Why kernel crash in ipc/sem.c: 1300 ?

Issue

• Recently one of our servers crashed. We've got a partial vmcore so we were able to get to this information and we found out that the crash was on purpose:

Kernel BUG at ipc/sem.c:1300
invalid opcode: 0000 [1] SMP
last sysfs file: /devices/system/cpu/cpu7/topology/thread_siblings
CPU 1

Pid: 6677, comm: DHL_AS400_JOBMW Tainted: PF    ---- 2.6.18-308.11.1.el5 #1
RIP: 0010:[<ffffffff800454f1>]  [<ffffffff800454f1>] exit_sem+0x77/0x157

crash>dis exit_sem+0x77
0xffffffff800454f1 <exit_sem+119>:      ud2a

ud2a - is an undefined assembler function used for crashes

also sem.c can be checked:
sed -n 1300p /usr/src/debug/kernel-2.6.18/linux-2.6.18-308.11.1.el5.x86_64/ipc/sem.c
                BUG_ON(sem_checkid(sma,u->semid));

apparently BUG_ON function triggered the crash.