CID 316512: Untrusted loop bound (TAINTED_SCALAR)

*** CID 316512:    (TAINTED_SCALAR)
/lib/dns/rdata/generic/sig_24.c: 199 in totext_sig()
193     
194     	/*
195     	 * Time signed.
196     	 */
197     	when = uint32_fromregion(&sr);
198     	isc_region_consume(&sr, 4);
>>>     CID 316512:    (TAINTED_SCALAR)
>>>     Passing tainted expression "when" to "dns_time32_totext", which uses it as a loop boundary.
199     	RETERR(dns_time32_totext(when, target));
200     	RETERR(str_totext(" ", target));
201     
202     	/*
203     	 * Footprint.
204     	 */
/lib/dns/rdata/generic/sig_24.c: 187 in totext_sig()
181     
182     	/*
183     	 * Sig exp.
184     	 */
185     	exp = uint32_fromregion(&sr);
186     	isc_region_consume(&sr, 4);
>>>     CID 316512:    (TAINTED_SCALAR)
>>>     Passing tainted expression "exp" to "dns_time32_totext", which uses it as a loop boundary.
187     	RETERR(dns_time32_totext(exp, target));
188     
189     	if ((tctx->flags & DNS_STYLEFLAG_MULTILINE) != 0) {
190     		RETERR(str_totext(" (", target));
191     	}
192     	RETERR(str_totext(tctx->linebreak, target));