From: Maxim Mikityanskiy maxim@isovalent.com
The goal of this series is to extend the verifier's capabilities of tracking scalars when they are spilled to stack, especially when the spill or fill is narrowing. It also contains a fix by Eduard for infinite loop detection and a state pruning optimization by Eduard that compensates for a verification complexity regression introduced by tracking unbounded scalars. These improvements reduce the surface of false rejections that I saw while working on Cilium codebase.
Patch 1 (Maxim): Fix for an existing test, it will matter later in the series.
Patches 2-3 (Eduard): Fixes for false rejections in infinite loop detection that happen in the selftests when my patches are applied.
Patches 4-5 (Maxim): Fix the inconsistency of find_equal_scalars that was possible if 32-bit spills were made.
Patches 6-11 (Maxim): Support the case when boundary checks are first performed after the register was spilled to the stack.
Patches 12-13 (Maxim): Support narrowing fills.
Patches 14-15 (Eduard): Optimization for state pruning in stacksafe() to mitigate the verification complexity regression.
veristat -e file,prog,states -f '!states_diff<50' -f '!states_pct<10' -f '!states_a<10' -f '!states_b<10' -C ...
* Without patch 14:
File Program States (A) States (B) States (DIFF) -------------------- ------------ ---------- ---------- ---------------- bpf_xdp.o tail_lb_ipv6 3877 2936 -941 (-24.27%) pyperf180.bpf.o on_event 8422 10456 +2034 (+24.15%) pyperf600.bpf.o on_event 22259 37319 +15060 (+67.66%) pyperf600_iter.bpf.o on_event 400 540 +140 (+35.00%) strobemeta.bpf.o on_event 4702 13435 +8733 (+185.73%)
* With patch 14:
File Program States (A) States (B) States (DIFF) -------------------- ------------ ---------- ---------- -------------- bpf_xdp.o tail_lb_ipv6 3877 2937 -940 (-24.25%) pyperf600_iter.bpf.o on_event 400 500 +100 (+25.00%)
v2 changes:
Fixed comments in patch 1, moved endianness checks to header files in patch 12 where possible, added Eduard's ACKs.
Eduard Zingerman (4): bpf: make infinite loop detection in is_state_visited() exact selftests/bpf: check if imprecise stack spills confuse infinite loop detection bpf: Optimize state pruning for spilled scalars selftests/bpf: states pruning checks for scalar vs STACK_{MISC,ZERO}
Maxim Mikityanskiy (11): selftests/bpf: Fix the u64_offset_to_skb_data test bpf: Make bpf_for_each_spilled_reg consider narrow spills selftests/bpf: Add a test case for 32-bit spill tracking bpf: Add the assign_scalar_id_before_mov function bpf: Add the get_reg_width function bpf: Assign ID to scalars on spill selftests/bpf: Test assigning ID to scalars on spill bpf: Track spilled unbounded scalars selftests/bpf: Test tracking spilled unbounded scalars bpf: Preserve boundaries and track scalars on narrowing fill selftests/bpf: Add test cases for narrowing fill
include/linux/bpf_verifier.h | 4 +- include/linux/filter.h | 12 + kernel/bpf/verifier.c | 155 ++++- .../bpf/progs/verifier_direct_packet_access.c | 2 +- .../selftests/bpf/progs/verifier_loops1.c | 24 + .../selftests/bpf/progs/verifier_spill_fill.c | 533 +++++++++++++++++- .../testing/selftests/bpf/verifier/precise.c | 6 +- 7 files changed, 685 insertions(+), 51 deletions(-)