bsg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
	struct bsg_device *bd = file->private_data;
	ssize_t bytes_written;
	int ret;
 
 	dprintk("%s: write %Zd bytes\n", bd->name, count);
 
	if (unlikely(segment_eq(get_fs(), KERNEL_DS)))
		return -EINVAL;

 	bsg_set_block(bd, file);
 
 	bytes_written = 0;
	ret = __bsg_write(bd, buf, count, &bytes_written,
			  file->f_mode & FMODE_WRITE);

	*ppos = bytes_written;

	/*
	 * return bytes written on non-fatal errors
	 */
	if (!bytes_written || err_block_err(ret))
		bytes_written = ret;

	dprintk("%s: returning %Zd\n", bd->name, bytes_written);
	return bytes_written;
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.