// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/fs/msdos/namei.c
 *
 *  Written 1992,1993 by Werner Almesberger
 *  Hidden files 1995 by Albert Cahalan <albert@ccs.neu.edu> <adc@coe.neu.edu>
 *  Rewritten for constant inumbers 1999 by Al Viro
 */

#include <linux/module.h>
#include <linux/iversion.h>
#include "fat.h"

/* Characters that are undesirable in an MS-DOS file name */
static unsigned char bad_chars[] = "*?<>|\"";
static unsigned char bad_if_strict[] = "+=,; ";

/***** Formats an MS-DOS file name. Rejects invalid names. */
static int msdos_format_name(const unsigned char *name, int len,
                             unsigned char *res, struct fat_mount_options *opts)
        /*
         * name is the proposed name, len is its length, res is
         * the resulting name, opts->name_check is either (r)elaxed,
         * (n)ormal or (s)trict, opts->dotsOK allows dots at the
         * beginning of name (for hidden files)
         */
{
        unsigned char *walk;
        unsigned char c;
        int space;

        if (name[0] == '.') {   /* dotfile because . and .. already done */
                if (opts->dotsOK) {
                        /* Get rid of dot - test for it elsewhere */
                        name++;
                        len--;
                } else
                        return -EINVAL;
        }
        /*
         * disallow names that _really_ start with a dot
         */
        space = 1;
        c = 0;
        for (walk = res; len && walk - res < 8; walk++) {
                c = *name++;
                len--;
                if (opts->name_check != 'r' && strchr(bad_chars, c))
                        return -EINVAL;
                if (opts->name_check == 's' && strchr(bad_if_strict, c))
                        return -EINVAL;
                if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
                        return -EINVAL;
                if (c < ' ' || c == ':' || c == '\\')
                        return -EINVAL;
        /*
         * 0xE5 is legal as a first character, but we must substitute
         * 0x05 because 0xE5 marks deleted files.  Yes, DOS really
         * does this.
         * It seems that Microsoft hacked DOS to support non-US
         * characters after the 0xE5 character was already in use to
         * mark deleted files.
         */
                if ((res == walk) && (c == 0xE5))
                        c = 0x05;
                if (c == '.')
                        break;
                space = (c == ' ');
                *walk = (!opts->nocase && c >= 'a' && c <= 'z') ? c - 32 : c;
        }
        if (space)
                return -EINVAL;
        if (opts->name_check == 's' && len && c != '.') {
                c = *name++;
                len--;
                if (c != '.')
                        return -EINVAL;
        }
        while (c != '.' && len--)
                c = *name++;
        if (c == '.') {
                while (walk - res < 8)
                        *walk++ = ' ';
                while (len > 0 && walk - res < MSDOS_NAME) {
                        c = *name++;
                        len--;
                        if (opts->name_check != 'r' && strchr(bad_chars, c))
                                return -EINVAL;
                        if (opts->name_check == 's' &&
                            strchr(bad_if_strict, c))
                                return -EINVAL;
                        if (c < ' ' || c == ':' || c == '\\')
                                return -EINVAL;
                        if (c == '.') {
                                if (opts->name_check == 's')
                                        return -EINVAL;
                                break;
                        }
                        if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
                                return -EINVAL;
                        space = c == ' ';
                        if (!opts->nocase && c >= 'a' && c <= 'z')
                                *walk++ = c - 32;
                        else
                                *walk++ = c;
                }
                if (space)
                        return -EINVAL;
                if (opts->name_check == 's' && len)
                        return -EINVAL;
        }
        while (walk - res < MSDOS_NAME)
                *walk++ = ' ';

        return 0;
}

/***** Locates a directory entry.  Uses unformatted name. */
static int msdos_find(struct inode *dir, const unsigned char *name, int len,
                      struct fat_slot_info *sinfo)
{
        struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
        unsigned char msdos_name[MSDOS_NAME];
        int err;

        err = msdos_format_name(name, len, msdos_name, &sbi->options);
        if (err)
                return -ENOENT;

        err = fat_scan(dir, msdos_name, sinfo);
        if (!err && sbi->options.dotsOK) {
                if (name[0] == '.') {
                        if (!(sinfo->de->attr & ATTR_HIDDEN))
                                err = -ENOENT;
                } else {
                        if (sinfo->de->attr & ATTR_HIDDEN)
                                err = -ENOENT;
                }
                if (err)
                        brelse(sinfo->bh);
        }
        return err;
}

/*
 * Compute the hash for the msdos name corresponding to the dentry.
 * Note: if the name is invalid, we leave the hash code unchanged so
 * that the existing dentry can be used. The msdos fs routines will
 * return ENOENT or EINVAL as appropriate.
 */
static int msdos_hash(const struct dentry *dentry, struct qstr *qstr)
{
        struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
        unsigned char msdos_name[MSDOS_NAME];
        int error;

        error = msdos_format_name(qstr->name, qstr->len, msdos_name, options);
        if (!error)
                qstr->hash = full_name_hash(dentry, msdos_name, MSDOS_NAME);
        return 0;
}

/*
 * Compare two msdos names. If either of the names are invalid,
 * we fall back to doing the standard name comparison.
 */
static int msdos_cmp(const struct dentry *dentry,
                unsigned int len, const char *str, const struct qstr *name)
{
        struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
        unsigned char a_msdos_name[MSDOS_NAME], b_msdos_name[MSDOS_NAME];
        int error;

        error = msdos_format_name(name->name, name->len, a_msdos_name, options);
        if (error)
                goto old_compare;
        error = msdos_format_name(str, len, b_msdos_name, options);
        if (error)
                goto old_compare;
        error = memcmp(a_msdos_name, b_msdos_name, MSDOS_NAME);
out:
        return error;

old_compare:
        error = 1;
        if (name->len == len)
                error = memcmp(name->name, str, len);
        goto out;
}

static const struct dentry_operations msdos_dentry_operations = {
        .d_hash         = msdos_hash,
        .d_compare      = msdos_cmp,
};

/*
 * AV. Wrappers for FAT sb operations. Is it wise?
 */

/***** Get inode using directory and name */
static struct dentry *msdos_lookup(struct inode *dir, struct dentry *dentry,
                                   unsigned int flags)
{
        struct super_block *sb = dir->i_sb;
        struct fat_slot_info sinfo;
        struct inode *inode;
        int err;

        mutex_lock(&MSDOS_SB(sb)->s_lock);
        err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
        switch (err) {
        case -ENOENT:
                inode = NULL;
                break;
        case 0:
                inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
                brelse(sinfo.bh);
                break;
        default:
                inode = ERR_PTR(err);
        }
        mutex_unlock(&MSDOS_SB(sb)->s_lock);
        return d_splice_alias(inode, dentry);
}

/***** Creates a directory entry (name is already formatted). */
static int msdos_add_entry(struct inode *dir, const unsigned char *name,
                           int is_dir, int is_hid, int cluster,
                           struct timespec64 *ts, struct fat_slot_info *sinfo)
{
        struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
        struct msdos_dir_entry de;
        __le16 time, date;
        int err;

        memcpy(de.name, name, MSDOS_NAME);
        de.attr = is_dir ? ATTR_DIR : ATTR_ARCH;
        if (is_hid)
                de.attr |= ATTR_HIDDEN;
        de.lcase = 0;
        fat_time_unix2fat(sbi, ts, &time, &date, NULL);
        de.cdate = de.adate = 0;
        de.ctime = 0;
        de.ctime_cs = 0;
        de.time = time;
        de.date = date;
        fat_set_start(&de, cluster);
        de.size = 0;

        err = fat_add_entries(dir, &de, 1, sinfo);
        if (err)
                return err;

        fat_truncate_time(dir, ts, FAT_UPDATE_CMTIME);
        if (IS_DIRSYNC(dir))
                (void)fat_sync_inode(dir);
        else
                mark_inode_dirty(dir);

        return 0;
}

/***** Create a file */
static int msdos_create(struct mnt_idmap *idmap, struct inode *dir,
                        struct dentry *dentry, umode_t mode, bool excl)
{
        struct super_block *sb = dir->i_sb;
        struct inode *inode = NULL;
        struct fat_slot_info sinfo;
        struct timespec64 ts;
        unsigned char msdos_name[MSDOS_NAME];
        int err, is_hid;

        mutex_lock(&MSDOS_SB(sb)->s_lock);

        err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
                                msdos_name, &MSDOS_SB(sb)->options);
        if (err)
                goto out;
        is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
        /* Have to do it due to foo vs. .foo conflicts */
        if (!fat_scan(dir, msdos_name, &sinfo)) {
                brelse(sinfo.bh);
                err = -EINVAL;
                goto out;
        }

        ts = current_time(dir);
        err = msdos_add_entry(dir, msdos_name, 0, is_hid, 0, &ts, &sinfo);
        if (err)
                goto out;
        inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
        brelse(sinfo.bh);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                goto out;
        }
        fat_truncate_time(inode, &ts, FAT_UPDATE_ATIME | FAT_UPDATE_CMTIME);
        /* timestamp is already written, so mark_inode_dirty() is unneeded. */

        d_instantiate(dentry, inode);
out:
        mutex_unlock(&MSDOS_SB(sb)->s_lock);
        if (!err)
                err = fat_flush_inodes(sb, dir, inode);
        return err;
}

/***** Remove a directory */
static int msdos_rmdir(struct inode *dir, struct dentry *dentry)
{
        struct super_block *sb = dir->i_sb;
        struct inode *inode = d_inode(dentry);
        struct fat_slot_info sinfo;
        int err;

        mutex_lock(&MSDOS_SB(sb)->s_lock);
        err = fat_dir_empty(inode);
        if (err)
                goto out;
        err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
        if (err)
                goto out;

        err = fat_remove_entries(dir, &sinfo);  /* and releases bh */
        if (err)
                goto out;
        if (dir->i_nlink >= 3)
                drop_nlink(dir);
        else {
                fat_fs_error(sb, "parent dir link count too low (%u)",
                        dir->i_nlink);
        }

        clear_nlink(inode);
        fat_detach(inode);
out:
        mutex_unlock(&MSDOS_SB(sb)->s_lock);
        if (!err)
                err = fat_flush_inodes(sb, dir, inode);

        return err;
}

/***** Make a directory */
static struct dentry *msdos_mkdir(struct mnt_idmap *idmap, struct inode *dir,
                                  struct dentry *dentry, umode_t mode)
{
        struct super_block *sb = dir->i_sb;
        struct fat_slot_info sinfo;
        struct inode *inode;
        unsigned char msdos_name[MSDOS_NAME];
        struct timespec64 ts;
        int err, is_hid, cluster;

        mutex_lock(&MSDOS_SB(sb)->s_lock);

        err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
                                msdos_name, &MSDOS_SB(sb)->options);
        if (err)
                goto out;
        is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
        /* foo vs .foo situation */
        if (!fat_scan(dir, msdos_name, &sinfo)) {
                brelse(sinfo.bh);
                err = -EINVAL;
                goto out;
        }

        ts = current_time(dir);
        cluster = fat_alloc_new_dir(dir, &ts);
        if (cluster < 0) {
                err = cluster;
                goto out;
        }
        err = msdos_add_entry(dir, msdos_name, 1, is_hid, cluster, &ts, &sinfo);
        if (err)
                goto out_free;
        inc_nlink(dir);

        inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
        brelse(sinfo.bh);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                /* the directory was completed, just return a error */
                goto out;
        }
        set_nlink(inode, 2);
        fat_truncate_time(inode, &ts, FAT_UPDATE_ATIME | FAT_UPDATE_CMTIME);
        /* timestamp is already written, so mark_inode_dirty() is unneeded. */

        d_instantiate(dentry, inode);

        mutex_unlock(&MSDOS_SB(sb)->s_lock);
        fat_flush_inodes(sb, dir, inode);
        return NULL;

out_free:
        fat_free_clusters(dir, cluster);
out:
        mutex_unlock(&MSDOS_SB(sb)->s_lock);
        return ERR_PTR(err);
}

/***** Unlink a file */
static int msdos_unlink(struct inode *dir, struct dentry *dentry)
{
        struct inode *inode = d_inode(dentry);
        struct super_block *sb = inode->i_sb;
        struct fat_slot_info sinfo;
        int err;

        mutex_lock(&MSDOS_SB(sb)->s_lock);
        err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
        if (err)
                goto out;

        err = fat_remove_entries(dir, &sinfo);  /* and releases bh */
        if (err)
                goto out;
        clear_nlink(inode);
        fat_detach(inode);
out:
        mutex_unlock(&MSDOS_SB(sb)->s_lock);
        if (!err)
                err = fat_flush_inodes(sb, dir, inode);

        return err;
}

static int do_msdos_rename(struct inode *old_dir, unsigned char *old_name,
                           struct dentry *old_dentry,
                           struct inode *new_dir, unsigned char *new_name,
                           struct dentry *new_dentry, int is_hid)
{
        struct buffer_head *dotdot_bh;
        struct msdos_dir_entry *dotdot_de;
        struct inode *old_inode, *new_inode;
        struct fat_slot_info old_sinfo, sinfo;
        struct timespec64 ts;
        loff_t new_i_pos;
        int err, old_attrs, is_dir, update_dotdot, corrupt = 0;

        old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
        old_inode = d_inode(old_dentry);
        new_inode = d_inode(new_dentry);

        err = fat_scan(old_dir, old_name, &old_sinfo);
        if (err) {
                err = -EIO;
                goto out;
        }

        is_dir = S_ISDIR(old_inode->i_mode);
        update_dotdot = (is_dir && old_dir != new_dir);
        if (update_dotdot) {
                if (fat_get_dotdot_entry(old_inode, &dotdot_bh, &dotdot_de)) {
                        err = -EIO;
                        goto out;
                }
        }

        old_attrs = MSDOS_I(old_inode)->i_attrs;
        err = fat_scan(new_dir, new_name, &sinfo);
        if (!err) {
                if (!new_inode) {
                        /* "foo" -> ".foo" case. just change the ATTR_HIDDEN */
                        if (sinfo.de != old_sinfo.de) {
                                err = -EINVAL;
                                goto out;
                        }
                        if (is_hid)
                                MSDOS_I(old_inode)->i_attrs |= ATTR_HIDDEN;
                        else
                                MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
                        if (IS_DIRSYNC(old_dir)) {
                                err = fat_sync_inode(old_inode);
                                if (err) {
                                        MSDOS_I(old_inode)->i_attrs = old_attrs;
                                        goto out;
                                }
                        } else
                                mark_inode_dirty(old_inode);

                        inode_inc_iversion(old_dir);
                        fat_truncate_time(old_dir, NULL, FAT_UPDATE_CMTIME);
                        if (IS_DIRSYNC(old_dir))
                                (void)fat_sync_inode(old_dir);
                        else
                                mark_inode_dirty(old_dir);
                        goto out;
                }
        }

        ts = current_time(old_inode);
        if (new_inode) {
                if (err)
                        goto out;
                if (is_dir) {
                        err = fat_dir_empty(new_inode);
                        if (err)
                                goto out;
                }
                new_i_pos = MSDOS_I(new_inode)->i_pos;
                fat_detach(new_inode);
        } else {
                err = msdos_add_entry(new_dir, new_name, is_dir, is_hid, 0,
                                      &ts, &sinfo);
                if (err)
                        goto out;
                new_i_pos = sinfo.i_pos;
        }
        inode_inc_iversion(new_dir);

        fat_detach(old_inode);
        fat_attach(old_inode, new_i_pos);
        if (is_hid)
                MSDOS_I(old_inode)->i_attrs |= ATTR_HIDDEN;
        else
                MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
        if (IS_DIRSYNC(new_dir)) {
                err = fat_sync_inode(old_inode);
                if (err)
                        goto error_inode;
        } else
                mark_inode_dirty(old_inode);

        if (update_dotdot) {
                fat_set_start(dotdot_de, MSDOS_I(new_dir)->i_logstart);
                mark_buffer_dirty_inode(dotdot_bh, old_inode);
                if (IS_DIRSYNC(new_dir)) {
                        err = sync_dirty_buffer(dotdot_bh);
                        if (err)
                                goto error_dotdot;
                }
                drop_nlink(old_dir);
                if (!new_inode)
                        inc_nlink(new_dir);
        }

        err = fat_remove_entries(old_dir, &old_sinfo);  /* and releases bh */
        old_sinfo.bh = NULL;
        if (err)
                goto error_dotdot;
        inode_inc_iversion(old_dir);
        fat_truncate_time(old_dir, &ts, FAT_UPDATE_CMTIME);
        if (IS_DIRSYNC(old_dir))
                (void)fat_sync_inode(old_dir);
        else
                mark_inode_dirty(old_dir);

        if (new_inode) {
                drop_nlink(new_inode);
                if (is_dir)
                        drop_nlink(new_inode);
        }
out:
        brelse(sinfo.bh);
        brelse(dotdot_bh);
        brelse(old_sinfo.bh);
        return err;

error_dotdot:
        /* data cluster is shared, serious corruption */
        corrupt = 1;

        if (update_dotdot) {
                fat_set_start(dotdot_de, MSDOS_I(old_dir)->i_logstart);
                mark_buffer_dirty_inode(dotdot_bh, old_inode);
                corrupt |= sync_dirty_buffer(dotdot_bh);
        }
error_inode:
        fat_detach(old_inode);
        fat_attach(old_inode, old_sinfo.i_pos);
        MSDOS_I(old_inode)->i_attrs = old_attrs;
        if (new_inode) {
                fat_attach(new_inode, new_i_pos);
                if (corrupt)
                        corrupt |= fat_sync_inode(new_inode);
        } else {
                /*
                 * If new entry was not sharing the data cluster, it
                 * shouldn't be serious corruption.
                 */
                int err2 = fat_remove_entries(new_dir, &sinfo);
                if (corrupt)
                        corrupt |= err2;
                sinfo.bh = NULL;
        }
        if (corrupt < 0) {
                fat_fs_error(new_dir->i_sb,
                             "%s: Filesystem corrupted (i_pos %lld)",
                             __func__, sinfo.i_pos);
        }
        goto out;
}

/***** Rename, a wrapper for rename_same_dir & rename_diff_dir */
static int msdos_rename(struct mnt_idmap *idmap,
                        struct inode *old_dir, struct dentry *old_dentry,
                        struct inode *new_dir, struct dentry *new_dentry,
                        unsigned int flags)
{
        struct super_block *sb = old_dir->i_sb;
        unsigned char old_msdos_name[MSDOS_NAME], new_msdos_name[MSDOS_NAME];
        int err, is_hid;

        if (flags & ~RENAME_NOREPLACE)
                return -EINVAL;

        mutex_lock(&MSDOS_SB(sb)->s_lock);

        err = msdos_format_name(old_dentry->d_name.name,
                                old_dentry->d_name.len, old_msdos_name,
                                &MSDOS_SB(old_dir->i_sb)->options);
        if (err)
                goto out;
        err = msdos_format_name(new_dentry->d_name.name,
                                new_dentry->d_name.len, new_msdos_name,
                                &MSDOS_SB(new_dir->i_sb)->options);
        if (err)
                goto out;

        is_hid =
             (new_dentry->d_name.name[0] == '.') && (new_msdos_name[0] != '.');

        err = do_msdos_rename(old_dir, old_msdos_name, old_dentry,
                              new_dir, new_msdos_name, new_dentry, is_hid);
out:
        mutex_unlock(&MSDOS_SB(sb)->s_lock);
        if (!err)
                err = fat_flush_inodes(sb, old_dir, new_dir);
        return err;
}

static const struct inode_operations msdos_dir_inode_operations = {
        .create         = msdos_create,
        .lookup         = msdos_lookup,
        .unlink         = msdos_unlink,
        .mkdir          = msdos_mkdir,
        .rmdir          = msdos_rmdir,
        .rename         = msdos_rename,
        .setattr        = fat_setattr,
        .getattr        = fat_getattr,
        .update_time    = fat_update_time,
};

static void setup(struct super_block *sb)
{
        MSDOS_SB(sb)->dir_ops = &msdos_dir_inode_operations;
        set_default_d_op(sb, &msdos_dentry_operations);
        sb->s_flags |= SB_NOATIME;
}

static int msdos_fill_super(struct super_block *sb, struct fs_context *fc)
{
        return fat_fill_super(sb, fc, setup);
}

static int msdos_get_tree(struct fs_context *fc)
{
        return get_tree_bdev(fc, msdos_fill_super);
}

static int msdos_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
        return fat_parse_param(fc, param, false);
}

static const struct fs_context_operations msdos_context_ops = {
        .parse_param    = msdos_parse_param,
        .get_tree       = msdos_get_tree,
        .reconfigure    = fat_reconfigure,
        .free           = fat_free_fc,
};

static int msdos_init_fs_context(struct fs_context *fc)
{
        int err;

        /* Initialize with is_vfat == false */
        err = fat_init_fs_context(fc, false);
        if (err)
                return err;

        fc->ops = &msdos_context_ops;
        return 0;
}

static struct file_system_type msdos_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "msdos",
        .kill_sb        = kill_block_super,
        .fs_flags       = FS_REQUIRES_DEV | FS_ALLOW_IDMAP,
        .init_fs_context = msdos_init_fs_context,
        .parameters     = fat_param_spec,
};
MODULE_ALIAS_FS("msdos");

static int __init init_msdos_fs(void)
{
        return register_filesystem(&msdos_fs_type);
}

static void __exit exit_msdos_fs(void)
{
        unregister_filesystem(&msdos_fs_type);
}

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Werner Almesberger");
MODULE_DESCRIPTION("MS-DOS filesystem support");

module_init(init_msdos_fs)
module_exit(exit_msdos_fs)