Re: panic in arptimer in r289937

Hi Adrian,

On 10/31/15 16:01, Alexander V. Chernikov wrote:
>
>
> 31.10.2015, 16:46, "Adrian Chadd" <adrian_at_freebsd.org>:
>> On 31 October 2015 at 09:34, Alexander V. Chernikov
>> <melifaro_at_freebsd.org> wrote:
>>>   31.10.2015, 05:32, "Adrian Chadd" <adrian_at_freebsd.org>:
>>>>   Hiya,
>>>>
>>>>   Here's a panic from arptimer:
>>>   Hi Adrian,
>>>
>>>   As far as I see, line 205 in if_ether.c is IF_AFDATA_LOCK(ifp) which happens after LLE_WUNLOCK().
>>>   So, it looks like (pre-cached) ifp had been freed before locking ifdata.
>>>   Do you have any more details on that? (e.g. was some interface detached at that moment, is it reproducible, etc..)
>>>
>>>   From a quick glance, potential use-after-free has been possible for quite a long time, but I wonder why it hasn't been observed before.
>>>   Probably lltable_free() changes might have triggered that.
>>>
>>>   I'll take a deeper look on that and reply.
>>

Observed on an idle box with projects/hps_head too:

> panic: bogus refcnt 0 on lle 0xfffff8016508ca00
> cpuid = 7
> KDB: stack backtrace:
> db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe03e4e8c7e0
> vpanic() at vpanic+0x182/frame 0xfffffe03e4e8c860
> kassert_panic() at kassert_panic+0x126/frame 0xfffffe03e4e8c8d0
> llentry_free() at llentry_free+0x136/frame 0xfffffe03e4e8c900
> arptimer() at arptimer+0x20e/frame 0xfffffe03e4e8c950
> softclock_call_cc() at softclock_call_cc+0x170/frame 0xfffffe03e4e8c9c0
> softclock() at softclock+0x47/frame 0xfffffe03e4e8c9e0
> intr_event_execute_handlers() at intr_event_execute_handlers+0x96/frame 0xfffffe03e4e8ca20
> ithread_loop() at ithread_loop+0xa6/frame 0xfffffe03e4e8ca70
> fork_exit() at fork_exit+0x84/frame 0xfffffe03e4e8cab0
> fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe03e4e8cab0
> --- trap 0, rip = 0, rsp = 0, rbp = 0 ---

Looks like callout_reset() must be examined too, and was missed by:

https://svnweb.freebsd.org/changeset/base/290805

Can you try the attached patch?

Randall: Can you fix this ASAP?

--HPS