Date: Fri, 4 Dec 2015 20:52:48 +0100 From: Hans Petter Selasky <hps@selasky.org> To: "Alexander V. Chernikov" <melifaro@freebsd.org>, Adrian Chadd <adrian@freebsd.org> Cc: FreeBSD Net <freebsd-net@freebsd.org>, freebsd-current <freebsd-current@freebsd.org>, Randall Stewart <rrs@netflix.com> Subject: Re: panic in arptimer in r289937 Message-ID: <5661EF10.8060300@selasky.org> In-Reply-To: <5661EAAF.1010906@selasky.org> References: <CAJ-VmonvVyTNuYv_as41yPCFdfR5T3FE45DP9MKAc-eyzXzPUg@mail.gmail.com> <2739461446298483@web2h.yandex.ru> <CAJ-Vmo=JjHonDqOYK%2BJDaf9581dRU5_KoaSTnY27JnzQm0v56w@mail.gmail.com> <1733241446303675@web19h.yandex.ru> <5661EAAF.1010906@selasky.org>
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On 12/04/15 20:34, Hans Petter Selasky wrote: > Hi Adrian, > > On 10/31/15 16:01, Alexander V. Chernikov wrote: >> >> >> 31.10.2015, 16:46, "Adrian Chadd" <adrian@freebsd.org>: >>> On 31 October 2015 at 09:34, Alexander V. Chernikov >>> <melifaro@freebsd.org> wrote: >>>> 31.10.2015, 05:32, "Adrian Chadd" <adrian@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 > Hi, Randall: I see for 11-current, callout_reset() doesn't return -1 when the callout is stopped like with callout_stop(). Is this a bug or a feature? Why can't the callout_reset() and callout_stop() functions use the same return values? In nd6_llinfo_settimer_locked() the return value of both callout_reset() and callout_stop() is checked for positive values, but not in the other places mentioned by my patch. --HPS
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