weird panic at mount

Trying to mount root from ufs:/dev/gpt/rootfs [rw]...
<118>Setting hostuuid: 6e6fa481-535f-11cb-9756-be6694d54790.
<118>Setting hostid: 0xa94c64a9.
<118>Starting file system checks:
<118>/dev/gpt/rootfs: FILE SYSTEM CLEAN; SKIPPING CHECKS
<118>/dev/gpt/rootfs: clean, 1877279 free (13871 frags, 232926 blocks, 0.4% fragmentation)
<118>/dev/gpt/homefs: FILE SYSTEM CLEAN; SKIPPING CHECKS
<118>/dev/gpt/homefs: clean, 116318576 free (1184592 frags, 14391748 blocks, 0.5% fragmentation)
<118>/dev/gpt/varfs: FILE SYSTEM CLEAN; SKIPPING CHECKS
<118>/dev/gpt/varfs: clean, 5448483 free (1267 frags, 680902 blocks, 0.0% fragmentation)
<118>Mounting local filesystems:


Fatal trap 9: general protection fault while in kernel mode
cpuid = 7; apic id = 07
instruction pointer	= 0x20:0xffffffff8073cea7
stack pointer	        = 0x28:0xfffffe033db0b250
frame pointer	        = 0x28:0xfffffe033db0b260
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		= 72 (mount)

Reading symbols from /boot/kernel/drm2.ko...Reading symbols from /usr/lib/debug//boot/kernel/drm2.ko.debug...done.
done.
Reading symbols from /boot/modules/fdescfs.ko...Reading symbols from /usr/lib/debug//boot/modules/fdescfs.ko.debug...done.
done.
doadump (textdump=1034988016) at /home/git/head/sys/kern/kern_shutdown.c:318
318		dumptid = curthread->td_tid;
(kgdb) #0  doadump (textdump=1034988016)
    at /home/git/head/sys/kern/kern_shutdown.c:318
#1  0xffffffff803fc015 in db_fncall_generic (addr=-2139568144, 
    rv=0xfffffe033db0a9a0, nargs=0, args=0xfffffe033db0a9b0)
    at /home/git/head/sys/ddb/db_command.c:581
#2  0xffffffff803fb5d4 in db_fncall (dummy1=-2185103365408, dummy2=false, 
    dummy3=0, dummy4=0xfffffe033db0aae0 "")
    at /home/git/head/sys/ddb/db_command.c:629
#3  0xffffffff803faf3e in db_command (
    last_cmdp=0xffffffff8170af40 <db_last_command>, cmd_table=0x0, dopager=1)
    at /home/git/head/sys/ddb/db_command.c:453
#4  0xffffffff803faad9 in db_command_loop ()
    at /home/git/head/sys/ddb/db_command.c:506
#5  0xffffffff803ff92a in db_trap (type=9, code=0)
    at /home/git/head/sys/ddb/db_main.c:248
#6  0xffffffff807f7361 in kdb_trap (type=9, code=0, tf=0xfffffe033db0b190)
    at /home/git/head/sys/kern/subr_kdb.c:654
#7  0xffffffff80ceb7bc in trap_fatal (frame=0xfffffe033db0b190, eva=0)
    at /home/git/head/sys/amd64/amd64/trap.c:819
#8  0xffffffff80ceabf1 in trap (frame=0xfffffe033db0b190)
    at /home/git/head/sys/amd64/amd64/trap.c:553
#9  0xffffffff80cec2ca in trap_check (frame=0xfffffe033db0b190)
    at /home/git/head/sys/amd64/amd64/trap.c:625
#10 <signal handler called>
#11 0xffffffff8073cea7 in prison_allow (
    cred=0xffffffff819620f8 <w_locklistdata+242216>, flag=4096)
    at /home/git/head/sys/kern/kern_jail.c:2523
#12 0xffffffff81e2102c in fdesc_mount (mp=0xfffff8000771e6d0)
    at /home/git/head/sys/modules/fdescfs/../../fs/fdescfs/fdesc_vfsops.c:85
#13 0xffffffff808b8bf8 in vfs_domount_first (td=0xfffff800075fca80, 
    vfsp=0xffffffff81e221f8 <fdescfs_vfsconf>, 
    fspath=0xfffff800073ca780 "/dev/fd", vp=0xfffff8000777e000, fsflags=0, 
    optlist=0xfffffe033db0b798) at /home/git/head/sys/kern/vfs_mount.c:825
#14 0xffffffff808b4fa5 in vfs_domount (td=0xfffff800075fca80, 
    fstype=0xfffff80007279f20 "fdescfs", fspath=0xfffff80007279f00 "/dev/fd", 
    fsflags=0, optlist=0xfffffe033db0b798)
    at /home/git/head/sys/kern/vfs_mount.c:1114
#15 0xffffffff808b4088 in vfs_donmount (td=0xfffff800075fca80, fsflags=0, 
    fsoptions=0xfffff80007360000) at /home/git/head/sys/kern/vfs_mount.c:675
#16 0xffffffff808b37c4 in sys_nmount (td=0xfffff800075fca80, 
    uap=0xfffffe033db0ba58) at /home/git/head/sys/kern/vfs_mount.c:420
#17 0xffffffff80cece75 in syscallenter (td=0xfffff800075fca80, 
    sa=0xfffffe033db0ba48)
    at /home/git/head/sys/amd64/amd64/../../kern/subr_syscall.c:135
#18 0xffffffff80cec67a in amd64_syscall (td=0xfffff800075fca80, traced=0)
    at /home/git/head/sys/amd64/amd64/trap.c:925
#19 <signal handler called>
#20 0x0000000800a8394a in ?? ()
Backtrace stopped: Cannot access memory at address 0x7fffffffdce8
(kgdb) 
(kgdb) up 11
#11 0xffffffff8073cea7 in prison_allow (cred=0xffffffff819620f8 <w_locklistdata+242216>, flag=0x1000)
    at /home/git/head/sys/kern/kern_jail.c:2523
2523		return (cred->cr_prison->pr_allow & flag);
(kgdb) l
2518	int
2519	prison_allow(struct ucred *cred, unsigned flag)
2520	{
2521	
2522		/* This is an atomic read, so no locking is necessary. */
2523		return (cred->cr_prison->pr_allow & flag);
2524	}
2525	
2526	/*
2527	 * Remove a prison reference.  If that was the last reference, remove the
(kgdb) p *cred->cr_prison
Cannot access memory at address 0x10000000000fe
(kgdb) p *cred
$1 = {cr_ref = 0x0, cr_uid = 0x0, cr_ruid = 0x816f9500, cr_svuid = 0xffffffff, cr_ngroups = 0x80de6efd, 
  cr_rgid = 0xffffffff, cr_svgid = 0x14fb, cr_uidinfo = 0xfffff80003a3ef10, cr_ruidinfo = 0xffffffff80e75cef, 
  cr_prison = 0x10000000000fe, cr_loginclass = 0xfffff800073ff420, cr_flags = 0x80e55a4b, cr_pspare2 = {
    0x10000000001be, 0xfffff8000777e098}, cr_label = 0xffffffff80e55a4b, cr_audit = {ai_auid = 0x1ba, ai_mask = {
      am_success = 0x10000, am_failure = 0x81a59e00}, ai_termid = {at_port = 0xffffffff, at_type = 0x80ecb56d, 
      at_addr = {0xffffffff, 0x4c9, 0x10000, 0x0}}, ai_asid = 0x0, ai_flags = 0x0}, cr_groups = 0xfffff80007870800, 
  cr_agroups = 0x80ec4b1b, cr_smallgroups = {0xffffffff, 0x578, 0x10000, 0x819c8580, 0xffffffff, 0x80ec4b1b, 
    0xffffffff, 0x353a, 0x10000, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}}