Kernel panics at fput() function due to unassign module zing_mm

Issue

• System panic with following calltraces in kernel ring buffer.

[2052288.335060] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
[2052288.344539] IP: [<ffffffff8119b521>] __fput+0x21/0x210
[2052288.350754] PGD 662cfe1067 PUD 64f43f0067 PMD 0 
[2052288.356420] Oops: 0000 [#1] SMP 
[2052288.360503] last sysfs file: /sys/devices/system/cpu/online
[2052288.367179] CPU 28 
[2052288.369531] Modules linked in: iptable_filter ip_tables mtdchar onload(U) sfc_char(U) sfc_resource(U) sfc_affinity(U) onload_cplane(P)(U) zing_mm(U) bonding ipmi_devint
f ipmi_si ipmi_msghandler microcode iTCO_wdt iTCO_vendor_support cdc_ether usbnet mii i2c_i801 lpc_ich mfd_core shpchp sg ses enclosure ext4 jbd2 mbcache sd_mod crc_t10dif s
fc(U) igb dca i2c_algo_bit i2c_core ptp pps_core crc32c_intel be2iscsi bnx2i cnic uio cxgb4i iw_cxgb4 iw_cm cxgb4 cxgb3i libcxgbi iw_cxgb3 ib_core ib_addr ipv6 cxgb3 mdio li
biscsi_tcp qla4xxx iscsi_boot_sysfs libiscsi scsi_transport_iscsi megaraid_sas wmi dm_mirror dm_region_hash dm_log dm_mod [last unloaded: scsi_wait_scan]
[2052288.439050] 
[2052288.441161] Pid: 8296, comm: ps Tainted: P 
2052288.456092] RIP: 0010:[<ffffffff8119b521>]  [<ffffffff8119b521>] __fput+0x21/0x210
[2052288.465272] RSP: 0018:ffff88805143ba38  EFLAGS: 00010292
[2052288.471652] RAX: 0000000000000000 RBX: ffff8866ba6ebc80 RCX: 0000000000000000
[2052288.480317] RDX: 0000000000000000 RSI: ffff8865074d4300 RDI: ffff8866ba6ebc80
[2052288.488981] RBP: ffff88805143ba78 R08: 0000000000000000 R09: ffff8865074d4300
[2052288.497646] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8866539d7bb0
[2052288.506313] R13: ffff8860f0d0f060 R14: 00000000004008cc R15: ffff882399ae6780
[2052288.515074] FS:  00007f68fb5677a0(0000) GS:ffff8860f0d00000(0000) knlGS:0000000000000000
[2052288.524814] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[2052288.531688] CR2: 0000000000000010 CR3: 0000007fce95b000 CR4: 00000000001407e0
[2052288.540355] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[2052288.549027] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[2052288.557793] Process ps (pid: 8296, threadinfo ffff888051438000, task ffff8862fb233520)
[2052288.567337] Stack:
[2052288.570038]  ffff8866539d7bb0 0000000000000000 00000000004008cc ffff8864e6eaf468
[2052288.578616] <d> ffff8866539d7bb0 ffff8860f0d0f060 00000000004008cc ffff882399ae6780
[2052288.587965] <d> ffff88805143ba88 ffffffff8119b735 ffff88805143baa8 ffffffff8115d5c5
[2052288.597764] Call Trace:
[2052288.600959]  [<ffffffff8119b735>] fput+0x25/0x30
[2052288.606581]  [<ffffffff8115d5c5>] remove_vma+0x45/0x90
[2052288.612783]  [<ffffffff8115d6d8>] exit_mmap+0xc8/0x180
[2052288.618986]  [<ffffffff810799bc>] mmput+0x6c/0x120
[2052288.624791]  [<ffffffff8120d7bb>] do_task_stat+0x67b/0x8d0
[2052288.631378]  [<ffffffff8120da24>] proc_tgid_stat+0x14/0x20
[2052288.637972]  [<ffffffff8120a014>] proc_single_show+0x64/0xa0
[2052288.644756]  [<ffffffff811bfc32>] seq_read+0xf2/0x400
[2052288.650289] type=1103 audit(1510101840.110:6422283): user pid=8325 uid=0 auid=4294967295 ses=1 msg='op=PAM:setcred acct="ettcc_p" exe="/opt/boksm/lib/boks_sshd" hostname=localhost addr=10.95.246.67 terminal=ssh res=success'
[2052288.650348] type=1006 audit(1510101840.110:6422284): pid=8325 uid=0 old auid=4294967295 new auid=159935 old ses=1 new ses=917554
[2052288.650580] type=1105 audit(1510101840.111:6422285): user pid=8325 uid=0 auid=159935 ses=917554 msg='op=PAM:session_open acct="ettcc_p" exe="/opt/boksm/lib/boks_sshd" hostname=localhost addr=10.95.246.67 terminal=ssh res=success'
[2052288.717543]  [<ffffffff8119a3a5>] vfs_read+0xb5/0x1a0
[2052288.723646]  [<ffffffff8119b156>] ? fget_light_pos+0x16/0x50
[2052288.730433]  [<ffffffff8119a6f1>] sys_read+0x51/0xb0
[2052288.736442]  [<ffffffff810ee25e>] ? __audit_syscall_exit+0x25e/0x290
[2052288.744005]  [<ffffffff8100b0d2>] system_call_fastpath+0x16/0x1b
[2052288.751168] Code: ee ff c9 c3 66 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 41 55 41 54 53 48 83 ec 18 0f 1f 44 00 00 48 8b 47 18 48 89 fb 48 89 45 c8 <48> 8b 50 10 4c 8b 7f 10 48 89 55 c0 e8 be de 3a 00 4c 8b 73 18 
[2052288.774346] RIP  [<ffffffff8119b521>] __fput+0x21/0x210
[2052288.780747]  RSP <ffff88805143ba38>
[2052288.785090] CR2: 0000000000000010