Adding two BigIntegers by putting mutiple digits in a linked list

Based on feedback on an earlier question, I decided to implement the addition of two big ints by putting multiple digits in a node of a linked list. Can somebody take a look at my code and let me know if I am on the right track.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>


typedef struct node{
    int data;
    struct node* next;
} LList;

void printList(LList * list);

LList* pushToResult(LList* resultList,int entry){
    LList * temp = malloc(sizeof(LList));
    temp -> data = entry;
    temp -> next = resultList;
    resultList = temp;
    return resultList;
}

char* substr(char const* input,size_t start,size_t len){
    char *nstr = malloc(len+1);
    memcpy(nstr,input+start,len);
    nstr[len] = '\0';
    return nstr;
}

LList* convertToList(char* line){
    int i;
    int strSize = strlen(line);
    //Eight elements in every node
    int maxelem = 8;
    int currentPartition = 0;
    int currentIndex = 0;
    int totalPartitions = strSize/maxelem;
    LList* temp = NULL;

    for(i = 0;i < strSize - 1;i = i+maxelem){
        if(currentPartition >= totalPartitions){
            break;
        }

        char * currStr = substr(line,i,maxelem);
        int number = atoi(currStr);
        if(temp == NULL){
            temp = malloc(sizeof(LList));
            temp -> data = number;
            temp -> next = NULL;
        }else{
            LList * current = malloc(sizeof(LList));
            current -> data = number;
            current -> next = temp;
            temp = current;
        }
        currentIndex = i;
        currentPartition++;
    }
    currentIndex = currentIndex + maxelem;
    if((currentIndex > 0) && (currentIndex < (strSize - 1))){
        char * remainingStr = substr(line,currentIndex,strSize-1);
        int remainingNum = atoi(remainingStr);
        LList * current = malloc(sizeof(LList));
        current -> data = remainingNum;
        current -> next = temp;
        temp = current;
    }
    return temp;
}


void printList(LList * list){
    LList * counter = list;
    while( counter != NULL){
        printf(" %d ",counter -> data);
        counter = counter -> next;
    }
    printf("\n\n");
}

int main(){
    //Read number 1 from the input file into a linked list
    //The unit's place is the head and the most significant number is the tail
    //Read number 2 from the input file into a linked list
    //The unit's place is the head and the most significant number is the tail
    //Create temporary List where the elements will be added
    //Create the carry variable that will consist of the element's carry over after addition


    int counter = 0;
    ssize_t read;
    size_t len = 0;
    char * line = NULL;

    int carry = 0;  
    LList* num1 = NULL;
    LList* num2 = NULL;
    LList* result = NULL;   

    FILE * input = fopen("input.txt","r");
    if(input == NULL){
        exit(EXIT_FAILURE);
    }
    while((read = getline(&line,&len,input)) != -1){
        printf("Read the line %s",line);
        //If it's the first line
        if(counter == 0){
            num1 = convertToList(line);
            printf("Printing the list containing the num1(it will be in reversed order)\n");
            printList(num1);
        }else{
            num2 = convertToList(line);
            printf("Printing the list containing the num2(it will be in reversed order)\n");
            printList(num2);
        }
        counter++;
    }

    fclose(input);  

    while((num1 != NULL) || (num2 != NULL)){
        if(num1 != NULL){
            carry = carry + (num1->data);
            num1 = num1 -> next;
        }
        if(num2 != NULL){
            carry = carry + (num2 -> data);
            num2 = num2 -> next;
        }
        //Get the carry and the left over
        int carryOver = carry / 100000000;
        int leftOver = carry % 100000000;

        //put the left over in the result linked list
        //printf("Pushing the result into the result list");
        result = pushToResult(result,leftOver);
        carry = carryOver;

    }
    //Done with traversing the linked lists,if the carry is zero no need to push the value to the result
    //else push the value to the result
    if(carry != 0){
        result = pushToResult(result,carry);
    }

    //Print the result here
    printf("Printing out the result of the addition\n");
    printList(result);

}