linux-kernel - Re: [PATCH v4] net: fix refcount bug in sk_psock

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Message-ID: <20220803153706.oo47lv3kvkpb7yem@kafai-mbp.dhcp.thefacebook.com>
Date:   Wed, 3 Aug 2022 08:37:06 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Hawkins Jiawei <yin31149@...il.com>,
        syzbot+5f26f85569bd179c18ce@...kaller.appspotmail.com,
        18801353760@....com, andrii@...nel.org, ast@...nel.org,
        borisp@...dia.com, bpf@...r.kernel.org, daniel@...earbox.net,
        davem@...emloft.net, edumazet@...gle.com, jakub@...udflare.com,
        john.fastabend@...il.com, kgraul@...ux.ibm.com, kpsingh@...nel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        pabeni@...hat.com, paskripkin@...il.com, skhan@...uxfoundation.org,
        songliubraving@...com, syzkaller-bugs@...glegroups.com, yhs@...com,
        Wen Gu <guwen@...ux.alibaba.com>
Subject: Re: [PATCH v4] net: fix refcount bug in sk_psock_get (2)

On Wed, Aug 03, 2022 at 08:14:13AM -0700, Jakub Kicinski wrote:
> On Wed,  3 Aug 2022 20:41:22 +0800 Hawkins Jiawei wrote:
> > -/* Pointer stored in sk_user_data might not be suitable for copying
> > - * when cloning the socket. For instance, it can point to a reference
> > - * counted object. sk_user_data bottom bit is set if pointer must not
> > - * be copied.
> > +/* flag bits in sk_user_data
> > + *
> > + * SK_USER_DATA_NOCOPY - Pointer stored in sk_user_data might
> > + * not be suitable for copying when cloning the socket.
> > + * For instance, it can point to a reference counted object.
> > + * sk_user_data bottom bit is set if pointer must not be copied.
> > + *
> > + * SK_USER_DATA_BPF    - Managed by BPF
> 
> I'd use this opportunity to add more info here, BPF is too general.
> Maybe "Pointer is used by a BPF reuseport array"? Martin, WDYT?
SGTM.  Thanks.