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SubjectRe: selftests: tc-testing: tdc.sh: WARNING: at kernel/locking/lockdep.c:1226 lockdep_register_key
On Tue, Apr 30, 2024 at 12:30 PM Eric Dumazet <edumazet@google.com> wrote:
>
> On Tue, Apr 30, 2024 at 12:17 PM Davide Caratti <dcaratti@redhat.com> wrote:
> >
> > hello,
> >
> > On Tue, Apr 30, 2024 at 12:17 AM Naresh Kamboju
> > <naresh.kamboju@linaro.org> wrote:
> > >
> > > While running selftests: tc-testing: tdc.sh the following kernel warnings,
> > > kernel Bug, kernel oops and kernel panic noticed with Linux next-20240429
> > > tag kernel as per the available data.
> > >
> > > This build config is from kselftest merge config[1].
> > >
> > > Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
> > >
> > > selftests: tc-testing: tdc.sh log and crash log
> >
> > the problem is created by [1]. I think that at least we need to guard
> > against failures to allocate sch->cpu_bstats and sch->cpu_qstats,
> > otherwise the dynamic key is registered but never unregistered (though
> > the key is freed in the error path of of qdisc_alloc() ). But there
> > might be also something else; however, I can reproduce some similar
> > splat, will follow-up on the list.
> >
> > sorry for the noise,
> > --
> > davide
> >
> > [1] https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=af0cb3fa3f9ed258d14abab0152e28a0f9593084
> >
>
> I just had 5 or 6 syzbot reports about this issue.
>
> I tested the following fix.
>
> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
> index 31dfd6c7405b01e22fe1b8c80944e2bed7d30ddc..d3f6006b563ccd8827b7af362ce9dceaa78f8841
> 100644
> --- a/net/sched/sch_generic.c
> +++ b/net/sched/sch_generic.c
> @@ -982,6 +982,7 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
>
> return sch;
> errout1:
> + lockdep_unregister_key(&sch->root_lock_key);
> kfree(sch);
> errout:
> return ERR_PTR(err);

Davide, I will let you send a formal fix. Let me know if you want me
to release a syzbot report.

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