netdev - Re: [PATCH v4 bpf-next 07/13] bpf: selftest: Add ref_tracking verifier test for bpf

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Date:   Fri, 25 Sep 2020 09:30:23 +0100
From:   Lorenz Bauer <lmb@...udflare.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH v4 bpf-next 07/13] bpf: selftest: Add ref_tracking
 verifier test for bpf_skc casting

On Fri, 25 Sep 2020 at 01:04, Martin KaFai Lau <kafai@...com> wrote:
>
> The patch tests for:
> 1. bpf_sk_release() can be called on a tcp_sock btf_id ptr.
>
> 2. Ensure the tcp_sock btf_id pointer cannot be used
>    after bpf_sk_release().
>
> Signed-off-by: Martin KaFai Lau <kafai@...com>

Acked-by: Lorenz Bauer <lmb@...udflare.com>

> ---
>  .../selftests/bpf/verifier/ref_tracking.c     | 47 +++++++++++++++++++
>  1 file changed, 47 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/verifier/ref_tracking.c b/tools/testing/selftests/bpf/verifier/ref_tracking.c
> index 056e0273bf12..006b5bd99c08 100644
> --- a/tools/testing/selftests/bpf/verifier/ref_tracking.c
> +++ b/tools/testing/selftests/bpf/verifier/ref_tracking.c
> @@ -854,3 +854,50 @@
>         .errstr = "Unreleased reference",
>         .result = REJECT,
>  },
> +{
> +       "reference tracking: bpf_sk_release(btf_tcp_sock)",
> +       .insns = {
> +       BPF_SK_LOOKUP(sk_lookup_tcp),
> +       BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
> +       BPF_EXIT_INSN(),
> +       BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
> +       BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
> +       BPF_EMIT_CALL(BPF_FUNC_skc_to_tcp_sock),
> +       BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 3),
> +       BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
> +       BPF_EMIT_CALL(BPF_FUNC_sk_release),
> +       BPF_EXIT_INSN(),
> +       BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
> +       BPF_EMIT_CALL(BPF_FUNC_sk_release),
> +       BPF_EXIT_INSN(),
> +       },
> +       .prog_type = BPF_PROG_TYPE_SCHED_CLS,
> +       .result = ACCEPT,
> +       .result_unpriv = REJECT,
> +       .errstr_unpriv = "unknown func",
> +},
> +{
> +       "reference tracking: use ptr from bpf_skc_to_tcp_sock() after release",
> +       .insns = {
> +       BPF_SK_LOOKUP(sk_lookup_tcp),
> +       BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
> +       BPF_EXIT_INSN(),
> +       BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
> +       BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
> +       BPF_EMIT_CALL(BPF_FUNC_skc_to_tcp_sock),
> +       BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 3),
> +       BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
> +       BPF_EMIT_CALL(BPF_FUNC_sk_release),
> +       BPF_EXIT_INSN(),
> +       BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),
> +       BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
> +       BPF_EMIT_CALL(BPF_FUNC_sk_release),
> +       BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_7, 0),
> +       BPF_EXIT_INSN(),
> +       },
> +       .prog_type = BPF_PROG_TYPE_SCHED_CLS,
> +       .result = REJECT,
> +       .errstr = "invalid mem access",
> +       .result_unpriv = REJECT,
> +       .errstr_unpriv = "unknown func",
> +},
> --
> 2.24.1
>


-- 
Lorenz Bauer  |  Systems Engineer
6th Floor, County Hall/The Riverside Building, SE1 7PB, UK

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