Re: [PATCH v3] hfs: remove BUG() from hfs_release_folio()/hfs_test_inode()/hfs_write_inode()

[Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>]

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);