segment fault error in encrypt files smaller than 1Kbyte

Question

i write this program for encrypt any file with any size but if file will smaller than 1Kbyte my program give me segment fault error whats wrong?

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

long int findsize(char file_name[]) 
{
    FILE* fp = fopen(file_name, "r"); 

    if (fp == NULL) { 
        printf("File Not Found!\n"); 
        return -1; 
    } 

    fseek(fp, 0L, SEEK_END); 

    long int res = ftell(fp); 

    fclose(fp); 

    return res; 
} 

int main ()
{
    FILE *fptr;
    char path[256];
    char* data;
    int passcode;

    printf("Enter the path of file : ");
    scanf("%s",path);
    long int file_size = findsize(path);

    data = malloc(file_size);

    fptr = fopen(path,"rb");

    int i = 0;
    while (!feof(fptr))
        data[i++] = fgetc(fptr);
    fclose(fptr);

    fptr = fopen(path, "wb");

    for (int j=0; j<i-1; j++)
        fputc((data[j] ^ 0x60), fptr);
    fclose(fptr);
    free(data);

    return 0;
}

my program can encrypt files bigger than 1GByte but. what should i do?