I want to rotate a linked list that contains a number. 123 should be rotated to 231. The function created 23 but the last character stays empty, why?

typedef struct node node;  
struct node{
    char digit;
    node* p;
};

void rotate(node** head){

    node* walk= (*head);
    node* prev= (*head);
    char temp= walk->digit;

    while(walk->p!=NULL){

        walk->digit=walk->p->digit;

        walk= walk->p;
        }

    walk->digit=temp;
}

How I create the list:

node* convert_to_list(int num){ 
   node * curr, * head;

   int i=0,length=0; 

   char *arr=NULL;

   head = NULL;

   length =(int) log10(((double) num))+1;
   arr =(char*) malloc((length)*sizeof(char));          //allocate memory 

   sprintf (arr, "%d" ,num); //(num, buf, 10);

    for(i=length;i>=0;i--) {
      curr = (node *)malloc(sizeof(node));
      (curr)->digit =  arr[i];
      (curr)->p = head;
      head = curr;
   }

   curr = head;

   return curr;
}