ENAMETOOLONG;
527 
528                 op = &outname[*outlen * sizeof(wchar_t)];
529         } else {
530                 for (i = 0, ip = name, op = outname, *outlen = 0;
531                          i < len && *outlen < FAT_LFN_LEN;
532                          *outlen += 1) {
533                         if (escape && (*ip == ':')) {
534                                 u8 uc[2];
535 
536                                 if (i > len - 5)
537                                         return -EINVAL;
538 
539                                 if (hex2bin(uc, ip + 1, 2) < 0)
540                                         return -EINVAL;
541 
542                                 *(wchar_t *)op = uc[0] << 8 | uc[1];
543 
544                                 op += 2;
545                                 ip += 5;
546                                 i += 5;
547                         } else {
548                                 charlen = nls->char2uni(ip, len - i,
549                                                         (wchar_t *)op);
550                                 if (charlen < 0)
551                                         return -EINVAL;
552                                 ip += charlen;
553                                 i += charlen;
554                                 op += 2;
555                         }
556                 }
557                 if (i < len)
558                         return -ENAMETOOLONG;
559         }
560 
561         *longlen = *outlen;
562         if (*outlen % 13) {
563                 *op++ = 0;
564                 *op++ = 0;
565                 *outlen += 1;
566                 if (*outlen % 13) {
567                         fill = 13 - (*outlen % 13);
568                         for (i = 0; i < fill; i++) {
569                                 *op++ = 0xff;
570                                 *op++ = 0xff;
571                         }
572                         *outlen += fill;
573                 }
574         }
575 
576         return 0;
577 }
578 
579 static int vfat_build_slots(struct inode *dir, const unsigned char *name,
580                             int len, int is_dir, int cluster,
581                             struct timespec64 *ts,
582                             struct msdos_dir_slot *slots, int *nr_slots)
583 {
584         struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
585         struct fat_mount_options *opts = &sbi->options;
586         struct msdos_dir_slot *ps;
587         struct msdos_dir_entry *de;
588         unsigned char cksum, lcase;
589         unsigned char msdos_name[MSDOS_NAME];
590         wchar_t *uname;
591         __le16 time, date;
592         u8 time_cs;
593         int err, ulen, usize, i;
594         loff_t offset;
595 
596         *nr_slots = 0;
597 
598         uname = __getname();
599         if (!uname)
600                 return -ENOMEM;
601 
602         err = xlate_to_uni(name, len, (unsigned char *)uname, &ulen, &usize,
603                            opts->unicode_xlate, opts->utf8, sbi->nls_io);
604         if (err)
605                 goto out_free;
606 
607         err = vfat_is_used_badchars(uname, ulen);
608         if (err)
609                 goto out_free;
610 
611         err = vfat_create_shortname(dir, sbi->nls_disk, uname, ulen,
612                                     msdos_name, &lcase);
613         if (err < 0)
614                 goto out_free;
615         else if (err == 1) {
616                 de = (struct msdos_dir_entry *)slots;
617                 err = 0;
618                 goto shortname;
619         }
620 
621         /* build the entry of long file name */
622         cksum = fat_checksum(msdos_name);
623 
624         *nr_slots = usize / 13;
625         for (ps = slots, i = *nr_slots; i > 0; i--, ps++) {
626                 ps->id = i;
627                 ps->attr = ATTR_EXT;
628                 ps->reserved = 0;
629                 ps->alias_checksum = cksum;
630                 ps->start = 0;
631                 offset = (i - 1) * 13;
632                 fatwchar_to16(ps->name0_4, uname + offset, 5);
633                 fatwchar_to16(ps->name5_10, uname + offset + 5, 6);
634                 fatwchar_to16(ps->name11_12, uname + offset + 11, 2);
635         }
636         slots[0].id |= 0x40;
637         de = (struct msdos_dir_entry *)ps;
638 
639 shortname:
640         /* build the entry of 8.3 alias name */
641         (*nr_slots)++;
642         memcpy(de->name, msdos_name, MSDOS_NAME);
643         de->attr = is_dir ? ATTR_DIR : ATTR_ARCH;
644         de->lcase = lcase;
645         fat_time_unix2fat(sbi, ts, &time, &date, &time_cs);
646         de->time = de->ctime = time;
647         de->date = de->cdate = de->adate = date;
648         de->ctime_cs = time_cs;
649         fat_set_start(de, cluster);
650         de->size = 0;
651 out_free:
652         __putname(uname);
653         return err;
654 }
655 
656 static int vfat_add_entry(struct inode *dir, const struct qstr *qname,
657                           int is_dir, int cluster, struct timespec64 *ts,
658                           struct fat_slot_info *sinfo)
659 {
660         struct msdos_dir_slot *slots;
661         unsigned int len;
662         int err, nr_slots;
663 
664         len = vfat_striptail_len(qname);
665         if (len == 0)
666                 return -ENOENT;
667 
668         slots = kmalloc_array(MSDOS_SLOTS, sizeof(*slots), GFP_NOFS);
669         if (slots == NULL)
670                 return -ENOMEM;
671 
672         err = vfat_build_slots(dir, qname->name, len, is_dir, cluster, ts,
673                                slots, &nr_slots);
674         if (err)
675                 goto cleanup;
676 
677         err = fat_add_entries(dir, slots, nr_slots, sinfo);
678         if (err)
679                 goto cleanup;
680 
681         /* update timestamp */
682         fat_truncate_time(dir, ts, S_CTIME|S_MTIME);
683         if (IS_DIRSYNC(dir))
684                 (void)fat_sync_inode(dir);
685         else
686                 mark_inode_dirty(dir);
687 cleanup:
688         kfree(slots);
689         return err;
690 }
691 
692 static int vfat_find(struct inode *dir, const struct qstr *qname,
693                      struct fat_slot_info *sinfo)
694 {
695         unsigned int len = vfat_striptail_len(qname);
696         if (len == 0)
697                 return -ENOENT;
698         return fat_search_long(dir, qname->name, len, sinfo);
699 }
700 
701 static struct dentry *vfat_lookup(struct inode *dir, struct dentry *dentry,
702                                   unsigned int flags)
703 {
704         struct super_block *sb = dir->i_sb;
705         struct fat_slot_info sinfo;
706         struct inode *inode;
707         struct dentry *alias;
708         int err;
709 
710         mutex_lock(&MSDOS_SB(sb)->s_lock);
711 
712         err = vfat_find(dir, &dentry->d_name, &sinfo);
713         if (err) {
714                 if (err == -ENOENT) {
715                         inode = NULL;
716                         goto out;
717                 }
718                 goto error;
719         }
720 
721         inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
722         brelse(sinfo.bh);
723         if (IS_ERR(inode)) {
724                 err = PTR_ERR(inode);
725                 goto error;
726         }
727 
728         alias = d_find_alias(inode);
729         /*
730          * Checking "alias->d_parent == dentry->d_parent" to make sure
731          * FS is not corrupted (especially double linked dir).
732          */
733         if (alias && alias->d_parent == dentry->d_parent) {
734                 /*
735                  * This inode has non anonymous-DCACHE_DISCONNECTED
736                  * dentry. This means, the user did ->lookup() by an
737                  * another name (longname vs 8.3 alias of it) in past.
738                  *
739                  * Switch to new one for reason of locality if possible.
740                  */
741                 if (!S_ISDIR(inode->i_mode))
742                         d_move(alias, dentry);
743                 iput(inode);
744                 mutex_unlock(&MSDOS_SB(sb)->s_lock);
745                 return alias;
746         } else
747                 dput(alias);
748 
749 out:
750         mutex_unlock(&MSDOS_SB(sb)->s_lock);
751         if (!inode)
752                 vfat_d_version_set(dentry, inode_query_iversion(dir));
753         return d_splice_alias(inode, dentry);
754 error:
755         mutex_unlock(&MSDOS_SB(sb)->s_lock);
756         return ERR_PTR(err);
757 }
758 
759 static int vfat_create(struct user_namespace *mnt_userns, struct inode *dir,
760                        struct dentry *dentry, umode_t mode, bool excl)
761 {
762         struct super_block *sb = dir->i_sb;
763         struct inode *inode;
764         struct fat_slot_info sinfo;
765         struct timespec64 ts;
766         int err;
767 
768         mutex_lock(&MSDOS_SB(sb)->s_lock);
769 
770         ts = current_time(dir);
771         err = vfat_add_entry(dir, &dentry->d_name, 0, 0, &ts, &sinfo);
772         if (err)
773                 goto out;
774         inode_inc_iversion(dir);
775 
776         inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
777         brelse(sinfo.bh);
778         if (IS_ERR(inode)) {
779                 err = PTR_ERR(inode);
780                 goto out;
781         }
782         inode_inc_iversion(inode);
783         fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
784         /* timestamp is already written, so mark_inode_dirty() is unneeded. */
785 
786         d_instantiate(dentry, inode);
787 out:
788         mutex_unlock(&MSDOS_SB(sb)->s_lock);
789         return err;
790 }
791 
792 static int vfat_rmdir(struct inode *dir, struct dentry *dentry)
793 {
794         struct inode *inode = d_inode(dentry);
795         struct super_block *sb = dir->i_sb;
796         struct fat_slot_info sinfo;
797         int err;
798 
799         mutex_lock(&MSDOS_SB(sb)->s_lock);
800 
801         err = fat_dir_empty(inode);
802         if (err)
803                 goto out;
804         err = vfat_find(dir, &dentry->d_name, &sinfo);
805         if (err)
806                 goto out;
807 
808         err = fat_remove_entries(dir, &sinfo);  /* and releases bh */
809         if (err)
810                 goto out;
811         drop_nlink(dir);
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));
817 out:
818         mutex_unlock(&MSDOS_SB(sb)->s_lock);
819 
820         return err;
821 }
822 
823 static 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));
843 out:
844         mutex_unlock(&MSDOS_SB(sb)->s_lock);
845 
846         return err;
847 }
848 
849 static int vfat_mkdir(struct user_namespace *mnt_userns, 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         fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
882         /* timestamp is already written, so mark_inode_dirty() is unneeded. */
883 
884         d_instantiate(dentry, inode);
885 
886         mutex_unlock(&MSDOS_SB(sb)->s_lock);
887         return 0;
888 
889 out_free:
890         fat_free_clusters(dir, cluster);
891 out:
892         mutex_unlock(&MSDOS_SB(sb)->s_lock);
893         return err;
894 }
895 
896 static int vfat_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
897                        struct dentry *old_dentry, struct inode *new_dir,
898                        struct dentry *new_dentry, unsigned int flags)
899 {
900         struct buffer_head *dotdot_bh;
901         struct msdos_dir_entry *dotdot_de;
902         struct inode *old_inode, *new_inode;
903         struct fat_slot_info old_sinfo, sinfo;
904         struct timespec64 ts;
905         loff_t new_i_pos;
906         int err, is_dir, update_dotdot, corrupt = 0;
907         struct super_block *sb = old_dir->i_sb;
908 
909         if (flags & ~RENAME_NOREPLACE)
910                 return -EINVAL;
911 
912         old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
913         old_inode = d_inode(old_dentry);
914         new_inode = d_inode(new_dentry);
915         mutex_lock(&MSDOS_SB(sb)->s_lock);
916         err = vfat_find(old_dir, &old_dentry->d_name, &old_sinfo);
917         if (err)
918                 goto out;
919 
920         is_dir = S_ISDIR(old_inode->i_mode);
921         update_dotdot = (is_dir && old_dir != new_dir);
922         if (update_dotdot) {
923                 if (fat_get_dotdot_entry(old_inode, &dotdot_bh, &dotdot_de)) {
924                         err = -EIO;
925                         goto out;
926                 }
927         }
928 
929         ts = current_time(old_dir);
930         if (new_inode) {
931                 if (is_dir) {
932                         err = fat_dir_empty(new_inode);
933                         if (err)
934                                 goto out;
935                 }
936                 new_i_pos = MSDOS_I(new_inode)->i_pos;
937                 fat_detach(new_inode);
938         } else {
939                 err = vfat_add_entry(new_dir, &new_dentry->d_name, is_dir, 0,
940                                      &ts, &sinfo);
941                 if (err)
942                         goto out;
943                 new_i_pos = sinfo.i_pos;
944         }
945         inode_inc_iversion(new_dir);
946 
947         fat_detach(old_inode);
948         fat_attach(old_inode, new_i_pos);
949         if (IS_DIRSYNC(new_dir)) {
950                 err = fat_sync_inode(old_inode);
951                 if (err)
952                         goto error_inode;
953         } else
954                 mark_inode_dirty(old_inode);
955 
956         if (update_dotdot) {
957                 fat_set_start(dotdot_de, MSDOS_I(new_dir)->i_logstart);
958                 mark_buffer_dirty_inode(dotdot_bh, old_inode);
959                 if (IS_DIRSYNC(new_dir)) {
960                         err = sync_dirty_buffer(dotdot_bh);
961                         if (err)
962                                 goto error_dotdot;
963                 }
964                 drop_nlink(old_dir);
965                 if (!new_inode)
966                         inc_nlink(new_dir);
967         }
968 
969         err = fat_remove_entries(old_dir, &old_sinfo);  /* and releases bh */
970         old_sinfo.bh = NULL;
971         if (err)
972                 goto error_dotdot;
973         inode_inc_iversion(old_dir);
974         fat_truncate_time(old_dir, &ts, S_CTIME|S_MTIME);
975         if (IS_DIRSYNC(old_dir))
976                 (void)fat_sync_inode(old_dir);
977         else
978                 mark_inode_dirty(old_dir);
979 
980         if (new_inode) {
981                 drop_nlink(new_inode);
982                 if (is_dir)
983                         drop_nlink(new_inode);
984                 fat_truncate_time(new_inode, &ts, S_CTIME);
985         }
986 out:
987         brelse(sinfo.bh);
988         brelse(dotdot_bh);
989         brelse(old_sinfo.bh);
990         mutex_unlock(&MSDOS_SB(sb)->s_lock);
991 
992         return err;
993 
994 error_dotdot:
995         /* data cluster is shared, serious corruption */
996         corrupt = 1;
997 
998         if (update_dotdot) {
999                 fat_set_start(dotdot_de, MSDOS_I(old_dir)->i_logstart);
1000                 mark_buffer_dirty_inode(dotdot_bh, old_inode);
1001                 corrupt |= sync_dirty_buffer(dotdot_bh);
1002         }
1003 error_inode:
1004         fat_detach(old_inode);
1005         fat_attach(old_inode, old_sinfo.i_pos);
1006         if (new_inode) {
1007                 fat_attach(new_inode, new_i_pos);
1008                 if (corrupt)
1009                         corrupt |= fat_sync_inode(new_inode);
1010         } else {
1011                 /*
1012                  * If new entry was not sharing the data cluster, it
1013                  * shouldn't be serious corruption.
1014                  */
1015                 int err2 = fat_remove_entries(new_dir, &sinfo);
1016                 if (corrupt)
1017                         corrupt |= err2;
1018                 sinfo.bh = NULL;
1019         }
1020         if (corrupt < 0) {
1021                 fat_fs_error(new_dir->i_sb,
1022                              "%s: Filesystem corrupted (i_pos %lld)",
1023                              __func__, sinfo.i_pos);
1024         }
1025         goto out;
1026 }
1027 
1028 static const struct inode_operations vfat_dir_inode_operations = {
1029         .create         = vfat_create,
1030         .lookup         = vfat_lookup,
1031         .unlink         = vfat_unlink,
1032         .mkdir          = vfat_mkdir,
1033         .rmdir          = vfat_rmdir,
1034         .rename         = vfat_rename,
1035         .setattr        = fat_setattr,
1036         .getattr        = fat_getattr,
1037         .update_time    = fat_update_time,
1038 };
1039 
1040 static void setup(struct super_block *sb)
1041 {
1042         MSDOS_SB(sb)->dir_ops = &vfat_dir_inode_operations;
1043         if (MSDOS_SB(sb)->options.name_check != 's')
1044                 sb->s_d_op = &vfat_ci_dentry_ops;
1045         else
1046                 sb->s_d_op = &vfat_dentry_ops;
1047 }
1048 
1049 static int vfat_fill_super(struct super_block *sb, void *data, int silent)
1050 {
1051         return fat_fill_super(sb, data, silent, 1, setup);
1052 }
1053 
1054 static struct dentry *vfat_mount(struct file_system_type *fs_type,
1055                        int flags, const char *dev_name,
1056                        void *data)
1057 {
1058         return mount_bdev(fs_type, flags, dev_name, data, vfat_fill_super);
1059 }
1060 
1061 static struct file_system_type vfat_fs_type = {
1062         .owner          = THIS_MODULE,
1063         .name           = "vfat",
1064         .mount          = vfat_mount,
1065         .kill_sb        = kill_block_super,
1066         .fs_flags       = FS_REQUIRES_DEV | FS_ALLOW_IDMAP,
1067 };
1068 MODULE_ALIAS_FS("vfat");
1069 
1070 static int __init init_vfat_fs(void)
1071 {
1072         return register_filesystem(&vfat_fs_type);
1073 }
1074 
1075 static void __exit exit_vfat_fs(void)
1076 {
1077         unregister_filesystem(&vfat_fs_type);
1078 }
1079 
1080 MODULE_LICENSE("GPL");
1081 MODULE_DESCRIPTION("VFAT filesystem support");
1082 MODULE_AUTHOR("Gordon Chaffee");
1083 
1084 module_init(init_vfat_fs)
1085 module_exit(exit_vfat_fs)
1086 

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