dlm caused a kernel panic in the dlm_user_add_ast function with message "BUG: unable to handle kernel NULL pointer dereference at 0000000000000020" on RHEL 7

Issue

• A kernel panic occurred as shown below.

[533438.890256] BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
[533438.891622] IP: [<ffffffffa3d8ba8c>] _raw_spin_lock+0xc/0x30
[533438.892874] PGD 80000004d243d067 PUD 1abd387067 PMD 0
[533438.894135] Oops: 0002 [#1] SMP
[533438.895411] Modules linked in: iptable_filter tcp_diag udp_diag inet_diag unix_diag af_packet_diag netlink_diag xfs gfs2 dlm secvm2(POE) secfs2(POE) ib_core nfsv3 nfs_acl nfs_layout_nfsv41_files rpcsec_gss_krb5 nfsv4 dns_resolver nfs lockd grace fscache team_mode_activebackup team iTCO_wdt iTCO_vendor_support dm_round_robin sb_edac intel_powerclamp coretemp intel_rapl iosf_mbi kvm_intel kvm irqbypass crc32_pclmul ghash_clmulni_intel aesni_intel lrw gf128mul glue_helper ablk_helper cryptd pcspkr i2c_i801 mgag200 i2c_algo_bit ttm drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm lpc_ich hpilo drm_panel_orientation_quirks hpwdt sg ioatdma dca ipmi_si wmi dm_multipath pcc_cpufreq ipmi_devintf ipmi_msghandler acpi_power_meter binfmt_misc auth_rpcgss sunrpc ip_tables ext4 mbcache jbd2 sd_mod
[533438.904220]  sr_mod cdrom crc_t10dif crct10dif_generic qla2xxx ahci bnx2x libahci libata crct10dif_pclmul crct10dif_common crc32c_intel serio_raw tg3 nvme_fc nvme_fabrics nvme_core hpsa mdio scsi_transport_fc libcrc32c ptp scsi_transport_sas pps_core scsi_tgt dm_mirror dm_region_hash dm_log dm_mod
[533438.909147] CPU: 20 PID: 169970 Comm: kworker/u65:5 Kdump: loaded Tainted: P           OE  ------------   3.10.0-1160.42.2.el7.x86_64 #1
[533438.912461] Hardware name: HP ProLiant DL380 Gen9/ProLiant DL380 Gen9, BIOS P89 04/29/2021
[533438.914180] Workqueue: dlm_recv process_recv_sockets [dlm]
[533438.915852] task: ffff9a5e9e3fc200 ti: ffff9a710c878000 task.ti: ffff9a710c878000
[533438.917319] RIP: 0010:[<ffffffffa3d8ba8c>]  [<ffffffffa3d8ba8c>] _raw_spin_lock+0xc/0x30
[533438.918337] RSP: 0018:ffff9a710c87ba88  EFLAGS: 00010246
[533438.919956] RAX: 0000000000000000 RBX: ffff9a78349b7528 RCX: 00000000fffefffe
[533438.921560] RDX: 0000000000000001 RSI: 0000000000000001 RDI: 0000000000000020
[533438.923238] RBP: ffff9a710c87bad0 R08: 0000000000030001 R09: 0000000000bdb1b8
[533438.924710] R10: 0000000000000020 R11: 0000000000000000 R12: 00000000ffffffff
[533438.925755] R13: 0000000000030001 R14: 0000000000bdb1b8 R15: ffff9a8fec7238c8
[533438.926674] FS:  0000000000000000(0000) GS:ffff9a713fd00000(0000) knlGS:0000000000000000
[533438.927849] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[533438.928767] CR2: 0000000000000020 CR3: 00000009b821e000 CR4: 00000000001607e0
[533438.929695] Call Trace:
[533438.930595]  [<ffffffffc085a4b9>] ? dlm_user_add_ast+0xd9/0x290 [dlm]
[533438.931781]  [<ffffffffc08423c9>] dlm_add_cb+0xd9/0x1a0 [dlm]
[533438.932702]  [<ffffffffc0846453>] queue_cast.isra.41+0x53/0xe0 [dlm]
[533438.933879]  [<ffffffffc084714c>] _receive_unlock_reply+0xec/0x100 [dlm]
[533438.935250]  [<ffffffffc084a74f>] _receive_message+0x43f/0x14a0 [dlm]
[533438.936280]  [<ffffffffa3cdffb0>] ? inet_recvmsg+0x80/0xb0
[533438.937837]  [<ffffffffa3c364f5>] ? sock_recvmsg+0xc5/0x100
[533438.938986]  [<ffffffffa3d875b2>] ? mutex_lock+0x12/0x2f
[533438.940626]  [<ffffffffc084cb55>] dlm_receive_buffer+0x195/0x1d0 [dlm]
[533438.941692]  [<ffffffffc0851e24>] dlm_process_incoming_buffer+0xf4/0x1f0 [dlm]
[533438.942806]  [<ffffffffc0853649>] receive_from_sock+0x129/0x330 [dlm]
[533438.943939]  [<ffffffffc08521ec>] process_recv_sockets+0x2c/0x40 [dlm]
[533438.945396]  [<ffffffffa36bde8f>] process_one_work+0x17f/0x440
[533438.946881]  [<ffffffffa36befa6>] worker_thread+0x126/0x3c0
[533438.948618]  [<ffffffffa36bee80>] ? manage_workers.isra.26+0x2a0/0x2a0
[533438.950280]  [<ffffffffa36c5e61>] kthread+0xd1/0xe0
[533438.951254]  [<ffffffffa36c5d90>] ? insert_kthread_work+0x40/0x40
[533438.952704]  [<ffffffffa3d95df7>] ret_from_fork_nospec_begin+0x21/0x21
[533438.953945]  [<ffffffffa36c5d90>] ? insert_kthread_work+0x40/0x40
[533438.955422] Code: 5d c3 0f 1f 44 00 00 85 d2 74 e4 0f 1f 40 00 eb ed 66 0f 1f 44 00 00 b8 01 00 00 00 5d c3 90 0f 1f 44 00 00 31 c0 ba 01 00 00 00 <f0> 0f b1 17 85 c0 75 01 c3 55 89 c6 48 89 e5 e8 48 22 ff ff 5d
[533438.958418] RIP  [<ffffffffa3d8ba8c>] _raw_spin_lock+0xc/0x30
[533438.959453]  RSP <ffff9a710c87ba88>
[533438.961031] CR2: 0000000000000020