C language debugging - free memory

typedef struct node{

int data;

struct node* next;

}node_t;

typedef struct stack{

int count; // count keeps track of how many items

// are in the stack.

unsigned int capacity; // Stores the maximum size of our stack

node_t* head; // head points to a node on the top of our stack.

}stack_t;

//Write a function to free stack - use valgrind to check

void free_stack(stack_t* s){

free(s); // By doing this we still have memory leakage, how can I free the data in node_t?

}