From: Maxim Mikityanskiy <maxim@xxxxxxxxxxxxx>
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%)
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 | 2 +-
kernel/bpf/verifier.c | 160 +++++-
.../bpf/progs/verifier_direct_packet_access.c | 2 +-
.../selftests/bpf/progs/verifier_loops1.c | 24 +
.../selftests/bpf/progs/verifier_spill_fill.c | 529 +++++++++++++++++-
.../testing/selftests/bpf/verifier/precise.c | 6 +-
6 files changed, 677 insertions(+), 46 deletions(-)
--
2.42.1
