netdev - Re: [PATCH bpf v2] flow_dissector: Drop BPF flow dissector prog ref on netns cleanup

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Date:   Thu, 21 May 2020 11:14:27 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     Jakub Sitnicki <jakub@...udflare.com>, bpf <bpf@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        kernel-team <kernel-team@...udflare.com>
Subject: Re: [PATCH bpf v2] flow_dissector: Drop BPF flow dissector prog ref
 on netns cleanup

On Thu, May 21, 2020 at 8:21 AM <sdf@...gle.com> wrote:
>
> On 05/21, Jakub Sitnicki wrote:
> > When attaching a flow dissector program to a network namespace with
> > bpf(BPF_PROG_ATTACH, ...) we grab a reference to bpf_prog.
>
> > If netns gets destroyed while a flow dissector is still attached, and
> > there
> > are no other references to the prog, we leak the reference and the program
> > remains loaded.
>
> > Leak can be reproduced by running flow dissector tests from selftests/bpf:
>
> >    # bpftool prog list
> >    # ./test_flow_dissector.sh
> >    ...
> >    selftests: test_flow_dissector [PASS]
> >    # bpftool prog list
> >    4: flow_dissector  name _dissect  tag e314084d332a5338  gpl
> >            loaded_at 2020-05-20T18:50:53+0200  uid 0
> >            xlated 552B  jited 355B  memlock 4096B  map_ids 3,4
> >            btf_id 4
> >    #
>
> > Fix it by detaching the flow dissector program when netns is going away.
>
> > Fixes: d58e468b1112 ("flow_dissector: implements flow dissector BPF hook")
> > Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
> Reviewed-by: Stanislav Fomichev <sdf@...gle.com>

Applied. Thanks