Comment 33 for bug 1861235

Picking the previous bad object (which I'm pretty sure should still be intact):

$ modinfo zfs | grep ^version
version: 0.7.5-1ubuntu16.10+lp1861235
$ uname -a
Linux wopr 4.15.0-126-generic #129-Ubuntu SMP Mon Nov 23 18:53:38 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
$ sudo zdb -dddd srv/backups/millbarge/rpool/var/log 529
Dataset srv/backups/millbarge/rpool/var/log [ZPL], ID 39694, cr_txg 23197757, 554M, 274 objects, rootbp DVA[0]=<1:1d000d42000:1000> DVA[1]=<2:24416f4b000:1000> [L0 DMU objset] sha256 uncompressed LE contiguous unique double size=800L/800P birth=23437543L/23437543P fill=274 cksum=cf5fcb2f986c768c:7cc8638aeb1a5162:9de9f236f072e16:40c6a08d90b54951

    Object lvl iblk dblk dsize dnsize lsize %full type
dn->dn_nblkptr >= 1 (0x0 >= 0x1)
ASSERT at ../../module/zfs/dnode.c:278:dnode_verify()Aborted
$ dmesg | tail
[ 43.017302] Ebtables v2.0 registered
[ 44.977437] L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details.
[ 47.047114] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
[ 47.047966] virbr0: port 1(virbr0-nic) entered blocking state
[ 47.047968] virbr0: port 1(virbr0-nic) entered disabled state
[ 47.048063] device virbr0-nic entered promiscuous mode
[ 47.433533] nf_conntrack version 0.5.0 (65536 buckets, 262144 max)
[ 47.971009] virbr0: port 1(virbr0-nic) entered blocking state
[ 47.971013] virbr0: port 1(virbr0-nic) entered listening state
[ 48.321853] virbr0: port 1(virbr0-nic) entered disabled state
$