From: Martin KaFai Lau <kafai@fb.com>
To: Jakub Sitnicki <jakub@cloudflare.com>
Cc: <bpf@vger.kernel.org>, <netdev@vger.kernel.org>,
<kernel-team@cloudflare.com>, Andrii Nakryiko <andriin@fb.com>
Subject: Re: [PATCH bpf-next v2 2/3] bpf, netns: Keep attached programs in bpf_prog_array
Date: Tue, 23 Jun 2020 14:24:52 -0700 [thread overview]
Message-ID: <20200623212452.titgpyrxx56u3lyd@kafai-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <87sgelmrba.fsf@cloudflare.com>
On Tue, Jun 23, 2020 at 10:59:37PM +0200, Jakub Sitnicki wrote:
> On Tue, Jun 23, 2020 at 09:33 PM CEST, Martin KaFai Lau wrote:
> > On Tue, Jun 23, 2020 at 12:34:58PM +0200, Jakub Sitnicki wrote:
> >
> > [ ... ]
> >
> >> @@ -93,8 +108,16 @@ static int bpf_netns_link_update_prog(struct bpf_link *link,
> >> goto out_unlock;
> >> }
> >>
> >> + run_array = rcu_dereference_protected(net->bpf.run_array[type],
> >> + lockdep_is_held(&netns_bpf_mutex));
> >> + if (run_array)
> >> + ret = bpf_prog_array_replace_item(run_array, link->prog, new_prog);
> >> + else
> > When will this happen?
>
> This will never happen, unless there is a bug. As long as there is a
> link attached, run_array should never be detached (null). Because it can
> be handled gracefully, we fail the bpf(LINK_UPDATE) syscall.
>
> Your question makes me think that perhaps it should trigger a warning,
> with WARN_ON_ONCE, to signal clearly to the reader that this is an
> unexpected state.
>
> WDYT?
Thanks for confirming and the explanation.
If it will never happen, I would skip the "if (run_array)". That
will help the code reading in the future.
I would not WARN also.
next prev parent reply other threads:[~2020-06-23 21:25 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-23 10:34 [PATCH bpf-next v2 0/3] bpf, netns: Prepare for multi-prog attachment Jakub Sitnicki
2020-06-23 10:34 ` [PATCH bpf-next v2 1/3] flow_dissector: Pull BPF program assignment up to bpf-netns Jakub Sitnicki
2020-06-23 10:34 ` [PATCH bpf-next v2 2/3] bpf, netns: Keep attached programs in bpf_prog_array Jakub Sitnicki
2020-06-23 19:33 ` Martin KaFai Lau
2020-06-23 20:59 ` Jakub Sitnicki
2020-06-23 21:24 ` Martin KaFai Lau [this message]
2020-06-24 17:33 ` Jakub Sitnicki
2020-06-24 17:18 ` Jakub Sitnicki
2020-06-24 17:47 ` Andrii Nakryiko
2020-06-24 18:13 ` Jakub Sitnicki
2020-06-24 18:24 ` Andrii Nakryiko
2020-06-24 18:37 ` Jakub Sitnicki
2020-06-23 10:34 ` [PATCH bpf-next v2 3/3] bpf, netns: Keep a list of attached bpf_link's Jakub Sitnicki
2020-06-29 14:56 ` [PATCH bpf-next v2 0/3] bpf, netns: Prepare for multi-prog attachment Daniel Borkmann
2020-06-29 14:57 ` Daniel Borkmann
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