Messages in this thread | | | Date | Fri, 17 Mar 2023 11:14:37 -0700 | From | John Fastabend <> | Subject | Re: [PATCH v2] kernel: bpf: stackmap: fix a possible sleep-in-atomic bug in bpf_mmap_unlock_get_irq_work() |
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Alexei Starovoitov wrote: > On Fri, Mar 17, 2023 at 03:52:27AM +0000, starmiku1207184332@gmail.com wrote: > > context because of its possible sleep operation. However, mmap_read_unlock() > > is unsafely called in a preempt disabled context when spin_lock() or > > rcu_read_lock() has been called. > > Why is that unsafe? > See __up_read(). It's doing preempt_disable().
Yep I didn't see the issue either that is why I asked for the stack trace. If its a bug we would want a reproducer as well seems like it should be trivially tested in selftests.
> > > > - if (irqs_disabled()) { > > + if (in_atomic() || irqs_disabled()) { > > We cannot do this. It will significantly hurt stack traces with build_id.
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