static int fuse_copy_fill(struct fuse_copy_state *cs)
{
	unsigned long offset;
	int err;

	unlock_request(cs->fc, cs->req);
	fuse_copy_finish(cs);
	if (cs->pipebufs) {
		struct pipe_buffer *buf = cs->pipebufs;

		if (!cs->write) {
			err = buf->ops->confirm(cs->pipe, buf);
			if (err)
				return err;

			BUG_ON(!cs->nr_segs);
			cs->currbuf = buf;
			cs->mapaddr = buf->ops->map(cs->pipe, buf, 0);
			cs->len = buf->len;
			cs->buf = cs->mapaddr + buf->offset;
			cs->pipebufs++;
			cs->nr_segs--;
		} else {
			struct page *page;

			if (cs->nr_segs == cs->pipe->buffers)
				return -EIO;

			page = alloc_page(GFP_HIGHUSER);
			if (!page)
				return -ENOMEM;

			buf->page = page;
			buf->offset = 0;
			buf->len = 0;

			cs->currbuf = buf;
			cs->mapaddr = kmap(page);
			cs->buf = cs->mapaddr;
			cs->len = PAGE_SIZE;
			cs->pipebufs++;
			cs->nr_segs++;
		}
	} else {
		if (!cs->seglen) {
			BUG_ON(!cs->nr_segs);
			cs->seglen = cs->iov[0].iov_len;
			cs->addr = (unsigned long) cs->iov[0].iov_base;
			cs->iov++;
			cs->nr_segs--;
		}
		err = get_user_pages_fast(cs->addr, 1, cs->write, &cs->pg);
		if (err < 0)
			return err;
		BUG_ON(err != 1);
		offset = cs->addr % PAGE_SIZE;
		cs->mapaddr = kmap(cs->pg);
		cs->buf = cs->mapaddr + offset;
		cs->len = min(PAGE_SIZE - offset, cs->seglen);
		cs->seglen -= cs->len;
		cs->addr += cs->len;
	}

	return lock_request(cs->fc, cs->req);
}

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.