From:   Xu Kuohai <xukuohai@huaweicloud.com>
To:     bpf@vger.kernel.org, linux-kselftest@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        John Fastabend <john.fastabend@gmail.com>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        Mykola Lysenko <mykolal@fb.com>, Shuah Khan <shuah@kernel.org>
Subject: [PATCH bpf-next 0/2] bpf: add bound tracking for BPF_MOD
Date:   Sun,  5 Mar 2023 22:31:17 -0500
Message-Id: <20230306033119.2634976-1-xukuohai@huaweicloud.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: Xu Kuohai <xukuohai@huawei.com>

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