free(): invalid pointer 0x842e3344,problem with free

i've written a code that simply forks a process,executes a command thru
execve() and exits,wherein i've used
char *fildes;
allocated a char sting to fildes by
char *itoa(int x)
filedes=itoa(3);

and then execve(args[0],args,env);
wherein on of the contents of args[0] is fildes.

now when i do
free(fildes);

I get error
*** glibc detected *** free(): invalid pointer: 0x080a6bfe ***
Aborted.

can u tell wotz prob with the code.
ANY INPUT IS APPRECIATED

 

wotz the solution for it???
the thing is that i've used this program inthe initrd image ,though this error occurs
everytime but my system does boot.but the main problem is once in every 3-4 boots the system panics, and i believe this is the cause of it.

so wot can be the solution???

 

Assigning a value to a pointer is NOT allocating it. You can only free a pointer that your have gotten from malloc or its variants.