Re: [syzbot] [bpf?] [trace?] WARNING: locking bug in __lock_task_sighand

[Puranjay Mohan]

Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> writes:

> Puranjay, Andrii and All,
>
> looks like if (irqs_disabled()) is not enough.
> Should we change it to preemptible() ?
>
> It will likely make it async all the time,
> but in this it's an ok trade off?
>

Yes, as BPF programs can run in all kinds of contexts.

We should replace 'if (irqs_disabled())' with 'if (!preemptible())'

because the definition is:

#define preemptible()	(preempt_count() == 0 && !irqs_disabled())

and we need if ((preempt_count() != 0) || irqs_disabled()), in both
these cases we want to make it async.

I will try to test the fix as Syzbot has now found a reproducer.

Thanks,
Puranjay

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