# Re: \[PATCH 3/6\] fs-verity: add FS\_IOC\_READ\_VERITY\_METADATA ioctl

- From: Chao Yu \<hidden\>
- Date: 2021-02-07 08:35:41 
- List: linux-ext4
- Page: https://ratatoskr.run/linux-ext4/2021/02/199438
- Thread: https://ratatoskr.run/linux-fscrypt/2021/01/197428/t.md

```text
On 2021/2/7 16:01, Eric Biggers wrote:
> On Sun, Feb 07, 2021 at 03:46:43PM +0800, Chao Yu wrote:
>> Hi Eric,
>>
>> On 2021/1/16 2:18, Eric Biggers wrote:
>>> +static int f2fs_ioc_read_verity_metadata(struct file *filp, unsigned long arg)
>>> +{
>>> +	if (!f2fs_sb_has_verity(F2FS_I_SB(file_inode(filp))))
>>> +		return -EOPNOTSUPP;
>>
>> One case is after we update kernel image, f2fs module may no longer support
>> compress algorithm which current file was compressed with, to avoid triggering
>> IO with empty compress engine (struct f2fs_compress_ops pointer):
>>
>> It needs to add f2fs_is_compress_backend_ready() check condition here?
>>
>> Thanks,
>>
>>> +
>>> +	return fsverity_ioctl_read_metadata(filp, (const void __user *)arg);
>>> +}
>
> In that case it wouldn't have been possible to open the file, because
> f2fs_file_open() checks for it.  So it's not necessary to repeat the same check
> in every operation on the file descriptor.

Oh, yes, it's safe now.

I'm thinking we need to remove the check in f2fs_file_open(), because the check
will fail metadata access/update (via f{g,s}etxattr/ioctl), however original
intention of that check is only to avoid syscalls to touch compressed data w/o
the engine, anyway this is another topic.

The whole patchset looks fine to me, feel free to add:

Reviewed-by: Chao Yu <redacted>

Thanks,

>
> - Eric
> .
>
```