static void nfs4_close_prepare(struct rpc_task *task, void *data)
{
	struct nfs4_closedata *calldata = data;
	struct nfs4_state *state = calldata->state;
	struct inode *inode = calldata->inode;
	int call_close = 0;

	dprintk("%s: begin!\n", __func__);
	if (nfs_wait_on_sequence(calldata->arg.seqid, task) != 0)
		return;

	task->tk_msg.rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_OPEN_DOWNGRADE];
	calldata->arg.fmode = FMODE_READ|FMODE_WRITE;
	spin_lock(&state->owner->so_lock);
	/* Calculate the change in open mode */
	if (state->n_rdwr == 0) {
		if (state->n_rdonly == 0) {
			call_close |= test_bit(NFS_O_RDONLY_STATE, &state->flags);
			call_close |= test_bit(NFS_O_RDWR_STATE, &state->flags);
			calldata->arg.fmode &= ~FMODE_READ;
		}
		if (state->n_wronly == 0) {
			call_close |= test_bit(NFS_O_WRONLY_STATE, &state->flags);
			call_close |= test_bit(NFS_O_RDWR_STATE, &state->flags);
			calldata->arg.fmode &= ~FMODE_WRITE;
		}
	}
	spin_unlock(&state->owner->so_lock);

	if (!call_close) {
		/* Note: exit _without_ calling nfs4_close_done */
		task->tk_action = NULL;
		goto out;
	}

	if (calldata->arg.fmode == 0) {
		task->tk_msg.rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_CLOSE];
		if (calldata->roc &&
		    pnfs_roc_drain(inode, &calldata->roc_barrier, task))
			goto out;
	}

	nfs_fattr_init(calldata->res.fattr);
	calldata->timestamp = jiffies;
	if (nfs4_setup_sequence(NFS_SERVER(inode),
				&calldata->arg.seq_args,
				&calldata->res.seq_res,
				task) != 0)
		nfs_release_seqid(calldata->arg.seqid);
	else
		rpc_call_start(task);
out:
	dprintk("%s: done!\n", __func__);
}

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.