env info:

• kernal version : 5.4.0-182-generic #202-Ubuntu
• tcp client : iSCSI Initiator over TCP/IP
• tcp server : iSCSI target on same host
• bpf program : https://github.com/addozhang/ebpf-sockops, which is berified for validity on same host by iperf3.

After modified the SERVER_PORT in bpf_sockmap.h, I recompile and reload the ebpf program. The problem occurs when I tried to use iSCSI initiator to login the iSCSI Target, with the following kern log.

kern.log

May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.120960] ------------[ cut here ]------------
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.120961] refcount_t: saturated; leaking memory.
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.120995] WARNING: CPU: 0 PID: 9557 at lib/refcount.c:19 refcount_warn_saturate+0x8e/0xf0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.120999] Modules linked in: iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi xfs isofs nls_iso8859_1 dm_multipath scsi_dh_rdac scsi_dh_emc scsi_dh_alua binfmt_misc joydev input_leds serio_raw sch_fq_codel ipmi_devintf efi_pstore ipmi_msghandler msr ip_tables x_tables autofs4 btrfs zstd_compress raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear hid_generic usbhid hid bochs_drm drm_vram_helper ttm drm_kms_helper syscopyarea sysfillrect virtio_net sysimgblt fb_sys_fops net_failover psmouse failover drm virtio_blk virtio_scsi floppy
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121041] CPU: 0 PID: 9557 Comm: kworker/u2:3 Not tainted 5.4.0-182-generic #202-Ubuntu
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121043] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121049] Workqueue: iscsi_q_3 iscsi_xmitworker [libiscsi]
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121055] RIP: 0010:refcount_warn_saturate+0x8e/0xf0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121057] Code: 97 54 6e 01 01 e8 70 1f 58 00 0f 0b 5d c3 80 3d 89 54 6e 01 00 75 b1 48 c7 c7 d8 f7 17 b1 c6 05 79 54 6e 01 01 e8 50 1f 58 00 <0f> 0b 5d c3 80 3d 66 54 6e 01 00 75 91 48 c7 c7 30 f8 17 b1 c6 05
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121058] RSP: 0018:ffffa2e400c1b850 EFLAGS: 00010282
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121059] RAX: 0000000000000000 RBX: ffff92eb10129b00 RCX: 0000000000000006
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121060] RDX: 0000000000000007 RSI: 0000000000000096 RDI: ffff92eb6fa1c8c0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121061] RBP: ffffa2e400c1b850 R08: 0000000000000377 R09: 0000000000000004
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121061] R10: 0000000000000000 R11: 0000000000000001 R12: ffffa2e400c1bcd8
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121062] R13: ffffa2e400c1bcd8 R14: ffff92eb4d181b28 R15: ffff92eb4d181e28
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121063] FS:  0000000000000000(0000) GS:ffff92eb6fa00000(0000) knlGS:0000000000000000
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121064] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121065] CR2: 0000556533aa376c CR3: 000000040d2fa000 CR4: 00000000000006f0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121068] Call Trace:
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121079]  ? show_regs.cold+0x1a/0x1f
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121082]  ? __warn+0x98/0xe0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121083]  ? refcount_warn_saturate+0x8e/0xf0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121086]  ? report_bug+0xd1/0x100
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121089]  ? do_error_trap+0x9b/0xc0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121091]  ? do_invalid_op+0x3c/0x50
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121092]  ? refcount_warn_saturate+0x8e/0xf0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121095]  ? invalid_op+0x1e/0x30
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121097]  ? refcount_warn_saturate+0x8e/0xf0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121100]  tcp_bpf_sendmsg+0x393/0x3e0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121104]  ? perf_event_output+0x65/0x90
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121108]  ? bpf_perf_event_output+0x114/0x170
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121110]  ? trace_call_bpf+0x69/0xe0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121112]  ? __sock_sendmsg+0x1/0x70
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121114]  ? kprobe_perf_func+0x23e/0x290
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121117]  ? sched_clock_cpu+0x11/0xb0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121120]  ? __update_load_avg_se+0x23b/0x320
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121121]  ? __sock_sendmsg+0x1/0x70
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121122]  ? __sock_sendmsg+0x5/0x70
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121123]  ? kprobe_dispatcher+0x5d/0x70
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121124]  ? __sock_sendmsg+0x1/0x70
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121127]  ? kprobe_ftrace_handler+0x90/0xf0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121128]  ? sock_sendmsg+0x68/0xa0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121131]  ? ftrace_ops_assist_func+0x8d/0x120
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121133]  ? 0xffffffffc087f0da
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121143]  ? _cond_resched+0x19/0x30
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121146]  ? aa_sk_perm+0x43/0x1b0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121148]  inet_sendmsg+0x6c/0x70
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121149]  __sock_sendmsg+0x5e/0x70
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121150]  sock_sendmsg+0x68/0xa0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121152]  ? default_wake_function+0x12/0x20
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121154]  ? pollwake+0x72/0x90
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121157]  ? iscsi_tcp_segment_done+0x88/0x3c0 [libiscsi_tcp]
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121159]  ? iscsi_tcp_segment_done+0x396/0x3c0 [libiscsi_tcp]
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121161]  ? __wake_up_common+0x7e/0x140
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121162]  kernel_sendmsg+0x2c/0x40
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121164]  iscsi_sw_tcp_xmit_segment+0x7c/0x130 [iscsi_tcp]
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121166]  iscsi_sw_tcp_pdu_xmit+0x6e/0x1a0 [iscsi_tcp]
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121168]  iscsi_tcp_task_xmit+0x10a/0x2a0 [libiscsi_tcp]
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121171]  iscsi_xmit_task+0xa7/0x150 [libiscsi]
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121173]  iscsi_xmitworker+0x5e/0x320 [libiscsi]
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121177]  ? __schedule+0x2eb/0x740
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121178]  process_one_work+0x1eb/0x3b0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121180]  worker_thread+0x4d/0x400
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121182]  kthread+0x104/0x140
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121183]  ? process_one_work+0x3b0/0x3b0
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121184]  ? kthread_park+0x90/0x90
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121186]  ret_from_fork+0x35/0x40
May 22 17:22:25 vm233-ubuntu-20 kernel: [95215.121188] ---[ end trace 993bf458f9f5818c ]---

I tried to use a client-side library of libiscsi(https://github.com/sahlberg/libiscsi), and the iSCSI initiator login succeed then.
Seems like the error was from native iSCSI initiator.Did I trigger any known kernel issues, and how can I further investigate?