Re: [PATCH bpf-next 3/4] selftests/bpf: Add test for abnormal cnt during multi-kprobe attachment

[Jiri Olsa <olsajiri@gmail.com>]

On Mon, Dec 11, 2023 at 07:28:42PM +0800, Hou Tao wrote:
> From: Hou Tao <houtao1@huawei.com>
> 
> If an abnormally huge cnt is used for multi-kprobes attachment, the
> following warning will be reported:
> 
>   ------------[ cut here ]------------
>   WARNING: CPU: 1 PID: 392 at mm/util.c:632 kvmalloc_node+0xd9/0xe0
>   Modules linked in: bpf_testmod(O)
>   CPU: 1 PID: 392 Comm: test_progs Tainted: G ...... 6.7.0-rc3+ #32
>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
>   ......
>   RIP: 0010:kvmalloc_node+0xd9/0xe0
>    ? __warn+0x89/0x150
>    ? kvmalloc_node+0xd9/0xe0
>    bpf_kprobe_multi_link_attach+0x87/0x670
>    __sys_bpf+0x2a28/0x2bc0
>    __x64_sys_bpf+0x1a/0x30
>    do_syscall_64+0x36/0xb0
>    entry_SYSCALL_64_after_hwframe+0x6e/0x76
>   RIP: 0033:0x7fbe067f0e0d
>   ......
>    </TASK>
>   ---[ end trace 0000000000000000 ]---
> 
> So add a test to ensure the warning is fixed.
> 
> Signed-off-by: Hou Tao <houtao1@huawei.com>

Acked-by: Jiri Olsa <jolsa@kernel.org>

thanks,
jirka

> ---
>  .../selftests/bpf/prog_tests/kprobe_multi_test.c   | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> index 4041cfa670eb..a340b6047657 100644
> --- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> +++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
> @@ -300,6 +300,20 @@ static void test_attach_api_fails(void)
>  	if (!ASSERT_EQ(libbpf_get_error(link), -EINVAL, "fail_5_error"))
>  		goto cleanup;
>  
> +	/* fail_6 - abnormal cnt */
> +	opts.addrs = (const unsigned long *) addrs;
> +	opts.syms = NULL;
> +	opts.cnt = INT_MAX;
> +	opts.cookies = NULL;
> +
> +	link = bpf_program__attach_kprobe_multi_opts(skel->progs.test_kprobe_manual,
> +						     NULL, &opts);
> +	if (!ASSERT_ERR_PTR(link, "fail_6"))
> +		goto cleanup;
> +
> +	if (!ASSERT_EQ(libbpf_get_error(link), -ENOMEM, "fail_6_error"))
> +		goto cleanup;
> +
>  cleanup:
>  	bpf_link__destroy(link);
>  	kprobe_multi__destroy(skel);
> -- 
> 2.29.2
>