[PATCH bpf-next v2 0/2] bpf: add bound tracking for BPF_MOD

[Xu Kuohai]

From: Xu Kuohai <xukuohai@xxxxxxxxxx>

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 %= 1   // 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.

v2:
- fix build warning reported by kernel test robot <lkp@xxxxxxxxx> [0]
- add two more cases and update commit message

[0] https://lore.kernel.org/oe-kbuild-all/202303060036.zK05OC5M-lkp@xxxxxxxxx

v1: https://lore.kernel.org/bpf/20230306033119.2634976-1-xukuohai@xxxxxxxxxxxxxxx

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 | 320 +++++++++++++++++++++
 2 files changed, 413 insertions(+), 5 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/verifier/mod.c

-- 
2.30.2