On Wed, 2025-07-23 at 11:16 +0900, Tetsuo Handa wrote:
> With below change, legitimate HFS filesystem images can be mounted.
>
> But is crafted HFS filesystem images can not be mounted expected result?
>
> # losetup -a
> /dev/loop0: [0001]:7185 (/memfd:syzkaller (deleted))
> # mount -t hfs /dev/loop0 /mnt/
> mount: /mnt: filesystem was mounted, but any subsequent operation failed: Operation not permitted.
> # fsck.hfs /dev/loop0
> ** /dev/loop0
> Executing fsck_hfs (version 540.1-Linux).
> ** Checking HFS volume.
> Invalid extent entry
> (3, 0)
> ** The volume could not be verified completely.
> # mount -t hfs /dev/loop0 /mnt/
> mount: /mnt: filesystem was mounted, but any subsequent operation failed: Operation not permitted.
>
> Also, are IDs which should be excluded from make_bad_inode() conditions
> same for HFS_CDR_FIL and HFS_CDR_DIR ?
>
>
> --- a/fs/hfs/inode.c
> +++ b/fs/hfs/inode.c
> @@ -358,6 +358,8 @@ static int hfs_read_inode(struct inode *inode, void *data)
> inode->i_op = &hfs_file_inode_operations;
> inode->i_fop = &hfs_file_operations;
> inode->i_mapping->a_ops = &hfs_aops;
> + if (inode->i_ino < HFS_FIRSTUSER_CNID)
> + goto check_reserved_ino;
> break;
> case HFS_CDR_DIR:
> inode->i_ino = be32_to_cpu(rec->dir.DirID);
> @@ -368,6 +370,24 @@ static int hfs_read_inode(struct inode *inode, void *data)
> inode_set_atime_to_ts(inode, inode_set_ctime_to_ts(inode, hfs_m_to_utime(rec->dir.MdDat))));
> inode->i_op = &hfs_dir_inode_operations;
> inode->i_fop = &hfs_dir_operations;
> + if (inode->i_ino < HFS_FIRSTUSER_CNID)
> + goto check_reserved_ino;
> + break;
> + default:
> + make_bad_inode(inode);
> + }
> + return 0;
> +check_reserved_ino:
> + switch (inode->i_ino) {
> + case HFS_POR_CNID:
> + case HFS_ROOT_CNID:
> + case HFS_EXT_CNID:
> + case HFS_CAT_CNID:
> + case HFS_BAD_CNID:
> + case HFS_ALLOC_CNID:
> + case HFS_START_CNID:
> + case HFS_ATTR_CNID:
> + case HFS_EXCH_CNID:
> break;
> default:
> make_bad_inode(inode);
I have missed that this list contains [1]:
#define HFS_POR_CNID 1 /* Parent Of the Root */
#define HFS_ROOT_CNID 2 /* ROOT directory */
Of course, hfs_read_inode() can be called for the root directory and parent of
the root cases. So, HFS_POR_CNID and HFS_ROOT_CNID are legitimate values.
However, the other constants cannot be used because they should be described in
superblock (MDB) and Catalog File cannot have the records for them.
Thanks,
Slava.
[1] https://elixir.bootlin.com/linux/v6.16-rc7/source/fs/hfs/hfs.h#L41
