linux-kernel - [PATCH v2 0/3] bpf: switch to new usercopy helpers

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Date:   Wed, 16 Oct 2019 02:41:35 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     christian.brauner@...ntu.com
Cc:     ast@...nel.org, bpf@...r.kernel.org, daniel@...earbox.net,
        kafai@...com, linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        songliubraving@...com, yhs@...com
Subject: [PATCH v2 0/3] bpf: switch to new usercopy helpers

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

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

/* v2 */
- rebase onto bpf-next

/* 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 | 46 +++++++++++++++++---------------------------
 1 file changed, 18 insertions(+), 28 deletions(-)

-- 
2.23.0