Re: [PATCH] cgroup: Fix crash with CLONE_INTO_CGROUP and v1 cgroups

[Yosry Ahmed]

On Mon, Oct 10, 2022 at 12:51 PM Tejun Heo <tj@xxxxxxxxxx> wrote:
>
> Hello,
>
> On Mon, Oct 10, 2022 at 11:50:50AM -0700, Yosry Ahmed wrote:
> > The purpose of f3a2aebdd6 was to make cgroup_get_from_fd() support
> > cgroup1, which IIUC makes sense. It was unrelated to IDs.
>
> Ah, right you are. For some reason, I thought this was ID based.
>
> > There are currently two users of
> > cgroup_get_from_file()/cgroup_get_from_fd() AFAICT, one of which is
> > the fork code fixed by this commit, the second is BPF cgroup prog
> > attachment. I can send another patch to add explicit filtering in the
> > BPF attachment code as well.
> >
> > Alternatively, we can have separate functions that do the filtering if
> > needed. For example:
> > cgroup_get_from_fd() / cgroup_get_from_file() -> support both v1 and v2
> > cgroup_get_dfl_from_fd() / cgroup_get_dfl_from_file() -> support only v2
> >
> > We can then use the versions with filtering for all the current users
> > except cgroup_iter (that needs to support both v1 and v2). WDYT?
>
> Yes, but please leave the existing ones v2 only and add new ones which
> allows cgroup1 too.

Any suggestions for the new names though? Given that the new ones
would be the ones that will support both versions, I am not sure how
to name them differently in a meaningful way. Maybe something like
cgroup_get_all_from_[fd/file]() ?

IMO, we can rename the current versions to
cgroup_get_dfl_from_[fd/file](), and the new ones (which support both)
as cgroup_get_from_fd/file(). In this case it's obvious that one
version specifically works on "dfl", aka cgroup2.

Alternatively, we can have separate versions for v1,
cgroup1_get_from_[fd/file](), but then callers that want both v1 and
v2 will have to make 2 separate calls unnecessarily.

Thoughts?

>
> Thanks.
>
> --
> tejun