pf: check if a group has a kif before dereferencing it

It's possible for interface groups to not have had a pfi_kkif assigned to
them, so before we pass that pointer to pfi_kkif_update() we must check if it's
actually set.

We've seen panics such as this, where we get an address update for an interface
that belongs to a group without associated pfi_kkif:

	Tracing pid 12 tid 100034 td 0xfffff80100d2a000
	kdb_enter() at kdb_enter+0x33/frame 0xfffffe0067eed340
	panic() at panic+0x43/frame 0xfffffe0067eed3a0
	trap_pfault() at trap_pfault+0x3c9/frame 0xfffffe0067eed3f0
	calltrap() at calltrap+0x8/frame 0xfffffe0067eed3f0
	--- trap 0xc, rip = 0xffffffff8102ebd5, rsp = 0xfffffe0067eed4c0, rbp = 0xfffffe0067eed500 ---
	pfi_kkif_update() at pfi_kkif_update+0x15/frame 0xfffffe0067eed500
	pfi_kkif_update() at pfi_kkif_update+0x1fc/frame 0xfffffe0067eed550
	pfi_ifaddr_event() at pfi_ifaddr_event+0x82/frame 0xfffffe0067eed5a0
	srcaddr_change_event() at srcaddr_change_event+0xa7/frame 0xfffffe0067eed610
	in6_update_ifa() at in6_update_ifa+0xd52/frame 0xfffffe0067eed790
	in6_ifadd() at in6_ifadd+0x29a/frame 0xfffffe0067eed8b0
	nd6_ra_input() at nd6_ra_input+0xf65/frame 0xfffffe0067eeda90
	icmp6_input() at icmp6_input+0x3c8/frame 0xfffffe0067eedc10
	ip6_input() at ip6_input+0xa15/frame 0xfffffe0067eedcf0
	sppp_input() at sppp_input+0x502/frame 0xfffffe0067eedd80
	pppoe_data_input() at pppoe_data_input+0x1e7/frame 0xfffffe0067eeddf0
	swi_net() at swi_net+0x128/frame 0xfffffe0067eede60
	ithread_loop() at ithread_loop+0x239/frame 0xfffffe0067eedef0
	fork_exit() at fork_exit+0x7b/frame 0xfffffe0067eedf30
	fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe0067eedf30

Note that pf doesn't assign pfi_kkif objects to groups created before pf has
fully started (see V_pf_vnet_active check in pfi_attach_group_event()), which is
one possible way for this to happen.

Reported by:	garga
Sponsored by:	Rubicon Communications, LLC ("Netgate")

1 files changed, 4 insertions, 2 deletions

diff --git a/sys/netpfil/pf/pf_if.c b/sys/netpfil/pf/pf_if.c
index e2200c15c704..f3be036ef745 100644
--- a/sys/netpfil/pf/pf_if.c
+++ b/sys/netpfil/pf/pf_if.c
@@ -655,8 +655,10 @@ pfi_kkif_update(struct pfi_kkif *kif)
 	/* again for all groups kif is member of */
 	if (kif->pfik_ifp != NULL) {
 		CK_STAILQ_FOREACH(ifgl, &kif->pfik_ifp->if_groups, ifgl_next)
-			pfi_kkif_update((struct pfi_kkif *)
-			    ifgl->ifgl_group->ifg_pf_kif);
+			if (ifgl->ifgl_group->ifg_pf_kif) {
+				pfi_kkif_update((struct pfi_kkif *)
+				    ifgl->ifgl_group->ifg_pf_kif);
+			}
 	}
 }