[PATCH bpf-next v4 0/3] bpf: switch to new usercopy helpers

[Christian Brauner]

Hey everyone,

This is v4. If you still feel that I should leave this code alone then
simply ignore it. I won't send another version. Relevant tests pass and
I've verified that other failures were already present without this
patch series applied.

The misplaced min check has been moved after copy_struct_from_user() so
no non-zero bytes can be missed by copy_struct_from_user().

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.

/* v1 */
Link: https://lore.kernel.org/r/20191009160907.10981-1-christian.brauner@xxxxxxxxxx

/* v2 */
Link: https://lore.kernel.org/r/20191016004138.24845-1-christian.brauner@xxxxxxxxxx
- rebase onto bpf-next

/* v3 */
Link: https://lore.kernel.org/r/20191016034432.4418-1-christian.brauner@xxxxxxxxxx

/* Reference */
[1]: f5a1a536fa14 ("lib: introduce copy_struct_from_user() helper")

Christian Brauner (3):
  bpf: use check_zeroed_user() in bpf_check_uarg_tail_zero()
  bpf: use copy_struct_from_user() in bpf_prog_get_info_by_fd()
  bpf: use copy_struct_from_user() in bpf() syscall

 kernel/bpf/syscall.c | 39 ++++++++++++---------------------------
 1 file changed, 12 insertions(+), 27 deletions(-)

-- 
2.23.0