[PATCH bpf-next v4 0/5] bpf: Improve 64bits bounds refinement

[Paul Chaignon <paul.chaignon@gmail.com>]

This patchset improves the 64bits bounds refinement when the s64 ranges
crosses the sign boundary. The first patch explains the small addition
to __reg64_deduce_bounds. The last one explains why we need a third
round of __reg_deduce_bounds. The third patch adds a selftest with a
more complete example of the impact on verification. The second and
fourth patches update the existing selftests to take the new refinement
into account.

This patchset should reduce the number of kernel warnings hit by
syzkaller due to invariant violations [1]. It was also tested with
Agni [2] (and Cilium's CI for good measure).

Link: https://syzkaller.appspot.com/bug?extid=c711ce17dd78e5d4fdcf [1]
Link: https://github.com/bpfverif/agni [2]

Changes in v4:
  - Fixed outdated test comment, noticed by Eduard.
  - Rebased.
Changes in v3:
  - Added a 5th patch to call __reg_deduce_bounds a third time in
    reg_bounds_sync following tests from Eduard.
  - Fixed broken indentations in the first patch.
Changes in v2 (all on Eduard's suggestions):
  - Added two tests to ensure we cover all cases of u64/s64 overlap.
  - Improved tests to check deduced ranges with __msg.
  - Improved code comments.

Paul Chaignon (5):
  bpf: Improve bounds when s64 crosses sign boundary
  selftests/bpf: Update reg_bound range refinement logic
  selftests/bpf: Test cross-sign 64bits range refinement
  selftests/bpf: Test invariants on JSLT crossing sign
  bpf: Add third round of bounds deduction

 kernel/bpf/verifier.c                         |  53 ++++++++
 .../selftests/bpf/prog_tests/reg_bounds.c     |  14 ++
 .../selftests/bpf/progs/verifier_bounds.c     | 120 +++++++++++++++++-
 3 files changed, 186 insertions(+), 1 deletion(-)

-- 
2.43.0