linux-kernel - Re: [PATCH v2 1/3] bpf: Allow NULL buffers in bpf_dynptr_slice(

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Message-ID: <bcc5fbaf-83f3-cc05-67b3-512b44818321@iogearbox.net>
Date:   Wed, 19 Jul 2023 16:51:51 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Daniel Rosenberg <drosen@...gle.com>, bpf <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Shuah Khan <shuah@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Joanne Koong <joannelkoong@...il.com>,
        Mykola Lysenko <mykolal@...com>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Android Kernel Team <kernel-team@...roid.com>
Subject: Re: [PATCH v2 1/3] bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)

On 7/19/23 1:21 AM, Jakub Kicinski wrote:
> On Tue, 18 Jul 2023 16:17:24 -0700 Alexei Starovoitov wrote:
>> Which would encourage bnxt-like hacks.
>> I don't like it tbh.
>> At least skb_pointer_if_linear() has a clear meaning.
>> It's more run-time overhead, since buffer__opt is checked early,
>> but that's ok.
> 
> Alright, your version fine by me, too. Thanks!

Looks good to me too. Agree that the !buffer check should not live in
__skb_header_pointer() and is better handled in the bpf_dynptr_slice()
internals.

Thanks,
Daniel