netdev - Re: [OFFLIST RFC 3/4] bpf: Support bpf_kptr

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Message-ID: <CAMB2axM_t_traLzMYJn+J1fKtfLygSRHw7VrsKsVrDaNwsgqPQ@mail.gmail.com>
Date: Tue, 23 Jul 2024 17:08:59 -0700
From: Amery Hung <ameryhung@...il.com>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: andrii@...nel.org, bpf@...r.kernel.org, daniel@...earbox.net, 
	jhs@...atatu.com, jiri@...nulli.us, martin.lau@...nel.org, 
	netdev@...r.kernel.org, sdf@...gle.com, sinquersw@...il.com, toke@...hat.com, 
	xiyou.wangcong@...il.com, yangpeihao@...u.edu.cn, yepeilin.cs@...il.com, 
	donald.hunter@...il.com
Subject: Re: [OFFLIST RFC 3/4] bpf: Support bpf_kptr_xchg into local kptr

On Mon, Jul 22, 2024 at 5:18 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Fri, Jul 19, 2024 at 05:21:18PM +0000, Amery Hung wrote:
> > From: Dave Marchevsky <davemarchevsky@...com>
> >
> > Signed-off-by: Dave Marchevsky <davemarchevsky@...com>
>
> Amery,
> please add your SOB after Dave's when you're sending patches like this.
>
> Remove OFFLIST in subject... and resend cc-ing bpf@...r.
>
> Add proper commit log.

Got it.

>
> > -     if (meta->func_id == BPF_FUNC_kptr_xchg && type_is_alloc(type)) {
> > +     if (meta->func_id == BPF_FUNC_kptr_xchg && type_is_alloc(type) && regno > 1) {
>
> I don't understand the point of regno > 1. Pls explain/add comment.
>
> Patches 1 and 2 make sense.

I believe this patchset is incomplete, and it will trigger a refcount
bug when running local_kptr_stash/local_kptr_stash_simple. I will
finish and resend this individual series.

Thank you,
Amery