Генератор случайного пароля. Утечка памяти - C (СИ)

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Формулировка задачи:

Написал программу для генерации случайного пароля/ключа. 
#include <stdio.h>
#include <stdlib.h>
 
#define DEFAULT_KEY_LENGTH 500
#define MAX_KEY_LENGTH     1000000
 
int main(int argc, char **argv)
{
    FILE *fp;
    char *password;
    char ch;
    unsigned int i, length;
    
    fp = fopen( "/dev/urandom", "r" );
    
    if( fp == NULL )
    {
        fprintf( stderr, "Error while opening /dev/urandom\n" );
        return 1;
    }
    
    length = DEFAULT_KEY_LENGTH;
    
    if( argc > 1 )
    {
        length = atoi(argv[1]);
        if( length < 1 || length > MAX_KEY_LENGTH )
        {
            fprintf( stderr, "Variable number must be between 1 and %d\n", MAX_KEY_LENGTH );
            return 2;
        }
    }
    
    i = 0;
    password = malloc( (length+1)*sizeof(char) );
    
    if (password == NULL)
    {
        fprintf( stderr, "Malloc error\n" );
        return 3;
    }
    
    while (i <= length)
    {
        ch = fgetc(fp);
        
        if ( (ch>=48 && ch<=57) || (ch>=65 && ch<=90) || (ch>=97 && ch<=122) )
        {
            password[i] = ch;
            i++;
        }
    }
    
    fclose( fp );
    
    while( i )
    {
        fputc( password[i], stdout );
        i--;
    }
    
    free( password );
    
    fputc( '\n', stdout );
    
    return 0;
}
Все работает. Проблема только в утечке памяти.
==7796== Memcheck, a memory error detector ==7796== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al. ==7796== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info ==7796== Command: ./password 10 ==7796== --7796-- Valgrind options: --7796-- --suppressions=/usr/lib/valgrind/debian-libc6-dbg.supp --7796-- -v --7796-- --leak-check=yes --7796-- Contents of /proc/version: --7796-- Linux version 3.11.0-12-generic (buildd@allspice) (gcc version 4.8.1 (Ubuntu/Linaro 4.8.1-10ubuntu7) ) #19-Ubuntu SMP Wed Oct 9 16:20:46 UTC 2013 --7796-- Arch and hwcaps: AMD64, amd64-sse3-cx16-avx --7796-- Page sizes: currently 4096, max supported 4096 --7796-- Valgrind library directory: /usr/lib/valgrind --7796-- Reading syms from /home/dmitry/Desktop/password/password --7796-- Reading syms from /lib/x86_64-linux-gnu/ld-2.17.so --7796-- Considering /lib/x86_64-linux-gnu/ld-2.17.so .. --7796-- .. CRC mismatch (computed 51e60a7a wanted 521e3c74) --7796-- Considering /usr/lib/debug/lib/x86_64-linux-gnu/ld-2.17.so .. --7796-- .. CRC is valid --7796-- Considering /usr/lib/debug/lib/x86_64-linux-gnu/ld-2.17.so .. --7796-- .. CRC is valid --7796-- Reading syms from /usr/lib/valgrind/memcheck-amd64-linux --7796-- Considering /usr/lib/valgrind/memcheck-amd64-linux .. --7796-- .. CRC mismatch (computed c436d3d9 wanted 99aa3883) --7796-- object doesn't have a symbol table --7796-- object doesn't have a dynamic symbol table --7796-- Scheduler: using generic scheduler lock implementation. --7796-- Reading suppressions file: /usr/lib/valgrind/debian-libc6-dbg.supp --7796-- Reading suppressions file: /usr/lib/valgrind/default.supp ==7796== embedded gdbserver: reading from /tmp/vgdb-pipe-from-vgdb-to-7796-by-dmitry-on-??? ==7796== embedded gdbserver: writing to /tmp/vgdb-pipe-to-vgdb-from-7796-by-dmitry-on-??? ==7796== embedded gdbserver: shared mem /tmp/vgdb-pipe-shared-mem-vgdb-7796-by-dmitry-on-??? ==7796== ==7796== TO CONTROL THIS PROCESS USING vgdb (which you probably ==7796== don't want to do, unless you know exactly what you're doing, ==7796== or are doing some strange experiment): ==7796== /usr/lib/valgrind/../../bin/vgdb --pid=7796 ...command... ==7796== ==7796== TO DEBUG THIS PROCESS USING GDB: start GDB like this ==7796== /path/to/gdb ./password ==7796== and then give GDB the following command ==7796== target remote | /usr/lib/valgrind/../../bin/vgdb --pid=7796 ==7796== --pid is optional if only one valgrind process is running ==7796== --7796-- REDIR: 0x4018f40 (strlen) redirected to 0x3806e491 (???) --7796-- Reading syms from /usr/lib/valgrind/vgpreload_core-amd64-linux.so --7796-- Considering /usr/lib/valgrind/vgpreload_core-amd64-linux.so .. --7796-- .. CRC mismatch (computed 826470ab wanted a8b7e9f3) --7796-- object doesn't have a symbol table --7796-- Reading syms from /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so --7796-- Considering /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so .. --7796-- .. CRC mismatch (computed d4fd7975 wanted b90a895a) --7796-- object doesn't have a symbol table --7796-- REDIR: 0x4018db0 (index) redirected to 0x4c2d480 (index) --7796-- REDIR: 0x4018e30 (strcmp) redirected to 0x4c2e560 (strcmp) --7796-- Reading syms from /lib/x86_64-linux-gnu/libc-2.17.so --7796-- Considering /lib/x86_64-linux-gnu/libc-2.17.so .. --7796-- .. CRC mismatch (computed 2c8ee98b wanted da4a7364) --7796-- Considering /usr/lib/debug/lib/x86_64-linux-gnu/libc-2.17.so .. --7796-- .. CRC is valid --7796-- Considering /usr/lib/debug/lib/x86_64-linux-gnu/libc-2.17.so .. --7796-- .. CRC is valid --7796-- REDIR: 0x4ec1980 (strcasecmp) redirected to 0x4a25720 (_vgnU_ifunc_wrapper) --7796-- REDIR: 0x4ebdd10 (strnlen) redirected to 0x4a25720 (_vgnU_ifunc_wrapper) --7796-- REDIR: 0x4ec3c50 (strncasecmp) redirected to 0x4a25720 (_vgnU_ifunc_wrapper) --7796-- REDIR: 0x4ec0790 (memset) redirected to 0x4a25720 (_vgnU_ifunc_wrapper) --7796-- REDIR: 0x4ec0740 (memcpy@GLIBC_2.2.5) redirected to 0x4a25720 (_vgnU_ifunc_wrapper) --7796-- REDIR: 0x4ebf700 (__GI_strrchr) redirected to 0x4c2d2a0 (__GI_strrchr) --7796-- REDIR: 0x4eb7470 (malloc) redirected to 0x4c2a270 (malloc) --7796-- REDIR: 0x4eb7900 (free) redirected to 0x4c2b5a0 (free) ==7796== Invalid read of size 1 ==7796== at 0x400952: main (in /home/dmitry/Desktop/password/password) ==7796== Address 0x51fc2cb is 0 bytes after a block of size 11 alloc'd ==7796== at 0x4C2A2DB: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==7796== by 0x4008AE: main (in /home/dmitry/Desktop/password/password) ==7796== JrdDd7hUAO ==7796== ==7796== HEAP SUMMARY: ==7796== in use at exit: 0 bytes in 0 blocks ==7796== total heap usage: 2 allocs, 2 frees, 579 bytes allocated ==7796== ==7796== All heap blocks were freed -- no leaks are possible ==7796== ==7796== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 2 from 2) ==7796== ==7796== 1 errors in context 1 of 1: ==7796== Invalid read of size 1 ==7796== at 0x400952: main (in /home/dmitry/Desktop/password/password) ==7796== Address 0x51fc2cb is 0 bytes after a block of size 11 alloc'd ==7796== at 0x4C2A2DB: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==7796== by 0x4008AE: main (in /home/dmitry/Desktop/password/password) ==7796== --7796-- --7796-- used_suppression: 2 dl-hack3-cond-1 ==7796== ==7796== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 2 from 2)
То есть, как я понимаю, проблема совсем не в malloc, а в чем-то другом... Как это исправить. И скажите, какие у вас есть замечания по коду. Спасибо.

Решение задачи: «Генератор случайного пароля. Утечка памяти»

textual
Листинг программы 
#include <stdio.h>
#include <stdlib.h>
 
#define DEFAULT_KEY_LENGTH 500
#define MAX_KEY_LENGTH     1000000
 
int main(int argc, char **argv)
{
    FILE *fp;
    char *password;
    char ch;
    unsigned int i, length;
    
    fp = fopen( "/dev/urandom", "r" );
    
    if( fp == NULL )
    {
        fprintf( stderr, "Error while opening /dev/urandom\n" );
        return 1;
    }
    
    length = DEFAULT_KEY_LENGTH;
    
    if( argc > 1 )
    {
        length = atoi(argv[1]);
        if( length < 1 || length > MAX_KEY_LENGTH )
        {
            fprintf( stderr, "Variable number must be between 1 and %d\n", MAX_KEY_LENGTH );
            return 2;
        }
    }
    
    i = 0;
    password = calloc( length+1, sizeof(char) );
    
    if (password == NULL)
    {
        fprintf( stderr, "Malloc error\n" );
        return 3;
    }
    
    while (i <= length)
    {
        ch = fgetc(fp);
        
        if ( isalpha( ch ) )
        {
            password[i] = ch;
            i++;
        }
    }
    
    fclose( fp );
    printf("%s\n", password);
    free( password );
    
    return 0;
}

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