SMB2_close_flags(const unsigned int xid, struct cifs_tcon *tcon,
		 u64 persistent_fid, u64 volatile_fid, int flags)
{
	struct smb_rqst rqst;
	struct smb2_close_rsp *rsp = NULL;
	struct cifs_ses *ses = tcon->ses;
	struct kvec iov[1];
	struct kvec rsp_iov;
	int resp_buftype = CIFS_NO_BUFFER;
	int rc = 0;

	cifs_dbg(FYI, "Close\n");

	if (!ses || !(ses->server))
		return -EIO;

	if (smb3_encryption_required(tcon))
		flags |= CIFS_TRANSFORM_REQ;

	memset(&rqst, 0, sizeof(struct smb_rqst));
	memset(&iov, 0, sizeof(iov));
	rqst.rq_iov = iov;
	rqst.rq_nvec = 1;

	rc = SMB2_close_init(tcon, &rqst, persistent_fid, volatile_fid);
	if (rc)
		goto close_exit;

	rc = cifs_send_recv(xid, ses, &rqst, &resp_buftype, flags, &rsp_iov);
	rsp = (struct smb2_close_rsp *)rsp_iov.iov_base;

	if (rc != 0) {
		cifs_stats_fail_inc(tcon, SMB2_CLOSE_HE);
		trace_smb3_close_err(xid, persistent_fid, tcon->tid, ses->Suid,
				     rc);
		goto close_exit;
	}

	atomic_dec(&tcon->num_remote_opens);

	/* BB FIXME - decode close response, update inode for caching */

close_exit:
	SMB2_close_free(&rqst);
	free_rsp_buf(resp_buftype, rsp);
	return rc;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.