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

Christian Brauner
2019-10-09T16:09:20Z

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.

Thanks!
Christian

/* 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 | 38 ++++++++++++--------------------------
1 file changed, 12 insertions(+), 26 deletions(-)

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2.23.0