Problems with LD_PRELOAD and calloc() interposition for certain executables

Question

Relating to a previous question of mine

I\'ve successfully interposed malloc, but calloc seems to be more problematic.

That is with ce

Answer 1

I know I am a bit late (6 years). But I wanted to override calloc() today and faced a problem because dlsym() internally uses calloc(). I solved it using a simple technique and thought of sharing it here:

static unsigned char buffer[8192];

void *calloc(size_t nmemb, size_t size)
{
    if (calloc_ptr == NULL) // obtained from dlsym
            return buffer;

    init(); // uses dlsym() to find address of the real calloc()

    return calloc_ptr(len);
}

void free(void *in)
{
    if (in == buffer)
        return;

    free_ptr(in);
}

buffer satisfies the need of dlsym() till the real calloc() has been located and my calloc_ptr function pointer initialized.