Details of this crash can be found after the VM is rebooted. Here is the kernel BUG (nthred.c) that is hit:
NOTE: I used Codenomicon ISCSI testing to hit this issue!
[75999.447928] [33903]: iscsi-scst: Creating connection 00000000b60b426d for sid 0x3f20000000000, cid 0 (initiator iqn.1994-09.org.freebsd:iscsi)
[75999.471707] [33887]: iscsi-scst: Logout received from initiator iqn.1994-09.org.freebsd:iscsi
[75999.471718] [33889]: iscsi-scst: Closing connection at initiator's iqn.1994-09.org.freebsd:iscsi request
[75999.471815] [34498]: scst: TM fn NEXUS_LOSS_SESS/6 (mcmd 0000000087b23588, initiator iqn.1994-09.org.freebsd:iscsi, target iqn.2012-05.local:mailbox.target.ryan00001)
[75999.471831] [33884]: scst: TM fn 6 (mcmd 0000000087b23588) finished, status 0
[75999.471838] [34498]: iscsi-scst: Freeing conn 00000000b60b426d (sess=00000000f4d68531, 0x3f20000000000 0, initiator iqn.1994-09.org.freebsd:iscsi)
[75999.471848] [34498]: iscsi-scst: Freeing session 00000000f4d68531 (SID 3f20000000000)
[76035.304588] [33903]: scst: Using security group "access_group" for initiator "iqn.1994-09.org.freebsd:iscsi" (target iqn.2012-05.local:mailbox.target.ryan00001)
[76035.305532] [33903]: iscsi-scst: Session 00000000f4d68531 created: target 0000000000f93e99, tid 1, sid 0x4f30000000000, initiator iqn.1994-09.org.freebsd:iscsi
[76035.305536] [33903]: iscsi-scst: Negotiated parameters: InitialR2T Yes, ImmediateData Yes, MaxConnections 1, MaxRecvDataSegmentLength 1048576, MaxXmitDataSegmentLength 8192,
[76035.305538] [33903]: iscsi-scst: MaxBurstLength 262144, FirstBurstLength 65536, DefaultTime2Wait 0, DefaultTime2Retain 0,
[76035.305539] [33903]: iscsi-scst: MaxOutstandingR2T 1, DataPDUInOrder Yes, DataSequenceInOrder Yes, ErrorRecoveryLevel 0,
[76035.305540] [33903]: iscsi-scst: HeaderDigest None, DataDigest None, OFMarker No, IFMarker No, OFMarkInt 2048, IFMarkInt 2048, RDMAExtensions No
[76035.305542] [33903]: iscsi-scst: Target parameters set for session 4f30000000000: QueuedCommands 32, Response timeout 90, Nop-In interval 30, Nop-In timeout 30
[76035.305582] [33903]: iscsi-scst: Creating connection 00000000b60b426d for sid 0x4f30000000000, cid 0 (initiator iqn.1994-09.org.freebsd:iscsi)
[76035.419640] [34506]: iscsi-scst: ERROR: error 0 at sid:cid 0x4f30000000000:0, cmnd 0000000031af3b7e
[76035.419646] [34506]: iscsi-scst: ERROR: Sending data failed: initiator iqn.1994-09.org.freebsd:iscsi (conn 00000000b60b426d), write_size 8240, write_state 1, res 0
[76035.419696] [33889]: iscsi-scst: CRITICAL ERROR: 0 6 25
[76035.419717] ------------[ cut here ]------------
[76035.419718] kernel BUG at /root/ontap-mediator/dist/scst/scst-3.5.0/iscsi-scst/kernel/nthread.c:1506!
[76035.419754] invalid opcode: 0000 [#1] SMP PTI
[76035.419757] CPU: 0 PID: 33889 Comm: iscsiwr0_1 Kdump: loaded Tainted: G OE --------- - - 4.18.0-240.el8.x86_64 #1
[76035.419758] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/03/2018
[76035.419765] RIP: 0010:iscsi_send+0x820/0x850 [iscsi_scst]
[76035.419767] Code: 02 6e c0 41 b8 e1 05 00 00 48 c7 c1 c8 e4 6d c0 48 c7 c6 e8 14 6e c0 83 e2 3f 52 48 c7 c2 c4 14 6e c0 50 6a 00 e8 00 21 17 00 <0f> 0b e8 e9 f1 bd d3 8b 85 08 01 00 00 bb f5 ff ff ff 89 44 24 14
[76035.419768] RSP: 0018:ffffb87081823de8 EFLAGS: 00010292
[76035.419770] RAX: 0000000000000036 RBX: ffff8ee397ff3440 RCX: 0000000000000000
[76035.419771] RDX: 0000000000000007 RSI: 0000000000000246 RDI: 0000000000000246
[76035.419772] RBP: ffff8ee3edec1400 R08: 0000000000000585 R09: 0000000000000040
[76035.419773] R10: 2a2a2a524f525245 R11: 353220362030203a R12: ffff8ee397ff3488
[76035.419774] R13: ffff8ee39536e180 R14: ffff8ee3edec14b8 R15: ffff8ee397ff34a0
[76035.419775] FS: 0000000000000000(0000) GS:ffff8ee3ffc00000(0000) knlGS:0000000000000000
[76035.419776] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[76035.419777] CR2: 00007fbaba5a3000 CR3: 0000000027e0a001 CR4: 00000000003606f0
[76035.419813] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[76035.419814] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[76035.419815] Call Trace:
[76035.419829] ? __schedule+0x2ae/0x700
[76035.419833] istwr+0x120/0x3b0 [iscsi_scst]
[76035.419840] ? finish_wait+0x80/0x80
[76035.419844] ? iscsi_send+0x850/0x850 [iscsi_scst]
[76035.419846] kthread+0x112/0x130
[76035.419848] ? kthread_flush_work_fn+0x10/0x10
[76035.419850] ret_from_fork+0x35/0x40
[76035.419852] Modules linked in: scst_vdisk(OE) isert_scst(OE) iscsi_scst(OE) scst(OE) dlm xt_CHECKSUM ipt_MASQUERADE xt_conntrack ipt_REJECT nf_nat_tftp nft_objref nf_conntrack_tftp nft_counter tun bridge stp llc rpcrdma ib_isert iscsi_target_mod ib_iser libiscsi scsi_transport_iscsi target_core_mod ib_srp scsi_transport_srp ib_ipoib nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nf_tables_set rdma_ucm ib_uverbs ib_umad nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 rdma_cm iw_cm ib_cm ib_core ip6_tables nft_compat ip_set nf_tables nfnetlink vsock_loopback vmw_vsock_virtio_transport_common vmw_vsock_vmci_transport vsock sunrpc intel_rapl_msr intel_rapl_common sb_edac crct10dif_pclmul crc32_pclmul ghash_clmulni_intel vmw_balloon intel_rapl_perf joydev pcspkr vmw_vmci i2c_piix4 ip_tables xfs libcrc32c vmwgfx drm_kms_helper sr_mod cdrom ata_generic syscopyarea sysfillrect sysimgblt fb_sys_fops ttm sd_mod sg drm
[76035.419968] ata_piix crc32c_intel libata serio_raw vmxnet3 vmw_pvscsi dm_mirror dm_region_hash dm_log dm_mod fuse [last unloaded: dlm]
Any clues/hints what might be going on here?