Only call memmove if the rdata length is non zero

This avoids undefined behaviour on zero length rdata where the
data pointer is NULL.

diff --git a/lib/dns/rdataslab.c b/lib/dns/rdataslab.c
index f7b51df14729f39e271ceca0a803ccc0a4832f4f..941e60a3181285c9e2e25ad14fc6d12f59bc2085 100644 (file)
--- a/lib/dns/rdataslab.c
+++ b/lib/dns/rdataslab.c
@@ -361,7 +361,9 @@ dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
                                            ? DNS_RDATASLAB_OFFLINE
                                            : 0;
                }
-               memmove(rawbuf, x[i].rdata.data, x[i].rdata.length);
+               if (x[i].rdata.length != 0) {
+                       memmove(rawbuf, x[i].rdata.data, x[i].rdata.length);
+               }
                rawbuf += x[i].rdata.length;
        }