[PATCH v3 0/3] bpf: switch to new usercopy helpers

Christian Brauner
2019-10-16T03:45:06Z

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.

This series can also be pulled:

The following changes since commit 5bc60de50dfea235634fdf38cbc992fb968d113b:

selftests: bpf: Don't try to read files without read permission (2019-10-15 16:27:25 -0700)

are available in the Git repository at:

git@gitolite.kernel.org:pub/scm/linux/kernel/git/brauner/linux tags/bpf-copy-struct-from-user

for you to fetch changes up to 31a197d406cc01451e98312665d116c2dbb08202:

bpf: use copy_struct_from_user() in bpf() syscall (2019-10-16 05:32:38 +0200)

----------------------------------------------------------------
bpf-copy-struct-from-user

----------------------------------------------------------------
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 | 45 ++++++++++++++++-----------------------------
1 file changed, 16 insertions(+), 29 deletions(-)

Thanks!
Christian

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

/* v2 */
Link: https://lore.kernel.org/r/20191016004138.24845-1-christian.brauner@ubuntu.com
- 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 | 45 ++++++++++++++++----------------------------
1 file changed, 16 insertions(+), 29 deletions(-)

--
2.23.0