Kernel panic in xacct_add_tsk() function.

Issue

• Kernel panic with following call traces.

Unable to handle kernel NULL pointer dereference at 00000000000000b0 RIP: 
 [<ffffffff800c232a>] xacct_add_tsk+0x59/0xde
PGD 40411e067 PUD 4591a8067 PMD 0 
Oops: 0000 [1] SMP 
last sysfs file: /devices/pci0000:00/0000:00:00.0/local_cpus
CPU 12 
Modules linked in: ipmi_si mpt2sas scsi_transport_sas mptctl mptbase ipmi_devintf ipmi_msghandler dell_rbu seos(PU) lockd sunrpc cpufreq_ondemand acpi_cpufreq freq_table mperf bonding be2iscsi ib_iser rdma_cm ib_cm iw_cm ib_sa ib_mad ib_core ib_addr iscsi_tcp bnx2i cnic ipv6 xfrm_nalgo crypto_api uio cxgb3i libcxgbi cxgb3 8021q libiscsi_tcp libiscsi2 scsi_transport_iscsi2 scsi_transport_iscsi emcpvlumd(PU) emcpxcrypt(PU) emcpdm(PU) emcpgpx(PU) emcpmpx(PU) emcp(PU) video backlight sbs power_meter hwmon i2c_ec i2c_core dell_wmi wmi button battery asus_acpi acpi_memhotplug ac parport_pc lp parport joydev sr_mod cdrom sg tpm_tis tpm i7core_edac tpm_bios serio_raw bnx2 edac_mc pcspkr dm_raid45 dm_message dm_region_hash dm_mem_cache dm_snapshot dm_zero dm_mirror dm_log dm_mod usb_storage lpfc scsi_transport_fc ata_piix libata shpchp megaraid_sas sd_mod scsi_mod ext3 jbd uhci_hcd ohci_hcd ehci_hcd
Pid: 6220, comm: iotop Tainted: P     ---- 2.6.18-308.8.2.el5 #1
RIP: 0010:[<ffffffff800c232a>]  [<ffffffff800c232a>] xacct_add_tsk+0x59/0xde
RSP: 0018:ffff810412f23810  EFLAGS: 00010202
RAX: 0000000000000000 RBX: ffff810412f23928 RCX: ffff810412f23998
RDX: 0000000000000000 RSI: ffff810c485c7100 RDI: ffff810412f23928
RBP: ffff810c485c7100 R08: 00000000000312fc R09: 0000000000000000
R10: ffff810412f23928 R11: 0000000000000014 R12: ffff810c485c7110
R13: ffff810412f23b08 R14: 0000000000007295 R15: 0000000000000014
FS:  00002b465f2b3170(0000) GS:ffff8106951ce6c0(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000000b0 CR3: 00000003191be000 CR4: 00000000000006a0
Process iotop (pid: 6220, threadinfo ffff810412f22000, task ffff81067bd557a0)
Stack:  ffffffff800c1de3 0000000000000004 000000000000000c 0000000003659e72
 0000000000000010 00000000098a2c04 0000c29f93378df6 0000000002817315
 00000159c108d5e7 000000000b471b76 000000000e3ca8b7 0000000000006873
Call Trace:
 [<ffffffff800c1de3>] taskstats_user_cmd+0x269/0x5d5
 [<ffffffff80063002>] thread_return+0x62/0xfe
 [<ffffffff80011ba7>] do_select+0x41f/0x43c
 [<ffffffff80250c8c>] genl_rcv_msg+0x19b/0x1d2
 [<ffffffff8024ed89>] netlink_run_queue+0x84/0x149
 [<ffffffff80250af1>] genl_rcv_msg+0x0/0x1d2
 [<ffffffff8003f897>] memcpy_toiovec+0x36/0x66
 [<ffffffff802507c0>] genl_rcv+0x34/0x59
 [<ffffffff8024f1c5>] netlink_data_ready+0x12/0x50
 [<ffffffff8024e374>] netlink_sendskb+0x26/0x40
 [<ffffffff8024f1a0>] netlink_sendmsg+0x2b6/0x2c9
 [<ffffffff80054e8d>] sock_sendmsg+0xf8/0x14a
 [<ffffffff800a34a7>] autoremove_wake_function+0x0/0x2e
 [<ffffffff8010c354>] proc_pid_permission+0x35/0x7f
 [<ffffffff8000f6ed>] generic_permission+0x52/0xca
 [<ffffffff80230951>] sys_sendto+0x131/0x164
 [<ffffffff80063002>] thread_return+0x62/0xfe
 [<ffffffff8000c770>] _atomic_dec_and_lock+0x39/0x57
 [<ffffffff8005d28d>] tracesys+0xd5/0xe0

Code: 48 8b 80 b0 00 00 00 48 c1 e0 0c 48 c1 e8 0a 48 89 87 d0 00 
RIP  [<ffffffff800c232a>] xacct_add_tsk+0x59/0xde
 RSP <ffff810412f23810>