Commit d6cd20cc5 ("netinet6: fix ndp proxying") caused us to panic when
unloading pfsync:
Fatal trap 12: page fault while in kernel mode
cpuid = 19; apic id = 38
fault virtual address = 0x20
fault code = supervisor read data, page not present
instruction pointer = 0x20:0xffffffff80dfe7f4
stack pointer = 0x28:0xfffffe015d4f8ac0
frame pointer = 0x28:0xfffffe015d4f8ae0
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 = 5477 (kldunload)
trap number = 12
panic: page fault
cpuid = 19
time = 1654023100
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe015d4f8880
vpanic() at vpanic+0x17f/frame 0xfffffe015d4f88d0
panic() at panic+0x43/frame 0xfffffe015d4f8930
trap_fatal() at trap_fatal+0x387/frame 0xfffffe015d4f8990
trap_pfault() at trap_pfault+0xab/frame 0xfffffe015d4f89f0
calltrap() at calltrap+0x8/frame 0xfffffe015d4f89f0
--- trap 0xc, rip = 0xffffffff80dfe7f4, rsp = 0xfffffe015d4f8ac0, rbp = 0xfffffe015d4f8ae0 ---
in6_purge_proxy_ndp() at in6_purge_proxy_ndp+0x14/frame 0xfffffe015d4f8ae0
if_purgeaddrs() at if_purgeaddrs+0x24/frame 0xfffffe015d4f8b90
if_detach_internal() at if_detach_internal+0x1c2/frame 0xfffffe015d4f8bf0
if_detach() at if_detach+0x71/frame 0xfffffe015d4f8c20
pfsync_clone_destroy() at pfsync_clone_destroy+0x1dd/frame 0xfffffe015d4f8c70
if_clone_destroyif() at if_clone_destroyif+0x239/frame 0xfffffe015d4f8cc0
if_clone_detach() at if_clone_detach+0xc8/frame 0xfffffe015d4f8cf0
vnet_pfsync_uninit() at vnet_pfsync_uninit+0xda/frame 0xfffffe015d4f8d10
vnet_deregister_sysuninit() at vnet_deregister_sysuninit+0x85/frame 0xfffffe015d4f8d40
linker_file_sysuninit() at linker_file_sysuninit+0x147/frame 0xfffffe015d4f8d70
linker_file_unload() at linker_file_unload+0x269/frame 0xfffffe015d4f8db0
kern_kldunload() at kern_kldunload+0x18d/frame 0xfffffe015d4f8e00
amd64_syscall() at amd64_syscall+0x12e/frame 0xfffffe015d4f8f30
fast_syscall_common() at fast_syscall_common+0xf8/frame 0xfffffe015d4f8f30
--- syscall (444, FreeBSD ELF64, sys_kldunloadf), rip = 0x1601eab28cba, rsp = 0x1601e9c363f8, rbp = 0x1601e9c36c50 ---
This happens because ifp->if_afdata[AF_INET6] is NULL. Check for this,
just as we already do in a few other places.
See also c139b3c19b ("arp/nd: Cope with late calls to
iflladdr_event").
Reviewed by: melifaro
Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D35374
a7f20faa07