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Date:      Fri, 4 Dec 2015 20:34:07 +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:  <5661EAAF.1010906@selasky.org>
In-Reply-To: <1733241446303675@web19h.yandex.ru>
References:  <CAJ-VmonvVyTNuYv_as41yPCFdfR5T3FE45DP9MKAc-eyzXzPUg@mail.gmail.com> <2739461446298483@web2h.yandex.ru> <CAJ-Vmo=JjHonDqOYK%2BJDaf9581dRU5_KoaSTnY27JnzQm0v56w@mail.gmail.com> <1733241446303675@web19h.yandex.ru>

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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

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diff --git a/sys/dev/oce/oce_if.c b/sys/dev/oce/oce_if.c
index 826cd3c..1cca876 100644
--- a/sys/dev/oce/oce_if.c
+++ b/sys/dev/oce/oce_if.c
@@ -343,7 +343,7 @@ oce_attach(device_t dev)
 
 	callout_init(&sc->timer, 1);
 	rc = callout_reset(&sc->timer, 2 * hz, oce_local_timer, sc);
-	if (rc)
+	if (rc > 0)
 		goto stats_free;
 
 	return 0;
diff --git a/sys/netinet/if_ether.c b/sys/netinet/if_ether.c
index dfba0b2..0aec1c4 100644
--- a/sys/netinet/if_ether.c
+++ b/sys/netinet/if_ether.c
@@ -420,7 +420,7 @@ arpresolve_full(struct ifnet *ifp, int is_gw, int create, struct mbuf *m,
 		la->la_expire = time_uptime;
 		canceled = callout_reset(&la->lle_timer, hz * V_arpt_down,
 		    arptimer, la);
-		if (canceled)
+		if (canceled > 0)
 			LLE_REMREF(la);
 		la->la_asked++;
 		LLE_WUNLOCK(la);
@@ -1084,7 +1084,7 @@ arp_mark_lle_reachable(struct llentry *la)
 		la->la_expire = time_uptime + V_arpt_keep;
 		canceled = callout_reset(&la->lle_timer,
 		    hz * V_arpt_keep, arptimer, la);
-		if (canceled)
+		if (canceled > 0)
 			LLE_REMREF(la);
 	}
 	la->la_asked = 0;

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