// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/fs/fat/dir.c
 *
 *  directory handling functions for fat-based filesystems
 *
 *  Written 1992,1993 by Werner Almesberger
 *
 *  Hidden files 1995 by Albert Cahalan <albert@ccs.neu.edu> <adc@coe.neu.edu>
 *
 *  VFAT extensions by Gordon Chaffee <chaffee@plateau.cs.berkeley.edu>
 *  Merged with msdos fs by Henrik Storner <storner@osiris.ping.dk>
 *  Rewritten for constant inumbers. Plugged buffer overrun in readdir(). AV
 *  Short name translation 1999, 2001 by Wolfram Pienkoss <wp@bszh.de>
 */

#include <linux/slab.h>
#include <linux/compat.h>
#include <linux/filelock.h>
#include <linux/hex.h>
#include <linux/uaccess.h>
#include <linux/iversion.h>
#include "fat.h"

/*
 * Maximum buffer size of short name.
 * [(MSDOS_NAME + '.') * max one char + nul]
 * For msdos style, ['.' (hidden) + MSDOS_NAME + '.' + nul]
 */
#define FAT_MAX_SHORT_SIZE      ((MSDOS_NAME + 1) * NLS_MAX_CHARSET_SIZE + 1)
/*
 * Maximum buffer size of unicode chars from slots.
 * [(max longname slots * 13 (size in a slot) + nul) * sizeof(wchar_t)]
 */
#define FAT_MAX_UNI_CHARS       ((MSDOS_SLOTS - 1) * 13 + 1)
#define FAT_MAX_UNI_SIZE        (FAT_MAX_UNI_CHARS * sizeof(wchar_t))

static inline unsigned char fat_tolower(unsigned char c)
{
        return ((c >= 'A') && (c <= 'Z')) ? c+32 : c;
}

static inline loff_t fat_make_i_pos(struct super_block *sb,
                                    struct buffer_head *bh,
                                    struct msdos_dir_entry *de)
{
        return ((loff_t)bh->b_blocknr << MSDOS_SB(sb)->dir_per_block_bits)
                | (de - (struct msdos_dir_entry *)bh->b_data);
}

static inline void fat_dir_readahead(struct inode *dir, sector_t iblock,
                                     sector_t phys)
{
        struct super_block *sb = dir->i_sb;
        struct msdos_sb_info *sbi = MSDOS_SB(sb);
        struct buffer_head *bh;
        int sec;

        /* This is not a first sector of cluster, or sec_per_clus == 1 */
        if ((iblock & (sbi->sec_per_clus - 1)) || sbi->sec_per_clus == 1)
                return;
        /* root dir of FAT12/FAT16 */
        if (!is_fat32(sbi) && (dir->i_ino == MSDOS_ROOT_INO))
                return;

        bh = sb_find_get_block(sb, phys);
        if (bh == NULL || !buffer_uptodate(bh)) {
                for (sec = 0; sec < sbi->sec_per_clus; sec++)
                        sb_breadahead(sb, phys + sec);
        }
        brelse(bh);
}

/* Returns the inode number of the directory entry at offset pos. If bh is
   non-NULL, it is brelse'd before. Pos is incremented. The buffer header is
   returned in bh.
   AV. Most often we do it item-by-item. Makes sense to optimize.
   AV. OK, there we go: if both bh and de are non-NULL we assume that we just
   AV. want the next entry (took one explicit de=NULL in vfat/namei.c).
   AV. It's done in fat_get_entry() (inlined), here the slow case lives.
   AV. Additionally, when we return -1 (i.e. reached the end of directory)
   AV. we make bh NULL.
 */
static int fat__get_entry(struct inode *dir, loff_t *pos,
                          struct buffer_head **bh, struct msdos_dir_entry **de)
{
        struct super_block *sb = dir->i_sb;
        sector_t phys, iblock;
        unsigned long mapped_blocks;
        int err, offset;

next:
        brelse(*bh);
        *bh = NULL;
        iblock = *pos >> sb->s_blocksize_bits;
        err = fat_bmap(dir, iblock, &phys, &mapped_blocks, 0, false);
        if (err || !phys)
                return -1;      /* beyond EOF or error */

        fat_dir_readahead(dir, iblock, phys);

        *bh = sb_bread(sb, phys);
        if (*bh == NULL) {
                fat_msg_ratelimit(sb, KERN_ERR,
                        "Directory bread(block %llu) failed", (llu)phys);
                /* skip this block */
                *pos = (iblock + 1) << sb->s_blocksize_bits;
                goto next;
        }

        offset = *pos & (sb->s_blocksize - 1);
        *pos += sizeof(struct msdos_dir_entry);
        *de = (struct msdos_dir_entry *)((*bh)->b_data + offset);

        return 0;
}

static inline int fat_get_entry(struct inode *dir, loff_t *pos,
                                struct buffer_head **bh,
                                struct msdos_dir_entry **de)
{
        /* Fast stuff first */
        if (*bh && *de &&
           (*de - (struct msdos_dir_entry *)(*bh)->b_data) <
                                MSDOS_SB(dir->i_sb)->dir_per_block - 1) {
                *pos += sizeof(struct msdos_dir_entry);
                (*de)++;
                return 0;
        }
        return fat__get_entry(dir, pos, bh, de);
}

/*
 * Convert Unicode 16 to UTF-8, translated Unicode, or ASCII.
 * If uni_xlate is enabled and we can't get a 1:1 conversion, use a
 * colon as an escape character since it is normally invalid on the vfat
 * filesystem. The following four characters are the hexadecimal digits
 * of Unicode value. This lets us do a full dump and restore of Unicode
 * filenames. We could get into some trouble with long Unicode names,
 * but ignore that right now.
 * Ahem... Stack smashing in ring 0 isn't fun. Fixed.
 */
static int uni16_to_x8(struct super_block *sb, unsigned char *ascii,
                       const wchar_t *uni, int len, struct nls_table *nls)
{
        int uni_xlate = MSDOS_SB(sb)->options.unicode_xlate;
        const wchar_t *ip;
        wchar_t ec;
        unsigned char *op;
        int charlen;

        ip = uni;
        op = ascii;

        while (*ip && ((len - NLS_MAX_CHARSET_SIZE) > 0)) {
                ec = *ip++;
                charlen = nls->uni2char(ec, op, NLS_MAX_CHARSET_SIZE);
                if (charlen > 0) {
                        op += charlen;
                        len -= charlen;
                } else {
                        if (uni_xlate == 1) {
                                *op++ = ':';
                                op = hex_byte_pack(op, ec >> 8);
                                op = hex_byte_pack(op, ec);
                                len -= 5;
                        } else {
                                *op++ = '?';
                                len--;
                        }
                }
        }

        if (unlikely(*ip)) {
                fat_msg(sb, KERN_WARNING,
                        "filename was truncated while converting.");
        }

        *op = 0;
        return op - ascii;
}

static inline int fat_uni_to_x8(struct super_block *sb, const wchar_t *uni,
                                unsigned char *buf, int size)
{
        struct msdos_sb_info *sbi = MSDOS_SB(sb);
        if (sbi->options.utf8)
                return utf16s_to_utf8s(uni, FAT_MAX_UNI_CHARS,
                                UTF16_HOST_ENDIAN, buf, size);
        else
                return uni16_to_x8(sb, buf, uni, size, sbi->nls_io);
}

static inline int
fat_short2uni(struct nls_table *t, unsigned char *c, int clen, wchar_t *uni)
{
        int charlen;

        charlen = t->char2uni(c, clen, uni);
        if (charlen < 0) {
                *uni = 0x003f;  /* a question mark */
                charlen = 1;
        }
        return charlen;
}

static inline int
fat_short2lower_uni(struct nls_table *t, unsigned char *c,
                    int clen, wchar_t *uni)
{
        int charlen;
        wchar_t wc;

        charlen = t->char2uni(c, clen, &wc);
        if (charlen < 0) {
                *uni = 0x003f;  /* a question mark */
                charlen = 1;
        } else if (charlen <= 1) {
                unsigned char nc = t->charset2lower[*c];

                if (!nc)
                        nc = *c;

                charlen = t->char2uni(&nc, 1, uni);
                if (charlen < 0) {
                        *uni = 0x003f;  /* a question mark */
                        charlen = 1;
                }
        } else
                *uni = wc;

        return charlen;
}

static inline int
fat_shortname2uni(struct nls_table *nls, unsigned char *buf, int buf_size,
                  wchar_t *uni_buf, unsigned short opt, int lower)
{
        int len = 0;

        if (opt & VFAT_SFN_DISPLAY_LOWER)
                len =  fat_short2lower_uni(nls, buf, buf_size, uni_buf);
        else if (opt & VFAT_SFN_DISPLAY_WIN95)
                len = fat_short2uni(nls, buf, buf_size, uni_buf);
        else if (opt & VFAT_SFN_DISPLAY_WINNT) {
                if (lower)
                        len = fat_short2lower_uni(nls, buf, buf_size, uni_buf);
                else
                        len = fat_short2uni(nls, buf, buf_size, uni_buf);
        } else
                len = fat_short2uni(nls, buf, buf_size, uni_buf);

        return len;
}

static inline int fat_name_match(struct msdos_sb_info *sbi,
                                 const unsigned char *a, int a_len,
                                 const unsigned char *b, int b_len)
{
        if (a_len != b_len)
                return 0;

        if (sbi->options.name_check != 's')
                return !nls_strnicmp(sbi->nls_io, a, b, a_len);
        else
                return !memcmp(a, b, a_len);
}

enum { PARSE_INVALID = 1, PARSE_NOT_LONGNAME, PARSE_EOF, };

/**
 * fat_parse_long - Parse extended directory entry.
 *
 * @dir: Pointer to the inode that represents the directory.
 * @pos: On input, contains the starting position to read from.
 *       On output, updated with the new position.
 * @bh: Pointer to the buffer head that may be used for reading directory
 *       entries. May be updated.
 * @de: On input, points to the current directory entry.
 *      On output, points to the next directory entry.
 * @unicode: Pointer to a buffer where the parsed Unicode long filename will be
 *            stored.
 * @nr_slots: Pointer to a variable that will store the number of longname
 *             slots found.
 *
 * This function returns zero on success, negative value on error, or one of
 * the following:
 *
 * %PARSE_INVALID - Directory entry is invalid.
 * %PARSE_NOT_LONGNAME - Directory entry does not contain longname.
 * %PARSE_EOF - Directory has no more entries.
 */
static int fat_parse_long(struct inode *dir, loff_t *pos,
                          struct buffer_head **bh, struct msdos_dir_entry **de,
                          wchar_t **unicode, unsigned char *nr_slots)
{
        struct msdos_dir_slot *ds;
        unsigned char id, slot, slots, alias_checksum;

        if (!*unicode) {
                *unicode = __getname();
                if (!*unicode) {
                        brelse(*bh);
                        return -ENOMEM;
                }
        }
parse_long:
        ds = (struct msdos_dir_slot *)*de;
        id = ds->id;
        if (!(id & 0x40))
                return PARSE_INVALID;
        slots = id & ~0x40;
        if (slots > 20 || !slots)       /* ceil(256 * 2 / 26) */
                return PARSE_INVALID;
        *nr_slots = slots;
        alias_checksum = ds->alias_checksum;

        slot = slots;
        while (1) {
                int offset;

                slot--;
                offset = slot * 13;
                fat16_towchar(*unicode + offset, ds->name0_4, 5);
                fat16_towchar(*unicode + offset + 5, ds->name5_10, 6);
                fat16_towchar(*unicode + offset + 11, ds->name11_12, 2);

                if (ds->id & 0x40)
                        (*unicode)[offset + 13] = 0;
                if (fat_get_entry(dir, pos, bh, de) < 0)
                        return PARSE_EOF;
                if (slot == 0)
                        break;
                ds = (struct msdos_dir_slot *)*de;
                if (ds->attr != ATTR_EXT)
                        return PARSE_NOT_LONGNAME;
                if ((ds->id & ~0x40) != slot)
                        goto parse_long;
                if (ds->alias_checksum != alias_checksum)
                        goto parse_long;
        }
        if ((*de)->name[0] == DELETED_FLAG)
                return PARSE_INVALID;
        if ((*de)->attr == ATTR_EXT)
                goto parse_long;
        if (IS_FREE((*de)->name) || ((*de)->attr & ATTR_VOLUME))
                return PARSE_INVALID;
        if (fat_checksum((*de)->name) != alias_checksum)
                *nr_slots = 0;

        return 0;
}

/**
 * fat_parse_short - Parse MS-DOS (short) directory entry.
 * @sb:         superblock
 * @de:         directory entry to parse
 * @name:       FAT_MAX_SHORT_SIZE array in which to place extracted name
 * @dot_hidden: Nonzero == prepend '.' to names with ATTR_HIDDEN
 *
 * Returns the number of characters extracted into 'name'.
 */
static int fat_parse_short(struct super_block *sb,
                           const struct msdos_dir_entry *de,
                           unsigned char *name, int dot_hidden)
{
        const struct msdos_sb_info *sbi = MSDOS_SB(sb);
        int isvfat = sbi->options.isvfat;
        int nocase = sbi->options.nocase;
        unsigned short opt_shortname = sbi->options.shortname;
        struct nls_table *nls_disk = sbi->nls_disk;
        wchar_t uni_name[14];
        unsigned char c, work[MSDOS_NAME];
        unsigned char *ptname = name;
        int chi, chl, i, j, k;
        int dotoffset = 0;
        int name_len = 0, uni_len = 0;

        if (!isvfat && dot_hidden && (de->attr & ATTR_HIDDEN)) {
                *ptname++ = '.';
                dotoffset = 1;
        }

        memcpy(work, de->name, sizeof(work));
        /* For an explanation of the special treatment of 0x05 in
         * filenames, see msdos_format_name in namei_msdos.c
         */
        if (work[0] == 0x05)
                work[0] = 0xE5;

        /* Filename */
        for (i = 0, j = 0; i < 8;) {
                c = work[i];
                if (!c)
                        break;
                chl = fat_shortname2uni(nls_disk, &work[i], 8 - i,
                                        &uni_name[j++], opt_shortname,
                                        de->lcase & CASE_LOWER_BASE);
                if (chl <= 1) {
                        if (!isvfat)
                                ptname[i] = nocase ? c : fat_tolower(c);
                        i++;
                        if (c != ' ') {
                                name_len = i;
                                uni_len  = j;
                        }
                } else {
                        uni_len = j;
                        if (isvfat)
                                i += min(chl, 8-i);
                        else {
                                for (chi = 0; chi < chl && i < 8; chi++, i++)
                                        ptname[i] = work[i];
                        }
                        if (chl)
                                name_len = i;
                }
        }

        i = name_len;
        j = uni_len;
        fat_short2uni(nls_disk, ".", 1, &uni_name[j++]);
        if (!isvfat)
                ptname[i] = '.';
        i++;

        /* Extension */
        for (k = 8; k < MSDOS_NAME;) {
                c = work[k];
                if (!c)
                        break;
                chl = fat_shortname2uni(nls_disk, &work[k], MSDOS_NAME - k,
                                        &uni_name[j++], opt_shortname,
                                        de->lcase & CASE_LOWER_EXT);
                if (chl <= 1) {
                        k++;
                        if (!isvfat)
                                ptname[i] = nocase ? c : fat_tolower(c);
                        i++;
                        if (c != ' ') {
                                name_len = i;
                                uni_len  = j;
                        }
                } else {
                        uni_len = j;
                        if (isvfat) {
                                int offset = min(chl, MSDOS_NAME-k);
                                k += offset;
                                i += offset;
                        } else {
                                for (chi = 0; chi < chl && k < MSDOS_NAME;
                                     chi++, i++, k++) {
                                                ptname[i] = work[k];
                                }
                        }
                        if (chl)
                                name_len = i;
                }
        }

        if (name_len > 0) {
                name_len += dotoffset;

                if (sbi->options.isvfat) {
                        uni_name[uni_len] = 0x0000;
                        name_len = fat_uni_to_x8(sb, uni_name, name,
                                                 FAT_MAX_SHORT_SIZE);
                }
        }

        return name_len;
}

/*
 * Return values: negative -> error/not found, 0 -> found.
 */
int fat_search_long(struct inode *inode, const unsigned char *name,
                    int name_len, struct fat_slot_info *sinfo)
{
        struct super_block *sb = inode->i_sb;
        struct msdos_sb_info *sbi = MSDOS_SB(sb);
        struct buffer_head *bh = NULL;
        struct msdos_dir_entry *de;
        unsigned char nr_slots;
        wchar_t *unicode = NULL;
        unsigned char bufname[FAT_MAX_SHORT_SIZE];
        loff_t cpos = 0;
        int err, len;

        err = -ENOENT;
        while (1) {
                if (fat_get_entry(inode, &cpos, &bh, &de) == -1)
                        goto end_of_dir;
parse_record:
                nr_slots = 0;
                if (de->name[0] == DELETED_FLAG)
                        continue;
                if (de->attr != ATTR_EXT && (de->attr & ATTR_VOLUME))
                        continue;
                if (de->attr != ATTR_EXT && IS_FREE(de->name))
                        continue;
                if (de->attr == ATTR_EXT) {
                        int status = fat_parse_long(inode, &cpos, &bh, &de,
                                                    &unicode, &nr_slots);
                        if (status < 0) {
                                err = status;
                                goto end_of_dir;
                        } else if (status == PARSE_INVALID)
                                continue;
                        else if (status == PARSE_NOT_LONGNAME)
                                goto parse_record;
                        else if (status == PARSE_EOF)
                                goto end_of_dir;
                }

                /* Never prepend '.' to hidden files here.
                 * That is done only for msdos mounts (and only when
                 * 'dotsOK=yes'); if we are executing here, it is in the
                 * context of a vfat mount.
                 */
                len = fat_parse_short(sb, de, bufname, 0);
                if (len == 0)
                        continue;

                /* Compare shortname */
                if (fat_name_match(sbi, name, name_len, bufname, len))
                        goto found;

                if (nr_slots) {
                        void *longname = unicode + FAT_MAX_UNI_CHARS;
                        int size = PATH_MAX - FAT_MAX_UNI_SIZE;

                        /* Compare longname */
                        len = fat_uni_to_x8(sb, unicode, longname, size);
                        if (fat_name_match(sbi, name, name_len, longname, len))
                                goto found;
                }
        }

found:
        nr_slots++;     /* include the de */
        sinfo->slot_off = cpos - nr_slots * sizeof(*de);
        sinfo->nr_slots = nr_slots;
        sinfo->de = de;
        sinfo->bh = bh;
        sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);
        err = 0;
end_of_dir:
        if (unicode)
                __putname(unicode);

        return err;
}
EXPORT_SYMBOL_GPL(fat_search_long);

struct fat_ioctl_filldir_callback {
        struct dir_context ctx;
        void __user *dirent;
        int result;
        /* for dir ioctl */
        const char *longname;
        int long_len;
        const char *shortname;
        int short_len;
};

static int __fat_readdir(struct inode *inode, struct file *file,
                         struct dir_context *ctx, int short_only,
                         struct fat_ioctl_filldir_callback *both)
{
        struct super_block *sb = inode->i_sb;
        struct msdos_sb_info *sbi = MSDOS_SB(sb);
        struct buffer_head *bh;
        struct msdos_dir_entry *de;
        unsigned char nr_slots;
        wchar_t *unicode = NULL;
        unsigned char bufname[FAT_MAX_SHORT_SIZE];
        int isvfat = sbi->options.isvfat;
        const char *fill_name = NULL;
        int fake_offset = 0;
        loff_t cpos;
        int short_len = 0, fill_len = 0;
        int ret = 0;

        mutex_lock(&sbi->s_lock);

        cpos = ctx->pos;
        /* Fake . and .. for the root directory. */
        if (inode->i_ino == MSDOS_ROOT_INO) {
                if (!dir_emit_dots(file, ctx))
                        goto out;
                if (ctx->pos == 2) {
                        fake_offset = 1;
                        cpos = 0;
                }
        }
        if (cpos & (sizeof(struct msdos_dir_entry) - 1)) {
                ret = -ENOENT;
                goto out;
        }

        bh = NULL;
get_new:
        if (fat_get_entry(inode, &cpos, &bh, &de) == -1)
                goto end_of_dir;
parse_record:
        nr_slots = 0;
        /*
         * Check for long filename entry, but if short_only, we don't
         * need to parse long filename.
         */
        if (isvfat && !short_only) {
                if (de->name[0] == DELETED_FLAG)
                        goto record_end;
                if (de->attr != ATTR_EXT && (de->attr & ATTR_VOLUME))
                        goto record_end;
                if (de->attr != ATTR_EXT && IS_FREE(de->name))
                        goto record_end;
        } else {
                if ((de->attr & ATTR_VOLUME) || IS_FREE(de->name))
                        goto record_end;
        }

        if (isvfat && de->attr == ATTR_EXT) {
                int status = fat_parse_long(inode, &cpos, &bh, &de,
                                            &unicode, &nr_slots);
                if (status < 0) {
                        bh = NULL;
                        ret = status;
                        goto end_of_dir;
                } else if (status == PARSE_INVALID)
                        goto record_end;
                else if (status == PARSE_NOT_LONGNAME)
                        goto parse_record;
                else if (status == PARSE_EOF)
                        goto end_of_dir;

                if (nr_slots) {
                        void *longname = unicode + FAT_MAX_UNI_CHARS;
                        int size = PATH_MAX - FAT_MAX_UNI_SIZE;
                        int len = fat_uni_to_x8(sb, unicode, longname, size);

                        fill_name = longname;
                        fill_len = len;
                        /* !both && !short_only, so we don't need shortname. */
                        if (!both)
                                goto start_filldir;

                        short_len = fat_parse_short(sb, de, bufname,
                                                    sbi->options.dotsOK);
                        if (short_len == 0)
                                goto record_end;
                        /* hack for fat_ioctl_filldir() */
                        both->longname = fill_name;
                        both->long_len = fill_len;
                        both->shortname = bufname;
                        both->short_len = short_len;
                        fill_name = NULL;
                        fill_len = 0;
                        goto start_filldir;
                }
        }

        short_len = fat_parse_short(sb, de, bufname, sbi->options.dotsOK);
        if (short_len == 0)
                goto record_end;

        fill_name = bufname;
        fill_len = short_len;

start_filldir:
        ctx->pos = cpos - (nr_slots + 1) * sizeof(struct msdos_dir_entry);
        if (fake_offset && ctx->pos < 2)
                ctx->pos = 2;

        if (!memcmp(de->name, MSDOS_DOT, MSDOS_NAME)) {
                if (!dir_emit_dot(file, ctx))
                        goto fill_failed;
        } else if (!memcmp(de->name, MSDOS_DOTDOT, MSDOS_NAME)) {
                if (!dir_emit_dotdot(file, ctx))
                        goto fill_failed;
        } else {
                unsigned long inum;
                loff_t i_pos = fat_make_i_pos(sb, bh, de);
                struct inode *tmp = fat_iget(sb, i_pos);
                if (tmp) {
                        inum = tmp->i_ino;
                        iput(tmp);
                } else
                        inum = iunique(sb, MSDOS_ROOT_INO);
                if (!dir_emit(ctx, fill_name, fill_len, inum,
                            (de->attr & ATTR_DIR) ? DT_DIR : DT_REG))
                        goto fill_failed;
        }

record_end:
        fake_offset = 0;
        ctx->pos = cpos;
        goto get_new;

end_of_dir:
        if (fake_offset && cpos < 2)
                ctx->pos = 2;
        else
                ctx->pos = cpos;
fill_failed:
        brelse(bh);
        if (unicode)
                __putname(unicode);
out:
        mutex_unlock(&sbi->s_lock);

        return ret;
}

static int fat_readdir(struct file *file, struct dir_context *ctx)
{
        return __fat_readdir(file_inode(file), file, ctx, 0, NULL);
}

#define FAT_IOCTL_FILLDIR_FUNC(func, dirent_type)                          \
static bool func(struct dir_context *ctx, const char *name, int name_len,  \
                             loff_t offset, u64 ino, unsigned int d_type)  \
{                                                                          \
        struct fat_ioctl_filldir_callback *buf =                           \
                container_of(ctx, struct fat_ioctl_filldir_callback, ctx); \
        struct dirent_type __user *d1 = buf->dirent;                       \
        struct dirent_type __user *d2 = d1 + 1;                            \
                                                                           \
        if (buf->result)                                                   \
                return false;                                              \
        buf->result++;                                                     \
                                                                           \
        if (name != NULL) {                                                \
                /* dirent has only short name */                           \
                if (name_len >= sizeof(d1->d_name))                        \
                        name_len = sizeof(d1->d_name) - 1;                 \
                                                                           \
                if (put_user(0, &d2->d_name[0])                 ||         \
                    put_user(0, &d2->d_reclen)                  ||         \
                    copy_to_user(d1->d_name, name, name_len)    ||         \
                    put_user(0, d1->d_name + name_len)          ||         \
                    put_user(name_len, &d1->d_reclen))                     \
                        goto efault;                                       \
        } else {                                                           \
                /* dirent has short and long name */                       \
                const char *longname = buf->longname;                      \
                int long_len = buf->long_len;                              \
                const char *shortname = buf->shortname;                    \
                int short_len = buf->short_len;                            \
                                                                           \
                if (long_len >= sizeof(d1->d_name))                        \
                        long_len = sizeof(d1->d_name) - 1;                 \
                if (short_len >= sizeof(d1->d_name))                       \
                        short_len = sizeof(d1->d_name) - 1;                \
                                                                           \
                if (copy_to_user(d2->d_name, longname, long_len)        || \
                    put_user(0, d2->d_name + long_len)                  || \
                    put_user(long_len, &d2->d_reclen)                   || \
                    put_user(ino, &d2->d_ino)                           || \
                    put_user(offset, &d2->d_off)                        || \
                    copy_to_user(d1->d_name, shortname, short_len)      || \
                    put_user(0, d1->d_name + short_len)                 || \
                    put_user(short_len, &d1->d_reclen))                    \
                        goto efault;                                       \
        }                                                                  \
        return true;                                                       \
efault:                                                                    \
        buf->result = -EFAULT;                                             \
        return false;                                                      \
}

FAT_IOCTL_FILLDIR_FUNC(fat_ioctl_filldir, __fat_dirent)

static int fat_ioctl_readdir(struct inode *inode, struct file *file,
                             void __user *dirent, filldir_t filldir,
                             int short_only, int both)
{
        struct fat_ioctl_filldir_callback buf = {
                .ctx.actor = filldir,
                .dirent = dirent
        };
        int ret;

        buf.dirent = dirent;
        buf.result = 0;
        inode_lock_shared(inode);
        buf.ctx.pos = file->f_pos;
        ret = -ENOENT;
        if (!IS_DEADDIR(inode)) {
                ret = __fat_readdir(inode, file, &buf.ctx,
                                    short_only, both ? &buf : NULL);
                file->f_pos = buf.ctx.pos;
        }
        inode_unlock_shared(inode);
        if (ret >= 0)
                ret = buf.result;
        return ret;
}

static long fat_dir_ioctl(struct file *filp, unsigned int cmd,
                          unsigned long arg)
{
        struct inode *inode = file_inode(filp);
        struct __fat_dirent __user *d1 = (struct __fat_dirent __user *)arg;
        int short_only, both;

        switch (cmd) {
        case VFAT_IOCTL_READDIR_SHORT:
                short_only = 1;
                both = 0;
                break;
        case VFAT_IOCTL_READDIR_BOTH:
                short_only = 0;
                both = 1;
                break;
        default:
                return fat_generic_ioctl(filp, cmd, arg);
        }

        /*
         * Yes, we don't need this put_user() absolutely. However old
         * code didn't return the right value. So, app use this value,
         * in order to check whether it is EOF.
         */
        if (put_user(0, &d1->d_reclen))
                return -EFAULT;

        return fat_ioctl_readdir(inode, filp, d1, fat_ioctl_filldir,
                                 short_only, both);
}

#ifdef CONFIG_COMPAT
#define VFAT_IOCTL_READDIR_BOTH32       _IOR('r', 1, struct compat_dirent[2])
#define VFAT_IOCTL_READDIR_SHORT32      _IOR('r', 2, struct compat_dirent[2])

FAT_IOCTL_FILLDIR_FUNC(fat_compat_ioctl_filldir, compat_dirent)

static long fat_compat_dir_ioctl(struct file *filp, unsigned cmd,
                                 unsigned long arg)
{
        struct inode *inode = file_inode(filp);
        struct compat_dirent __user *d1 = compat_ptr(arg);
        int short_only, both;

        switch (cmd) {
        case VFAT_IOCTL_READDIR_SHORT32:
                short_only = 1;
                both = 0;
                break;
        case VFAT_IOCTL_READDIR_BOTH32:
                short_only = 0;
                both = 1;
                break;
        default:
                return fat_generic_ioctl(filp, cmd, (unsigned long)arg);
        }

        /*
         * Yes, we don't need this put_user() absolutely. However old
         * code didn't return the right value. So, app use this value,
         * in order to check whether it is EOF.
         */
        if (put_user(0, &d1->d_reclen))
                return -EFAULT;

        return fat_ioctl_readdir(inode, filp, d1, fat_compat_ioctl_filldir,
                                 short_only, both);
}
#endif /* CONFIG_COMPAT */

const struct file_operations fat_dir_operations = {
        .llseek         = generic_file_llseek,
        .read           = generic_read_dir,
        .iterate_shared = fat_readdir,
        .unlocked_ioctl = fat_dir_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = fat_compat_dir_ioctl,
#endif
        .fsync          = fat_file_fsync,
        .setlease       = generic_setlease,
};

static int fat_get_short_entry(struct inode *dir, loff_t *pos,
                               struct buffer_head **bh,
                               struct msdos_dir_entry **de)
{
        while (fat_get_entry(dir, pos, bh, de) >= 0) {
                /* free entry or long name entry or volume label */
                if (!IS_FREE((*de)->name) && !((*de)->attr & ATTR_VOLUME))
                        return 0;
        }
        return -ENOENT;
}

/*
 * The ".." entry can not provide the "struct fat_slot_info" information
 * for inode, nor a usable i_pos. So, this function provides some information
 * only.
 *
 * Since this function walks through the on-disk inodes within a directory,
 * callers are responsible for taking any locks necessary to prevent the
 * directory from changing.
 */
int fat_get_dotdot_entry(struct inode *dir, struct buffer_head **bh,
                         struct msdos_dir_entry **de)
{
        loff_t offset = 0;

        *de = NULL;
        while (fat_get_short_entry(dir, &offset, bh, de) >= 0) {
                if (!strncmp((*de)->name, MSDOS_DOTDOT, MSDOS_NAME))
                        return 0;
        }
        return -ENOENT;
}
EXPORT_SYMBOL_GPL(fat_get_dotdot_entry);

/* See if directory is empty */
int fat_dir_empty(struct inode *dir)
{
        struct buffer_head *bh;
        struct msdos_dir_entry *de;
        loff_t cpos;
        int result = 0;

        bh = NULL;
        cpos = 0;
        while (fat_get_short_entry(dir, &cpos, &bh, &de) >= 0) {
                if (strncmp(de->name, MSDOS_DOT   , MSDOS_NAME) &&
                    strncmp(de->name, MSDOS_DOTDOT, MSDOS_NAME)) {
                        result = -ENOTEMPTY;
                        break;
                }
        }
        brelse(bh);
        return result;
}
EXPORT_SYMBOL_GPL(fat_dir_empty);

/*
 * fat_subdirs counts the number of sub-directories of dir. It can be run
 * on directories being created.
 */
int fat_subdirs(struct inode *dir)
{
        struct buffer_head *bh;
        struct msdos_dir_entry *de;
        loff_t cpos;
        int count = 0;

        bh = NULL;
        cpos = 0;
        while (fat_get_short_entry(dir, &cpos, &bh, &de) >= 0) {
                if (de->attr & ATTR_DIR)
                        count++;
        }
        brelse(bh);
        return count;
}

/*
 * Scans a directory for a given file (name points to its formatted name).
 * Returns an error code or zero.
 */
int fat_scan(struct inode *dir, const unsigned char *name,
             struct fat_slot_info *sinfo)
{
        struct super_block *sb = dir->i_sb;

        sinfo->slot_off = 0;
        sinfo->bh = NULL;
        while (fat_get_short_entry(dir, &sinfo->slot_off, &sinfo->bh,
                                   &sinfo->de) >= 0) {
                if (!strncmp(sinfo->de->name, name, MSDOS_NAME)) {
                        sinfo->slot_off -= sizeof(*sinfo->de);
                        sinfo->nr_slots = 1;
                        sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);
                        return 0;
                }
        }
        return -ENOENT;
}
EXPORT_SYMBOL_GPL(fat_scan);

/*
 * Scans a directory for a given logstart.
 * Returns an error code or zero.
 */
int fat_scan_logstart(struct inode *dir, int i_logstart,
                      struct fat_slot_info *sinfo)
{
        struct super_block *sb = dir->i_sb;

        sinfo->slot_off = 0;
        sinfo->bh = NULL;
        while (fat_get_short_entry(dir, &sinfo->slot_off, &sinfo->bh,
                                   &sinfo->de) >= 0) {
                if (fat_get_start(MSDOS_SB(sb), sinfo->de) == i_logstart) {
                        sinfo->slot_off -= sizeof(*sinfo->de);
                        sinfo->nr_slots = 1;
                        sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);
                        return 0;
                }
        }
        return -ENOENT;
}

static int __fat_remove_entries(struct inode *dir, loff_t pos, int nr_slots)
{
        struct super_block *sb = dir->i_sb;
        struct buffer_head *bh;
        struct msdos_dir_entry *de, *endp;
        int err = 0, orig_slots;

        while (nr_slots) {
                bh = NULL;
                if (fat_get_entry(dir, &pos, &bh, &de) < 0) {
                        err = -EIO;
                        break;
                }

                orig_slots = nr_slots;
                endp = (struct msdos_dir_entry *)(bh->b_data + sb->s_blocksize);
                while (nr_slots && de < endp) {
                        de->name[0] = DELETED_FLAG;
                        de++;
                        nr_slots--;
                }
                mark_buffer_dirty_inode(bh, dir);
                if (IS_DIRSYNC(dir))
                        err = sync_dirty_buffer(bh);
                brelse(bh);
                if (err)
                        break;

                /* pos is *next* de's position, so this does `- sizeof(de)' */
                pos += ((orig_slots - nr_slots) * sizeof(*de)) - sizeof(*de);
        }

        return err;
}

int fat_remove_entries(struct inode *dir, struct fat_slot_info *sinfo)
{
        struct super_block *sb = dir->i_sb;
        struct msdos_dir_entry *de;
        struct buffer_head *bh;
        int err = 0, nr_slots;

        /*
         * First stage: Remove the shortname. By this, the directory
         * entry is removed.
         */
        nr_slots = sinfo->nr_slots;
        de = sinfo->de;
        sinfo->de = NULL;
        bh = sinfo->bh;
        sinfo->bh = NULL;
        while (nr_slots && de >= (struct msdos_dir_entry *)bh->b_data) {
                de->name[0] = DELETED_FLAG;
                de--;
                nr_slots--;
        }
        mark_buffer_dirty_inode(bh, dir);
        if (IS_DIRSYNC(dir))
                err = sync_dirty_buffer(bh);
        brelse(bh);
        if (err)
                return err;
        inode_inc_iversion(dir);

        if (nr_slots) {
                /*
                 * Second stage: remove the remaining longname slots.
                 * (This directory entry is already removed, and so return
                 * the success)
                 */
                err = __fat_remove_entries(dir, sinfo->slot_off, nr_slots);
                if (err) {
                        fat_msg(sb, KERN_WARNING,
                               "Couldn't remove the long name slots");
                }
        }

        fat_truncate_time(dir, NULL, FAT_UPDATE_ATIME | FAT_UPDATE_CMTIME);
        if (IS_DIRSYNC(dir))
                (void)fat_sync_inode(dir);
        else
                mark_inode_dirty(dir);

        return 0;
}
EXPORT_SYMBOL_GPL(fat_remove_entries);

static int fat_zeroed_cluster(struct inode *dir, sector_t blknr, int nr_used,
                              struct buffer_head **bhs, int nr_bhs)
{
        struct super_block *sb = dir->i_sb;
        sector_t last_blknr = blknr + MSDOS_SB(sb)->sec_per_clus;
        int err, i, n;

        /* Zeroing the unused blocks on this cluster */
        blknr += nr_used;
        n = nr_used;
        while (blknr < last_blknr) {
                bhs[n] = sb_getblk(sb, blknr);
                if (!bhs[n]) {
                        err = -ENOMEM;
                        goto error;
                }
                /* Avoid race with userspace read via bdev */
                lock_buffer(bhs[n]);
                memset(bhs[n]->b_data, 0, sb->s_blocksize);
                set_buffer_uptodate(bhs[n]);
                unlock_buffer(bhs[n]);
                mark_buffer_dirty_inode(bhs[n], dir);

                n++;
                blknr++;
                if (n == nr_bhs) {
                        if (IS_DIRSYNC(dir)) {
                                err = fat_sync_bhs(bhs, n);
                                if (err)
                                        goto error;
                        }
                        for (i = 0; i < n; i++)
                                brelse(bhs[i]);
                        n = 0;
                }
        }
        if (IS_DIRSYNC(dir)) {
                err = fat_sync_bhs(bhs, n);
                if (err)
                        goto error;
        }
        for (i = 0; i < n; i++)
                brelse(bhs[i]);

        return 0;

error:
        for (i = 0; i < n; i++)
                bforget(bhs[i]);
        return err;
}

int fat_alloc_new_dir(struct inode *dir, struct timespec64 *ts)
{
        struct super_block *sb = dir->i_sb;
        struct msdos_sb_info *sbi = MSDOS_SB(sb);
        struct buffer_head *bhs[MAX_BUF_PER_PAGE];
        struct msdos_dir_entry *de;
        sector_t blknr;
        __le16 date, time;
        u8 time_cs;
        int err, cluster;

        err = fat_alloc_clusters(dir, &cluster, 1);
        if (err)
                goto error;

        blknr = fat_clus_to_blknr(sbi, cluster);
        bhs[0] = sb_getblk(sb, blknr);
        if (!bhs[0]) {
                err = -ENOMEM;
                goto error_free;
        }

        fat_time_unix2fat(sbi, ts, &time, &date, &time_cs);

        de = (struct msdos_dir_entry *)bhs[0]->b_data;
        /* Avoid race with userspace read via bdev */
        lock_buffer(bhs[0]);
        /* filling the new directory slots ("." and ".." entries) */
        memcpy(de[0].name, MSDOS_DOT, MSDOS_NAME);
        memcpy(de[1].name, MSDOS_DOTDOT, MSDOS_NAME);
        de->attr = de[1].attr = ATTR_DIR;
        de[0].lcase = de[1].lcase = 0;
        de[0].time = de[1].time = time;
        de[0].date = de[1].date = date;
        if (sbi->options.isvfat) {
                /* extra timestamps */
                de[0].ctime = de[1].ctime = time;
                de[0].ctime_cs = de[1].ctime_cs = time_cs;
                de[0].adate = de[0].cdate = de[1].adate = de[1].cdate = date;
        } else {
                de[0].ctime = de[1].ctime = 0;
                de[0].ctime_cs = de[1].ctime_cs = 0;
                de[0].adate = de[0].cdate = de[1].adate = de[1].cdate = 0;
        }
        fat_set_start(&de[0], cluster);
        fat_set_start(&de[1], MSDOS_I(dir)->i_logstart);
        de[0].size = de[1].size = 0;
        memset(de + 2, 0, sb->s_blocksize - 2 * sizeof(*de));
        set_buffer_uptodate(bhs[0]);
        unlock_buffer(bhs[0]);
        mark_buffer_dirty_inode(bhs[0], dir);

        err = fat_zeroed_cluster(dir, blknr, 1, bhs, MAX_BUF_PER_PAGE);
        if (err)
                goto error_free;

        return cluster;

error_free:
        fat_free_clusters(dir, cluster);
error:
        return err;
}
EXPORT_SYMBOL_GPL(fat_alloc_new_dir);

static int fat_add_new_entries(struct inode *dir, void *slots, int nr_slots,
                               int *nr_cluster, struct msdos_dir_entry **de,
                               struct buffer_head **bh)
{
        struct super_block *sb = dir->i_sb;
        struct msdos_sb_info *sbi = MSDOS_SB(sb);
        struct buffer_head *bhs[MAX_BUF_PER_PAGE];
        sector_t blknr, start_blknr, last_blknr;
        unsigned long size, copy;
        int err, i, n, offset, cluster[2];

        /*
         * The minimum cluster size is 512bytes, and maximum entry
         * size is 32*slots (672bytes).  So, iff the cluster size is
         * 512bytes, we may need two clusters.
         */
        size = nr_slots * sizeof(struct msdos_dir_entry);
        *nr_cluster = (size + (sbi->cluster_size - 1)) >> sbi->cluster_bits;
        BUG_ON(*nr_cluster > 2);

        err = fat_alloc_clusters(dir, cluster, *nr_cluster);
        if (err)
                goto error;

        /*
         * First stage: Fill the directory entry.  NOTE: This cluster
         * is not referenced from any inode yet, so updates order is
         * not important.
         */
        i = n = copy = 0;
        do {
                start_blknr = blknr = fat_clus_to_blknr(sbi, cluster[i]);
                last_blknr = start_blknr + sbi->sec_per_clus;
                while (blknr < last_blknr) {
                        bhs[n] = sb_getblk(sb, blknr);
                        if (!bhs[n]) {
                                err = -ENOMEM;
                                goto error_nomem;
                        }

                        /* fill the directory entry */
                        copy = min(size, sb->s_blocksize);
                        /* Avoid race with userspace read via bdev */
                        lock_buffer(bhs[n]);
                        memcpy(bhs[n]->b_data, slots, copy);
                        set_buffer_uptodate(bhs[n]);
                        unlock_buffer(bhs[n]);
                        mark_buffer_dirty_inode(bhs[n], dir);
                        slots += copy;
                        size -= copy;
                        if (!size)
                                break;
                        n++;
                        blknr++;
                }
        } while (++i < *nr_cluster);

        memset(bhs[n]->b_data + copy, 0, sb->s_blocksize - copy);
        offset = copy - sizeof(struct msdos_dir_entry);
        get_bh(bhs[n]);
        *bh = bhs[n];
        *de = (struct msdos_dir_entry *)((*bh)->b_data + offset);

        /* Second stage: clear the rest of cluster, and write outs */
        err = fat_zeroed_cluster(dir, start_blknr, ++n, bhs, MAX_BUF_PER_PAGE);
        if (err)
                goto error_free;

        return cluster[0];

error_free:
        brelse(*bh);
        *bh = NULL;
        n = 0;
error_nomem:
        for (i = 0; i < n; i++)
                bforget(bhs[i]);
        fat_free_clusters(dir, cluster[0]);
error:
        return err;
}

int fat_add_entries(struct inode *dir, void *slots, int nr_slots,
                    struct fat_slot_info *sinfo)
{
        struct super_block *sb = dir->i_sb;
        struct msdos_sb_info *sbi = MSDOS_SB(sb);
        struct buffer_head *bh, *prev, *bhs[3]; /* 32*slots (672bytes) */
        struct msdos_dir_entry *de;
        int err, free_slots, i, nr_bhs;
        loff_t pos;

        sinfo->nr_slots = nr_slots;

        /* First stage: search free directory entries */
        free_slots = nr_bhs = 0;
        bh = prev = NULL;
        pos = 0;
        err = -ENOSPC;
        while (fat_get_entry(dir, &pos, &bh, &de) > -1) {
                /* check the maximum size of directory */
                if (pos >= FAT_MAX_DIR_SIZE)
                        goto error;

                if (IS_FREE(de->name)) {
                        if (prev != bh) {
                                get_bh(bh);
                                bhs[nr_bhs] = prev = bh;
                                nr_bhs++;
                        }
                        free_slots++;
                        if (free_slots == nr_slots)
                                goto found;
                } else {
                        for (i = 0; i < nr_bhs; i++)
                                brelse(bhs[i]);
                        prev = NULL;
                        free_slots = nr_bhs = 0;
                }
        }
        if (dir->i_ino == MSDOS_ROOT_INO) {
                if (!is_fat32(sbi))
                        goto error;
        } else if (MSDOS_I(dir)->i_start == 0) {
                fat_msg(sb, KERN_ERR, "Corrupted directory (i_pos %lld)",
                       MSDOS_I(dir)->i_pos);
                err = -EIO;
                goto error;
        }

found:
        err = 0;
        pos -= free_slots * sizeof(*de);
        nr_slots -= free_slots;
        if (free_slots) {
                /*
                 * Second stage: filling the free entries with new entries.
                 * NOTE: If this slots has shortname, first, we write
                 * the long name slots, then write the short name.
                 */
                int size = free_slots * sizeof(*de);
                int offset = pos & (sb->s_blocksize - 1);
                int long_bhs = nr_bhs - (nr_slots == 0);

                /* Fill the long name slots. */
                for (i = 0; i < long_bhs; i++) {
                        int copy = umin(sb->s_blocksize - offset, size);
                        memcpy(bhs[i]->b_data + offset, slots, copy);
                        mark_buffer_dirty_inode(bhs[i], dir);
                        offset = 0;
                        slots += copy;
                        size -= copy;
                }
                if (long_bhs && IS_DIRSYNC(dir))
                        err = fat_sync_bhs(bhs, long_bhs);
                if (!err && i < nr_bhs) {
                        /* Fill the short name slot. */
                        int copy = umin(sb->s_blocksize - offset, size);
                        memcpy(bhs[i]->b_data + offset, slots, copy);
                        mark_buffer_dirty_inode(bhs[i], dir);
                        if (IS_DIRSYNC(dir))
                                err = sync_dirty_buffer(bhs[i]);
                }
                for (i = 0; i < nr_bhs; i++)
                        brelse(bhs[i]);
                if (err)
                        goto error_remove;
        }

        if (nr_slots) {
                int cluster, nr_cluster;

                /*
                 * Third stage: allocate the cluster for new entries.
                 * And initialize the cluster with new entries, then
                 * add the cluster to dir.
                 */
                cluster = fat_add_new_entries(dir, slots, nr_slots, &nr_cluster,
                                              &de, &bh);
                if (cluster < 0) {
                        err = cluster;
                        goto error_remove;
                }
                err = fat_chain_add(dir, cluster, nr_cluster);
                if (err) {
                        fat_free_clusters(dir, cluster);
                        goto error_remove;
                }
                if (dir->i_size & (sbi->cluster_size - 1)) {
                        fat_fs_error(sb, "Odd directory size");
                        dir->i_size = (dir->i_size + sbi->cluster_size - 1)
                                & ~((loff_t)sbi->cluster_size - 1);
                }
                dir->i_size += nr_cluster << sbi->cluster_bits;
                MSDOS_I(dir)->mmu_private += nr_cluster << sbi->cluster_bits;
        }
        sinfo->slot_off = pos;
        sinfo->de = de;
        sinfo->bh = bh;
        sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);

        return 0;

error:
        brelse(bh);
        for (i = 0; i < nr_bhs; i++)
                brelse(bhs[i]);
        return err;

error_remove:
        brelse(bh);
        if (free_slots)
                __fat_remove_entries(dir, pos, free_slots);
        return err;
}
EXPORT_SYMBOL_GPL(fat_add_entries);