linux-kernel - Re: [PATCH] bpf: verifier: avoid fall-through warnings

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Message-ID: <CAEf4BzaG=cQWAVNNj0hy4Ui7mHzXZgxs8J3rKbxjjVdEGdNkvA@mail.gmail.com>
Date:   Tue, 11 Jun 2019 10:22:54 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Lawrence Brakmo <brakmo@...com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] bpf: verifier: avoid fall-through warnings

On Tue, Jun 11, 2019 at 7:05 AM Gustavo A. R. Silva
<gustavo@...eddedor.com> wrote:
>
> In preparation to enabling -Wimplicit-fallthrough, this patch silences
> the following warning:

Your patch doesn't apply cleanly to neither bpf nor bpf-next tree.
Could you please rebase and re-submit? Please also include which tree
(probably bpf-next) you are designating this patch to in subject
prefix.

>
> kernel/bpf/verifier.c: In function ‘check_return_code’:
> kernel/bpf/verifier.c:5509:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    if (env->prog->expected_attach_type == BPF_CGROUP_UDP4_RECVMSG ||
>       ^
> kernel/bpf/verifier.c:5512:2: note: here
>   case BPF_PROG_TYPE_CGROUP_SKB:
>   ^~~~
>
> Warning level 3 was used: -Wimplicit-fallthrough=3
>
> Notice that it's much clearer to explicitly add breaks in each case
> (that actually contains some code), rather than letting the code to
> fall through.
>
> This patch is part of the ongoing efforts to enable
> -Wimplicit-fallthrough.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>  kernel/bpf/verifier.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 1e9d10b32984..e9fc28991548 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -5509,11 +5509,13 @@ static int check_return_code(struct bpf_verifier_env *env)
>                 if (env->prog->expected_attach_type == BPF_CGROUP_UDP4_RECVMSG ||
>                     env->prog->expected_attach_type == BPF_CGROUP_UDP6_RECVMSG)
>                         range = tnum_range(1, 1);
> +               break;
>         case BPF_PROG_TYPE_CGROUP_SKB:
>                 if (env->prog->expected_attach_type == BPF_CGROUP_INET_EGRESS) {
>                         range = tnum_range(0, 3);
>                         enforce_attach_type_range = tnum_range(2, 3);
>                 }
> +               break;
>         case BPF_PROG_TYPE_CGROUP_SOCK:
>         case BPF_PROG_TYPE_SOCK_OPS:
>         case BPF_PROG_TYPE_CGROUP_DEVICE:
> --
> 2.21.0
>