[PATCH bpf-next 0/2] bpf: add bound tracking for BPF_MOD

Xu Kuohai
2023-03-05T14:31:47Z

dst_reg is marked as unknown when BPF_MOD instruction is verified, causing
the following bpf prog to be incorrectly rejected.

0: r0 = 0
1: r0 %= 10 // r0 is marked as unknown
2: r1 = 0
3: r1 += 1
4: if r1 < r0 goto pc-2 // verifier concludes the loop is unbounded
5: exit

To teach verifier to accept the above prog, this series adds bound tracking
for BPF_MOD.

Xu Kuohai (2):
bpf: add bound tracking for BPF_MOD
selftests/bpf: check if verifier tracks dst_reg bound for BPF_MOD

kernel/bpf/verifier.c | 98 +++++++-
tools/testing/selftests/bpf/verifier/mod.c | 247 +++++++++++++++++++++
2 files changed, 340 insertions(+), 5 deletions(-)
create mode 100644 tools/testing/selftests/bpf/verifier/mod.c

--
2.30.2