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From:   Hao Luo <haoluo@google.com>
Date:   Thu, 3 Mar 2022 11:15:57 -0800
Message-ID: <CA+khW7h=VhCgw+gzAegu6BcNTgwHvdxh6ayueKM5qiAD+fk2Uw@mail.gmail.com>
Subject: Re: [PATCH bpf-next v1 1/9] bpf: Add mkdir, rmdir, unlink syscalls
 for prog_bpf_syscall
To:     Yonghong Song <yhs@fb.com>
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>,
        KP Singh <kpsingh@kernel.org>,
        Shakeel Butt <shakeelb@google.com>,
        Joe Burton <jevburton.kernel@gmail.com>,
        Tejun Heo <tj@kernel.org>, joshdon@google.com, sdf@google.com,
        bpf@vger.kernel.org, linux-kernel@vger.kernel.org
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On Thu, Mar 3, 2022 at 11:13 AM Yonghong Song <yhs@fb.com> wrote:
>
>
>
> On 3/3/22 10:56 AM, Hao Luo wrote:
> > On Wed, Mar 2, 2022 at 12:55 PM Yonghong Song <yhs@fb.com> wrote:
> >> On 2/25/22 3:43 PM, Hao Luo wrote:
> >>> @@ -5086,6 +5086,29 @@ union bpf_attr {
> >>>     *  Return
> >>>     *          0 on success, or a negative error in case of failure. On error
> >>>     *          *dst* buffer is zeroed out.
> >>> + *
> >>> + * long bpf_mkdir(const char *pathname, int pathname_sz, u32 mode)
> >>
> >> Can we make pathname_sz to be u32 instead of int? pathname_sz should
> >> never be negative any way.
> >>
> >> Also, I think it is a good idea to add 'u64 flags' parameter for all
> >> three helpers, so we have room in the future to tune for new use cases.
> >>
> >
> > SG. Will make this change.
> >
> > Actually, I think I need to cap patthname_sz from above, to ensure
> > pathname_sz isn't too big. Is that necessary? I see there are other
> > helpers that don't have this type of check.
>
> There is no need. The verifier should ensure the memory held by pathname
> will have at least size of pathname_sz.
>

SG. Thanks!