xattr.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 1,455 行 · 第 1/3 页

/*
 * Inode operation setxattr()
 *
 * dentry->d_inode->i_sem down
 */
int
reiserfs_setxattr (struct dentry *dentry, const char *name, const void *value,
                   size_t size, int flags)
{
    struct reiserfs_xattr_handler *xah = find_xattr_handler_prefix (name);
    int err;
    int lock;

    if (!xah || !reiserfs_xattrs(dentry->d_sb) ||
        get_inode_sd_version (dentry->d_inode) == STAT_DATA_V1)
        return -EOPNOTSUPP;

    if (IS_RDONLY (dentry->d_inode))
        return -EROFS;

    if (IS_IMMUTABLE (dentry->d_inode) || IS_APPEND (dentry->d_inode))
        return -EROFS;

    reiserfs_write_lock_xattr_i (dentry->d_inode);
    lock = !has_xattr_dir (dentry->d_inode);
    if (lock)
        reiserfs_write_lock_xattrs (dentry->d_sb);
    else
        reiserfs_read_lock_xattrs (dentry->d_sb);
    err = xah->set (dentry->d_inode, name, value, size, flags);
    if (lock)
        reiserfs_write_unlock_xattrs (dentry->d_sb);
    else
        reiserfs_read_unlock_xattrs (dentry->d_sb);
    reiserfs_write_unlock_xattr_i (dentry->d_inode);
    return err;
}

/*
 * Inode operation removexattr()
 *
 * dentry->d_inode->i_sem down
 */
int
reiserfs_removexattr (struct dentry *dentry, const char *name)
{
    int err;
    struct reiserfs_xattr_handler *xah = find_xattr_handler_prefix (name);

    if (!xah || !reiserfs_xattrs(dentry->d_sb) ||
        get_inode_sd_version (dentry->d_inode) == STAT_DATA_V1)
        return -EOPNOTSUPP;

    if (IS_RDONLY (dentry->d_inode))
        return -EROFS;

    if (IS_IMMUTABLE (dentry->d_inode) || IS_APPEND (dentry->d_inode))
        return -EPERM;

    reiserfs_write_lock_xattr_i (dentry->d_inode);
    reiserfs_read_lock_xattrs (dentry->d_sb);

    /* Deletion pre-operation */
    if (xah->del) {
        err = xah->del (dentry->d_inode, name);
        if (err)
            goto out;
    }

    err = reiserfs_xattr_del (dentry->d_inode, name);

    dentry->d_inode->i_ctime = CURRENT_TIME;
    mark_inode_dirty (dentry->d_inode);

out:
    reiserfs_read_unlock_xattrs (dentry->d_sb);
    reiserfs_write_unlock_xattr_i (dentry->d_inode);
    return err;
}


/* This is what filldir will use:
 * r_pos will always contain the amount of space required for the entire
 * list. If r_pos becomes larger than r_size, we need more space and we
 * return an error indicating this. If r_pos is less than r_size, then we've
 * filled the buffer successfully and we return success */
struct reiserfs_listxattr_buf {
    int r_pos;
    int r_size;
    char *r_buf;
    struct inode *r_inode;
};

static int
reiserfs_listxattr_filler (void *buf, const char *name, int namelen,
                           loff_t offset, ino_t ino, unsigned int d_type)
{
    struct reiserfs_listxattr_buf *b = (struct reiserfs_listxattr_buf *)buf;
    int len = 0;
    if (name[0] != '.' || (namelen != 1 && (name[1] != '.' || namelen != 2))) {
        struct reiserfs_xattr_handler *xah = find_xattr_handler_prefix (name);
        if (!xah) return 0; /* Unsupported xattr name, skip it */

        /* We call ->list() twice because the operation isn't required to just
         * return the name back - we want to make sure we have enough space */
        len += xah->list (b->r_inode, name, namelen, NULL);

        if (len) {
            if (b->r_pos + len + 1 <= b->r_size) {
                char *p = b->r_buf + b->r_pos;
                p += xah->list (b->r_inode, name, namelen, p);
                *p++ = '\0';
            }
            b->r_pos += len + 1;
        }
    }

    return 0;
}
/*
 * Inode operation listxattr()
 *
 * Preliminary locking: we down dentry->d_inode->i_sem
 */
ssize_t
reiserfs_listxattr (struct dentry *dentry, char *buffer, size_t size)
{
    struct file *fp;
    struct dentry *dir;
    int err = 0;
    struct reiserfs_listxattr_buf buf;

    if (!dentry->d_inode)
        return -EINVAL;

    if (!reiserfs_xattrs(dentry->d_sb) ||
        get_inode_sd_version (dentry->d_inode) == STAT_DATA_V1)
        return -EOPNOTSUPP;

    reiserfs_read_lock_xattr_i (dentry->d_inode);
    reiserfs_read_lock_xattrs (dentry->d_sb);
    dir = open_xa_dir (dentry->d_inode, FL_READONLY);
    reiserfs_read_unlock_xattrs (dentry->d_sb);
    if (IS_ERR (dir)) {
        err = PTR_ERR (dir);
        if (err == -ENODATA)
            err = 0; /* Not an error if there aren't any xattrs */
        goto out;
    }

    fp = dentry_open (dir, NULL, O_RDWR);
    if (IS_ERR (fp)) {
        err = PTR_ERR (fp);
        /* dentry_open dputs the dentry if it fails */
        goto out;
    }

    buf.r_buf = buffer;
    buf.r_size = buffer ? size : 0;
    buf.r_pos = 0;
    buf.r_inode = dentry->d_inode;

    REISERFS_I(dentry->d_inode)->i_flags |= i_has_xattr_dir;

    err = xattr_readdir (fp, reiserfs_listxattr_filler, &buf);
    if (err)
        goto out_dir;

    if (buf.r_pos > buf.r_size && buffer != NULL)
        err = -ERANGE;
    else
        err = buf.r_pos;

out_dir:
    fput(fp);

out:
    reiserfs_read_unlock_xattr_i (dentry->d_inode);
    return err;
}

/* This is the implementation for the xattr plugin infrastructure */
static struct list_head xattr_handlers = LIST_HEAD_INIT (xattr_handlers);
static rwlock_t handler_lock = RW_LOCK_UNLOCKED;

static struct reiserfs_xattr_handler *
find_xattr_handler_prefix (const char *prefix)
{
    struct reiserfs_xattr_handler *xah = NULL;
    struct list_head *p;

    read_lock (&handler_lock);
    list_for_each (p, &xattr_handlers) {
        xah = list_entry (p, struct reiserfs_xattr_handler, handlers);
        if (strncmp (xah->prefix, prefix, strlen (xah->prefix)) == 0)
            break;
        xah = NULL;
    }

    read_unlock (&handler_lock);
    return xah;
}

static void
__unregister_handlers (void)
{
    struct reiserfs_xattr_handler *xah;
    struct list_head *p, *tmp;

    list_for_each_safe (p, tmp, &xattr_handlers) {
        xah = list_entry (p, struct reiserfs_xattr_handler, handlers);
        if (xah->exit)
            xah->exit();

        list_del_init (p);
    }
    INIT_LIST_HEAD (&xattr_handlers);
}

int __init
reiserfs_xattr_register_handlers (void)
{
    int err = 0;
    struct reiserfs_xattr_handler *xah;
    struct list_head *p;

    write_lock (&handler_lock);

    /* If we're already initialized, nothing to do */
    if (!list_empty (&xattr_handlers)) {
        write_unlock (&handler_lock);
        return 0;
    }

    /* Add the handlers */
    list_add_tail (&user_handler.handlers, &xattr_handlers);
    list_add_tail (&trusted_handler.handlers, &xattr_handlers);
#ifdef CONFIG_REISERFS_FS_SECURITY
    list_add_tail (&security_handler.handlers, &xattr_handlers);
#endif
#ifdef CONFIG_REISERFS_FS_POSIX_ACL
    list_add_tail (&posix_acl_access_handler.handlers, &xattr_handlers);
    list_add_tail (&posix_acl_default_handler.handlers, &xattr_handlers);
#endif

    /* Run initializers, if available */
    list_for_each (p, &xattr_handlers) {
        xah = list_entry (p, struct reiserfs_xattr_handler, handlers);
        if (xah->init) {
            err = xah->init ();
            if (err) {
                list_del_init (p);
                break;
            }
        }
    }

    /* Clean up other handlers, if any failed */
    if (err)
        __unregister_handlers ();

    write_unlock (&handler_lock);
    return err;
}

void
reiserfs_xattr_unregister_handlers (void)
{
    write_lock (&handler_lock);
    __unregister_handlers ();
    write_unlock (&handler_lock);
}

/* This will catch lookups from the fs root to .reiserfs_priv */
static int
xattr_lookup_poison (struct dentry *dentry, struct qstr *q1, struct qstr *name)
{
    struct dentry *priv_root = REISERFS_SB(dentry->d_sb)->priv_root;
    if (name->len == priv_root->d_name.len &&
        name->hash == priv_root->d_name.hash &&
        !memcmp (name->name, priv_root->d_name.name, name->len)) {
            return -ENOENT;
    } else if (q1->len == name->len &&
               !memcmp(q1->name, name->name, name->len))
        return 0;
    return 1;
}

static struct dentry_operations xattr_lookup_poison_ops = {
    .d_compare = xattr_lookup_poison,
};


/* We need to take a copy of the mount flags since things like
 * MS_RDONLY don't get set until *after* we're called.
 * mount_flags != mount_options */
int
reiserfs_xattr_init (struct super_block *s, int mount_flags)
{
  int err = 0;

  /* We need generation numbers to ensure that the oid mapping is correct
   * v3.5 filesystems don't have them. */
  if (!old_format_only (s)) {
    set_bit (REISERFS_XATTRS, &(REISERFS_SB(s)->s_mount_opt));
  } else if (reiserfs_xattrs_optional (s)) {
    /* Old format filesystem, but optional xattrs have been enabled
     * at mount time. Error out. */
    reiserfs_warning (s, "xattrs/ACLs not supported on pre v3.6 "
                      "format filesystem. Failing mount.");
    err = -EOPNOTSUPP;
    goto error;
  } else {
    /* Old format filesystem, but no optional xattrs have been enabled. This
     * means we silently disable xattrs on the filesystem. */
    clear_bit (REISERFS_XATTRS, &(REISERFS_SB(s)->s_mount_opt));
  }

  /* If we don't have the privroot located yet - go find it */
  if (reiserfs_xattrs (s) && !REISERFS_SB(s)->priv_root) {
      struct dentry *dentry;
      dentry = lookup_one_len (PRIVROOT_NAME, s->s_root,
                               strlen (PRIVROOT_NAME));
      if (!IS_ERR (dentry)) {
        if (!(mount_flags & MS_RDONLY) && !dentry->d_inode) {
            struct inode *inode = dentry->d_parent->d_inode;
            down (&inode->i_sem);
            err = inode->i_op->mkdir (inode, dentry, 0700);
            up (&inode->i_sem);
            if (err) {
                dput (dentry);
                dentry = NULL;
            }

            if (dentry && dentry->d_inode)
                reiserfs_warning (s, "Created %s on %s - reserved for "
                                  "xattr storage.", PRIVROOT_NAME,
                                  reiserfs_bdevname (inode->i_sb));
        } else if (!dentry->d_inode) {
            dput (dentry);
            dentry = NULL;
        }
      } else
        err = PTR_ERR (dentry);

      if (!err && dentry) {
          s->s_root->d_op = &xattr_lookup_poison_ops;
          REISERFS_I(dentry->d_inode)->i_flags |= i_priv_object;
          REISERFS_SB(s)->priv_root = dentry;
      } else if (!(mount_flags & MS_RDONLY)) { /* xattrs are unavailable */
          /* If we're read-only it just means that the dir hasn't been
           * created. Not an error -- just no xattrs on the fs. We'll
           * check again if we go read-write */
          reiserfs_warning (s, "xattrs/ACLs enabled and couldn't "
                            "find/create .reiserfs_priv. Failing mount.");
          err = -EOPNOTSUPP;
      }
  }

error:
   /* This is only nonzero if there was an error initializing the xattr
    * directory or if there is a condition where we don't support them. */
    if (err) {
          clear_bit (REISERFS_XATTRS, &(REISERFS_SB(s)->s_mount_opt));
          clear_bit (REISERFS_XATTRS_USER, &(REISERFS_SB(s)->s_mount_opt));
          clear_bit (REISERFS_POSIXACL, &(REISERFS_SB(s)->s_mount_opt));
    }

    /* The super_block MS_POSIXACL must mirror the (no)acl mount option. */
    s->s_flags = s->s_flags & ~MS_POSIXACL;
    if (reiserfs_posixacl (s))
	s->s_flags |= MS_POSIXACL;

    return err;
}

static int
__reiserfs_permission (struct inode *inode, int mask, struct nameidata *nd,
                       int need_lock)
{
	umode_t			mode = inode->i_mode;

	if (mask & MAY_WRITE) {
		/*
		 * Nobody gets write access to a read-only fs.
		 */
		if (IS_RDONLY(inode) &&
		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
			return -EROFS;

		/*
		 * Nobody gets write access to an immutable file.
		 */
		if (IS_IMMUTABLE(inode))
			return -EACCES;
	}

	/* We don't do permission checks on the internal objects.
	* Permissions are determined by the "owning" object. */
        if (is_reiserfs_priv_object (inode))
		return 0;

	if (current->fsuid == inode->i_uid) {
		mode >>= 6;
#ifdef CONFIG_REISERFS_FS_POSIX_ACL
	} else if (reiserfs_posixacl(inode->i_sb) &&
                   get_inode_sd_version (inode) != STAT_DATA_V1) {
                struct posix_acl *acl;

		/* ACL can't contain additional permissions if
		   the ACL_MASK entry is 0 */
		if (!(mode & S_IRWXG))
			goto check_groups;

                if (need_lock) {
		    reiserfs_read_lock_xattr_i (inode);
                    reiserfs_read_lock_xattrs (inode->i_sb);
		}
                acl = reiserfs_get_acl (inode, ACL_TYPE_ACCESS);
                if (need_lock) {
                    reiserfs_read_unlock_xattrs (inode->i_sb);
		    reiserfs_read_unlock_xattr_i (inode);
		}
                if (IS_ERR (acl)) {
                    if (PTR_ERR (acl) == -ENODATA)
                        goto check_groups;
                    return PTR_ERR (acl);
                }

                if (acl) {
                    int err = posix_acl_permission (inode, acl, mask);
                    posix_acl_release (acl);
                    if (err == -EACCES) {
                        goto check_capabilities;
                    }
                    return err;
		} else {
			goto check_groups;
                }
#endif
	} else {
check_groups:
		if (in_group_p(inode->i_gid))
			mode >>= 3;
	}

	/*
	 * If the DACs are ok we don't need any capability check.
	 */
	if (((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask))
		return 0;

check_capabilities:
	/*
	 * Read/write DACs are always overridable.
	 * Executable DACs are overridable if at least one exec bit is set.
	 */
	if (!(mask & MAY_EXEC) ||
	    (inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode))
		if (capable(CAP_DAC_OVERRIDE))
			return 0;

	/*
	 * Searching includes executable on directories, else just read.
	 */
	if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
		if (capable(CAP_DAC_READ_SEARCH))
			return 0;

	return -EACCES;
}

int
reiserfs_permission (struct inode *inode, int mask, struct nameidata *nd)
{
    return __reiserfs_permission (inode, mask, nd, 1);
}

int
reiserfs_permission_locked (struct inode *inode, int mask, struct nameidata *nd)
{
    return __reiserfs_permission (inode, mask, nd, 0);
}