geli(8) breaks after a couple hours of uptime

Yes, it's pretty much as weird as it sounds. All new machine, forklifted
the image from on old i386 machine running 8.x to current on amd64.

Everything seemingly works fine, attaching geli volumes shortly after
boot is fine, attached devices continue to work fine. There are no
strange crashes with this machine or anything, but when I try to attach
an USB volume the next day, geli attach segfaults.

This seems unrelated to USB however, as the same happens for md(4)
devices.

% geli status
        Name  Status  Components
gpt/swap.eli  ACTIVE  gpt/swap
    ada1.eli  ACTIVE  ada1

These all work fine, so I've rebuild geli with debugging symbols and
when you run geli init md1:

root_at_coyote:/usr/src/sbin/geom/class/eli# gdb geli
GNU gdb 6.1.1 [FreeBSD]
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "amd64-marcel-freebsd"...(no debugging symbols found)...
(gdb) r init md1
Starting program: /sbin/geli init md1
(no debugging symbols found)...(no debugging symbols found)...(no debugging symbols found)...(no debugging symbols found)...(no debugging symbols found)...(no debugging symbols found)...
Program received signal SIGSEGV, Segmentation fault.
0x0000000801c06307 in eli_genkey (req=0x801817040, md=0x7fffffff85c8, key=0x7fffffff9de0 "", new=true) at /usr/src/sbin/geom/class/eli/geom_eli.c:546
546     {
Current language:  auto; currently minimal
(gdb) bt
#0  0x0000000801c06307 in eli_genkey (req=0x801817040, md=0x7fffffff85c8, key=0x7fffffff9de0 "", new=true) at /usr/src/sbin/geom/class/eli/geom_eli.c:546
#1  0x0000000801c054a4 in eli_main (req=0x801817040, flags=<value optimized out>) at /usr/src/sbin/geom/class/eli/geom_eli.c:820
#2  0x000000000040298f in main ()
(gdb) l 818
813             }
814
815             md.md_keys = 0x01;
816             arc4rand(md.md_salt, sizeof(md.md_salt));
817             arc4rand(md.md_mkeys, sizeof(md.md_mkeys));
818
819             /* Generate user key. */
820             if (eli_genkey(req, &md, key, true) == NULL) {
821                     bzero(key, sizeof(key));
822                     bzero(&md, sizeof(md));


hu?
Uli