Re: [PATCH bpf-next] bpf:syscall: Log error code on trampoline unlink failure

[Leon Hwang]

On 16/7/26 15:03, xu.xin16@xxxxxxxxxx wrote:
>>>>> Well, the crash may happen when the kernel is booting, or too hard to reproduce,
>>>>> in which case, bpftrace does not work.
>>>>
>>>>
>>>> Do you enable kernel.panic_on_warn sysctl?
>>>>
>>>> If it's not enabled, the kernel won't crash, I think.
>>>
>>> I'd like to clarify that the panic in our case is not triggered by the WARN itself.
>>> Instead, the real crash is a use‑after‑free (UAF) that happens when one CPU is
>>> executing a trampoline while another CPU is concurrently freeing it. This results
>>> in an illegal instruction (or page fault) at the PC, which is fatal and will panic
>>> the kernel regardless of panic_on_warn – because it's an Oops with Fatal exception
>>> in interrupt.
>>
>>
>> Why not fix the root cause instead?
>>
>> If you want some help from upstream to fix the root cause, pls provide
>> the crash dmesg and the reproducing demo.
> 
> It's already fixed due to some OOT drivers.
> 
> I think if we have this patch, it can speed up trouble-shooting.

OK. Let's wait for Jiri's opinion.

Thanks,
Leon