Chapter 2, Example 2-3, "Overflowing Buffers on the Stack," page 19

If you are running a 2.6.x Linux kernel (like me), you will need to compile code with -fno-stack-protector:

todb@mazikeen:~/dev/sc$ gcc -mpreferred-stack-boundary=2 -fno-stack-protector -ggdb 2-3.c -o overflow

Otherwise, your buffer overflow will produce totally different (and usually very useful, but maybe not in this case) results:

todb@mazikeen:~/dev/sc$ ./overflow 
AAAAAAAAAAB
AAAAAAAAAAB
*** stack smashing detected ***: ./overflow terminated
======= Backtrace: =========
/lib/libc.so.6(__fortify_fail+0x4b)[0xb7ed005b]
/lib/libc.so.6(__fortify_fail+0x0)[0xb7ed0010]
./overflow[0x804842c]
./overflow[0x8048436]
/lib/libc.so.6(__libc_start_main+0xe5)[0xb7e03685]
./overflow[0x8048391]
======= Memory map: ========
08048000-08049000 r-xp 00000000 08:01 168557     /home/todb/dev/sc/overflow
08049000-0804a000 rw-p 00000000 08:01 168557     /home/todb/dev/sc/overflow
0804a000-0806b000 rw-p 0804a000 00:00 0          [heap]
b7dec000-b7ded000 rw-p b7dec000 00:00 0 
b7ded000-b7f2a000 r-xp 00000000 08:01 13388391   /lib/libc-2.8.90.so
b7f2a000-b7f2c000 r--p 0013d000 08:01 13388391   /lib/libc-2.8.90.so
b7f2c000-b7f2d000 rw-p 0013f000 08:01 13388391   /lib/libc-2.8.90.so
b7f2d000-b7f30000 rw-p b7f2d000 00:00 0 
b7f33000-b7f40000 r-xp 00000000 08:01 13385851   /lib/libgcc_s.so.1
b7f40000-b7f41000 r--p 0000c000 08:01 13385851   /lib/libgcc_s.so.1
b7f41000-b7f42000 rw-p 0000d000 08:01 13385851   /lib/libgcc_s.so.1
b7f42000-b7f45000 rw-p b7f42000 00:00 0 
b7f45000-b7f5f000 r-xp 00000000 08:01 13385969   /lib/ld-2.8.90.so
b7f5f000-b7f60000 r-xp b7f5f000 00:00 0          [vdso]
b7f60000-b7f61000 r--p 0001a000 08:01 13385969   /lib/ld-2.8.90.so
b7f61000-b7f62000 rw-p 0001b000 08:01 13385969   /lib/ld-2.8.90.so
bf866000-bf87b000 rw-p bffeb000 00:00 0          [stack]
Aborted (core dumped)

With -fno-stack-protection, the output looks a lot more like the book's:

todb@mazikeen:~/dev/sc$ ./overflow 
AAAAAAAABBBBBBBBCCCCCCCCDDDDDDDD
AAAAAAAABBBBBBBBCCCCCCCCDDDDDDDD
Segmentation fault (core dumped)

By disabling Linux (Debian's / Ubuntu's) stack protection, the gdb output looks a lot closer to what the book describes, as well.