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

From: Alexei Starovoitov
Date: Wed Oct 09 2019 - 19:06:35 EST

On Wed, Oct 9, 2019 at 9:09 AM Christian Brauner
<christian.brauner@xxxxxxxxxx> 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).