From: Willem Toorop <willem@nlnetlabs.nl>
Date: Sun, 21 Dec 2025 14:32:09 +0000 (+0100)
Subject: 2nd arg to memcpy may be NULL if size is 0
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d04a8d9badc0156650c2a1774c6d36f26f816f51;p=thirdparty%2Fldns.git

2nd arg to memcpy may be NULL if size is 0

Found with ldns_native2rdf_int16_data(0, NULL) being called from ldns_pkt_tsig_sign_next()
---

diff --git a/Changelog b/Changelog
index a44ac76e..6106b66b 100644
--- a/Changelog
+++ b/Changelog
@@ -2,6 +2,8 @@
 	* Fix #290: ldns-verify-zone prints to stdout instead of myerr
 	  Thanks RoyArends
 	* Fix memory leak in ldns-notify
+	* Prevent "null pointer pass as 2nd argument to memcpy" runtime
+	  error, when size is 0
 	
 1.9.0	2025-12-04
 	* PR #246: Make ldns_calc_keytag() available for CDNSKEY RR
diff --git a/rdata.c b/rdata.c
index 5befc9e7..429d109e 100644
--- a/rdata.c
+++ b/rdata.c
@@ -167,7 +167,9 @@ ldns_native2rdf_int16_data(size_t size, uint8_t *data)
 		return NULL;
 	}
 	ldns_write_uint16(rdf_data, size);
-	memcpy(rdf_data + 2, data, size);
+	if (size) {
+		memcpy(rdf_data + 2, data, size);
+	}
 	rdf = ldns_rdf_new(LDNS_RDF_TYPE_INT16_DATA, size + 2, rdf_data);
         if(!rdf)
                 LDNS_FREE(rdf_data);