Hi,

Unfortunately, the patch does not seem to solve the problem. Running Ubuntu 18.04 LTS with kernel 4.15.0-64, the crash still occurs with the same signature :

Oct 14 08:00:01 uzorldsp01 kernel: [109699.415372] BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
Oct 14 08:00:01 uzorldsp01 kernel: [109699.420042] IP: smb2_push_mandatory_locks+0x10d/0x3c0 [cifs]
Oct 14 08:00:01 uzorldsp01 kernel: [109699.420042] PGD 0 P4D 0
Oct 14 08:00:01 uzorldsp01 kernel: [109699.420042] Oops: 0000 [#1] SMP PTI
Oct 14 08:00:01 uzorldsp01 kernel: [109699.420042] Modules linked in: btrfs zstd_compress xor raid6_pq ufs qnx4 minix ntfs msdos jfs xfs dm_snapshot dm_bufio cmac arc4 md4 nls_utf8 cifs ccm fscache nf_conntr
ack_ipv4 nf_defrag_ipv4 xt_owner xt_conntrack nf_conntrack libcrc32c iptable_security sb_edac kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc aesni_intel aes_x86_64 crypto_simd
glue_helper cryptd intel_rapl_perf input_leds serio_raw hyperv_fb hv_balloon joydev mac_hid sch_fq_codel nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables x_tables autofs4 hid_generic hid_hyperv hv_util
s hv_storvsc ptp hyperv_keyboard hv_netvsc hid scsi_transport_fc pps_core psmouse i2c_piix4 pata_acpi hv_vmbus floppy
Oct 14 08:00:01 uzorldsp01 kernel: [109699.472261] CPU: 0 PID: 50766 Comm: kworker/0:0 Not tainted 4.15.0-64-generic #73-Ubuntu
Oct 14 08:00:01 uzorldsp01 kernel: [109699.472261] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090007  06/02/2017
Oct 14 08:00:01 uzorldsp01 kernel: [109699.472261] Workqueue: cifsoplockd cifs_oplock_break [cifs]
Oct 14 08:00:01 uzorldsp01 kernel: [109699.472261] RIP: 0010:smb2_push_mandatory_locks+0x10d/0x3c0 [cifs]
Oct 14 08:00:01 uzorldsp01 kernel: [109699.472261] RSP: 0000:ffffab360da2bdd8 EFLAGS: 00010246
Oct 14 08:00:01 uzorldsp01 kernel: [109699.472261] RAX: 0000000000000000 RBX: ffff9887646617d8 RCX: 0000000000000000
Oct 14 08:00:01 uzorldsp01 kernel: [109699.472261] RDX: 0000000000001000 RSI: 0000000000000000 RDI: ffff98876d006b80
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261] RBP: ffffab360da2be28 R08: ffff988568596000 R09: ffff98876d006b80
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261] R10: ffffab360da2bd98 R11: ffff988568596000 R12: 00000000000000aa
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261] R13: ffff9887646617d8 R14: ffff9887646617c0 R15: ffff988764d7f200
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261] FS:  0000000000000000(0000) GS:ffff98876d600000(0000) knlGS:0000000000000000
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261] CR2: 0000000000000038 CR3: 000000046d80a003 CR4: 00000000001606f0
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261] Call Trace:
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261]  cifs_oplock_break+0x131/0x410 [cifs]
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261]  process_one_work+0x1de/0x420
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261]  worker_thread+0x32/0x410
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261]  kthread+0x121/0x140
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261]  ? process_one_work+0x420/0x420
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261]  ? kthread_create_worker_on_cpu+0x70/0x70
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261]  ret_from_fork+0x35/0x40
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261] Code: c8 00 00 00 00 48 89 45 b0 49 39 c6 0f 84 e5 00 00 00 4d 89 fb 4d 8b 7e 10 49 8b 5e 18 4d 8d 6e 18 49 8b 87 90 00 00 00 4c 39 eb <48> 8b 40 38 48 89 4
5 d0 0f 84 ae 00 00 00 45 31 d2 4c 89 75 b8
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261] RIP: smb2_push_mandatory_locks+0x10d/0x3c0 [cifs] RSP: ffffab360da2bdd8
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261] CR2: 0000000000000038
Oct 14 08:00:02 uzorldsp01 kernel: [109699.472261] ---[ end trace ee6628b4e2b5174b ]---