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

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Date:   Tue, 11 Jun 2019 12:41:35 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.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 6/11/19 12:27 PM, Gustavo A. R. Silva wrote:
> 
> 
> On 6/11/19 12:22 PM, Andrii Nakryiko wrote:
>> 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.
>>
> 
> This patch applies cleanly to linux-next (tag next-20190611).
> 

It seems that this commit hasn't been merged into bpf/bpf-next yet:

983695fa676568fc0fe5ddd995c7267aabc24632

--
Gustavo

>>>
>>> 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
>>>