On Tue Oct 15, 2019 at 4:02 PM Alexei Starovoitov wrote: > On Tue, Oct 15, 2019 at 3:55 PM Christian Brauner > <christian.brau...@ubuntu.com> wrote: > > > > On Tue, Oct 15, 2019 at 03:45:54PM -0700, Alexei Starovoitov wrote: > > > On Thu, Oct 10, 2019 at 2:26 AM Christian Brauner > > > <christian.brau...@ubuntu.com> wrote: > > > > > > > > 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.brau...@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. > > > > > > -rc1 is now in bpf-next. > > > I took a look at patches and they look good overall. > > > > > > In patches 2 and 3 the zero init via "= {};" > > > should be unnecessary anymore due to > > > copy_struct_from_user() logic, right? > > > > Right, I can remove them. > > > > > > > > Could you also convert all other case in kernel/bpf/, > > > so bpf_check_uarg_tail_zero() can be removed ? > > > Otherwise the half-way conversion will look odd. > > > > Hm, I thought I did that and concluded that bpf_check_uarg_tail_zero() > > can't be removed because sometimes it is called to verify whether a > > given struct is zeroed but nothing is actually copied from userspace but > > rather to userspace. See for example > > v5.4-rc3:kernel/bpf/syscall.c:bpf_map_get_info_by_fd() > > All call sites where something is actually copied from userspace I've > > switched to copy_struct_from_user(). > > I see. You're right. > Could you update the comment in bpf_check_uarg_tail_zero() > to clarify that copy_struct_from_user() should be used whenever > possible instead ?
Yup, can do. Christian