Re: [PATCH 0/3] bpf: switch to new usercopy helpers

Christian Brauner
2019-10-10T09:26:57Z

On Wed, Oct 09, 2019 at 04:06:18PM -0700, Alexei Starovoitov wrote:
> On Wed, Oct 9, 2019 at 9:09 AM Christian Brauner
> <christian.brauner@ubuntu.com> wrote:
> >
> > Hey everyone,
> >
> > In v5.4-rc2 we added two new helpers check_zeroed_user() and
> > copy_struct_from_user() including selftests (cf. [1]). It is a generic
> > interface designed to copy a struct from userspace. The helpers will be
> > especially useful for structs versioned by size of which we have quite a
> > few.
> >
> > The most obvious benefit is that this helper lets us get rid of
> > duplicate code. We've already switched over sched_setattr(), perf_event_open(),
> > and clone3(). More importantly it will also help to ensure that users
> > implementing versioning-by-size end up with the same core semantics.
> >
> > This point is especially crucial since we have at least one case where
> > versioning-by-size is used but with slighly different semantics:
> > sched_setattr(), perf_event_open(), and clone3() all do do similar
> > checks to copy_struct_from_user() while rt_sigprocmask(2) always rejects
> > differently-sized struct arguments.
> >
> > This little series switches over bpf codepaths that have hand-rolled
> > implementations of these helpers.
>
> check_zeroed_user() is not in bpf-next.
> we will let this set sit in patchworks for some time until bpf-next
> is merged back into net-next and we fast forward it.
> Then we can apply it (assuming no conflicts).

Sounds good to me. Just ping me when you need me to resend rebase onto
bpf-next.

Christian