Re: [PATCH v2] btrfs-progs: common: make sure that qgroup id is in range

[Sidong Yang <realwakka@gmail.com>]

On Wed, Mar 17, 2021 at 07:36:47PM +0100, David Sterba wrote:
> On Tue, Mar 16, 2021 at 01:27:46PM +0000, Sidong Yang wrote:
> > When user assign qgroup with qgroup id that is too big to exceeds
> > range and invade level value, and it works without any error. but
> > this action would be make undefined error. this code make sure that
> > qgroup id doesn't exceed range(0 ~ 2^48-1).
> 
> Should the level be also validate? The function parse_qgroupid does not
> do full validation, so eg 0//0 would be parsed as a path and not as a
> typo, level larger than 64K will be silently clamped.

I agree. 0//0 would be parsed as path but it failed in
btrfs_util_is_subvolume() and goes to err. I understand that upper 16
bits of qgroupid is for level. so, The valid llevel range is [0~2^16-1].
But I can't get it that level larger than 64K will be clampled. 

one more question about that, I see that the ioctl calls just store the
qgroupid without any opeartion with level. is the level meaningless in
kernel?