linux-kernel - Re: [syzbot] [bpf?] WARNING: ODEBUG bug in tcx

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Message-ID: <d2a76d59-3282-d4ac-fbe5-40b0a07dbc51@iogearbox.net>
Date:   Fri, 28 Jul 2023 01:44:24 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Leon Romanovsky <leon@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        syzbot <syzbot+14736e249bce46091c18@...kaller.appspotmail.com>,
        andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
        haoluo@...gle.com, john.fastabend@...il.com, jolsa@...nel.org,
        kpsingh@...nel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, sdf@...gle.com, song@...nel.org,
        syzkaller-bugs@...glegroups.com, yhs@...com,
        Gal Pressman <gal@...dia.com>
Subject: Re: [syzbot] [bpf?] WARNING: ODEBUG bug in tcx_uninstall

On 7/27/23 7:41 AM, Leon Romanovsky wrote:
> On Wed, Jul 26, 2023 at 04:33:40PM -0700, Martin KaFai Lau wrote:
>> On 7/26/23 11:16 AM, Martin KaFai Lau wrote:
>>> On 7/26/23 10:01 AM, Leon Romanovsky wrote:
>>>> On Wed, Jul 26, 2023 at 08:23:12AM -0700, Jakub Kicinski wrote:
>>>>> On Wed, 26 Jul 2023 10:12:54 +0300 Leon Romanovsky wrote:
>>>>>>> Thanks, I'll take a look this evening.
>>>>>>
>>>>>> Did anybody post a fix for that?
>>>>>>
>>>>>> We are experiencing the following kernel panic in netdev commit
>>>>>> b57e0d48b300 (net-next/main) Merge branch '100GbE' of
>>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/tnguy/next-queue
>>>>>
>>>>> Not that I know, looks like this is with Daniel's previous fix already
>>>>> present, and syzbot is hitting it, too :(
>>>>
>>>> My naive workaround which restored our regression runs is:
>>>>
>>>> diff --git a/kernel/bpf/tcx.c b/kernel/bpf/tcx.c
>>>> index 69a272712b29..10c9ab830702 100644
>>>> --- a/kernel/bpf/tcx.c
>>>> +++ b/kernel/bpf/tcx.c
>>>> @@ -111,6 +111,7 @@ void tcx_uninstall(struct net_device *dev, bool ingress)
>>>>                           bpf_prog_put(tuple.prog);
>>>>                   tcx_skeys_dec(ingress);
>>>>           }
>>>> -       WARN_ON_ONCE(tcx_entry(entry)->miniq_active);
>>>> +       tcx_miniq_set_active(entry, false);
>>>
>>> Thanks for the report. I will look into it.
>>
>> I don't see how that may be triggered for now after Daniel's recent fix in
>> commit dc644b540a2d ("tcx: Fix splat in ingress_destroy upon
>> tcx_entry_free").
> 
> Both our regression and syzbot have this fix in the trees.
> 
>> Do you have a small reproducible case? Thanks.
> 
> Unfortunately no.

Thanks for the report, we found the root cause and will send a fix in the next
day or two.

Best,
Daniel