[PATCH bpf-next v2 0/2] bpf: add bound tracking for BPF_MOD
From: Xu Kuohai
Date: Thu Mar 23 2023 - 11:59:37 EST
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