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

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Message-ID: <20230726170133.GX11388@unreal>
Date:   Wed, 26 Jul 2023 20:01:33 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        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,
        martin.lau@...ux.dev, 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 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);
        tcx_entry_free(entry);
 }