I run two loadbalanced postfix MX servers, both kept kind of up-to-date with
tumbleweed. Part of that install, on both of them, is opendkim for mail
signing. Setup basically has been running flawlessly for a few years.

One system was updated about 40 days ago, to tumbleweed 20210810, which has
libunbound8-1.13.1-2.1.x86_64

Today I updated the other one to even newer tumbleweed, 20210929, which brought
newerlibunbound8-1.13.2-1.2.x86_64 package. And there, I experienced opendkim
hitting a segv, after ~1500 seconds of uptime, restarted it manually, and it
ran into a second one at ~3600 seconds of system uptime.

The dmesg output, see below, pointed at libunbound8. So I manually
force-downgraded just that package to the version that has been running on the
partner machine for some days - and the segvs are gone now after several hours.

Unfortunately, these are busy mailservers with multiple mails flowing through
each second, so I cannot pinpoint / reproduce the segv precisely, and I cannot
risk much experimenting on them. I hope this observations can help resolve the
issue, anyway.

So here's the dmesg output I saw:

2021-10-05T14:02:56.385231+02:00 phobos kernel: [ 1521.425408] opendkim[2552]:
segfault at 10 ip 00007fd1f33256aa sp 00007fd1eb7fd640 error 4 in
libunbound.so.8.
1.13[7fd1f328c000+cb000]
2021-10-05T14:02:56.385242+02:00 phobos kernel: [ 1521.425422] Code: fc 55 48
89 f5 53 48 83 ec 28 48 8b 9e 20 01 00 00 48 8b 43 10 4c 8b 38 4c 8b 50 08 48
8b 86
 30 01 00 00 48 8b 80 b8 00 00 00 <4c> 8b 58 10 48 c7 86 30 01 00 00 00 00 00
00 83 fa fe 0f 84 46 02
...
2021-10-05T14:38:48.875262+02:00 phobos kernel: [ 3674.051115] opendkim[11676]:
segfault at 10 ip 00007f96636696aa sp 00007f965b7fd640 error 4 in
libunbound.so.8.1.13[7f96635d0000+cb000]
2021-10-05T14:38:48.875273+02:00 phobos kernel: [ 3674.051128] Code: fc 55 48
89 f5 53 48 83 ec 28 48 8b 9e 20 01 00 00 48 8b 43 10 4c 8b 38 4c 8b 50 08 48
8b 86 30 01 00 00 48 8b 80 b8 00 00 00 <4c> 8b 58 10 48 c7 86 30 01 00 00 00 00
00 00 83 fa fe 0f 84 46 02