netdev - Re: [PATCH bpf v2 2/2] bpf/selftests: test that kernel rejects a TCP CC with an invalid license

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Message-ID: <20210325225848.ygdkq7ak54wjh7z5@kafai-mbp.dhcp.thefacebook.com>
Date:   Thu, 25 Mar 2021 15:58:48 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Clark Williams <williams@...hat.com>, <bpf@...r.kernel.org>,
        <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf v2 2/2] bpf/selftests: test that kernel rejects a TCP
 CC with an invalid license

On Thu, Mar 25, 2021 at 10:11:22PM +0100, Toke Høiland-Jørgensen wrote:
> This adds a selftest to check that the verifier rejects a TCP CC struct_ops
> with a non-GPL license.
> 
> v2:
> - Use a minimal struct_ops BPF program instead of rewriting bpf_dctcp's
>   license in memory.
> - Check for the verifier reject message instead of just the return code.
> 
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
> ---
>  .../selftests/bpf/prog_tests/bpf_tcp_ca.c     | 44 +++++++++++++++++++
>  .../selftests/bpf/progs/bpf_nogpltcp.c        | 19 ++++++++
>  2 files changed, 63 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/progs/bpf_nogpltcp.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
> index 37c5494a0381..a09c716528e1 100644
> --- a/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
> @@ -6,6 +6,7 @@
>  #include <test_progs.h>
>  #include "bpf_dctcp.skel.h"
>  #include "bpf_cubic.skel.h"
> +#include "bpf_nogpltcp.skel.h"
>  
>  #define min(a, b) ((a) < (b) ? (a) : (b))
>  
> @@ -227,10 +228,53 @@ static void test_dctcp(void)
>  	bpf_dctcp__destroy(dctcp_skel);
>  }
>  
> +static char *err_str = NULL;
> +static bool found = false;
Nit. These two inits are not needed.

> +
> +static int libbpf_debug_print(enum libbpf_print_level level,
> +			      const char *format, va_list args)
> +{
> +	char *log_buf;
> +
> +	if (level != LIBBPF_WARN ||
> +	    strcmp(format, "libbpf: \n%s\n")) {
> +		vprintf(format, args);
> +		return 0;
> +	}
> +
> +	log_buf = va_arg(args, char *);
> +	if (!log_buf)
> +		goto out;
> +	if (err_str && strstr(log_buf, err_str) != NULL)
> +		found = true;
> +out:
> +	printf(format, log_buf);
> +	return 0;
> +}
> +
> +static void test_invalid_license(void)
> +{
> +	libbpf_print_fn_t old_print_fn = NULL;
Nit. Same here.  Not need to init NULL.

Others lgtm.

Acked-by: Martin KaFai Lau <kafai@...com>

> +	struct bpf_nogpltcp *skel;
> +
> +	err_str = "struct ops programs must have a GPL compatible license";
> +	old_print_fn = libbpf_set_print(libbpf_debug_print);
> +
> +	skel = bpf_nogpltcp__open_and_load();
> +	if (CHECK(skel, "bpf_nogplgtcp__open_and_load()", "didn't fail\n"))
> +		bpf_nogpltcp__destroy(skel);
> +
> +	CHECK(!found, "errmsg check", "expected string '%s'", err_str);
> +
> +	libbpf_set_print(old_print_fn);
> +}