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Date:      Sat, 11 Aug 2018 11:04:37 +0200
From:      "Kristof Provost" <kp@FreeBSD.org>
To:        "FreeBSD Net" <freebsd-net@freebsd.org>
Cc:        mmacy@FreeBSD.org
Subject:   Panic during ci test run
Message-ID:  <34C6043C-FDD2-4812-AFF3-C61DEF7AE435@FreeBSD.org>

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The fibs_test:subnet_route_with_multiple_fibs_on_same_subnet test 
(/usr/tests/sys/netinet/) consistently provokes a panic.

Note that this requires:

  - test_suites.FreeBSD.fibs = '1 2' in /usr/local/etc/kyua/kyua.conf
  - net.fibs=3 in /boot/loader.conf
  - sysctl net.add_addr_allfibs=0

Then:

  - cd /usr/tests/sys/netinet/
  - sudo kyua test

This results in:

	Fatal trap 9: general protection fault while in kernel mode
	cpuid = 2; apic id = 02
	instruction pointer     = 0x20:0xffffffff80ded4c3
	stack pointer           = 0x28:0xfffffe0000427860
	frame pointer           = 0x28:0xfffffe00004278a0
	code segment            = base 0x0, limit 0xfffff, type 0x1b
	                        = DPL 0, pres 1, long 1, def32 0, gran 1
	processor eflags        = interrupt enabled, resume, IOPL = 0
	current process         = 0 (softirq_2)
	[ thread pid 0 tid 100021 ]
	Stopped at      inp_gcmoptions+0xe3:    movq    ll+0x33f(%rax),%r9
	db> bt
	Tracing pid 0 tid 100021 td 0xfffff80004605000
	inp_gcmoptions() at inp_gcmoptions+0xe3/frame 0xfffffe00004278a0
	epoch_call_task() at epoch_call_task+0x21a/frame 0xfffffe00004278f0
	gtaskqueue_run_locked() at gtaskqueue_run_locked+0x139/frame 
0xfffffe0000427940
	gtaskqueue_thread_loop() at gtaskqueue_thread_loop+0x88/frame 
0xfffffe0000427970
	fork_exit() at fork_exit+0x84/frame 0xfffffe00004279b0
	fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe00004279b0
	--- trap 0, rip = 0, rsp = 0, rbp = 0 ---


kgdb decodes that to:

	#0  __curthread () at ./machine/pcpu.h:230
	#1  doadump (textdump=0) at /usr/src/sys/kern/kern_shutdown.c:366
	#2  0xffffffff8043dd4b in db_dump (dummy=<optimized out>, 
dummy2=<unavailable>, dummy3=<unavailable>, dummy4=<unavailable>) at 
/usr/src/sys/ddb/db_command.c:574
	#3  0xffffffff8043db19 in db_command (last_cmdp=<optimized out>, 
cmd_table=<optimized out>, dopager=<optimized out>) at 
/usr/src/sys/ddb/db_command.c:481
	#4  0xffffffff8043d894 in db_command_loop () at 
/usr/src/sys/ddb/db_command.c:534
	#5  0xffffffff80440abf in db_trap (type=<optimized out>, 
code=<optimized out>) at /usr/src/sys/ddb/db_main.c:252
	#6  0xffffffff80bdef43 in kdb_trap (type=9, code=0, tf=<optimized out>) 
at /usr/src/sys/kern/subr_kdb.c:693
	#7  0xffffffff8107aee1 in trap_fatal (frame=0xfffffe00004277a0, eva=0) 
at /usr/src/sys/amd64/amd64/trap.c:906
	#8  0xffffffff8107a3bd in trap (frame=0xfffffe00004277a0) at 
/usr/src/sys/amd64/amd64/trap.c:203
	#9  <signal handler called>
	#10 inp_gcmoptions (ctx=0xfffff800142da5e0) at 
/usr/src/sys/netinet6/in6_mcast.c:1650
	#11 0xffffffff80bd9c7a in epoch_call_task (arg=<optimized out>) at 
/usr/src/sys/kern/subr_epoch.c:507
	#12 0xffffffff80bdd069 in gtaskqueue_run_locked 
(queue=0xfffff800040ceb00) at /usr/src/sys/kern/subr_gtaskqueue.c:332
	#13 0xffffffff80bdcde8 in gtaskqueue_thread_loop (arg=<optimized out>) 
at /usr/src/sys/kern/subr_gtaskqueue.c:507
	#14 0xffffffff80b53084 in fork_exit (callout=0xffffffff80bdcd60 
<gtaskqueue_thread_loop>, arg=0xfffffe0087e40038, 
frame=0xfffffe00004279c0) at /usr/src/sys/kern/kern_fork.c:1057
	#15 <signal handler called>

It looks like the inm has been freed at that point, so we try to 
dereference a freed pointer, and that doesn’t go well for us:

	(kgdb) fr 10
	#10 inp_gcmoptions (ctx=0xfffff800142da5e0) at 
/usr/src/sys/netinet6/in6_mcast.c:1650
	1650                            CURVNET_SET(ifp->if_vnet);
	(kgdb) p ifp
	$1 = (struct ifnet *) 0xdeadc0dedeadc0de
	(kgdb)
	(kgdb) l
	1645                    if (imf)
	1646                            im6f_leave(imf);
	1647                    inm = imo->im6o_membership[idx];
	1648                    ifp = inm->in6m_ifp;
	1649                    if (ifp != NULL) {
	1650                            CURVNET_SET(ifp->if_vnet);
	1651                            (void)in6_leavegroup(inm, imf);
	1652                            CURVNET_RESTORE();
	1653                    } else {
	1654                            (void)in6_leavegroup(inm, imf);
	(kgdb) p inm
	$2 = (struct in6_multi *) 0xfffff8001435b200
	(kgdb) p *inm
	$3 = {in6m_addr = {__u6_addr = {__u6_addr8 = 
"\336\300\255\336\336\300\255\336\336\300\255\336\336\300\255", 
<incomplete sequence \336>, __u6_addr16 = {49374, 57005, 49374,
	        57005, 49374, 57005, 49374, 57005}, __u6_addr32 = {3735929054, 
3735929054, 3735929054, 3735929054}}}, in6m_ifp = 0xdeadc0dedeadc0de, 
in6m_ifma = 0xdeadc0dedeadc0de,
	  in6m_refcount = 3735929054, in6m_state = 3735929054, in6m_timer = 
3735929054, in6m_mli = 0xdeadc0dedeadc0de, in6m_nrele = {sle_next = 
0xdeadc0dedeadc0de}, in6m_srcs = {
	    rbh_root = 0xdeadc0dedeadc0de}, in6m_nsrc = 16045693110842147038, 
in6m_scq = {mq_head = {stqh_first = 0xdeadc0dedeadc0de, stqh_last = 
0xdeadc0dedeadc0de},
	    mq_len = -559038242, mq_maxlen = -559038242}, in6m_lastgsrtv = 
{tv_sec = -2401050962867404578, tv_usec = -2401050962867404578}, 
in6m_sctimer = 49374, in6m_scrv = 57005,
	  in6m_st = {{iss_fmode = 49374, iss_asm = 57005, iss_ex = 49374, 
iss_in = 57005, iss_rec = 49374}, {iss_fmode = 57005, iss_asm = 49374, 
iss_ex = 57005, iss_in = 49374,
	      iss_rec = 57005}}}
	(kgdb)
	(kgdb) p nmships
	$4 = 1
	(kgdb) p *imf
	$6 = {im6f_sources = {rbh_root = 0x0}, im6f_nsrc = 0, im6f_st = 
"\002\001"}
	(kgdb)

Regards,
Kristof



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