Lighttpd

System: FPGA board, microblaze processor, Petalinux OS
Lighthttpd: v1.4.35

Problem description:
lighthttpd process sometimes crashes with the following message:
Oops: kernel access of bad area, sig: 11
CPU: 0 PID: 345 Comm: lighttpd Tainted: G O 3.17.0-svn696 #5

Steps used to reproduce the issue:
1) Boot the system
2) Open the web page (from remote PC). Web page periodically executes AJAX request (CGI scripts) with 15 seconds interval
3) Wait until the following message in the stdout (about 30 minutes):
Oops: kernel access of bad area, sig: 11
CPU: 0 PID: 345 Comm: lighttpd Tainted: G O 3.17.0-svn696 #5
task: efab6da0 ti: efafe000 task.ti: efafe000
Registers dump: mode=0
r1=BFE02A00, r2=00000000, r3=00000001, r4=FFFFFFF2
r5=1002F008, r6=10050208, r7=00000006, r8=00000000
r9=00000000, r10=484520EC, r11=00000005, r12=10027994
r13=00000000, r14=00000000, r15=10007EEC, r16=00000000
r17=1001BB4C, r18=00000002, r19=1002F008, r20=1002DFFC
r21=48456680, r22=00000000, r23=10050208, r24=00000001
r25=10050208, r26=100269E8, r27=4849BD10, r28=1002ED88
r29=00000010, r30=1002ED80, r31=1002ED88, rPC=1001BB48
msr=000055AA, ear=1008D024, esr=00000410, fsr=00000000

GDB Back Trace:
Program received signal SIGSEGV, Segmentation fault.
0xfffffff2 in ?? ()
(gdb) backtrace full
#0 0xfffffff2 in ?? ()
No symbol table info available.
#1 0x1001a554 in configparser (yyp=0x1002f008 <fdevent_linux_sysepoll_event_get_revent+156>, yymajor=1, yyminor=0x6, ctx=0x1) at configparser.c:1513
yyminorunion = {yy0 = 0x10007edc <main+3556>, yy27 = 268467932, yy40 = 0x10007edc <main+3556>, yy41 = 0x10007edc <main+3556>,
yy43 = 0x10007edc <main+3556>, yy78 = 0x10007edc <main+3556>, yy95 = 268467932}
yyact = 268758304
yyendofinput = 4
yyerrorhit = 268623868
yypParser = 0x1002f008 <fdevent_linux_sysepoll_event_get_revent+156>
#2 0x1000ce38 in connection_handle_write_prepare (srv=0x48452384, con=0x0) at connections.c:437
No locals.
#3 0x1002e004 in fdevent_select_event_get_revent (ev=0x78, ndx=13) at fdevent_select.c:86
revents = 1212490628
Backtrace stopped: frame did not save the PC