System crashed with error Unable to handle kernel NULL pointer dereference

Issue

System crashed with following error messages on console, need RCA

sdbg: Mode Sense: 00 00 00 00
sdbg: assuming drive cache: write through
scsi 7:0:0:1: rejecting I/O to dead device
Unable to handle kernel NULL pointer dereference at 0000000000000008 RIP: 
 [<ffffffff88488f87>] :emcp:emcp_open+0xa7/0x4e0
PGD 82913d067 PUD 828d06067 PMD 0 
Oops: 0000 [1] SMP 
last sysfs file: /block/sdbg/dev
CPU 12 
[...]
Pid: 15459, comm: hald-addon-stor Tainted: P      2.6.18-238.el5 #1
RIP: 0010:[<ffffffff88488f87>]  [<ffffffff88488f87>] :emcp:emcp_open+0xa7/0x4e0
[...]Process hald-addon-stor (pid: 15459, threadinfo ffff811018e00000, task ffff81100f2b80c0)
Stack:  ffff81011cb1ca18 ffffffff80063c57 ffff810829571d98 ffff810f6045e6c0
 ffff81011cb1caf0 ffff81011cb1ca00 ffff81011cb1ca00 ffff81011cb1ca00
 ffff810f6045e6c0 ffff81011cb1ca00 ffff81082ffe0400 ffffffff880aca80
Call Trace:
 [<ffffffff80063c57>] __mutex_lock_slowpath+0x68/0x9b
 [<ffffffff800e775d>] do_open+0xa2/0x30f
 [<ffffffff800e7c1e>] blkdev_open+0x0/0x4f
 [<ffffffff800e7c41>] blkdev_open+0x23/0x4f
 [<ffffffff8001ea94>] __dentry_open+0xd9/0x1dc
 [<ffffffff800274fd>] do_filp_open+0x2a/0x38
 [<ffffffff80063ce5>] do_nanosleep+0x47/0x70
 [<ffffffff80019f5c>] do_sys_open+0x44/0xbe
 [<ffffffff8005d116>] system_call+0x7e/0x83
Code: 48 8b 40 08 f6 80 cc 00 00 00 02 0f 85 d4 01 00 00 8b 05 ba 
RIP  [<ffffffff88488f87>] :emcp:emcp_open+0xa7/0x4e0
 RSP <ffff811018e01d88>