IPv6 panic (NULL * deref?) in nd6_ifnet_link_event

From: Bjoern A. Zeeb <bzeeb-lists_at_lists.zabbadoz.net>
Date: Sat, 10 May 2025 19:32:00 UTC
Hi,

main of the last days.

Fatal trap 12: page fault while in kernel mode
cpuid = 2; apic id = 02
fault virtual address   = 0x10
fault code              = supervisor read data, page not present
instruction pointer     = 0x20:0xffffffff80dbd769
stack pointer           = 0x28:0xfffffe0106296d60
frame pointer           = 0x28:0xfffffe0106296d70
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         = 12 (swi6: task queue)
rdi: fffff8002f997800 rsi: 000000000000001c rdx: 0000000000000000
rcx: 0000000000010000  r8: 0000000000000001  r9: ffffffffffffffff
rax: 0000000000000000 rbx: fffff8002f997a18 rbp: fffffe0106296d70
r10: ffffffff81c4a1e8 r11: 0000000000000001 r12: fffff80001210700
r13: fffff80001210728 r14: fffff8002f997800 r15: 0000000000000001
trap number             = 12
panic: page fault
cpuid = 2
time = 1746903751
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe0106296a90
vpanic() at vpanic+0x136/frame 0xfffffe0106296bc0
panic() at panic+0x43/frame 0xfffffe0106296c20
trap_pfault() at trap_pfault+0x48d/frame 0xfffffe0106296c90
calltrap() at calltrap+0x8/frame 0xfffffe0106296c90
--- trap 0xc, rip = 0xffffffff80dbd769, rsp = 0xfffffe0106296d60, rbp = 0xfffffe0106296d70 ---
nd6_ifnet_link_event() at nd6_ifnet_link_event+0x39/frame 0xfffffe0106296d70
do_link_state_change() at do_link_state_change+0x1b1/frame 0xfffffe0106296dc0
taskqueue_run_locked() at taskqueue_run_locked+0x1c2/frame 0xfffffe0106296e40
taskqueue_run() at taskqueue_run+0x4d/frame 0xfffffe0106296e60
ithread_loop() at ithread_loop+0x266/frame 0xfffffe0106296ef0
fork_exit() at fork_exit+0x82/frame 0xfffffe0106296f30
fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe0106296f30
--- trap 0x25b01e6e, rip = 0x52db004fa566ef34, rsp = 0xcadb9a4f3d667734, rbp = 0xde5a00adbd42c69c ---
KDB: enter: panic


(gdb) l * nd6_ifnet_link_event+0x39
0xffffffff80dbd769 is in nd6_ifnet_link_event (sys/netinet6/nd6_rtr.c:327).
322     static void
323     defrtr_ipv6_only_ipf_down(struct ifnet *ifp)
324     {
325
326             IF_AFDATA_WLOCK(ifp);
327             ND_IFINFO(ifp)->flags &= ~ND6_IFF_IPV6_ONLY;
328             IF_AFDATA_WUNLOCK(ifp);
329     }
330     #endif  /* EXPERIMENTAL */
331


-- 
Bjoern A. Zeeb                                                     r15:7