file.c

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/*
 *  linux/fs/fat/file.c
 *
 *  Written 1992,1993 by Werner Almesberger
 *
 *  regular file handling primitives for fat-based filesystems
 */

#include <linux/capability.h>
#include <linux/module.h>
#include <linux/compat.h>
#include <linux/mount.h>
#include <linux/time.h>
#include <linux/buffer_head.h>
#include <linux/writeback.h>
#include <linux/backing-dev.h>
#include <linux/blkdev.h>
#include <linux/fsnotify.h>
#include <linux/security.h>
#include "fat.h"

static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
{
    u32 attr;

    mutex_lock(&inode->i_mutex);
    attr = fat_make_attrs(inode);
    mutex_unlock(&inode->i_mutex);

    return put_user(attr, user_attr);
}

static int fat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
{
    struct inode *inode = file->f_path.dentry->d_inode;
    struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
    int is_dir = S_ISDIR(inode->i_mode);
    u32 attr, oldattr;
    struct iattr ia;
    int err;

    err = get_user(attr, user_attr);
    if (err)
        goto out;

    err = mnt_want_write_file(file);
    if (err)
        goto out;
    mutex_lock(&inode->i_mutex);

    /*
     * ATTR_VOLUME and ATTR_DIR cannot be changed; this also
     * prevents the user from turning us into a VFAT
     * longname entry.  Also, we obviously can't set
     * any of the NTFS attributes in the high 24 bits.
     */
    attr &= 0xff & ~(ATTR_VOLUME | ATTR_DIR);
    /* Merge in ATTR_VOLUME and ATTR_DIR */
    attr |= (MSDOS_I(inode)->i_attrs & ATTR_VOLUME) |
        (is_dir ? ATTR_DIR : 0);
    oldattr = fat_make_attrs(inode);

    /* Equivalent to a chmod() */
    ia.ia_valid = ATTR_MODE | ATTR_CTIME;
    ia.ia_ctime = current_fs_time(inode->i_sb);
    if (is_dir)
        ia.ia_mode = fat_make_mode(sbi, attr, S_IRWXUGO);
    else {
        ia.ia_mode = fat_make_mode(sbi, attr,
            S_IRUGO | S_IWUGO | (inode->i_mode & S_IXUGO));
    }

    /* The root directory has no attributes */
    if (inode->i_ino == MSDOS_ROOT_INO && attr != ATTR_DIR) {
        err = -EINVAL;
        goto out_unlock_inode;
    }

    if (sbi->options.sys_immutable &&
        ((attr | oldattr) & ATTR_SYS) &&
        !capable(CAP_LINUX_IMMUTABLE)) {
        err = -EPERM;
        goto out_unlock_inode;
    }

    /*
     * The security check is questionable...  We single
     * out the RO attribute for checking by the security
     * module, just because it maps to a file mode.
     */
    err = security_inode_setattr(file->f_path.dentry, &ia);
    if (err)
        goto out_unlock_inode;

    /* This MUST be done before doing anything irreversible... */
    err = fat_setattr(file->f_path.dentry, &ia);
    if (err)
        goto out_unlock_inode;

    fsnotify_change(file->f_path.dentry, ia.ia_valid);
    if (sbi->options.sys_immutable) {
        if (attr & ATTR_SYS)
            inode->i_flags |= S_IMMUTABLE;
        else
            inode->i_flags &= ~S_IMMUTABLE;
    }

    fat_save_attrs(inode, attr);
    mark_inode_dirty(inode);
out_unlock_inode:
    mutex_unlock(&inode->i_mutex);
    mnt_drop_write_file(file);
out:
    return err;
}

long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
    struct inode *inode = filp->f_path.dentry->d_inode;
    u32 __user *user_attr = (u32 __user *)arg;

    switch (cmd) {
    case FAT_IOCTL_GET_ATTRIBUTES:
        return fat_ioctl_get_attributes(inode, user_attr);
    case FAT_IOCTL_SET_ATTRIBUTES:
        return fat_ioctl_set_attributes(filp, user_attr);
    default:
        return -ENOTTY; /* Inappropriate ioctl for device */
    }
}

#ifdef CONFIG_COMPAT
static long fat_generic_compat_ioctl(struct file *filp, unsigned int cmd,
                      unsigned long arg)

{
    return fat_generic_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
}
#endif

static int fat_file_release(struct inode *inode, struct file *filp)
{
    if ((filp->f_mode & FMODE_WRITE) &&
         MSDOS_SB(inode->i_sb)->options.flush) {
        fat_flush_inodes(inode->i_sb, inode, NULL);
        congestion_wait(BLK_RW_ASYNC, HZ/10);
    }
    return 0;
}

int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
{
    struct inode *inode = filp->f_mapping->host;
    int res, err;

    res = generic_file_fsync(filp, start, end, datasync);
    err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);

    return res ? res : err;
}


const struct file_operations fat_file_operations = {
    .llseek     = generic_file_llseek,
    .read       = do_sync_read,
    .write      = do_sync_write,
    .aio_read   = generic_file_aio_read,
    .aio_write  = generic_file_aio_write,
    .mmap       = generic_file_mmap,
    .release    = fat_file_release,
    .unlocked_ioctl = fat_generic_ioctl,
#ifdef CONFIG_COMPAT
    .compat_ioctl   = fat_generic_compat_ioctl,
#endif
    .fsync      = fat_file_fsync,
    .splice_read    = generic_file_splice_read,
};

static int fat_cont_expand(struct inode *inode, loff_t size)
{
    struct address_space *mapping = inode->i_mapping;
    loff_t start = inode->i_size, count = size - inode->i_size;
    int err;

    err = generic_cont_expand_simple(inode, size);
    if (err)
        goto out;

    inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
    mark_inode_dirty(inode);
    if (IS_SYNC(inode)) {
        int err2;

        /*
         * Opencode syncing since we don't have a file open to use
         * standard fsync path.
         */
        err = filemap_fdatawrite_range(mapping, start,
                           start + count - 1);
        err2 = sync_mapping_buffers(mapping);
        if (!err)
            err = err2;
        err2 = write_inode_now(inode, 1);
        if (!err)
            err = err2;
        if (!err) {
            err =  filemap_fdatawait_range(mapping, start,
                               start + count - 1);
        }
    }
out:
    return err;
}

/* Free all clusters after the skip'th cluster. */
static int fat_free(struct inode *inode, int skip)
{
    struct super_block *sb = inode->i_sb;
    int err, wait, free_start, i_start, i_logstart;

    if (MSDOS_I(inode)->i_start == 0)
        return 0;

    fat_cache_inval_inode(inode);

    wait = IS_DIRSYNC(inode);
    i_start = free_start = MSDOS_I(inode)->i_start;
    i_logstart = MSDOS_I(inode)->i_logstart;

    /* First, we write the new file size. */
    if (!skip) {
        MSDOS_I(inode)->i_start = 0;
        MSDOS_I(inode)->i_logstart = 0;
    }
    MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
    inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
    if (wait) {
        err = fat_sync_inode(inode);
        if (err) {
            MSDOS_I(inode)->i_start = i_start;
            MSDOS_I(inode)->i_logstart = i_logstart;
            return err;
        }
    } else
        mark_inode_dirty(inode);

    /* Write a new EOF, and get the remaining cluster chain for freeing. */
    if (skip) {
        struct fat_entry fatent;
        int ret, fclus, dclus;

        ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
        if (ret < 0)
            return ret;
        else if (ret == FAT_ENT_EOF)
            return 0;

        fatent_init(&fatent);
        ret = fat_ent_read(inode, &fatent, dclus);
        if (ret == FAT_ENT_EOF) {
            fatent_brelse(&fatent);
            return 0;
        } else if (ret == FAT_ENT_FREE) {
            fat_fs_error(sb,
                     "%s: invalid cluster chain (i_pos %lld)",
                     __func__, MSDOS_I(inode)->i_pos);
            ret = -EIO;
        } else if (ret > 0) {
            err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait);
            if (err)
                ret = err;
        }
        fatent_brelse(&fatent);
        if (ret < 0)
            return ret;

        free_start = ret;
    }
    inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);

    /* Freeing the remained cluster chain */
    return fat_free_clusters(inode, free_start);
}

void fat_truncate_blocks(struct inode *inode, loff_t offset)
{
    struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
    const unsigned int cluster_size = sbi->cluster_size;
    int nr_clusters;

    /*
     * This protects against truncating a file bigger than it was then
     * trying to write into the hole.
     */
    if (MSDOS_I(inode)->mmu_private > offset)
        MSDOS_I(inode)->mmu_private = offset;

    nr_clusters = (offset + (cluster_size - 1)) >> sbi->cluster_bits;

    fat_free(inode, nr_clusters);
    fat_flush_inodes(inode->i_sb, inode, NULL);
}

int fat_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
{
    struct inode *inode = dentry->d_inode;
    generic_fillattr(inode, stat);
    stat->blksize = MSDOS_SB(inode->i_sb)->cluster_size;
    return 0;
}
EXPORT_SYMBOL_GPL(fat_getattr);

static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
                 struct inode *inode, umode_t *mode_ptr)
{
    umode_t mask, perm;

    /*
     * Note, the basic check is already done by a caller of
     * (attr->ia_mode & ~FAT_VALID_MODE)
     */

    if (S_ISREG(inode->i_mode))
        mask = sbi->options.fs_fmask;
    else
        mask = sbi->options.fs_dmask;

    perm = *mode_ptr & ~(S_IFMT | mask);

    /*
     * Of the r and x bits, all (subject to umask) must be present. Of the
     * w bits, either all (subject to umask) or none must be present.
     *
     * If fat_mode_can_hold_ro(inode) is false, can't change w bits.
     */
    if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
        return -EPERM;
    if (fat_mode_can_hold_ro(inode)) {
        if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
            return -EPERM;
    } else {
        if ((perm & S_IWUGO) != (S_IWUGO & ~mask))
            return -EPERM;
    }

    *mode_ptr &= S_IFMT | perm;

    return 0;
}

static int fat_allow_set_time(struct msdos_sb_info *sbi, struct inode *inode)
{
    umode_t allow_utime = sbi->options.allow_utime;

    if (!uid_eq(current_fsuid(), inode->i_uid)) {
        if (in_group_p(inode->i_gid))
            allow_utime >>= 3;
        if (allow_utime & MAY_WRITE)
            return 1;
    }

    /* use a default check */
    return 0;
}

#define TIMES_SET_FLAGS (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)
/* valid file mode bits */
#define FAT_VALID_MODE  (S_IFREG | S_IFDIR | S_IRWXUGO)

int fat_setattr(struct dentry *dentry, struct iattr *attr)
{
    struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
    struct inode *inode = dentry->d_inode;
    unsigned int ia_valid;
    int error;

    /* Check for setting the inode time. */
    ia_valid = attr->ia_valid;
    if (ia_valid & TIMES_SET_FLAGS) {
        if (fat_allow_set_time(sbi, inode))
            attr->ia_valid &= ~TIMES_SET_FLAGS;
    }

    error = inode_change_ok(inode, attr);
    attr->ia_valid = ia_valid;
    if (error) {
        if (sbi->options.quiet)
            error = 0;
        goto out;
    }

    /*
     * Expand the file. Since inode_setattr() updates ->i_size
     * before calling the ->truncate(), but FAT needs to fill the
     * hole before it. XXX: this is no longer true with new truncate
     * sequence.
     */
    if (attr->ia_valid & ATTR_SIZE) {
        inode_dio_wait(inode);

        if (attr->ia_size > inode->i_size) {
            error = fat_cont_expand(inode, attr->ia_size);
            if (error || attr->ia_valid == ATTR_SIZE)
                goto out;
            attr->ia_valid &= ~ATTR_SIZE;
        }
    }

    if (((attr->ia_valid & ATTR_UID) &&
         (!uid_eq(attr->ia_uid, sbi->options.fs_uid))) ||
        ((attr->ia_valid & ATTR_GID) &&
         (!gid_eq(attr->ia_gid, sbi->options.fs_gid))) ||
        ((attr->ia_valid & ATTR_MODE) &&
         (attr->ia_mode & ~FAT_VALID_MODE)))
        error = -EPERM;

    if (error) {
        if (sbi->options.quiet)
            error = 0;
        goto out;
    }

    /*
     * We don't return -EPERM here. Yes, strange, but this is too
     * old behavior.
     */
    if (attr->ia_valid & ATTR_MODE) {
        if (fat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0)
            attr->ia_valid &= ~ATTR_MODE;
    }

    if (attr->ia_valid & ATTR_SIZE) {
        down_write(&MSDOS_I(inode)->truncate_lock);
        truncate_setsize(inode, attr->ia_size);
        fat_truncate_blocks(inode, attr->ia_size);
        up_write(&MSDOS_I(inode)->truncate_lock);
    }

    setattr_copy(inode, attr);
    mark_inode_dirty(inode);
out:
    return error;
}
EXPORT_SYMBOL_GPL(fat_setattr);

const struct inode_operations fat_file_inode_operations = {
    .setattr    = fat_setattr,
    .getattr    = fat_getattr,
};