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

[Leon Hwang]

On 16/7/26 14:26, 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.

Thanks,
Leon