static OPJ_BOOL opj_tcd_code_block_enc_allocate_data(opj_tcd_cblk_enc_t *
        p_code_block)
 {
     OPJ_UINT32 l_data_size;
 
    /* The +1 is needed for https://github.com/uclouvain/openjpeg/issues/835 */
    l_data_size = 1 + (OPJ_UINT32)((p_code_block->x1 - p_code_block->x0) *
                                    (p_code_block->y1 - p_code_block->y0) * (OPJ_INT32)sizeof(OPJ_UINT32));
 
     if (l_data_size > p_code_block->data_size) {
        if (p_code_block->data) {
            /* We refer to data - 1 since below we incremented it */
            opj_free(p_code_block->data - 1);
        }
        p_code_block->data = (OPJ_BYTE*) opj_malloc(l_data_size + 1);
        if (! p_code_block->data) {
            p_code_block->data_size = 0U;
            return OPJ_FALSE;
        }
        p_code_block->data_size = l_data_size;

        /* We reserve the initial byte as a fake byte to a non-FF value */
        /* and increment the data pointer, so that opj_mqc_init_enc() */
        /* can do bp = data - 1, and opj_mqc_byteout() can safely dereference */
        /* it. */
        p_code_block->data[0] = 0;
        p_code_block->data += 1; /*why +1 ?*/
    }
    return OPJ_TRUE;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.