[8794845.086660] BUG: unable to handle kernel NULL pointer dereference at (null)
[8794845.088500] IP: [<ffffffff8128f89c>] kref_get+0xc/0x30
[8794845.089355] PGD 812ca2067 PUD 6dd707067 PMD 0 
[8794845.090303] Oops: 0000 [#1] SMP 
[8794845.091005] last sysfs file: /sys/devices/system/cpu/online
[8794845.091861] CPU 3 
[8794845.092212] Modules linked in: ysec_firewall_kmod(U) tcp_diag inet_diag nf_conntrack_netlink nfnetlink nf_conntrack_ipv6 nf_defrag_ipv6 ip6_tables xt_multiport nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack iptable_filter ip_tables ipv6 virtio_balloon virtio_net virtio_console i2c_piix4 i2c_core ext4 jbd2 mbcache virtio_blk virtio_pci virtio_ring virtio pata_acpi ata_generic ata_piix dm_mirror dm_region_hash dm_log dm_mod [last unloaded: ysec_firewall_kmod]
[8794845.101913] 
[8794845.102621] Pid: 21908, comm: ysec_hids_mod_l Tainted: G        W  ---------------    2.6.32-504.16.2.el6.x86_64 #1 Alibaba Cloud Alibaba Cloud ECS
[8794845.105481] RIP: 0010:[<ffffffff8128f89c>]  [<ffffffff8128f89c>] kref_get+0xc/0x30
[8794845.107400] RSP: 0018:ffff88045f5a3e38  EFLAGS: 00010292
[8794845.108628] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00000000fffffff3
[8794845.110501] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[8794845.112371] RBP: ffff88045f5a3e48 R08: 0000000000000000 R09: ffff88050f507f00
[8794845.114133] R10: 0000000000000003 R11: 0000000000000206 R12: ffffffff8161b040
[8794845.115994] R13: 0000000000000040 R14: 00007f4b457f94d0 R15: 0000000000000000
[8794845.117865] FS:  00007f4b457fb700(0000) GS:ffff880030380000(0000) knlGS:0000000000000000
[8794845.119846] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[8794845.121055] CR2: 0000000000000000 CR3: 00000006f6837000 CR4: 00000000001406e0
[8794845.122807] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[8794845.124685] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[8794845.126558] Process ysec_hids_mod_l (pid: 21908, threadinfo ffff88045f5a2000, task ffff8806d43acab0)
[8794845.128689] Stack:
[8794845.129414]  ffff88045f5a3e68 0000000000000000 ffff88045f5a3e68 ffffffff810d6ae6
[8794845.131107] <d> ffffffff8161b040 ffff8806c03a3520 ffff88045f5a3ef8 ffffffff81203898
[8794845.133479] <d> 00007f4b457f9510 0000000000000000 ffff88045f5a3eb8 ffffffff8128c635
[8794845.136365] Call Trace:
[8794845.137127]  [<ffffffff810d6ae6>] pidns_get+0x26/0x30
[8794845.138367]  [<ffffffff81203898>] proc_ns_readlink+0xc8/0x180
[8794845.139665]  [<ffffffff8128c635>] ? _atomic_dec_and_lock+0x55/0x80
[8794845.141008]  [<ffffffff811ab151>] ? touch_atime+0x71/0x1a0
[8794845.142268]  [<ffffffff81193b0e>] sys_readlinkat+0xfe/0x120
[8794845.143536]  [<ffffffff81193b4b>] sys_readlink+0x1b/0x20
[8794845.144695]  [<ffffffff8100b072>] system_call_fastpath+0x16/0x1b