linux-kernel - Re: [PATCH] selftests: bpf: add malloc failures checks in bpf

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Date:   Mon, 23 Oct 2023 20:28:21 -0700
From:   Yonghong Song <yonghong.song@...ux.dev>
To:     Yuran Pereira <yuran.pereira@...mail.com>, shuah@...nel.org
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        martin.lau@...ux.dev, song@...nel.org, john.fastabend@...il.com,
        kpsingh@...nel.org, sdf@...gle.com, haoluo@...gle.com,
        jolsa@...nel.org, mykolal@...com, brauner@...nel.org,
        iii@...ux.ibm.com, kuifeng@...a.com, bpf@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests: bpf: add malloc failures checks in bpf_iter


On 10/23/23 7:59 PM, Yuran Pereira wrote:
> Since some malloc calls in bpf_iter may at times fail,
> this patch adds the appropriate fail checks, and ensures that
> any previously allocated resource is appropriately destroyed
> before returning the function.
>
> Signed-off-by: Yuran Pereira <yuran.pereira@...mail.com>
> ---
>   tools/testing/selftests/bpf/prog_tests/bpf_iter.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> index 1f02168103dd..6d47ea9211a4 100644
> --- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
> @@ -878,6 +878,11 @@ static void test_bpf_percpu_hash_map(void)
>   
>   	skel->rodata->num_cpus = bpf_num_possible_cpus();
>   	val = malloc(8 * bpf_num_possible_cpus());
> +	if (CHECK(!val, "malloc", "memory allocation failed: %s",
> +				strerror(errno))) {
> +		bpf_iter_bpf_percpu_hash_map__destroy(skel);
> +		return;
> +	}


Could you use !ASSERT_OK_PTR(...) instead of CHECK? bpf selftest
prefers to use ASSERT_* series of macros instead of CHECK.
In the above example, printing out strerror is not required,
see some other examples in the same folder.

Also bpf_iter.c has some other usages of CHECK macro.
Since you are touching this file, could you convert all
CHECK macros to ASSERT_* macros?

Basically you need two patches:
   patch 1: convert existing CHECK macros to ASSERT_* macros in bpf_iter.c.
            this should not check any functionality except error messages.
   patch 2: your patch with ASSERT_* macros.

You can use the following as your subject line:
   [PATCH bpf-next] selftests/bpf: Add malloc failure checks in bpf_iter

>   
>   	err = bpf_iter_bpf_percpu_hash_map__load(skel);
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_bpf_percpu_hash_map__load"))
> @@ -1057,6 +1062,11 @@ static void test_bpf_percpu_array_map(void)
>   
>   	skel->rodata->num_cpus = bpf_num_possible_cpus();
>   	val = malloc(8 * bpf_num_possible_cpus());
> +	if (CHECK(!val, "malloc", "memory allocation failed: %s",
> +				strerror(errno))) {
> +		bpf_iter_bpf_percpu_hash_map__destroy(skel);
> +		return;
> +	}
>   
>   	err = bpf_iter_bpf_percpu_array_map__load(skel);
>   	if (!ASSERT_OK_PTR(skel, "bpf_iter_bpf_percpu_array_map__load"))