namei_msdos.c

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/*
 *  linux/fs/msdos/namei.c
 *
 *  Written 1992,1993 by Werner Almesberger
 *  Hidden files 1995 by Albert Cahalan <[email protected]> <[email protected]>
 *  Rewritten for constant inumbers 1999 by Al Viro
 */

#include <linux/module.h>
#include <linux/time.h>
#include <linux/buffer_head.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, const struct inode *inode,
           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(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 *parent, const struct inode *pinode,
        const struct dentry *dentry, const struct inode *inode,
        unsigned int len, const char *str, const struct qstr *name)
{
    struct fat_mount_options *options = &MSDOS_SB(parent->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 timespec *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;

    dir->i_ctime = dir->i_mtime = *ts;
    if (IS_DIRSYNC(dir))
        (void)fat_sync_inode(dir);
    else
        mark_inode_dirty(dir);

    return 0;
}

/***** Create a file */
static int msdos_create(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 timespec 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_SEC;
    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;
    }
    inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
    /* 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 = dentry->d_inode;
    struct fat_slot_info sinfo;
    int err;

    mutex_lock(&MSDOS_SB(sb)->s_lock);
    /*
     * Check whether the directory is not in use, then check
     * whether it is empty.
     */
    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;
    drop_nlink(dir);

    clear_nlink(inode);
    inode->i_ctime = CURRENT_TIME_SEC;
    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 int msdos_mkdir(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 timespec 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_SEC;
    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);
    inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
    /* 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 0;

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

/***** Unlink a file */
static int msdos_unlink(struct inode *dir, struct dentry *dentry)
{
    struct inode *inode = dentry->d_inode;
    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);
    inode->i_ctime = CURRENT_TIME_SEC;
    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 timespec 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 = old_dentry->d_inode;
    new_inode = new_dentry->d_inode;

    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);

            old_dir->i_version++;
            old_dir->i_ctime = old_dir->i_mtime = CURRENT_TIME_SEC;
            if (IS_DIRSYNC(old_dir))
                (void)fat_sync_inode(old_dir);
            else
                mark_inode_dirty(old_dir);
            goto out;
        }
    }

    ts = CURRENT_TIME_SEC;
    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;
    }
    new_dir->i_version++;

    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;
    old_dir->i_version++;
    old_dir->i_ctime = old_dir->i_mtime = ts;
    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);
        new_inode->i_ctime = ts;
    }
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 inode *old_dir, struct dentry *old_dentry,
            struct inode *new_dir, struct dentry *new_dentry)
{
    struct super_block *sb = old_dir->i_sb;
    unsigned char old_msdos_name[MSDOS_NAME], new_msdos_name[MSDOS_NAME];
    int err, is_hid;

    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,
};

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

static int msdos_fill_super(struct super_block *sb, void *data, int silent)
{
    return fat_fill_super(sb, data, silent, 0, setup);
}

static struct dentry *msdos_mount(struct file_system_type *fs_type,
            int flags, const char *dev_name,
            void *data)
{
    return mount_bdev(fs_type, flags, dev_name, data, msdos_fill_super);
}

static struct file_system_type msdos_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "msdos",
    .mount      = msdos_mount,
    .kill_sb    = kill_block_super,
    .fs_flags   = FS_REQUIRES_DEV,
};

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)