Kernel panic in swiotlb_unmap_sg() function due to NULL pointer dereference.

Issue

• Kernel panic with following call traces;

Unable to handle kernel NULL pointer dereference at 0000000000000000 RIP: 
 [<ffffffff8015dc38>] swiotlb_unmap_sg+0x2b/0x123
PGD 0 
Oops: 0000 [1] SMP 
last sysfs file: /devices/pci0000:00/0000:00:1c.4/0000:02:00.3/irq
CPU 1 
Modules linked in: joydev bonding ipv6 xfrm_nalgo crypto_api dm_multipath scsi_dh video backlight sbs power_meter hwmon i2c_ec i2c_core dell_wmi wmi button battery asus_acpi acpi_memhotplug ac parport_pc lp parport sr_mod cdrom sg tpm_tis igb hpilo 8021q tpm pcspkr tpm_bios serio_raw dca 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 ahci libata shpchp ext3 jbd uhci_hcd ohci_hcd ehci_hcd hpvsa(PU) sd_mod scsi_mod
Pid: 662, comm: hpvsa/2 Tainted: P     ---- 2.6.18-308.el5 #1
RIP: 0010:[<ffffffff8015dc38>]  [<ffffffff8015dc38>] swiotlb_unmap_sg+0x2b/0x123
RSP: 0000:ffff81047db4bdc0  EFLAGS: 00010097
RAX: ffffffff80321be0 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 000000000000005b RSI: 0000000000000000 RDI: ffff81047f761870
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000078
R10: ffffc20010153c98 R11: ffffffff8015dc0d R12: 0000000000000000
R13: 000000000000005b R14: ffff81047f761870 R15: ffffffff800a322c
FS:  0000000000000000(0000) GS:ffff81047ff05840(0000) knlGS:0000000000000000
CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
CR2: 0000000000000000 CR3: 0000000000201000 CR4: 00000000000006a0
Process hpvsa/2 (pid: 662, threadinfo ffff81047db4a000, task ffff81047f79b100)
Stack:  ffff81047e67e000 ffff810075d02420 ffff8101951b7b40 ffff810037e05d80
 ffff81047e67e000 ffffffff8804383c 0000000000000000 0000000000000000
 ffff81047e67e000 ffff810037e05d80 ffff81047e67e078 0000000000000286
Call Trace:
 [<ffffffff8804383c>] :hpvsa:hpvsa_complete_scsi_command+0x2c/0x550
 [<ffffffff88043e49>] :hpvsa:ciss_cmd_completion+0x59/0xa0
 [<ffffffff880748f1>] :hpvsa:HAL_API_CISS_ReturnCompletion+0x91/0xa0
 [<ffffffff8807d5be>] :hpvsa:notify_completion+0x5e/0xa0
 [<ffffffff880ccf5e>] :hpvsa:logical_request_complete+0x30e/0x350
 [<ffffffff880cffee>] :hpvsa:Parse_Task+0x18e/0x300
 [<ffffffff880cfe60>] :hpvsa:Parse_Task+0x0/0x300
 [<ffffffff80032679>] kthread+0xfe/0x132
 [<ffffffff8005dfb1>] child_rip+0xa/0x11
 [<ffffffff800a322c>] keventd_create_kthread+0x0/0xc4
 [<ffffffff8003257b>] kthread+0x0/0x132
 [<ffffffff8005dfa7>] child_rip+0x0/0x11


Code: 48 8b 0b 48 8b 73 10 48 8b 39 48 c1 ef 33 48 89 f8 48 c1 e8 
RIP  [<ffffffff8015dc38>] swiotlb_unmap_sg+0x2b/0x123
 RSP <ffff81047db4bdc0>